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We reviewed all cases of Panton-Valentine leukocidin-producing Staphylococcus aureus (PVL-SA) bacteremia in Danish children between 2016 and 2021. We found 2 fatal cases with preceding viral prodrome due to severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Given the usual benign course of SARS-CoV-2 infection in children, awareness of possible superinfection with PVL-SA in a child with rapid deterioration is crucial to ensure adequate treatment, including antimicrobial drugs with antitoxin effect., Competing Interests: The authors have no conflicts of interest to disclose., (Copyright © 2022 Wolters Kluwer Health, Inc. All rights reserved.)

Introduction: Skin and soft tissue infections (SSTI) caused by Panton-Valentine leukocidin (PVL)-producing strains of Staphylococcus aureus (PVL-SA) are associated with recurrent skin abscesses. Secondary prevention, in conjunction with primary treatment of the infection, focuses on topical decolonization. Topical decolonization is a standard procedure in cases of recurrent PVL-SA skin infections and is recommended in international guidelines. However, this outpatient treatment is often not fully reimbursed by health insurance providers, which may interfere with successful PVL-SA decolonization., Aim: Our goal was to estimate the cost effectiveness of outpatient decolonization of patients with recurrent PVL-SA skin infections. We calculated the average cost of treatment for PVL-SA per outpatient decolonization procedure as well as per in-hospital stay., Methods: The study was conducted between 2014 and 2018 at a German tertiary care university hospital. The cohort analyzed was obtained from the hospital's microbiology laboratory database. Data on medical costs, DRG-based diagnoses, and ICD-10 patient data was obtained from the hospital's financial controlling department. We calculated the average cost of treatment for patients admitted for treatment of PVL-SA induced skin infections. The cost of outpatient treatment is based on the German regulations of drug prices for prescription drugs., Results: We analyzed a total of n = 466 swabs from n = 411 patients with recurrent skin infections suspected of carrying PVL-SA. PVL-SA was detected in 61.3% of all patients included in the study. Of those isolates, 80.6% were methicillin-susceptible, 19.4% methicillin-resistant. 89.8% of all patients were treated as outpatients. In 73.0% of inpatients colonized with PVL-SA the main diagnosis was SSTI. The median length of stay was 5.5 days for inpatients colonized with PVL-SA whose main diagnosis SSTI; the average cost was €2,283. The estimated costs per decolonization procedure in outpatients ranged from €50-€110, depending on the products used., Conclusion: Our data shows that outpatient decolonization offers a highly cost-effective secondary prevention strategy, which may prevent costly inpatient treatments. Therefore, health insurance companies should consider providing coverage of outpatient treatment of recurrent PVL-SA skin and soft tissue infections., Competing Interests: The authors have declared that no competing interests exist.

Necrotizing pneumonia induced by Panton-Valentine leukocidin-secreting Staphylococcus aureus is a rare but life-threatening infection that has been described in patients after they had influenza. We report a fatal case of this superinfection in a young adult who had coronavirus disease.

Objective: Panton-Valentine leukocidin-producing Staphylococcus aureus necrotizing pneumonia is an unusual cause of community-acquired pneumonia, although associated with a high case fatality. This infection mainly affects young individuals, without any history, and is most often preceded by flu-like symptoms., Method: We focused on patients presenting with Staphylococcus aureus necrotizing pneumonia in Reunion (Indian Ocean) admitted to the emergency department. We performed a retrospective study based on data collected from laboratory registers and medical files of patients presenting with Staphylococcus aureus necrotizing pneumonia in Reunion between December 2014 and December 2017., Results: A total of 16 patients were recruited for this study, with a median age of 40.5 years. More than half of patients had previously been admitted to the emergency department for acute respiratory distress syndrome or severe sepsis. Fourteen patients were admitted to the intensive care unit and six patients died (five premature deaths)., Conclusion: Physicians should be aware of this infection during the flu season and quickly adapt the specific antibiotic treatment, including a drug inhibiting toxin production. As methicillin-resistant Staphylococcus aureus is very rarely observed in Reunion, physicians can still adapt the empirical treatment, without glycopeptides., (Copyright © 2019 Elsevier Masson SAS. All rights reserved.)

Introduction: Methicillin-resistant Staphylococcus aureus (MRSA) is considered a major cause of healthcare-associated (HA) and community-acquired (CA) infections. Considering non-β-lactam susceptibility as a potential marker for mecC-MRSA and CA-MRSA, the aim of this study was to determine the frequency and the associated genetic lineages of non-beta-lactam-antibiotic susceptible MRSA (NBLS-MRSA) strains in a multicenter study in Spain., Methods: A collection of 45 NBLS-MRSA strains recovered in the period from January to June 2016 from 12 Spanish hospitals was analyzed. Molecular typing through spa-type characterization, agr group and multi-locus-sequence typing was performed. Methicillin-resistant genes (mecA and mecC) as well as immune evasion cluster (scn-chp-sak-sea-sep, considering scn gene as the marker of IEC system) and Panton-Valentine leukocidin (PVL) genes were determined with PCR/sequencing., Results: The NBLS-MRSA phenotype was uncommon in the 12 hospitals analyzed (NBLS-MRSA/MRSA frequency: 0.3%-7.7%). All strains contained the mecA gene (and none contained mecC). Twenty-two different spa-types were detected among NBLS-MRSA strains, with spa-t008/agr-I the most prevalent (27%). The main clonal complexes were (CC/%): CC8/42.2%, CC5/33.3% and CC30/4.4%, with ST8 and ST5 as the main sequence types. The PVL toxin was present in 38% of strains (with spa-types t008, t024, t019, t044, t068, t318 and t3060). The IEC genes were detected in 78% of strains: IEC type-B (n=17), type-F (n=16), type-A (n=1) and type-E (n=1); 10 MRSA isolates were scn-negative., Conclusion: The NBLS-MRSA phenotype is uncommon in the analyzed hospitals; although no mecC-positive strains were detected, it could be a good marker for MRSA PVL-positive isolates (38%), frequently associated with CA-MRSA infections., (Copyright © 2019 Elsevier España, S.L.U. and Sociedad Española de Enfermedades Infecciosas y Microbiología Clínica. All rights reserved.)

It is necessary to develop agents other than antimicrobials for the treatment of Staphylococcus aureus infections to prevent the emergence of antimicrobial-resistant strains. Particularly, anti-virulence agents against the Panton-Valentine leukocidin (PVL)-positive methicillin-resistant S. aureus (MRSA), USA300 clone, is desired due to its high pathogenicity. Here, we investigated the potential anti-virulence effect of Tokiinshi, which is a traditional Japanese medicine (Kampo) used for skin diseases, against the USA300 clone. A growth inhibition assay showed that a conventional dose (20 mg/ml) of Tokiinshi has bactericidal effects against the clinical USA300 clones. Notably, the growth inhibition effects of Tokiinshi against S. epidermidis strains, which are the major constituents of the skin microbiome, was a bacteriostatic effect. The data suggested that Tokiinshi is unlikely to affect skin flora of S. epidermidis. Furthermore, PVL production and the expression of its gene were significantly suppressed in the USA300 clone by a lower concentration (5 mg/ml) of Tokiinshi. This did not affect the number of viable bacteria. Moreover, Tokiinshi significantly suppressed the expression of the agrA gene, which regulates PVL gene expression. For the first time, our findings strongly suggest that Tokiinshi has the potential to attenuate the virulence of the USA300 clone by suppressing PVL production via agrA gene suppression., Competing Interests: The authors have declared that no competing interests exist.

Purpose: Potent extracellular toxins including alpha-haemolysin, Panton-Valentine leukocidin (PVL) and toxic-shock syndrome toxin 1 (TSST-1) significantly contribute to Staphylococcus aureus pathogenesis, thus, toxin suppression is a primary focus in treatment of staphylococcal disease. S. aureus maintains complex strategies to regulate toxin expression and previous data have demonstrated that subinhibitory concentrations of beta-lactam antibiotics can adversely increase S. aureus exotoxin production. The current study evaluates the effects of subinhibitory concentrations of tedizolid, a second-generation oxazolidinone derivative, on expression of staphylococcal exotoxins in both methicillin-resistant and methicillin-sensitive S. aureus., Methodology: S. aureus exotoxin expression levels were compared at 12 and 24 h following treatment with tedizolid, linezolid, nafcillin or vehicle control., Results: Our findings show that the level of antibiotic required to alter toxin production was strain-dependent and corresponds with the quantity of toxin produced, but both tedizolid and linezolid could effectively reduce expression of alpha-haemolysin, PVL and TSST-1 toxin at subinhibitory concentrations. In contrast, nafcillin showed less attenuation and, in some S. aureus strains, led to an increase in toxin expression. Tedizolid consistently inhibited toxin production at a lower overall drug concentration than comparator agents., Conclusion: Together, our data support that tedizolid has the potential to improve outcomes of infection due to its superior ability to inhibit S. aureus growth and attenuate exotoxin production.

A leukotoxin (LtxA) that is produced by Aggregatibacter actinomycetemcomitans (Aa) is an important virulence determinant in an aggressive form of periodontitis in adolescents. Understanding the function of this protein at the molecular level is critical to elucidating its role in the disease process. To accomplish genetic analysis of the protein structure and relating these observations to toxin function, we have developed an E. coli expression system for the generation and rapid purification of LtxA. Cloning the structural toxin gene, ltxA, from Aa strain JP2 under control of T7 promoter-1 of pCDFDuet-1 vector resulted in expression of a 114 KDa protein which could be easily purified by the presence of a carboxy-terminal engineered double hexahistidine (double-His 6 ) tag and was immunologically reactive with an anti-LtxA monoclonal antibody, but was not cytotoxic. Cloning a second gene, ltxC, an acyltransferase gene, into the vector under control of T7 promoter-2, resulted in expression of the biologically active LtxA. The toxin was extracted from E. coli inclusion bodies, purified by immobilized metal affinity chromatography, and refolded by dialysis. When compared by circular dichroism (CD) spectroscopy analysis, acylated recombinant LtxA has a secondary structure consistent with wt LtxA, while variations in α-helical structure of nonacylated LtxA were observed. No modifications in α-helix were found upon the toxin's binding with liposome-incorporated cholesterol. Our results suggest that pure, biologically active recombinant LtxA can be isolated by a one-step affinity chromatography from E. coli. The toxic and structural properties of the recombinant LtxA are similar to its wt counterpart., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Groin pain is a frequently occurring complaint in presentations to the Emergency Department. Muscular sprain is often a differential diagnosis, however serious conditions such as pyomyositis should not be ignored. This case report presents a child with atraumatic right groin pain, which was initially diagnosed as a muscular sprain. The patient later re-presented out of hours to the Emergency Department with what was found to be extensive pelvic abscesses. He was subsequently found to have bilateral pneumonia and later developed a pericardial effusion and osteomyelitis of the right iliac bone, sacroiliac joint and sacrum. With multiple surgical interventions and appropriate antibiotics, he made a full recovery and was discharged home after a total admission time of 41 days. The causative organism was found to be Panton-Valentine leucocidin-positive methicillin-susceptible Staphylococcus aureus ., Competing Interests: Competing interests: None declared., (© BMJ Publishing Group Ltd (unless otherwise stated in the text of the article) 2018. All rights reserved. No commercial use is permitted unless otherwise expressly granted.)

The amount of Panton-Valentine leukocidin (PVL) is diverse among Staphylococcus aureus isolates from different geographical regions, and its significance in some infections is disputed. However, data concerning this information in China are limited. Fifty-one lukSF-PV + methicillin-resistant Staphylococcus aureus (MRSA) isolates gathered from varying infections were used for PVL production using enzyme-linked immunosorbent assay, and the quantity was analyzed in correlation with PVL isoform, genetic background of the isolate, and disease category. All isolates generated PVL with a range of 0.43-360.87 μg/mL, of which 56.9% isolates (29/51) generated 51-200 μg/mL of PVL; 11.8% (6/51) yielded PVL more than 200 μg/mL, and the rest (31.4%, 16/51) produced PVL of ≤50 μg/mL. The amount of PVL was not related to its variant and infection type, although isolates from skin and soft tissue infection had relatively high mean and median. Clonal complex (CC) 22 isolates might be the producer of relatively high concentrations of PVL; however, the difference among CCs was not analyzed due to a small number of CC isolates. The relevance of PVL production with the infection type, toxin isoform, and genetic characteristic of isolates may vary by clone type and also needs to be further evaluated using a large sample size and best concentration on in vivo environment.

Synthetic cells, artificial cell-like particles, capable of autonomously synthesizing RNA and proteins based on a DNA template, are emerging platforms for studying cellular functions and for revealing the origins-of-life. Here, it is shown for the first time that artificial lipid-based vesicles, containing the molecular machinery necessary for transcription and translation, can be used to synthesize anticancer proteins inside tumors. The synthetic cells are engineered as stand-alone systems, sourcing nutrients from their biological microenvironment to trigger protein synthesis. When pre-loaded with template DNA, amino acids and energy-supplying molecules, up to 2 × 10 7 copies of green fluorescent protein are synthesized in each synthetic cell. A variety of proteins, having molecular weights reaching 66 kDa and with diagnostic and therapeutic activities, are synthesized inside the particles. Incubating synthetic cells, encoded to secrete Pseudomonas exotoxin A (PE) with 4T1 breast cancer cells in culture, resulted in killing of most of the malignant cells. In mice bearing 4T1 tumors, histological evaluation of the tumor tissue after a local injection of PE-producing particles indicates robust apoptosis. Synthetic cells are new platforms for synthesizing therapeutic proteins on-demand in diseased tissues., (© 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

Despite increasing reports of skin and soft tissue infections caused by community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) in Japan, the extent to which these strains cause nosocomial infections remains unknown, and this is especially true for bloodstream infections. In this study, we molecularly characterized MRSA isolates from Japanese blood samples. Among the 151 MRSA isolates collected from 53 medical facilities in 2011, 115 (76%) and 30 (20%) were classified as staphylococcal cassette chromosome mec (SCCmec) types II and IV, respectively, while the Panton-Valentine leukocidin (PVL) gene was detected in only two isolates. Among 66 MRSA isolates collected from Tokyo Medical University Hospital between 2012 and 2015, 43 (65%) and 20 (30%) were classifiable as SCCmec types II and IV, respectively. In 2015, highly virulent strains, such as the SCCmec type IV/PVL and SCCmec type IV/ toxic shock syndrome toxin-1 clonal types, increased in number. Therefore, the SCCmec type IV clone may cause invasive infections not only in community settings but also in healthcare settings in Japan.

Objectives: We report on an outbreak of skin and soft tissue infections (SSTI) among kindergarten families. We analyzed the transmission route and aimed to control the outbreak., Methods: The transmission route was investigated by nasal screening for Panton-Valentine leukocidin (PVL)-producing Staphylococcus aureus (PVL-SA), subsequent microbiological investigation including whole genome sequencing and a questionnaire-based analysis of epidemiological information. The control measures included distribution of outbreak information to all individuals at risk and implementation of a Staphylococcus aureus decontamination protocol., Results: Individuals from 7 of 19 families were either colonized or showed signs of SSTI such as massive abscesses or eye lid infections. We found 10 PVL-SA isolates in 9 individuals. In the WGS-analysis all isolates were found identical with a maximum of 17 allele difference. The clones were methicillin-susceptible but cotrimoxazole resistant. In comparison to PVL-SAs from an international strain collection, the outbreak clone showed close genetical relatedness to PVL-SAs from a non-European country. The questionnaire results showed frequent travels of one family to this area. The results also demonstrated likely transmission via direct contact between families. After initiation of Staphylococcus aureus decontamination no further case was detected., Conclusions: Our outbreak investigation showed the introduction of a PVL-SA strain into a kindergarten likely as a result of international travel and further transmission by direct contact. The implementation of a Staphylococcus aureus decontamination protocol was able to control the outbreak.

A 61-year-old male presented with community-onset pneumonia not responding to treatment despite given appropriate antibiotics. Computed tomography scan of the thorax showed large multiloculated pleural effusion with multiple cavitating foci within collapsed segments; lesions which were suggestive of necrotising pneumonia. Drainage of the effusion and culture revealed methicillin-resistant Staphylococcus aureus, which had the same antibiotic profile with the blood isolate and PVL gene positive.

The use of invasive techniques, such as intravascular catheter insertion, and the formation of biofilms in several devices by methicillin-resistant Staphylococcus aureus (MRSA) have contributed to the increased number of septic patients, morbidity and mortality. This study aimed to evaluate the virulence of strains through catheter colonization and identification of microbial biofilm, as well as pathological changes on the colonized skin. An experimental biofilm formation model utilized catheter fragments implanted subcutaneously in 25 Swiss mice. The technique consisted of inoculating a catheter fragment on the back of each animal, followed by intradermal inoculation of 50 μl of bacterial suspension at 1.0 × 10⁷ colony forming units/ml. After 96 h, catheters were removed for macroscopic analysis and evaluated through culture. Local skin fragments were also extracted for histopathology analysis. Staphylococcus aureus can adhere to catheters, colonize and form biofilms. The high amount of viable bacterial cells colonizing catheters and virulence factors can lead to severe infections of skin and adjacent tissues. [Int Microbiol 19(4): 199-207 (2016)]., (Copyright© by the Spanish Society for Microbiology and Institute for Catalan Studies.)

Since late 2014, multiple cases of abscesses and boils due to methicillin-susceptible Staphylococcus aureus (MSSA) expressing the Panton-Valentine leucocidin (PVL) were observed in Eritrean asylum seekers in Lausanne, Switzerland. Strains isolated from infected Eritrean and non-Eritrean patients were compared by whole genome sequencing to determine whether these numerous cases result from an outbreak. The genome of S. aureus PVL-producing strains were sequenced and compared. Clinical and epidemiological characteristics of patients infected by PVL-producing strains were investigated. This work reports 15 cases of infections due to PVL-producing strains affecting mostly asylum seekers (n = 10), people working with refugees and/or exposed to Africans (n = 3). Most infections were due to closely related strains of CC152 (n = 8) and CC15 (n = 3), two distantly related (>34 000 core single nucleotide polymorphisms) clonal complexes. An epidemiological link between the 15 cases could be ruled out by whole genome sequencing (33 to 172 core single nucleotide polymorphisms between the different strains of a given complex). Altogether, these results reflect the probable high incidence of CC15 and CC152 PVL-producing strains in eastern Africa. Clinicians facing unusual skin infections in African refugees (or in any person returning from this region of high endemicity) should consider S. aureus PVL-producer before suspecting rare infections such as leishmaniasis or rickettsiosis. Clinicians should also remember that PVL are frequently expressed by MSSA in some regions of the world and that antibiotics that are efficient on toxin expression, such as clindamycin, represent the best therapeutic option., (Copyright © 2016 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Staphylococcus aureus is a major etiologic agent of infections in children from the community and the hospital setting. The severity of these conditions is associated with virulence factors, including the Panton-Valentine leukocidin. Both methicillin resistant and sensitive Staphylococcus aureus produce this leukocidin although with varying frequency. We present two children with severe infection by sensitive Staphylococcus aureus producer of Panton-Valentine leukocidin with musculoskeletal and endovascular complications. It is essential the suspected diagnosis, appropriate antibiotic treatment and early surgical management to improve the approach of these infections. Epidemiological surveillance should be mantained to detect the frequency of infections caused by these bacteria., (Sociedad Argentina de Pediatría.)

Staphylococcus aureus is among the most important human pathogens. It is associated with different infections and is a major cause of skin and soft tissue infections (SSTIs). The aim of our study was to compare S. aureus isolates associated with SSTIs with isolates obtained from healthy carriers in the Central Slovenia region in terms of antimicrobial susceptibility, genetic diversity by clonal complex (CC)/sequence type, spa type, and by toxin gene profiling. In total, 274 S. aureus isolates were collected prospectively by culturing wound samples from 461 SSTI patients and nasal samples from 451 healthy carriers. We have demonstrated high heterogeneity in terms of CCs and spa type in both groups of isolates. The main clone among SSTI strains was Panton-Valentine leukocidin gene (pvl) positive CC121, whereas the main clone among carrier strains was CC45 carrying a large range of toxin genes. The main spa type in both groups was t091. Pvl was more frequently present in SSTI strains (31.2% SSTI vs 3.6% carrier strains) and staphylococcal enterotoxin C was more frequently present in carrier strains (1.6% SSTI vs 17.0% carrier strains). We have also demonstrated that methicillin-resistant S. aureus was a rare cause (2.8%) of SSTIs in our region., (© 2016 APMIS. Published by John Wiley & Sons Ltd.)

A prospective study (2007-2013) was undertaken to investigate clinical features and prognostic factors of necrotizing pneumonia caused by Staphylococcus aureus producing Panton-Valentine leukocidin (PVL) in the Czech Republic. Twelve cases of necrotizing pneumonia were detected in 12 patients (median age 25 years) without severe underlying disease. Eight cases occurred in December and January and the accumulation of cases in the winter months preceding the influenza season was statistically significant (P < 0·001). The course of pneumonia was very rapid, leading to early sepsis and/or septic shock in all but one patient. Seven patients died and mortality was fourfold higher in those patients presenting with primary pneumonia than with pneumonia complicating other staphylococcal/pyogenic infection elsewhere in the body. The S. aureus isolates displayed considerable genetic variability and were assigned to five lineages CC8 (n = 3), CC15 (n = 2), CC30 (n = 2), CC80 (n = 1), and CC121 (n = 3) and one was a singleton of ST154 (n = 1), all were reported to be associated with community-acquired infection. Four strains were methicillin resistant. The high case-fatality rate can only be reduced by improving the speed of diagnosis and a rapid test to detect S. aureus in the airways is needed.

A 76-year-old man was admitted to a community hospital due to a persistent high fever. He became afebrile after the administration of broad-spectrum antibiotics, but developed heart failure due to progressive aortic and mitral valve insufficiency and was transferred to our hospital. Although sequential blood cultures were negative, a broad-range polymerase chain reaction targeting the bacterial 16S-rRNA gene followed by the direct sequencing of whole blood revealed spa(+), mecA(-) and Panton-Valentine leukocidin (PVL)(+). He was finally diagnosed with infective endocarditis (IE) caused by PVL-producing methicillin-susceptible Staphylococcus aureus (MSSA), and underwent cardiac surgery. This is the first reported case of IE due to MSSA producing PVL.

Objectives: We set out to investigate the impact of common antibiotics on Panton-Valentine Leucocidin (PVL) expression by methicillin-sensitive Staphylococcus aureus (MSSA). PVL expression by methicillin-resistant S. aureus (MRSA) is reportedly enhanced by β-lactams, but inhibited by protein-synthesis inhibitors, a fact that has influenced management of infections associated with PVL. Although PVL is more frequently associated with MSSA than MRSA in the UK, the effect of antibiotics on PVL expression by MSSA has not been fully addressed., Methods: MSSA was cultured in vitro with varying concentrations of flucloxacillin, clindamycin or linezolid and PVL expression measured by qRT-PCR and Western blotting. A murine MSSA abscess model was developed to measure leucocidin expression in vivo following antibiotic treatment., Results: 9% (27/314) of MSSA isolates from patients with uncomplicated community skin/soft tissue infections were positive for PVL genes (lukFS-PV). PVL expression by MSSA in broth was unaffected by varying concentrations of flucloxacillin, clindamycin or linezolid. In a murine abscess model, treatment with flucloxacillin did, however, enhance in vivo MSSA lukF-PV transcription and this was sustained even when flucloxacillin was combined with clindamycin, or clindamycin plus linezolid. Notwithstanding increased leucocidin transcription, functional leucotoxin activity was not enhanced. Treatment with flucloxacillin plus clindamycin significantly decreased leucotoxin activity, but the addition of a second protein synthesis inhibitor, linezolid, did not confer benefit., Conclusions: Our results suggest flucloxacillin in combination with a single protein-synthesis inhibitor such as clindamycin would give the best treatment outcome., (Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.)

Objectives: The aim of our study was to evaluate the frequency of osteoarticular infections with Panton-Valentine leukocidin-positive (PVL) Staphylococcus aureus (PVL-SA) among patients admitted to the orthopedic ward at the Sahloul University Hospital (Sousse, Tunisia) and to study the characteristics of these strains and patients., Materials and Methods: We conducted a retrospective descriptive study over a 5-year period. Bacterial identification, antibiotic susceptibility, and molecular study (PCR to detect of the luk-PV gene that encodes PVL) were performed for 44 S. aureus isolates., Results: Panton-Valentine toxin was found in 41% of S. aureus cases, mainly males, and 39% of the PVL(+) cases were methicillin-sensitive (MSSA). These strains constitute a reservoir of PVL genes that can lead to the emergence and spread of PVL-SA clones resistant to methicillin (MRSA). In our series, PVL-MRSA accounted for 9% of all S. aureus isolates. Their profile and antibiotic resistance is that of clone ST80, frequently isolated in Europe and also reported in Algeria and Tunisia., Conclusion: It is desirable to test for PVL routinely in the laboratory to implement appropriate treatment and to monitor the epidemiology of these PVL-SA strains actively. Further measures should be undertaken to prevent and fight infections by these strains.

Methicillin-resistant Staphylococcus aureus (MRSA) producing Panton-Valentine leukocidin (PVL) is highly virulent. This study aimed to compare the efficacy of tigecycline versus vancomycin in experimental thigh abscess by a PVL-producing MRSA isolate. One hundred and ninety-six Wistar rats were divided into five groups: group A, controls; groups B and C, administered vancomycin starting 1 and 6 h after bacterial challenge respectively; groups D and E, administered tigecycline starting 1 and 6 h after bacterial challenge respectively. Treatment was continued every 12 hours for three consecutive days. Survival was recorded; separate animals were killed for quantitative cultures. Serum samples were collected for estimation of malondialdehyde (MDA). Survival of group D was prolonged compared to all other groups. The bacterial load of blood, liver, spleen and lung was significantly decreased within group D compared to group B at 36 hours. Treatment with tigecycline was accompanied by significant reduction of serum MDA at 24 hours. Tigecycline is comparable to vancomycin for the treatment of soft tissue infections by PVL-producing MRSA.

Staphylococcus aureus is an important pathogen within the context of cystic fibrosis lung disease. Case reports have identified a strong association between the toxin Panton-Valentine Leukocidin (PVL) and lethal necrotizing pneumonia in healthy immunocompetent patients. PVL+ strains of Staphylococcus aureus have also been identified in patients with cystic fibrosis. We describe a further case of pneumonia in a patient with cystic fibrosis, and outline potential transmission of the organism from healthy family members to this patient. We review the evidence regarding the pathogenicity of PVL toxin with a special reference to patients with cystic fibrosis. We outline current concerns regarding the potential transmission of the organism and possible treatment strategies., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

It is well known that some isolates of Staphylococcus aureus produce pathogenic toxin, Panton-Valentine leukocidin (PVL), and that the toxin has been reported to be highly associated with community acquired methicillin resistant S. aureus (CA-MRSA). Currently, the PCR method using specific primers for the PVL gene (LukS-PV-lukF-PV) have been widely used to detect PVL. In this study, we evaluated the PVL-RPLA "Seiken", diagnostic reagent based on a reserved passive latex agglutination reaction with a specific monoclonal antibody for detecting PVL. A total of 630 clinical isolates were used. PCR method detected 34 PVL-positive (28 MRSA and 6 MSSA), and, of these, PVL-RPLA "Seiken" read positive for 32 isolates (27 MRSA and 5 MSSA), the result indicating two false negative occurrences. The concordance rate was 99.7%. In addition the recommended BHI broth, CCY medium, Dolman broth and Todd-Hewitt broth were applied for toxin preparation media. Toxin concentration produced in CCY medium was significantly higher than those in the remaining culture medium (p < 0.05). PVL-RPLA "Seiken" is a method for detecting the PVL in the culture broth by antigen antibody reaction after an overnight shaking culture. This method does not require any expensive equipments or facilities. Thus this reagent provides us with rapid, easy-to-perform, less expensive test method to detect PVL in clinical microbiology laboratories.

We describe three cases of community-acquired necrotizing pneumonia which were caused by Panton-Valentine leucocidin-producing strains of Staphylococcus aureus (one of them methicillin sensitive). All cases were successfully treated without any sequelae for the patients due to the prompt initiation of adequate antimicrobial therapy. High suspicion toward this fatal pathogen was the key to the successful outcome of the patients., (Copyright © 2014 Elsevier Editora Ltda. All rights reserved.)

Emerging strain of Stapylococcus aureus (S. aureus) producer of the Panton-Valentine Leukocidine (PVL+) are becoming a new issue in public health. Those bacteria are accountable for serious cutaneous infection with a necrotic evolution, necrotizing pneumonia and severe osteoarticular infection. These last infections can be life-threatening and are at high risk of complications. Therefore, a multidisciplinary approach is necessary, in addition with an aggressive chirurgical treatment. We are here reporting 3 cases of osteoarticular infections by S. aureus PVL+ sensitive to methicilline, which illustrate the difficulties encountered in the management and treatment, as well as the potential for serious orthopedics complications.

The emergence of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) is a growing cause for concern. These strains are more virulent than health care-associated MRSA (HA-MRSA) due to higher levels of toxin expression. In a previous study, we showed that the high-level expression of PBP2a, the alternative penicillin binding protein encoded by the mecA gene on type II staphylococcal cassette chromosome mec (SCCmec) elements, reduced toxicity by interfering with the Agr quorum sensing system. This was not seen in strains carrying the CA-MRSA-associated type IV SCCmec element. These strains express significantly lower levels of PBP2a than the other MRSA type, which may explain their relatively high toxicity. We hypothesized that as oxacillin is known to increase mecA expression levels, it may be possible to attenuate the toxicity of CA-MRSA by using this antibiotic. Subinhibitory oxacillin concentrations induced PBP2a expression, repressed Agr activity, and, as a consequence, decreased phenol-soluble modulin (PSM) secretion by CA-MRSA strains. However, consistent with other studies, oxacillin also increased the expression levels of alpha-toxin and Panton-Valentine leucocidin (PVL). The net effect of these changes on the ability to lyse diverse cell types was tested, and we found that where the PSMs and alpha-toxin are important, oxacillin reduced overall lytic activity, but where PVL is important, it increased lytic activity, demonstrating the pleiotropic effect of oxacillin on toxin expression by CA-MRSA.

Panton-Valentine leukocidin (PVL; gene designation lukF/S-PV) is likely an important virulence factor for Staphylococcus aureus (S. aureus), as qualitative expression of the protein correlates with severity for specific clinical presentations, including skin and soft tissue infections (SSTIs). Development of genetic approaches for risk-assessment of patients with S. aureus infections may prove clinically useful, and whether lukF/S-PV gene expression correlates with specific clinical presentations for S. aureus has been largely unexplored. In the present study, we quantified lukS-PV mRNA among 96 S. aureus isolates to determine whether expression levels correlated with specific clinical presentations in adults and children. Expression level of lukS-PV mRNA among isolates from skin and soft tissue infections (SSTIs) was significantly greater than among isolates from blood stream infection (BSIs), and expression level of lukS-PV mRNA among BSI isolates from children was significantly greater than for BSI isolates among adults. Moreover, expression level of lukS-PV mRNA among community-acquired (CA) isolates was significantly greater than for hospital-acquired (HA) isolates. These data justify additional studies to determine the potential clinical utility for lukS-PV mRNA quantification as a predictive tool for severity of S. aureus infection.

We report the observation of a septic arthritis of the knee complicated within first 36 hours by multiorgan failure including acute respiratory distress syndrome (ARDS), heart failure, acute renal failure and disseminated intravascular coagulation (DIC). A diagnosis of staphylococcal arthritis was suspected confirmed by direct examination, and culture showed a Staphylococcus aureus sensitive to methicillin. The sample sent to the National Reference Centre for Staphylococci (Lyon, France) for genetic analysis confirmed the isolate positive for the PVL gene expression. The fulminating evolution of a septic S. aureus arthritis in an otherwise healthy man should probably evoke the possibility of LPV strain. Anti-PLV antibiotics with anti-staphylococcal activity, such as clindamycin and linezolid should be started without waiting for typing of the S. aureus strain., (Copyright © 2013 Société française de rhumatologie. Published by Elsevier SAS. All rights reserved.)

The ST8 methicillin-resistant Staphylococcus aureus (MRSA) with Staphylococcal cassette chromosome mec (SCCmec) type IVa, known as USA300, is a prevalent community-acquired MRSA (CA-MRSA) clone in the United States and has been spreading worldwide. The USA300 characteristically harbors Panton-Valentine Leukocidin (PVL) genes and the arginine catabolic mobile element (ACME, type I). Prevalence and molecular characteristics of PVL(+) and/or ACME(+) S. aureus were investigated in a university hospital located in northern Japan, for 1,366 S. aureus isolates, including 601 MRSA strains derived from clinical specimens collected from 2008 to 2010. The PVL gene was identified in three MRSA strains with SCCmec IV, which belonged to ST8, spa type t008, coagulase type III, and agr type I. Two PVL-positive MRSA strains had also type I ACME, and were isolated from skin abscess of outpatients who have not travelled abroad recently. One of these PVL(+)/ACME(+) strains carried tet(K), msrA, and aph(3')-IIIa, showing resistance to kanamycin, tetracycline, erythromycin, and ciprofloxacin, suggesting acquisition of more resistance than ST8 CA-MRSA reported in Japan previously. In contrast, another PVL(+)/ACME(+) strain and a PVL(+)/ACME(-) strain were susceptible to more antimicrobials and had less virulence factors than PVL(-)/ACME(+) MRSA strains. Besides the two PVL(+) MRSA strains, ACME (type-ΔII) was identified into seven MRSA strains with SCCmec II belonging to ST5, one of the three spa types (t002, t067, and t071), coagulase type II, and agr type II. These PVL(-)/ACME(+) MRSA strains showed multiple drug resistance and harbored various toxin genes as observed for ST5 PVL(-)/ACME(-) MRSA-II. The present study suggested the spread of ST8-MRSA-IV in northern Japan, and a potential significance of ACME-positive ST5-MRSA-II as an emerging MRSA clone in a hospital.

Background: An eight (8) months prospective study was carried out to control an outbreak of nosocomial pneumonia due to a Panton-Valentine Leukocidin (PVL) producing Staphylococcus aureus, in the paediatrics' unit at the Zou/Collines Departmental Hospital (CHDZ/C), (Benin)., Methods: Between 1(st) September 2004 and 30(th) May 2005 an investigation was conducted that involved the screening of all patients suspected to have nosocomial pneumonia, hospital environment sampling and the follow-up of cases until the end of hospital admission period. Isolates were identified, tested for antimicrobial susceptibility and analysed for PVL production. The study period was divided into Period I, corresponding to the outbreak period and Period II, after the complete renovation of the Unit along with hand washing promotion., Results: A total of 453 patients were admitted during the period of the study; (235 during Period I and 218 during Period II) in the malnourished children sector. Twenty eight (28) cases of pneumonia due to S. aureus were discovered and PVL-producing S. aureus constituted 61% (17/28) of identified cases. The mortality rate among the PVL- producing strains was 15/17 (88%) while it was 1/11 (9%) among non PVL-producing strains. Enhanced hygiene measures helped to terminate the outbreak., Conclusions: This study showed that PVL was strongly linked to nosocomial pneumonia. PVL-producing S aureus can be controlled in the hospital by a combination of the promotion of preventive measures, decontamination of the environment and the early use of the correct antibiotic at the appropriate dose and for an adequate duration.

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) can cause osteomyelitis with severe sepsis and/or local complications in which a Panton-Valentine leukocidin (PVL) role is suspected. In vitro sub-MIC antibiotic effects on growth and PVL production by 11 PVL(+) MRSA strains, including the major CA-MRSA clones (USA300, including the LAC strain; USA400; and USA1000), and 11 PVL(+) methicillin-susceptible S. aureus (MSSA) strains were tested in microplate culture. Time-kill analyses with ceftobiprole at its MIC were also run with LAC. Efficacies of ceftobiprole (40 mg/kg of body weight subcutaneously [s.c.] four times a day [q.i.d.]) or vancomycin (60 mg/kg intramuscularly [i.m.] twice a day [b.i.d.]) alone or combined with rifampin (10 mg/kg b.i.d.) against rabbit CA-MRSA osteomyelitis, induced by tibial injection of 3.4 × 10(7) CFU of LAC, were compared. Treatment, started 14 days postinoculation, lasted 14 days. In vitro, 6/11 strains cultured with sub-MICs of ceftobiprole produced 1.6- to 4.8-fold more PVL than did the controls, with no link to specific clones. Rifampin decreased PVL production by all tested strains. In time-kill analyses at the LAC MIC (0.75 mg/liter), PVL production rose transiently at 6 and 8 h and then declined 2-fold at 16 h, concomitant with a 2-log(10)-CFU-count decrease. In vivo, the mean log(10) CFU/g of bone for ceftobiprole (1.44 ± 0.40) was significantly lower than that for vancomycin (2.37 ± 1.22) (P = 0.034), with 7/10 versus 5/11 bones sterilized, respectively. Combination with rifampin enhanced ceftobiprole (1.16 ± 0.04 CFU/g of bone [P = 0.056], 11/11 sterile bones) and vancomycin (1.23 ± 0.06 CFU/g [P = 0.011], 11/11 sterile bones) efficacies. Ceftobiprole bactericidal activity and the rifampin anti-PVL effect could play a role in these findings, which should be of interest for treating CA-MRSA osteomyelitis.

Objective: The authors had for aim to describe the epidemiological and clinical characteristics, and the treatment of patients presenting with skin and soft tissue infections due to Panton-Valentine leukocidin (PVL) producing Staphylococcus aureus in the Nord-Pas-de-Calais (NPDC) region, North of France., Methods: We included patients presenting with PVL producing S. aureus infection from seven hospitals in the NPDC region, between February 2004 and April 2008. We retrospectively collected patient data using a standardized questionnaire. The features of patients presenting with skin and soft tissue were then analyzed., Results: PVL producing S. aureus was isolated from 64 patients. Fifty-four patients presented with skin and soft tissue infections. The mean age of patients was 23.8 years (63% male patients). The mean number of persons living with the infected patient was 4.5 (vs. 2.5 in NPDC). The lesions were abscesses with inflammatory signs in 64.8% of the cases (20% were necrotic). Among the patients, 70.3% carried a methicillin resistant strain. Antibiotics per os were used for 83.3% of patients; the first-line antibiotics were considered inadequate in 53.3% of the cases. Among the patients, 83.3% underwent surgery. Fourteen out of 38 patients with available data had been exposed to antibiotic therapy during the three months before hospital management., Conclusion: Recent exposure to antibiotics and living with a high number of persons are reasons to suspect a PVL producing S. aureus infection in patients with skin abscess., (Copyright © 2012 Elsevier Masson SAS. All rights reserved.)

Background: Community-acquired methicillin-resistant Staphylococcus aureus (caMRSA) is an emerging pathogen which causes potentially severe infections in young and healthy individuals due to the ability of most strains to produce Panton-Valentine leukocidin (PVL). The aim of this study was to evaluate the prevalence of PVL-positive (PVL(+))-MRSA strains in Western Austria in the period from December 2005 to May 2010 and to characterize the identified PVL(+)-MRSA strains., Methods: Six hundred and fifty MRSA strains from Innsbruck Medical University hospital, district hospitals, and general practitioners were investigated for the presence of lukS-lukF gene (encoding for PVL). Antimicrobial resistance testing, SCCmec-, agr-, MLST- and spa-typing, as well as arcA determination were performed on PVL(+)-MRSA., Results: Among 650 MRSA strains collected from various body sites from hospitalized patients and outpatients, 31 strains (4.8 %) were positive for lukS-lukF and thus identified as PVL(+)-MRSA. Agr-1 was the most common agr-type (n = 18, 58.1 %) and SCCmec-IV or variants IVa and IVc were the most common SCCmec types (n = 27, 87.1 %). All tested strains showed in-vitro susceptibility to vancomycin and rifampicin, but resistance against cotrimoxazol (6.4 %), clindamycin (9.7 %), gentamicin (9.7 %), fusidic acid (12.9 %), levofloxacin (12.9 %), and erythromycin (61.3 %) was found. Most lukS-lukF-positive MRSA detected in our survey shared ST8 and t008 and were positive for arcA., Conclusions: The major lukS-lukF-positive MRSA lineage found in our population was ST8, t008 and positive for arcA which is mainly found in the USA. In contrast, ST80 strains were not found as frequently in our region as in many other European countries.

Staphylococcus aureus harboured by Panton-Valentine leukocidin (PVL) is emerging as a serious problem worldwide. There has been an increase in the incidence of necrotizing lung infections in otherwise healthy young people with very high mortality rate associated with these strains. This report documents a confirmed case of necrotizing pneumonia due to methicillin-susceptible S. aureus (MSSA) harbouring Panton-Valentine leukocidin genes. An apparently healthy 49-year old man was admitted to our hospital for dyspnea and he quickly developed acute respiratory distress syndrome. MSSA harbouring Panton-Valentine leukocidin genes were cultured from the abscess fluid and from multiple blood specimens. Aggressive antibiotic therapy was started and intensive supportive care led finally to a complete recovery. Rapid identification of Panton-Valentine leukocidin in MSSA samples should be supposed when a young, immunocompetent patient, develops a necrotizing pneumonia. Bactericidal antistaphylococcal antibiotics are recommended for the treatment as soon as possible to avoid the potentially devastating consequences of this kind of S. aureus.

Panton-Valentine leukocidin (PVL)-producing Staphylococcus aureus results in leukocyte destruction and tissue necrosis (Pediatric Dermatology 2007;24:401). It can be associated with a spectrum of clinical manifestations that range from localized staphylococcal skin infections to sometimes severe necrotizing pneumonia (Clin Infect Dis 1999;29:1128). We report a case of four siblings, three brothers whose atopic dermatitis was complicated by cutaneous lesions and furunculosis, while their 21-month-old sister had a fatal PVL positive staphylococcal pneumonia., (© 2011 Wiley Periodicals, Inc.)

Aim: To examine the genetic diversity of Aggregatibacter actinomycetemcomitans in Thai adults., Materials and Methods: Subgingival plaque samples from 453 subjects were analysed for A. actinomycetemcomitans serotypes, the presence of the high leukotoxin-producing JP2 clone and cytolethal distending toxin genes (cdtABC) using the polymerase chain reaction technique. In subjects who were positive for cdtABC, restriction fragment length polymorphism analysis was used to identify a single nucleotide polymorphism (SNP) in the cdtB gene at amino acid position 281. The extent and severity of periodontal disease were compared between subjects harbouring different A. actinomycetemcomitans genotypes., Results: Eighty six subjects (19%) were positive for A. actinomycetemcomitans. The JP2 clone was not detected. Serotype c was the most prevalent (57%), followed by serotypes a (33%) and b (7%). Among A. actinomycetemcomitans-positive subjects, 27% were positive for cdtABC. All cdtABC-positive subjects possessed the SNP in the cdtB, which is involved with increased toxin activity. The presence of A. actinomycetemcomitans, but not a specific genotype, was significantly related to increased probing depth and periodontal attachment loss., Conclusions: Our results confirm the previous findings that genotype distribution of A. actinomycetemcomitans varies between ethnic groups. However, no clear relationship between a specific genotype and periodontal conditions was observed., (© 2012 John Wiley & Sons A/S.)

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) strain MW2 harbors a plethora of toxins to mediate its virulence. However, toxin expression and regulation with simulated clinical antimicrobial exposures are unclear. This study evaluated these relationships using an in vitro pharmacodynamic hollow-fiber infection model. Clinical doses of clindamycin, linezolid, minocycline, trimethoprim-sulfamethoxazole (SXT), and vancomycin were simulated over 72 h against MW2 in the hollow fiber model. Expression levels of lukSF-PV and enterotoxin genes sec4, sek, seq, and sel2 were quantified by real-time PCR. Panton-Valentine leukocidin (PVL) was quantified by enzyme-linked immunosorbent assay (ELISA), and cytotoxicity was determined on polymorphonuclear cells (PMNs). Vancomycin produced the maximum MW2 killing (2.53 log(10) CFU/ml) after the first dose, but the greatest sustained killing over 72 h occurred with linezolid and clindamycin. Vancomycin and minocycline induced gene upregulation from 0 to 8 h, followed by downregulation for the remaining simulation period. Clindamycin decreased gene expression in the first 24 h, followed by moderate increases (2.5-fold) thereafter. Linezolid increased gene expression 11.4- to 200.4-fold but inhibited PVL production (0.6 ± 0.3 versus 5.9 ± 0.2 μg/ml, linezolid versus control at 72 h; P < 0.05). Similar effects on PVL production occurred with clindamycin and minocycline. SXT increased PVL production at 48 h (2.8-fold) and 72 h (4.9-fold) of treatment (P < 0.05), resulting in increased PVL cytotoxicity on PMNs. Linezolid, clindamycin, and minocycline were the most effective agents on decreasing the virulence potential in CA-MRSA, notably after 8 h of treatment. SXT had minimal effects on toxin gene regulation, but it increased production and cytotoxicity of PVL toxin in the model and may enhance virulence when it is used to treat severe infections.

Recent advances in metagenomics research have generated a bounty of information that provides insight into the dynamic genetic exchange occurring between bacteriophage (phage) and their bacterial hosts. Metagenomic studies of the microbiomes from a variety of environments have shown that many of the genes sequenced are of phage origin. Among these genes are phage-encoded exotoxin genes. When phage that carry these genes infect an appropriate bacterial host, the bacterium undergoes lysogenic conversion, converting the bacterium from an avirulent strain to a pathogen that can cause human disease. Transfer of the exotoxin genes between bacteria has been shown to occur in marine environments, animal and human intestines and sewage treatment plants. Surprisingly, phage that encode exotoxin genes are commonly found in environments that lack the cognate bacteria commonly associated with the specific toxin-mediated disease and have been found to be associated with alternative environmental bacterial hosts. These findings suggest that the exotoxin genes may play a beneficial role for the bacterial host in nature, and that this environmental reservoir of exotoxin genes may play a role in the evolution of new bacterial pathogens.

Pneumonia caused by Panton-Valentine leukocidin-producing Staphylococcus aureus is associated with a high fatality rate. There have been few reported cases in HIV-1-co-infected patients. Here we report a fatal case of severe community-acquired pneumonia caused by Panton-Valentine leukocidin-producing S. aureus in a 45-year-old woman with HIV-2 infection.

Pseudomonas aeruginosa coordinates its virulence expression and establishment in the host in response to modification of its environment. During the infectious process, bacteria are exposed to and can detect eukaryotic products including hormones. It has been shown that P. aeruginosa is sensitive to natriuretic peptides, a family of eukaryotic hormones, through a cyclic nucleotide-dependent sensor system that modulates its cytotoxicity. We observed that pre-treatment of P. aeruginosa PAO1 with C-type natriuretic peptide (CNP) increases the capacity of the bacteria to kill Caenorhabditis elegans through diffusive toxin production. In contrast, brain natriuretic peptide (BNP) did not affect the capacity of the bacteria to kill C. elegans. The bacterial production of hydrogen cyanide (HCN) was enhanced by both BNP and CNP whereas the production of phenazine pyocyanin was strongly inhibited by CNP. The amount of 2-heptyl-4-quinolone (HHQ), a precursor to 2-heptyl-3-hydroxyl-4-quinolone (Pseudomonas quinolone signal; PQS), decreased after CNP treatment. The quantity of 2-nonyl-4-quinolone (HNQ), another quinolone which is synthesized from HHQ, was also reduced after CNP treatment. Conversely, both BNP and CNP significantly enhanced bacterial production of acylhomoserine lactone (AHL) [e.g. 3-oxo-dodecanoyl-homoserine lactone (3OC12-HSL) and butanoylhomoserine lactone (C4-HSL)]. These results correlate with an induction of lasI transcription 1 h after bacterial exposure to BNP or CNP. Concurrently, pre-treatment of P. aeruginosa PAO1 with either BNP or CNP enhanced PAO1 exotoxin A production, via a higher toxA mRNA level. At the same time, CNP led to elevated amounts of algC mRNA, indicating that algC is involved in C. elegans killing. Finally, we observed that in PAO1, Vfr protein is essential to the pro-virulent effect of CNP whereas the regulator PtxR supports only a part of the CNP pro-virulent activity. Taken together, these data reinforce the hypothesis that during infection natriuretic peptides, particularly CNP, could enhance the virulence of PAO1. This activity is relayed by Vfr and PtxR activation, and a general diagram of the virulence activation cascade involving AHL, HCN and exotoxin A is proposed.

A 41-year-old female presented with a superficial buttock abscess. In the preceding 6 months she had four other abscesses at different anatomical sites. Screening for diabetes and immunocompromise was negative. Review of microbiology revealed Methicillin resistant Staphylococcus aureus harbouring Panton-Valentine leukocidin (PVL) genes. PVL syndrome is an emerging disorder associated with recurrent necrotic skin lesions in the young, otherwise healthy population.