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Background The production and commercialization of tilapia (Oreochromis niloticus) is fundamentally important to the semi-arid region of northeastern Brazil. In this region, one of the main forms of commercialization occurs in street markets (fairs). A high incidence of methicillin-resistant Staphylococcus aureus (MRSA) strains was previously detected in different food-related environments in Brazil. However, limited data is available about the presence of MRSA in street markets commercializing tilapias. In this study, we identified Staphylococcus aureus from tilapia and utensils used in the commercialization of tilapia in the street markets of a semi-arid Brazilian municipality and characterized the virulence potential of the isolates by analyzing their b-lactam resistance, intercellular adhesion and enterotoxin genes. Methods The study used samples from the 5 main markets in the city. Phenotypic tests to determine antimicrobial resistance, exopolysaccharide (EPS) production, the potential for biofilm formation and cell surface hydrophobicity were conducted on S. aureus isolates. The presence of antimicrobial resistance genes (mecA and blaZ), potential biofilm production genes (icaA and icaD) and enterotoxin (se) genes was investigated. Results Coagulase-positive staphylococci (CoPS) were detected in samples from all markets in discordance with the legal limits in force. Twelve isolates were confirmed to be S. aureus. Ten isolates demonstrated multidrug resistance (MDR). All isolates were able to produce EPS and form biofilms. Eight isolates exhibited strong hydrophobicity and six a high potential for biofilm formation. Twelve isolates were positive for mecA, blaZ, icaD and sed. Conclusions Tilapia marketed in unsuitable conditions may be a vehicle for staphylococcal food poisoning and for the dissemination of MRSA to consumers. Additionally, the ability of the isolates to produce biofilms is an alert to the presence and persistence of these virulent microorganisms on utensils used for the commercial distribution of tilapia.

The clinical significance of long-term methicillin-resistant Staphylococcus aureus (MRSA) bacteremia remains unclear. We evaluated the clinical, microbiological characteristics, and clinical outcomes of long-term MRSA bacteremia. A nested case-control study was conducted in a prospective cohort of adult patients with MRSA bacteremia at a tertiary hospital between August 2008 and December 2017. Patients with long-term MRSA bacteremia (≥ 14 days) were compared with control patients, defined as having bacteremia that resolved in less than 3 days. The following variables were documented: heteroresistance phenotype, genotypes, agr dysfunction, and the presence of 41 virulence genes in isolates. Of the total 890 patients studied, 69 patients (7.8%) exhibited long-term MRSA bacteremia and 599 (67.3%) exhibited resolving bacteremia. The most common sources of long-term bacteremia were central venous catheter–related infection (39%) and osteomyelitis (19%). Independent risk factors for long-term MRSA bacteremia included male sex (adjusted odds ratio [aOR] = 2.43), community-acquired bacteremia (aOR = 2.93), the presence of a prosthetic device (aOR = 3.40), and osteomyelitis (aOR = 7.98). Metastatic infections developed more frequently in patients with long-term bacteremia than in those with resolving bacteremia (56.5% vs. 8.0%; P

Panton-Valentine leukocidin (PVL)-positive USA300 clone is a highly pathogenic and global epidemic community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) clone. Athletes are particularly vulnerable to CA-MRSA infection because of the frequency of skin trauma, close-contact situations, and sharing of equipment that is customary in the athletic setting. We experienced a case of Japanese collegiate football player with septic pulmonary emboli secondary to infectious iliofemoral deep venous thrombosis caused by the USA300 clone. Here, we screened the nasal carriage of USA300 clone colonization among asymptomatic teammate of the patient to elucidate the infection route. Among 69 nasal samples, CA-MRSA strains were found in 5.8% (four samples). Molecular epidemiological analyses showed that three of the CA-MRSA strains were USA300 clone. Furthermore, pulsed-field gel electrophoresis revealed that all nasal USA300 clones showed 100% identity with the USA300 clone isolated from their teammate with critical infection. Our findings indicate that nasal colonization of the PVL-positive CA-MRSA, especially USA300 clone, pose a threat among contact sport athletes in Japan likewise other countries. An immediate infection control strategy for contact sport athletes is necessary to prevent outbreaks of PVL-positive CA-MRSA infections.

Background Several reports designate the recent increase in community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) nasal carriage. Because of the scanty information regarding the nasal carriage sate of MRSA in the west of Iran, the purpose of the present study was to determine the frequency of CA-MRSA in Sanandaj city. Methods Swabs collected from anterior nares of 600 volunteers were analyzed for the presence of S. aureus. The isolates were further investigated for methicillin resistance by using the cefoxitin disk diffusion test, followed by PCR-amplification of the mecA gene. SCCmec types and the presence of the Panton-Valentine Leukocidin (pvl) encoding genes were determined through PCR. Finally, the antimicrobial susceptibility of the isolates was determined by the agar diffusion method. Results Nasal screening identified 181 S. aureus, of which 55 isolates were MRSA. SCCmec types IV and V were detected in MRSA at frequencies of 80 and 20%, respectively. The overall frequency of pvl genes among the MRSA isolates was 14.54%. MRSA isolates were highly susceptible (98.18%) to mupirocin, gentamicin, and fusidic acid. Conclusions The high prevalence of CA-MRSA carriage in the population could pose a serious public health concern for the region. Additionally, advent of drug-resistant pvl-positive strains demands continuous surveillance on the colonization state of CA-MRSA in order to prevent dissemination of the bacterium in the community.

Introduction: Staphylococcal colonization is a risk factor for healthcare-associated infections, which are frequent in Neonatal Intensive Care Units (NICU). This study analyzed microbiology, epidemiology and clinical aspects of Staphylococcus spp. colonizing neonates. Methodology: Nasal or periumbilical swabs were evaluated from 175 newborns admitted to a NICU of a Rio de Janeiro hospital from March to September 2009. Clinical data were obtained from the medical records. SCCmec typing and the mecA and Panton-Valentine Leukocidin (PVL) genes were detected by PCR. Clonal diversity was evaluated by pulsed-field gel electrophoresis. Results: Staphylococcus spp. isolates were detected in 98 (56%) neonates, 66.3% of them had birth weight ≤ 2500 g, 62.2% were preterm (˂ 37 weeks) and the mean length of hospitalization was 14.9 days. Among the 133 isolates identified, 48.1% were S. epidermidis, 23.3% S. haemolyticus and 13.5% S. aureus. Methicillin-resistant Staphylococcus isolate was detected in 77.6% of neonates. The methicillin-resistant S. aureus isolates carried the SCCmec type IV, while 94.6% of S. epidermidis and 85.7% of S. haemolyticus presented non-typeable cassettes. Among the S. aureus, 55.6% had PVL genes and the USA800 genotype was prevalent. Two genotypes of S. epidermidis and one of S. haemolyticus clustered 42.2% and 25.8% of the isolates, respectively. S haemolyticus colonization was associated with the use of parenteral nutrition and mechanical ventilation. Conclusion: High rate of neonates colonized by methicillin-resistant Staphylococcus species and the permanence of clones circulating in the NICU highlight the importance for continuous and preventive surveillance in this high-risk population.

Background Surgical site infection is a major postoperative complication after surgical procedures. The effectiveness of postoperative antimicrobial dressings in reducing surgical site infections is unclear and limited information is available on the efficacy of chlorhexidine gluconate (CHG)-impregnated postoperative dressings. Methods A pilot study was conducted to examine the efficacy of an innovative CHG-impregnated postoperative dressing in reducing the burden of methicillin-resistant Staphylococcus aureus (MRSA) in an in vivo porcine, incisional-wound model. Sutured incisional wounds were contaminated with MRSA and then covered with a CHG wound dressing, a placebo control, or a nonantimicrobial gauze. The surviving MRSA population was quantitatively cultured 3 days postprocedure. Results MRSA was not recovered from any of the 8 wounds that were treated with the CHG dressing (limit of detection, approximately 1.7 log10 colony-forming units [cfu]/g tissue). In contrast, the average microbial recovery from wounds treated with the placebo dressing was 4.2 log10 cfu/g and the average microbial recovery from wounds treated with the gauze dressing was 3.2 log10 cfu/g. Conclusions An innovative CHG dressing provided significant antimicrobial activity against MRSA contaminating a surgical wound in a porcine, incisional-wound model. Future clinical studies are needed to assess the efficacy of the CHG dressing to reduce the bacterial burden in postoperative wounds of surgical patients.

Objectives Most vancomycin-intermediate Staphylococcus aureus (VISA) and heterogeneous VISA (hVISA) are derived from hospital-associated MRSA due to treatment failure; however, the prevalence of hVISA/VISA in community settings remains unclear. Methods Four hundred and seventy-six community-associated isolates were collected between 2010 and 2011 during national surveillance for antimicrobial resistance in 31 county hospitals across China. Drug susceptibility evaluation and mecA detection were performed by using broth microdilution and PCR analysis, respectively. hVISA/VISA were identified by using macro-Etest and a modified population analysis profile (PAP)-AUC method. The genetic features of all hVISA/VISA isolates were genotyped. Results Among 476 isolates, MRSA and MSSA accounted for 19.7% (n = 94) and 80.3% (n = 382), respectively. Two VISA and 36 hVISA isolates were identified by PAP-AUC testing. The VISA isolates and 29 of the hVISA isolates were MRSA. The proportion of hVISA/VISA was significantly higher in MRSA (30.9%) than in MSSA (1.8%). The hVISA/VISA isolates were assigned to 18 STs classified into seven clonal complexes (CCs). CC121 (n = 12) followed by ST239 (n = 11) was the most prevalent hVISA/VISA clone. All ST239-hVISA/VISA were MRSA, while 12 CC121-hVISA isolates included 6 MSSA and 6 MRSA isolates. SCCmec III was predominant among MRSA-hVISA/VISA isolates. agr I and agr IV were detected in ST239 and CC121, respectively. All except two strains were positive for Panton–Valentine leucocidin genes. Conclusions To the best of our knowledge, this is the first report of CC121 as a prevalent hVISA clone in community settings, highlighting the necessity of surveillance and stricter infection control measures for this globally disseminated lineage.

Methicillin-resistant Staphylococcus aureus (MRSA) nasal carriage is a major risk factor for infection, namely among populations in the community with inherent prompting factors, such as the homeless. In Portugal, there are no data on S. aureus/MRSA nasal carriage among the homeless community. A total of 84 homeless individuals living in Lisbon (34 with no permanent address and 50 living in shelter) were nasally screened for S. aureus/ MRSA. All isolates were characterized to determine antimicrobial susceptibility and clonal type. A total of 43 (51.2%) S. aureus carriers were identified, including a single individual colonized with MRSA (1.2%). S. aureus carriage rate was higher among individuals with no permanent address (58.8% versus 46%), younger (45.7 ± 12.7 versus 52.5 ± 10.8 years), and with diagnosis of asthma (9% versus 0%). The single MRSA belonged to the EMRSA-15 clone (PFGE D, ST15-SCCmec IVh, and spa type t790). Almost half of the methicillin-susceptible S. aureus (MSSA) isolates (41.9%, n = 18) belonged to two major clones, ST398-t1451 (n = 13) and ST30-t399/t11980/t12808 associated with PFGE I (n = 5). A high proportion of isolates showed non-susceptibility to mupirocin (64%), erythromycin (45%), and fusidic acid (20%) and induced resistance to clindamycin (39%). None of the isolates harboured PVL. Our results suggest that the homeless population of Lisbon does not constitute a reservoir of MRSA in the community, but harbour the highly transmissible ST398-t1451 MSSA lineage.

Background/purpose: Methicillin-resistant Staphylococcus aureus (MRSA) can encode proteins which directly bind bacteria to many tissues and medical devices or catheters to trigger pathogenesis. However, the relationship between genetic backgrounds and virulent factors in MRSA isolates remained incompletely understood yet. Methods: MRSA isolates were collected from blood cultures of patients with infective endocarditis, bone/joint infection, skin/soft tissue infection, or catheter-related bacteremia in hemodialysis at a tertiary medical center between 2005 and 2011. MRSA isolates were characterized by the methods of spa, multilocus sequence, and staphylococcal cassette chromosome mec (SCCmec) typing. Identification of virulence gene expression was measured by Power SYBR Green PCR Master Mix. Results: Overall collected were 136 MRSA bacteremic isolates, including those from the cases of infective endocarditis (n = 23), bone/joint infection (n = 49), skin/soft tissue infection (n = 20), or catheter-related bacteremia in patients with acute kidney injury or end-stage renal stage receiving hemodialysis (n = 54). CC8-ST239-MRSA-SCCmec type III-spa type t037 was the most prevalent type observed in all of 136 MRSA bacteremic isolates. The prevalent genes in the group of infective endocarditis were clfA, clfB, fnbA, ebpS, eap, emp, sae, and eno; bone/joint infections clfA, emp, sae, and eno; skin/soft tissue infection eno; hemodialysis catheter-related bacteremia clfA and sae. The distribution of each gene was not statically different among four groups. Conclusions: A major MRSA lineage, CC8-ST239-MRSA-SCCmec type III-spa type t037, is noted among bacteremic MRSA isolates. No disease-specific virulent genes can be identified. Keywords: Bacteremia, Staphylococcus aureus, Virulence factors

Introduction: Methicillin resistant Staphylococcus aureus (MRSA), a major cause of zoonotic infections, has emerged globally in livestock, particularly pigs. People with occupational contact with food producing animals are at high risk of colonization. The aim of this study was to determine the prevalence of MRSA in pigs and abattoir workers throughout Trinidad and Tobago as well as their resistance to other antimicrobial agents. Methodology: Nasal and skin behind the ear swabs from pigs and nasal swabs from humans were enriched in Mueller Hinton broth with 6.5% sodium chloride, followed by phenol red mannitol broth with 75 mg/L aztreonam and 5 mg/L ceftizoxime. The enriched sample was then plated on both CHROMagar MRSA and Brilliance MRSA. All incubation was at 37ºC for approximately 24 h. Suspect MRSA isolates were confirmed as MRSA using the Penicillin-Binding Protein (PBP2a) test kit and polymerase chain reaction (PCR) to detect the mecA gene. Resistance of the S. aureus and MRSA isolates to 16 antimicrobial agents was determined using the disc diffusion method. Results: Of the 929 pigs and 44 humans sampled, MRSA strains were isolated at a frequency of 0.9% (8/929) and 2.3% (1/44) respectively. All isolates exhibited resistance to one or more of the 16 antimicrobial agents. Conclusions: The study demonstrated that pigs and workers at slaughter houses in Trinidad and Tobago harbour multidrug resistance S. aureus and MRSA. This is of public health significance as occupational exposure of humans can lead to an increased risk of infection and therapeutic failure.

Background Staphylococcus lugdunensis is a significant pathogen that causes community-acquired and nosocomial infections. The high prevalence of oxacillin-resistant S. lugdunensis (ORSL) is of major concern. Resistance to β-lactams is caused by acquisition of the staphylococcal cassette chromosome mec (SCCmec) element. The cassette is highly diverse, both structurally and genetically, among CoNS. Isolates carrying SCCmec II-ST6 are the major persistent clones in hospitals. Objectives To investigate the structure and evolutionary origin of a novel type II SCCmec element in an endemic ST6 S. lugdunensis clone. Methods The structure of the SCCmec II element carried by ST6 strain CGMH-SL118 was determined by WGS and compared with those reported previously. Results A novel 39 kb SCCmec element, SCCmecCGMH-SL118, with a unique mosaic structure comprising 41 ORFs integrated into the 3′ end of the rlmH gene, was observed. Some regions of SCCmecCGMH-SL118 were homologous to SCCmec IIa of the prototype MRSA strain N315. The structure of SCCmecCGMH-SL118 was similar to that of SCCmec IIb of the MRSA strain, JCSC3063, mainly lacking the aminoglycoside resistance determinant pUB110 in the J3 region but containing the insertion sequence IS256 in the J2 region. Notably, SCCmecCGMH-SL118 deletions in the J1 region compared with SCCmec types IIa and IIb, and a high homology to SCCmec elements of Staphylococcus aureus JCSC4610 and Staphylococcus haemolyticus strain 621 were found. Conclusions The genetic diversity of the type II SCCmec element in ORSL suggests that CoNS is a potential reservoir for interspecies transfer of SCCmec to S. aureus in hospitals.

We consider a deterministic model of Methicillin-resistant Staphylococcus aureus infections in hospitals with seasonal oscillations of the antibiotic prescription rate. The model compartments consist of uncolonized patients with or without antibiotic exposure, colonized patients with or without antibiotic exposure, uncontaminated or contaminated healthcare workers, and free-living bacteria in the environment. We apply optimal control theory to this seven-compartment periodic system of ordinary differential equations to reduce the number of colonized patients and density of bacteria in the environment while minimizing the cost associated with environmental cleaning and antibiotic use in a particular time period. Characterizations of optimal control strategies are formulated and the ways hospitals should adjust these strategies for different scenarios are discussed. Numerical simulations strongly suggest that environmental cleaning is essential in the control of MRSA infections and antibiotic usage is suggested to be maintained at the least possible level. Screening, isolating, and shortening the extremely lengthened stays of colonized patients with antibiotic use history are all effective intervention strategies.

Staphylococcus aureus (SA) is a major cause of bacteremia in children. Methicillin-resistant SA (MRSA) is considered a public health threat; however, the differences in the prognosis of children with methicillin-susceptible SA (MSSA) versus MRSA bacteremia are not well defined.Data from all SA bacteremia events in children (0-16 years) from 2002 to 2016 in a single Israeli tertiary center were collected. Positive cultures within 48 hours of hospitalization were considered community associated (CA). Those obtained afterward or from children hospitalized within the previous year were considered health-care associated (HA).We recorded 427 events, 284 (66%) were HA, 64 (15%) were MRSA and 9 (2%) were CA-MRSA. There was no increase in MRSA during the study period. In-hospital, 30-day and 1-year mortality were 3% (12 cases), 3.5% (16 cases), and 12% (50 cases), respectively. A multivariable analysis controlling for demographics, admitting department and prior morbidity showed an increased 1-year mortality in children with HA bacteremia (hazard ratio [HR] 4.1; 95% confidence interval [CI]: 1.3-12) and prior chronic disease (HR 3.4; 95% CI 1.2 to 9.0). MRSA was not independently associated with increased one-year mortality compared with MSSA: HR (95% CI: 1.4 [0.6-3.1]).Short-term pediatric mortality after SA bacteremia is low. HA-SA bacteremia has an increased long-term risk for mortality, particularly in children with chronic diseases. Our data suggest mortality was not increased for MRSA compared with MSSA bacteremia. The very low rate of CA-MRSA bacteremia justifies the current practice not to include glycopeptides in the empiric treatment of CA bacteremia in Israel.

Pediatric community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections are emerging worldwide. High CA-MRSA carriage rates were previously described in healthy Bedouin children. We assessed demographic, clinical and molecular characteristics of pediatric MRSA infections in southern Israel.The Soroka University Medical Center laboratory serves the entire population of southern Israel, divided into 2 ethnic groups, Bedouins and Jews. All in-hospital MRSA clinical isolates from children 0 to 18 years old obtained in 2016 were included. Health care-associated and community-associated infections were defined according to the Centers for Disease Control and Prevention case definition. All isolates were evaluated for staphylococcal cassette chromosome, Panton-Valentine leukocidin, S. aureus protein A type, pulsed field gel electrophoresis and antimicrobial susceptibility testing.Overall, 95 MRSA isolates (18% of all S. aureus), with 25 different MRSA strains, were identified. Twenty-eight isolates (29.5% of MRSA) belonged to the pediatric clone, rarely observed in Israel, staphylococcal cassette chromosome IV, Panton-Valentine leukocidin positive, S. aureus protein A type 002. All isolates demonstrated identical pulsed-field-gel-electrophoresis fingerprints. Eighty-two percent of infections caused by this clone were community-acquired, mainly observed in young Bedouin children, causing skin and soft-tissue infections. The new clone infection characteristics were similar to those of other CA-MRSA. All isolates of the pediatric clone were susceptible to trimethoprim/sulfamethoxazole, ciprofloxacin, gentamicin, tetracycline, rifampicin and vancomycin; 17.8% were nonsusceptible to erythromycin and clindamycin.The pediatric CA-MRSA clone, previously described only in sporadic cases in Israel, is emerging among healthy, young Bedouin children, typically causing skin and soft-tissue infections. Isolates are susceptible to a variety of non-beta-lactam antibiotics.

Methicillin-resistant Staphylococcus aureus (MRSA) remains an important cause of serious infection, for which vancomycin is often recommended as the first-choice antibiotic treatment. Appropriate vancomycin prescribing requires accurate measurement of minimum inhibitory concentrations (MICs) to avoid treatment failure, and yet determination can be challenging due to methodological difficulties associated with susceptibility testing. An International Working Group of infectious disease specialists and clinical/medical microbiologists reached a consensus that empirical MRSA infection therapies should be chosen regardless of the suspected origin of the infecting strain (e.g., community or hospital) due to the complex intermingling epidemiology of MRSA clones in these settings. Also, if an elevated vancomycin MIC in the susceptible range is obtained in routine testing, an alternative second method should be used for confirmation and to aid antibiotic therapy recommendations. There is no absolutely dependable method for the accurate determination of vancomycin MIC, but broth microdilution appears to be the most reliable.

The empiric antimicrobial therapy for bacteremia of long-term hemodialysis (HD) outpatients is currently based on the combination of vancomycin and gentamicin because of the high frequency of isolated Staphylococcus species. The vancomycin trough level range from 15 to 20 mcg/mL is expected for therapeutic success against methicillin-resistant Staphylococcus aureus with vancomycin minimum inhibitory concentration (MIC) ≥1.0 mcg/mL. Despite the availability of clinical practice guidelines for vancomycin therapeutic drug monitoring, these target serum concentrations are not reached in many patients.In this study, the authors investigated the vancomycin trough levels in 20 HD patients with S. aureus bacteremia and the antimicrobial susceptibility pattern of 45 S. aureus strains isolated from 45 HD patients. The vancomycin serum concentration was determined by chemiluminescent assay. The MIC was determined by broth microdilution method.None of the HD patients included in this study had vancomycin trough concentrations within the therapeutic range. Also, the vancomycin MIC for most methicillin-sensitive S. aureus isolated from bacteremia was ≥1.0 mcg/mL.The therapeutic range of vancomycin was not achieved, and vancomycin MIC was surprisingly high in methicillin-sensitive S. aureus.

Background Osteomyelitis is often challenging to treat. This analysis examined the clinical experience of patients with gram-positive osteomyelitis treated with ceftaroline fosamil in the phase 4 Clinical Assessment Program and Teflaro® Utilization Registry (CAPTURE) study. Methods Data including patient demographics, past illnesses, risk factors, disease characteristics, antibiotic use, pathogens isolated, and clinical outcome were collected between September 2013 and February 2015 by review of randomly ordered patient charts from participating sites in the United States. Clinical success was defined as discontinuation of ceftaroline fosamil following clinical cure with no further need for antibiotics or clinical improvement with switch to another antibiotic treatment. Results A total of 150 patients with gram-positive osteomyelitis were treated with ceftaroline fosamil. Most patients (117/150; 78.0%) were treated with 600 mg ceftaroline fosamil per dose; 143/150 patients (95.3%) received a dose every 12 h. The majority (89/150 patients; 59.3%) had been previously diagnosed with diabetes mellitus or peripheral arterial disease. Osteomyelitis was associated with hardware in 32/150 patients (21.3%). Methicillin-resistant and methicillin-susceptible Staphylococcus aureus (MRSA; MSSA) were the most commonly isolated pathogens, observed in 93/150 (62.0%) and 21/150 (14.0%) patients, respectively. Clinical success with ceftaroline fosamil therapy was observed in 139/150 (92.7%) patients overall, 81/89 (91.0%) patients with diabetes or peripheral arterial disease, and 18/20 (90.0%) patients who had hardware implanted before ceftaroline fosamil therapy (none had hardware removed during therapy). Patients who received prior antibiotic therapy or ceftaroline fosamil as monotherapy experienced clinical success rates of 93.9% (107/114) and 91% (91/100), respectively. Among patients who received concurrent antibiotic therapy, the clinical success rate was 96.0% (48/50). Patients who were infected with MRSA or MSSA had clinical success rates of 92.5% (86/93) and 100% (21/21), respectively. A total of 2/150 (1.3%) patients discontinued ceftaroline fosamil therapy because of adverse events. Conclusions Clinical success rates with ceftaroline fosamil were high in patients with gram-positive osteomyelitis, including those with diabetes or peripheral arterial disease and those with MRSA or MSSA. Electronic supplementary material The online version of this article (10.1186/s12879-019-3791-z) contains supplementary material, which is available to authorized users.

We identified 2 methicillin-resistant Staphylococcus aureus strains of sequence type 398 from surgical site infections in China. Genetic analysis and clinical data from these strains suggested that they were human-related but sporadic. Hemolysis analysis and mouse-skin infection models indicated a high virulence potential for these strains.

During August 1, 2014-July 31, 2015, in 2 counties in Minnesota, USA, incidence of invasive methicillin-susceptible Staphylococcus aureus (MSSA) (27.1 cases/100,000 persons) was twice that of invasive methicillin-resistant S. aureus (13.1 cases/100,000 persons). MSSA isolates were more genetically diverse and susceptible to more antimicrobial drugs than methicillin-resistant S. aureus isolates.

From 1 January to 31 December 2019, 39 institutions around Australia participated in the Australian Staphylococcus aureus Sepsis Outcome Programme (ASSOP). The aim of ASSOP 2019 was to determine the proportion of Staphylococcus aureus bacteraemia (SAB) isolates in Australia that are antimicrobial resistant, with particular emphasis on susceptibility to methicillin and on characterising the molecular epidemiology of the methicillin-resistant isolates. A total of 3,157 S. aureus bacteraemia episodes were reported, of which 79.8% were community-onset. 18.5% of S. aureus were methicillin resistant. The 30-day all-cause mortality associated with methicillin-resistant SAB was 14.0%, which was not significantly different from the 14.3% mortality associated with methicillin-susceptible SAB (p = 0.9). With the exception of the β-lactams and erythromycin, antimicrobial resistance in methicillin-susceptible S. aureus was rare. However, in addition to the β-lactams, approximately 36% of methicillin-resistant S. aureus (MRSA) were resistant to ciprofloxacin, 34% to erythromycin, 13% to tetracycline, 9% to gentamicin and 4% to co-trimoxazole. When applying the EUCAST breakpoints, teicoplanin resistance was detected in two S. aureus isolates. Resistance was not detected for vancomycin and linezolid. Resistance to non-beta-lactam antimicrobials was largely attributable to two healthcare-associated MRSA clones: ST22-IV [2B] (EMRSA-15) and ST239-III [3A] (Aus-2/3 EMRSA). ST22-IV [2B] (EMRSA-15) is the predominant healthcare-associated clone in Australia. Eighty percent of methicillin-resistant SAB, however, were due to community-associated clones. Although polyclonal, approximately 71.4% of community-associated clones were variously characterised as ST93-IV [2B] (Queensland CA-MRSA), ST5-IV [2B], ST45-VT [5C2&5], ST1-IV [2B], ST30-IV [2B], ST78-IV [2B] and ST8-IV [2B]. Community-associated MRSA (CA-MRSA), in particular the ST45-VT [5C2&5] clone, have acquired multiple antimicrobial resistance determinants including ciprofloxacin, erythromycin, clindamycin, gentamicin and tetracycline. The multiresistant ST45-VT [5C2&5] clone accounted for 12.7% of CA-MRSA. As CA-MRSA is well established in the Australian community, it is important that antimicrobial resistance patterns in community- and healthcare-associated SAB are monitored, as this information will guide therapeutic practices in treating S. aureus sepsis.

From 1 January to 31 December 2018, thirty-six institutions around Australia participated in the Australian Staphylococcus aureus Sepsis Outcome Programme (ASSOP). The aim of ASSOP 2018 was to determine the proportion of Staphylococcus aureus bacteraemia (SAB) isolates in Australia that are antimicrobial resistant, with particular emphasis on susceptibility to methicillin, and to characterise the molecular epidemiology of the methicillin-resistant isolates. A total of 2,673 S. aureus bacteraemia episodes were reported, of which 78.9% were community-onset. A total of 17.4% of S. aureus isolates were methicillin resistant. The 30-day all-cause mortality associated with methicillin-resistant SAB was 17.1% which was not significantly higher than the 13.6% mortality associated with methicillin-susceptible SAB (p = 0.1). With the exception of the β-lactams and erythromycin, antimicrobial resistance in methicillin-susceptible S. aureus was rare. However in addition to the β-lactams approximately 42% of methicillin-resistant S. aureus (MRSA) were resistant to erythromycin, 36% to ciprofloxacin and approximately 13% resistant to co-trimoxazole, tetracycline and gentamicin. When applying the EUCAST breakpoints teicoplanin resistance was detected in two S. aureus isolates. Resistance was not detected for vancomycin and linezolid. Resistance to non-beta-lactam antimicrobials was largely attributable to two healthcare-associated MRSA clones: ST22-IV [2B] (EMRSA-15) and ST239-III [3A] (Aus-2/3 EMRSA). The ST22-IV [2B] (EMRSA-15) clone is the predominant healthcare-associated clone in Australia. Seventy-eight percent of methicillin-resistant SAB episodes in 2018 were due to community-associated clones. Although polyclonal, approximately 76.3% of community-associated clones were characterised as ST93-IV [2B] (Queensland CA-MRSA), ST5-IV [2B], ST45-VT [5C2&5], ST1-IV [2B], ST30-IV [2B], ST78-IV [2B] and ST97-IV [2B]. Community-associated MRSA, in particular the ST45-VT [5C2&5] clone, has acquired multiple antimicrobial resistance determinants including ciprofloxacin, erythromycin, clindamycin, gentamicin and tetracycline. The ST45-VT [5C2&5] clone accounted for 11.7% of CA-MRSA. As CA-MRSA is well established in the Australian community, it is important that antimicrobial resistance patterns in community- and healthcare-associated SAB are monitored, as this information will guide therapeutic practices in treating S. aureus sepsis.

Background In the Netherlands there is a lack of data regarding resistance of Staphylococcus pseudintermedius to the systemic antimicrobial drugs used for the treatment of superficial pyoderma. Objectives To assess antimicrobial resistance, with emphasis on resistance to clindamycin and meticillin, in clinical isolates of S. pseudintermedius isolated from dogs with superficial pyoderma. Results were compared between dogs with and without a history of systemic antimicrobial therapy during the previous year. Animals A retrospective study of 237 referral cases presented to an academic teaching hospital between 2014 and 2019, with the clinical and microbiological diagnosis of superficial pyoderma. Methods and materials All clinical isolates were identified primarily by MALDI‐TOF mass spectrometry. Antimicrobial susceptibility was tested either by an agar diffusion method (2014–2016) or by broth microdilution. Antimicrobial history in the preceding year was obtained from medical records. Results Meticillin‐resistant S. pseudintermedius (MRSP) was isolated from 8% of superficial pyoderma cases. Within the meticillin‐susceptible S. pseudintermedius (MSSP) population, clindamycin resistance was significantly more common in isolates derived from dogs with histories of antimicrobial treatment (37.7%) compared to dogs with no histories of exposure (21.7%; P = 0.03). Conclusions Given the high prevalence of clindamycin resistance in MSSP isolated from dogs with prior antimicrobial exposure, it is recommended that bacterial culture and susceptibility testing be pursued before prescribing systemic antimicrobials. Clindamycin should be regarded as the preferred treatment option if susceptibility is confirmed, due to its narrow spectrum and reduced selective pressure for MRSP., Background – In the Netherlands there is a lack of data regarding resistance of Staphylococcus pseudintermedius to the systemic antimicrobial drugs used for the treatment of superficial pyoderma. Objectives – To assess antimicrobial resistance, with emphasis on resistance to clindamycin and meticillin, in clinical isolates of S. pseudintermedius isolated from dogs with superficial pyoderma. Results were compared between dogs with and without a history of systemic antimicrobial therapy during the previous year. Conclusions – Given the high prevalence of clindamycin resistance in MSSP isolated from dogs with prior antimicrobial exposure, it is recommended that bacterial culture and susceptibility testing be pursued before prescribing systemic antimicrobials. Clindamycin should be regarded as the preferred treatment option if susceptibility is confirmed, due to its narrow spectrum and reduced selective pressure for MRSP.

Resistance to meticillin and vancomycin in Staphylococcus aureus significantly complicates the management of severe infections like bacteraemia, endocarditis or osteomyelitis. Here, we review the molecular mechanisms and genomic epidemiology of resistance to these agents, with a focus on how genomics has provided insights into the emergence and evolution of major meticillin-resistant S. aureus clones. We also provide insights on the use of bacterial whole-genome sequencing to inform management of S. aureus infections and for control of transmission at the hospital and in the community.

This study defined the prevalence of enterotoxin gene-positive Staphylococcus aureus strains among food handlers and non-food processing healthy nasal S. aureus carriers in central Iran. Meticillin-resistant S. aureus (MRSA) strains were diagnosed by cefoxitin disk diffusion. PCR was used to detect the mecA, Sa442, and enterotoxin genes. Out of the 1113 food handlers, 224 (20.1%) were nasal carriers of S. aureus and 157 (70.1%) of these isolates were positive for one or more enterotoxin genes. The most prevalent enterotoxin gene was sei (40.2%), followed by seg (35.3%), sea (23.5%), seb (15.2%), sec (5.5%), and seh (2.7%). See and sed genes were not found. Sixty seven (42.7%) of enterotoxin gene-positive isolates possessed a single enterotoxin gene, and 64 (40.8%), 23 (14.7%), and 3 (1.9%) contained two, three, or four enterotoxin genes, respectively. The most frequently detected gene combination was sei/seg (n = 35, 22.3%). Thirty seven (16.5%) isolates were diagnosed as MRSA, and 27 (73%) of these strains were positive for at least one enterotoxin gene. Out of 546 healthy controls, 100 individuals were identified as S. aureus nasal carriers; among the strains, 39 (39%) were positive for at least one enterotoxin gene. Only one (1%) CA-MRSA was identified among the strains from the volunteers. A high prevalence of meticillin resistant and enterotoxin-positive S. aureus were documented in food handlers. We suggest that this may be due to the frequent handling of contaminated foodstuffs and that this is possibly related to the elevated frequencies of acquired staphylococcal food poisoning in this population.

Accurate and rapid identification of methicillin-resistant Staphylococcus aureus (MRSA) is of important clinical significance. In this study, a novel aptamer-based fluorometric assay was developed for detection of MRSA in clinical samples by coupling with immunomagnetic separation . The S. aureus cells in clinical specimens were enriched by magnetic separation. Following lysis by staphylococcal lysin , the PBP2a proteins were released from S. aureus cells and detected by the aptamer-based fluorometric assay. Without lengthy period of bacteria cultivation in the traditional susceptibility testing, this test has an overall testing time of only 2 h with the detection limit of 2.63 × 103 and 1.38 × 103 CFU/mL in PBS and spiked nasal swab, respectively. Since it is simple, rapid and sensitive, this method could be used for the detection of MRSA in various clinical samples.

We evaluated the in vitro activity of apramycin against clinical strains of vancomycin-intermediate and methicillin-resistant and -suseptible Staphylococcus aureus. Apramycin demonstrated an MIC(50)/MIC(90) of 8/16 µg/mL. No strains had an MIC above the epidemiological cutoff value of 32 µg/mL, suggesting apramycin resistance mechanisms are rare in this strain population. The mounting evidence for broad-spectrum in vitro activity of apramycin against S. aureus and other bacterial species suggests that further exploration of apramycin or derivatives as repurposed human therapeutics is warranted.

This study investigated the transmission cycle of methicillin-resistant Staphylococcus aureus (MRSA) and Staphylococcus pseudintermedius (MRSP) in small companion animal veterinary practice. Sampling was undertaken at two small animal veterinary hospitals in Sydney, Australia. Samples were collected from 46 veterinary personnel, 79 personnel-owned dogs and cats, 151 clinically normal canine hospital admissions and 25 environmental sites. Nasal swabs were collected from veterinary personnel. Nasal, oral and perineal swabs were collected from animals. Methicillin resistance was detected by growth on BrillianceTM MRSA 2 Agar and confirmed by cefoxitin and oxacillin broth microdilution for S. aureus and S. pseudintermedius, respectively. MRSA and MRSP isolates were characterised using whole genome sequencing including mecA gene screening and multilocus sequence typing. MRSA was isolated from four (8%) veterinary personnel but no animals. MRSP was isolated from 11/151 (7%) of canine hospital admissions and 4/53 (8%) of personnel-owned dogs but no veterinary personnel or cats. No MRSA or MRSP was isolated from the environment. MRSP isolates were resistant to significantly more antimicrobial classes than MRSA. The main MRSP clone carried by canine patients (ST496) was distinct to that carried by personnel-owned dogs (ST64). One veterinary nurse, who carried Panton Valentine leucocidin-positive ST338 MRSA, also owned a ST749 MRSP-positive dog. Besides MRSP-positive dogs from the same household sharing the same clone of MRSP, MRSA and MRSP were not shared between humans, animals or environment. Therefore, in the non-outbreak setting of this study, there was limited MRS transmission between veterinary personnel, their pets, patients or the veterinary environment.

Background Cystic fibrosis (CF) is an autosomal recessive disease associated with chronic airway infections by Staphylococcus aureus as one of the earliest and most prevalent pathogens. We conducted a retrospective study to determine the S. aureus infection status of CF patients treated since 1994 at two certified CF-centres in Munster, Germany, to get insights into the dynamics of S. aureus airway infection and the clinical impact on lung function on a long-term perspective. Materials and methods We used data from our microbiological database collected between 1994 and 2016 for patients treated at two centres in Munster, Germany, respectively, to determine the infection status for S. aureus. Furthermore, the resistance to selected antibiotics was determined for all patients’ isolates and for 15 patients on a longitudinal basis. In addition, the prevalence of adaptive phenotypes such as small colony variants (SCVs) and mucoid S. aureus was assessed. Results For this study, 2867 patient years with respiratory specimens (mean of 9.3 years for every patient, range 1–22 years) were evaluated for 283 CF patients (median age of 7 years at the beginning of the observation period, range 0–57 years, 51% male). 18% of patients were rarely infected by S. aureus (≤24% of observation years), 20% of patients intermittently (25–49%) and 61% persistently (≥50% of observation period). Susceptibility testing for 12969 S. aureus isolates resulted in resistance to methicillin in 9%, trimethoprim/sulfamethoxazole in 10%, levofloxacin in 14%, gentamicin in 20%, erythromycin and/or clindamycin in 30% and penicillin in 80% of all isolates. S. aureus isolates of 15 patients revealed dynamics of resistance with increase, decrease and loss of resistant isolates to the analysed antibiotics during the study period. SCVs were isolated at least once from 42% (n = 118) of patients and mucoid isolates from 2% (n = 7) of patients. In the last study year, 89 patients were infected by S. aureus only, 44 patients by S. aureus and Pseudomonas aeruginosa and 18 by P. aeruginosa only. Patients infected by S. aureus only were younger and had better lung function compared to the other two groups. Conclusions We determined a high percentage of patients with persistent S. aureus infection. During persistence, mostly fluctuation of resistance against various antibiotics was observed in the isolates indicating acquisition and loss of resistance genes by S. aureus. The prevalence of adaptive phenotypes during long-term persistence was high for SCVs (42% of patients), but low for mucoid isolates (2% of patients), which might be underestimated for mucoid phenotypes due to the retrospective study design and the difficulty to detect mucoid isolates in primary cultures. While patients with S. aureus only had better lung function and were younger, no difference was found between the group of P. aeruginosa and S. aureus co-infection and P. aeruginosa only with previous S. aureus infection.

Recently, the dissemination of community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) into hospitals has frequently been reported worldwide. Hospital-acquired MRSA (HA-MRSA) strains exhibit high-level resistance to multiple antimicrobial agents, whereas CA-MRSA strains are usually susceptible to non-β-lactams. Thus, it is predicted that the antibiogram of the HA-MRSA population would change along with the change in genotype of MRSA. Here, we investigated the changes in the MRSA population along with the MRSA antibiogram in a hospital between 2010 and 2016. Staphylococcal cassette chromosome (SCC) mec typing showed that the predominant HA-MRSA strains in the hospital dramatically changed from SCCmec type II, which is the major type of HA-MRSA, to SCCmec type IV, which is the major type of CA-MRSA. Multilocus sequence typing revealed that the predominant SCCmec type IV strain was a clonal complex (CC) 8 clone, which is mainly found among CA-MRSA. Furthermore, the CC1-SCCmec type IV (CC1-IV) clone significantly increased. Both the CC8-IV and CC1-IV clones exhibited high antimicrobial susceptibility. The antibiogram change of the HA-MRSA population was consistent with the antimicrobial susceptibilities and increased prevalence of the CC8-IV and CC1-IV clones. Our data reveal that the change in the genotypes of MRSA strains could impact the antibiogram of HA-MRSA population.

Persistent methicillin-resistant Staphylococcus aureus (MRSA) bacteremia (PB) represents an important subset of S. aureus endovascular infections. In this study, we investigated potential genetic mechanisms underlying the persistent outcomes. Compared with resolving bacteremia (RB) isolates (defined as isolates associated with negative results of blood cultures 2–4 days after initiation of therapy), PB strains (defined as isolates associated with positive results of blood cultures ≥7 days after initiation of therapy) had significantly earlier onset activation of key virulence regulons and structural genes (eg, sigB, sarA, sae, and cap5), higher expression of purine biosynthesis genes (eg, purF), and faster growth rates, with earlier entrance into stationary phase. Importantly, an isogenic strain set featuring a wild-type MRSA isolate, a purF mutant strain, and a purF-complemented strain and use of strategic purine biosynthesis inhibitors implicated a causal relationship between purine biosynthesis and the in vivo persistent outcomes. These observations suggest that purine biosynthesis plays a key role in the outcome of PB and may represent a new target for enhanced efficacy in treating life-threatening MRSA infections.

We investigated the clinical predictors of methicillin-resistance and their impact on mortality in 371 patients withStaphylococcus aureusbacteraemia identified from two prospective multi-centre studies. Methicillin resistantS. aureus(MRSA) accounted for 42.2% of community-onset and 74.5% of hospital-onset cases. No significant clinical difference was found between patients infected with MRSAvs.methicillin-sensitiveS. aureus(MSSA), except that the former were more likely to have had hospital-onset bacteraemia and received antibiotics in the preceding 90 days. After stratifying according to the acquisition site, prior antibiotic use was the only independent predictor of having MRSA in both community-onset and hospital-onset cases. The frequency of inappropriate empirical antibiotic therapy was higher in patients with MRSA than in those with MSSA bacteraemia. However, methicillin resistance was not a predictor of mortality in patients and the clinical characteristics and outcomes of both MRSA and MSSA bacteraemia were similar. This study indicates that there are no definitive clinical or epidemiological risk factors which could distinguish MRSA from MSSA cases with the exception of the previous use of antibiotics for having MRSA bacteraemia, which emphasises the prudent use of glycopeptide treatment of patients at risk for invasive MRSA infections.

The increasing use of chlorhexidine for methicillin-resistant Staphylococcus aureus (MRSA) decolonization has raised concerns about the emergence of resistance to or tolerance of this antiseptic. We examined the frequency and characteristics of qacA/B chlorhexidine tolerance genes among MRSA isolates in a surgical intensive care unit (ICU) where MRSA-colonized patients are decolonized by chlorhexidine bathing. The MRSA isolates were evaluated for chlorhexidine susceptibility, mupirocin resistance, molecular typing, agr functionality, and the heterogeneous vancomycin-intermediate S. aureus (hVISA) phenotype according to the presence of the qacA/B genes. Overall, 119 MRSA isolates were obtained from active surveillance cultures (93, 78.2%) and clinical cultures (26, 21.8%) between 2012 and 2014. Among these isolates, 39 (32.8%) carried the qacA/B genes, and 23 (19.3%) exhibited mupirocin resistance. Most qacA/B-positive isolates (36/39, 92.3%) were identified as ST5-SCCmecII (69.2%) and ST239-SCCmecIII (23.1%), which are common healthcare-associated (HA)-MRSA strains in Korea. Multivariate analysis found that qacA/B-positive MRSA isolates were associated with agr dysfunction (OR, 4.87; 95% CI, 1.71-13.87) and the hVISA phenotype (OR, 4.09; 95% CI, 1.48-11.34). In conclusion, our study showed that qacA/B carriage was common among MRSA isolates in an ICU where chlorhexidine is commonly used for decolonization. qacA/B carriage was significantly associated with agr dysfunction and the hVISA phenotype. These features may confer a selective advantage on HA-MRSA strains, including ST5-SCCmecII and ST239-SCCmecIII, in the ICU setting.

For patients with possible Staphylococcus aureus infection, providers must decide whether to treat empirically for methicillin-resistant S. aureus (MRSA). Nares MRSA colonization screening tests could inform decisions regarding empiric MRSA-active antibiotic use.1,2

We report a case of severe disseminated infection in an immunocompetent man caused by an emerging lineage of methicillin-sensitive Staphylococcus aureus clonal complex 398. Genes encoding classic virulence factors were absent. The patient made a slow recovery after multiple surgical interventions and a protracted course of intravenous flucloxacillin.

Background: High prevalence of methicillin resistance among clinical isolates of Staphylococcus pseudintermedius obtained from dogs was reported in Seoul metropolitan area, South Korea. However, no information on genetic lineage and clonal spread is currently available. Objective: The aim is to identify the genetic diversity of methicillin-resistant or -susceptible S. pseudintermedius (MRSP and MSSP, respectively) from healthy dogs. Animals and methods: From 119 healthy dogs, 29 isolates consisting of 20 MRSP and 9 MSSP were collected from June 2013 to February 2014. Phenotypic features, antibiogram, multilocus sequence type (MLST), Staphylococcal cassette chromosome mec (SCCmec) type and spa gene type were analyzed. Results: MLST showed 24 sequence types (STs), including 20 new STs that were genetically distinct from the previous STs in other geographic areas. SCCmec typing revealed that all isolates had SCCmec type V, a predominant type in North America. spa gene typing was successful in only 13 isolates (10 MRSP and 3 MSSP) and revealed two known types (t02 and t06), as well as one novel type (t73). Conclusion: Our cumulative data indicate the presence of various populations of S. pseudintermedius in clinically normal dogs in Seoul metropolitan area.

The prevalence of Panton-Valentine leukocidin gene (pvl)-positive community-acquired methicillin-resistant Staphylococcus aureus USA300 clone, which is designated as the ST8-staphylococcal cassette chromosome (SCC) mec type IV (ST8-IV) lineage, is a major public health concern worldwide. Thus, to elucidate the prevalence and characteristics of pvl-positive community-onset MRSA in Japan, we conducted a molecular epidemiological analysis for 854 S. aureus isolates obtained from outpatients with skin infections during 2013 and 2014. The isolation rate of MRSA was 25.6% (219 isolates), and the ratio of pvl-positive MRSA was 13.2% (29 isolates). Notably, the proportion (93.8%) of pvl-positive isolates was particularly high among MRSA isolates from Ishigaki island in Okinawa. Pulsed-field gel electrophoresis and multilocus sequence typing showed that the pulsotype C isolates (11 isolates) were typical USA300 clones with arginine catabolic mobile element (ACME) type I-CC8-IV lineages and prevalent on the main island of Japan (Honshu). Pulsotypes A (11 isolates) and B (four isolates) consisted of ACME-negative CC8-IV clones and were specific for Ishigaki island. Both USA300 and Okinawa-Ishigaki specific clones were associated with deep-seated skin infections, such as furuncle and cellulitis. Pulsotypes D (two isolates) and E (one isolate) were ACME-negative clonal complex (CC) 59-IV clones and were related to superficial skin infections, such as impetigo. Our findings revealed that pvl-positive MRSA associated with deep-seated skin infections are spreading in Japanese communities, particularly in Ishigaki, Okinawa.

We examined the burden of methicillin-resistant Staphylococcus aureus (MRSA) on the clothing of MRSA carriers in a hospital and long-term care facility and assessed the potential for clothing to be a source of transmission. Of 50 MRSA carriers studied, 37 (74%) had MRSA recovered from clothing. For a subset of carriers with clothing contamination, transfer of MRSA from clothing to gloved hands and to a wheelchair occurred in 8 of 13 (62%) and 5 of 10 (50%) carriers, respectively. These findings suggest that measures to reduce clothing contamination should be investigated as a potential means to reduce MRSA transmission in healthcare settings.

Clinical isolates of Staphylococcus aureus (n=3929) collected by 54 medical center laboratories in 12 countries in 2014-2016 were tested for in vitro susceptibility to tedizolid, linezolid, and 11 comparators using Clinical and Laboratory Standards Institute (CLSI) broth microdilution methodology with minimum inhibitory concentrations (MICs) interpreted by CLSI M100-S26 (2016) criteria. All isolates of S. aureus tested were susceptible to both tedizolid (MIC, ≤0.5μg/mL) and linezolid (MIC, ≤4μg/mL). The concentration of tedizolid that inhibited 90% of isolates (MIC90) was 0.5μg/mL, 4-fold lower than linezolid (MIC90, 2μg/mL). Tedizolid MIC frequency distributions were equivalent for methicillin-susceptible (MSSA; n=2090; MIC90, 0.25μg/mL) and methicillin-resistant (MRSA; n=1839; MIC90, 0.25μg/mL) S. aureus. We conclude that tedizolid possesses more potent in vitro activity than linezolid against recently collected isolates of S. aureus, including isolates of MRSA, and that resistance to currently marketed oxazolidinones (tedizolid and linezolid) remains very uncommon.

Few studies have evaluated the clinical impact of polymerase chain reaction (PCR) for Staphylococcus aureus bloodstream infections in resource-limited settings that lack direct antimicrobial stewardship intervention. This retrospective cohort study compared patients with standard microbiological identification (n=343) to those with additional identification by (PCR) (n=130). Time to initiation of optimal therapy was similar between groups but substantially shorter in the PCR group for those infected with methicillin susceptible S. aureus (median 40.0h vs. 28.3h, P=0.001). After controlling for confounding factors including infectious diseases consultation, the PCR group had a shorter time to initiation of optimal therapy by 9.7h (95% CI 4.3-15.0h). Clinical outcomes were similar in the non-PCR and PCR groups. While time to initiation of optimal therapy was shorter in the PCR group, greater reductions may be realized through additional education, direct antimicrobial stewardship intervention, or additional clinician notification.

Methicillin-resistant Staphylococcus aureus (MRSA) has been one of the most important antibiotic-resistant pathogen in many parts of the world over the past decades. This cross-sectional study was conducted to investigate MRSA isolated between July 2013 and July 2014 in Karaj, Iran. All tested isolates were collected in teaching hospitals from personnel, patients, and surfaces and each MRSA was analyzed by SCCmec and spa typing. Antibiotic susceptibility testing was accomplished by disk diffusion method. Out of 49 MRSA isolates from the Karaj’s teaching hospitals, 82%, 10%, and 6% of the isolates were SCCmec types III, II, and I, respectively. The main spa type in this study was spa t030 with frequency as high as 75.5% from intensive care unit (ICU) of the hospitals and high rate of resistance to rifampicin (53%) was found in MRSA isolates. In conclusion, high frequency of spa t030 with SCCmec type III and MRSA phenotype illustrated circulating of one of the antibiotic-resistant strains in ICU of Karaj’s teaching hospitals and emphasizes the need for ongoing molecular surveillance, antibiotic susceptibility monitoring, and infection control.

SUMMARYThis study aimed to examine the epidemiology and treatment outcomes of community-onset purulent staphylococcal skin and soft tissue infections (SSTI) in Central Australia. We performed a prospective observational study of patients hospitalised with community-onset purulent staphylococcal SSTI (n= 160). Indigenous patients accounted for 78% of cases. Patients were predominantly young adults; however, there were high rates of co-morbid disease. Community-associated methicillin-resistantStaphylococcus aureus(CA-MRSA) was the dominant phenotype, accounting for 60% of cases. Hospitalisation during the preceding 6 months, and haemodialysis dependence were significant predictors of CA-MRSA infection on univariate analysis. Clinical presentation and treatment outcomes were found to be comparable for methicillin-susceptibleS. aureus(MSSA) and methicillin-resistant cases. All MRSA isolates were characterised as non-multi-resistant, with this term used interchangeably with CA-MRSA in this analysis. We did not find an association between receipt of an active antimicrobial agent within the first 48 h, and progression of infection; need for further surgical debridement; unplanned General Practitioner or hospital re-presentation; or need for further antibiotics. At least one adverse outcome was experienced by 39% of patients. Clindamycin resistance was common, while rates of trimethoprim–sulfamethoxazole resistance were low. This study suggested the possibility of healthcare-associated transmission of CA-MRSA. This is the first Australian report of CA-MRSA superseding MSSA as the cause of community onset staphylococcal SSTI.

Arginine catabolic mobile element (ACME) is a genomic island of staphylococcus and is considered to confer enhanced ability to survive and growth on host bacterial cells. ACME has been typically identified in Panton-Valentine Leukocidin (PVL)-positive ST8 methicillin-resistant Staphylococcus aureus (MRSA) with SCCmec type IVa (USA300 clone), and it is also found in other lineages at low frequency. Prevalence and molecular characteristics of PVL+and/or ACME+ MRSA were investigated for 624 clinical isolates collected from outpatients in northern Japan from 2013 to 2014. Both PVL genes and ACME type I were detected in nine isolates (1.4%), which were ST8-MRSA-SCCmec IVa/spa type t008/agr-I; whereas solely PVL genes were positive in two isolates, ST30-MRSA-SCCmec IV and ST59-MRSA-SCCmec V. ACME type II' (previously referred to as ACME ΔII) was detected in 36 isolates (5.8%) with SCCmec II and V (32 and 4 isolates, respectively), exhibiting an increased rate within SCCmec II-MRSA (7.1%) compared with our previous studies (0.86-4.5%, 2008-2011). ACME II'-positive MRSA strains were classified into ST5-SCCmec IIa/V or ST764-SCCmec IIa belonging to five different spa types, with t002 being dominant. They harbored mostly enterotoxin gene clusters (seg-sei-sem-sen-seo-seu) and some more enterotoxin genes (seb1, seb2, sec3, sel, sep), showing resistance to more antimicrobials than ST8-MRSA-SCCmec IVa. ACME-SCCmec composite island (CI) of the 36 ACME II'-positive MRSA was classified into five types (ii)-(vi), among which type (ii) (orfX-ΨSCCΔJ1 SCCmec I-ACME II'-SCCmec II) was dominant and subdivided into the A3 variant and the less common A2 variant. CI types (v) and (vi) were considered novel genetic organizations having speG (acetyltransferase genes for polyamines) in inserted SCC4610/SCC266-like genetic elements. The present study revealed increased prevalence and genetic diversity of the ST5/ST764-MRSA-SCCmec II with ACME II' in northern Japan.

Purpose. To examine whether the epidemiology of bacteraemia caused by methicillin-susceptible Staphylococcus aureus (MSSA) and methicillin-resistant S. aureus (MRSA) differed in children aged

We investigated the lytic activity of the bacteriophage endolysin (lysin) LysKΔamidase against live methicillin-resistant and-susceptible staphylococcal strains clinically isolated from bovine milk and humans from different origins of China. Antibiotic resistance patterns, multilocus sequence typing and SCCmec type of 137 staphylococcal strains isolated from bovine milk associated with bovine mastitis and human diseases were studied. A lytic enzyme, LysKΔamidase, was constructed by fusing the N-terminal 220 amino acids with the C-terminal 105 amino acids of staphylococcal phage lysin LysK. Herein, the antimicrobial activity of LysKΔamidase against 66 methicillin-resistant staphylococcal strains and 71 methicillin-susceptible staphylococcal strains isolated from bovine milk and from humans in China were studied. Our results show that the lysin displayed a broad lytic spectrum; in vitro treatment killed all 137 of the milk and clinical isolates of staphylococci strains tested, including MRSA, methicillin-susceptible S. aureus (MSSA), MR-Staphylococcus hominis ssp. homins, MR-Staphylococcus epidermidis and MR-Staphylococcus haemolyticus as evidenced by scanning electron microscopy, transmission electron microscopy, turbidity reduction assay and disruption of biofilms. The present results suggest that LysKΔamidase has the potential to be an alternative therapeutic agent against pathogenic methicillin-resistant and-susceptible staphylococcal strains isolated from China.