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Development of in vivo daptomycin resistance (DAP-R) among Staphylococcus aureus clinical isolates, in association with clinical treatment failures, has become a major therapeutic problem. This issue is especially relevant to methicillin-resistant S. aureus (MRSA) strains in the context of invasive endovascular infections. In the current study, we used three well-characterized and clinically-derived DAP-susceptible (DAP-S) vs. resistant (DAP-R) MRSA strain-pairs to elucidate potential genotypic mechanisms of the DAP-R phenotype. In comparison to the DAP-S parental strains, DAP-R isolates demonstrated (i) altered expression of two key determinants of net positive surface charge, either during exponential or stationary growth phases (i.e., dysregulation of dltA and mprF), (ii) a significant increase in the D-alanylated wall teichoic acid (WTA) content in DAP-R strains, reflecting DltA gain-in-function; (iii) heightened elaboration of lysinylated-phosphatidylglyderol (L-PG) in DAP-R strains, reflecting MprF gain-in-function; (iv) increased cell membrane (CM) fluidity, and (v) significantly reduced susceptibility to prototypic cationic host defense peptides of platelet and leukocyte origins. In the tested DAP-R strains, genes conferring positive surface charge were dysregulated, and their functionality altered. However, there were no correlations between relative surface positive charge or cell wall thickness and the observed DAP-R phenotype. Thus, charge repulsion mechanisms via altered surface charge may not be sufficient to explain the DAP-R outcome. Instead, changes in the compositional or biophysical order of the DAP CM target of such DAP-R strains (i.e., increased fluidity) may be essential to this phenotype. Taken together, DAP-R in S. aureus appears to involve multi-factorial and strain-specific adaptive mechanisms.

Objectives: To assess the in vitro antibacterial activity of ceftazidime/avibactam against a recent Italian collection of carbapenem-resistant Enterobacterales (CRE) isolated from urine specimens.Methods: Consecutive Gram-negative isolates from urine specimens, collected from inpatients in five Italian hospitals during the period October 2016 to February 2017, were screened for CRE phenotype using chromogenic selective medium and identified using MALDI-TOF MS. Antimicrobial susceptibility testing was performed by reference broth microdilution (BMD) and, for ceftazidime/avibactam, also by Etest® CZA. Results were interpreted according to the EUCAST breakpoints. All confirmed CRE were subjected to real-time PCR targeting blaKPC-type, blaVIM-type, blaNDM-type and blaOXA-48-type carbapenemase genes. Non-MBL-producing isolates resistant to ceftazidime/avibactam were subjected to WGS and their resistome and clonality were analysed.Results: Overall, 318 non-replicate presumptive CRE were collected following screening of 9405 isolates of Enterobacterales (3.4%) on chromogenic selective medium. Molecular analysis revealed that 216 isolates were positive for a carbapenemase gene (of which 92.1%, 2.8%, 1.4% and 1.4% were positive for blaKPC-type, blaOXA-48-type, blaNDM-type and blaVIM-type, respectively). Against the confirmed carbapenemase-producing Enterobacterales (CPE), ceftazidime/avibactam was the most active compound, followed by colistin (susceptibility rates 91.6% and 69.4%, respectively). Compared with BMD, Etest® for ceftazidime/avibactam yielded consistent results (100% category agreement). All class B β-lactamase producers were resistant to ceftazidime/avibactam, while OXA-48 and KPC producers were susceptible, with the exception of seven KPC-producing isolates (4.2%). The latter exhibited an MIC of 16 to >32 mg/L, belonged to ST512, produced KPC-3 and showed alterations in the OmpK35 and Ompk36 porins.Conclusions: Ceftazidime/avibactam showed potent in vitro activity against a recent Italian collection of CPE from urine. [ABSTRACT FROM AUTHOR]

Background: The aim of this study was to characterize the spread of carbapenemase-producing Klebsiella pneumoniae (CPKP) in a tertiary level hospital using ongoing active surveillance with rectal swab cultures. Furthermore, this study analyzed the presence of CPKP in the clinical samples (CS) of a single patient as well as the evolution of Colistin-sensitive strains (CoS) to Colistin-resistant strains (CoR). Methods: This study was performed from January 1, 2012 to December 31, 2014. In 2012, a survey was conducted in the Intensive Care Department. In autumn 2013, active monitoring was extended to the Surgery Department, and since mid-2014, the surveillance has included the Medical Department as well. Only the first isolated strain from each patient was included. Antimicrobial susceptibility testing was performed on CPKP isolates: Klebsiella pneumoniae carbapenemase, oxacillinase-48, Verona integron-encoded metallo-β-lactamase and New Delhi metallo-β-lactamase were detected using a validated in-house PCR method, and multilocus sequence typing (MLST) was used to investigate the clonal transmission of strains. Results: A total of 15,104 patients were included in the study, and 496 consecutive non-replicated strains of CPKP were collected: 149 strains were collected in 2012 (39 [26.2 %] from surveillance rectal swabs [SRS]), 133 strains were collected in 2013 (70 [52.6 %] from SRS) and 214 strains were collected in 2014 (164 [76.6 %] from SRS). We observed a significant increase in the percentage of positive SRS cases in 2014 relative to 2013 and 2012 (p = 0.0001 and p = 0.0172, respectively) and in the proportion of CPKP first isolated by SRS relative to those identified by CS (p < 0.0001). Among all available samples, the number of CoR isolated from SRS was higher in 2013 and 2014 compared with 2012 (p = 0.0019 and p = 0.008, respectively). ST-258 and ST-512 were more prevalent in the tested specimens, and a new single locus variant (SLV) of ST-512 (ST-745) was isolated. Conclusions: The results of this 3-year study of 15,104 patients highlight the clinical relevance of antimicrobial resistance as well as the drug-selection pressure of colistin therapy. The active surveillance in the three different departments increased the level of CPKP cases isolated by SRS. [ABSTRACT FROM AUTHOR]

The Tigecycline Evaluation and Surveillance Trial (T.E.S.T.) was initiated in 2004 to longitudinally monitor the activity of the broad-spectrum glycylcycline antimicrobial tigecycline, and a suite of comparator agents, against an array of clinically important bacterial pathogens worldwide. In this report, we examine the activity of tigecycline and comparators against a collection of 13,245 clinical isolates, both Grampositive (n = 4,078 and Gram-negative (n = 9,167), collected from 27 centres in Italy between 2004 and 2011. Susceptibility was established according to Clinical Laboratory Standards Institute guidelines. Tigecycline and linezolid exhibited very good activity against Gram-positive pathogens, with MIC90s ranging from 0.06 to 0.25 mg/L and 1-4 mg/L, respectively; vancomycin and the carbapenems also showed good activity against select Gram-positive pathogens. Tigecycline was the most active agent against Gram-negative pathogens (except P. aeruginosa), with MIC90s ranging from 0.25-2 mg/L (16 mg/L for P. aeruginosa). Amikacin and the carbapenems also possessed good activity against many Gram-negative pathogens here. ESBL-positive E. coli increased in prevalence from 2004 to 2011, while ESBL-positive Klebsiella spp., vancomycin-resistant enterococci and MRSA decreased in prevalence. Linezolid, tigecycline and vancomycin susceptibility were very stable over the course of this study, while susceptibility to ampicillin, piperacillin-tazobactam, ceftriaxone and levofloxacin varied over time according to pathogen; minocycline and cefepime susceptibility among several pathogens decreased during this study. [ABSTRACT FROM AUTHOR]

Abstract: Recent articles have described an increasing number of infections due to Panton–Valentine leukocidin PVL-positive community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) worldwide. We report a case of necrotizing pneumonia successfully treated with levofloxacin in Italy, sustained by a PVL-positive CA-MRSA, belonging to ST88 and carrying a staphylococcal chromosomal cassette mec type V. Further molecular characterization of isolates revealed that they were PVL positive, belonged to the agr IV allele, possessed a capsular type 8, and had an almost complete pathotype composed of leukocidins and numerous adhesins. In addition, the strains were strong biofilm producers. [Copyright &y& Elsevier]

A clinical isolate of Klebsiella pneumoniae highly resistant to third- and fourth-generation cephalosporins, cephamycins and aminoglycosides, was isolated in 1991 from urine. Analysis of a crude extract showed the presence of three β-lactamases with isoelectric points of 6.6, 7.5 and 8.2. The enzyme with pI 8.2 was transferred by conjugation into Escherichia coli K-12 J53 and was responsible for the resistance to third-generation cephalosporins and monobactams, but not to other antibiotics. Kinetic studies of partially purified β-lactamase from the transconjugant strain confirmed that the enzyme was able to hydrolyse ceftazidime, cefotaxime and aztreonam but not cephamycins. Analysis of the transconjugant showed the presence of two small non-conjugative plasmids of 14 and 6 kb. A polymerase chain reaction was performed using primers specific for the blaSHV gene and a fragment of the expected size (about 961 bp) was obtained with both the K. pneumoniae clinical isolate and the transconjugant. Nucleotide sequence analysis of the fragment showed that it encoded the enzyme SHV-12, derived from SHV-5 (with Gln-35 to Leu). This is the first report of an SHV-12-like enzyme isolated in Italy. [ABSTRACT FROM PUBLISHER]

The in vitro activity of levofloxacin and eight other antimicrobial agents against 60 clinical isolates of Stenotrophomonas maltophilia was determined by an agar dilution method using 104 and 106 cfu/spot inocula. At the lower inoculum, 85.0% of the isolates were susceptible to levofloxacin but only 58.3% were susceptible to ofloxacin; at the higher inoculum, 78.3% were susceptible to levofloxacin and 36.7% to ofloxacin. In time–kill studies, levofloxacin exerted bactericidal activity within 4 h. With ofloxacin and ciprofloxacin bacterial regrowth was observed after 8 h. Levofloxacin may represent an alternative drug in the treatment of infections caused by S. maltophilia. [ABSTRACT FROM PUBLISHER]

This article reports on a study which examined the molecular characteristics of intensive care unit (ICU) methicillin-resistant Staphylococcus aureus (MRSA) strains between 2011 and 2013. The researchers isolated the strains from blood cultures or respiratory samples. They conducted a sensitivity testing to vancomycin, daptomycin and linezolid. They concluded that the strains are predominant in the ICU setting and are mainly hospital-acquired.

• Prevalence of uncomplicated lower urinary tract infections (uUTIs) due to multidrug-resistant E. coli is increasing. • Guidelines recommend reducing fluoroquinolones use in favour of fosfomycin trometamol (FT). • Single-dose oral FT has similar efficacy and safety to comparator regimens in women with uUTIs. • FT is an effective alternative to fluoroquinolones for antimicrobial prophylaxis in prostate biopsy. The worldwide prevalence of uncomplicated lower urinary tract infections (uUTIs) caused by multidrug-resistant Escherichia coli is increasing. To address this emergency, international guidelines recommend reducing administration of fluoroquinolones, in the context of growing resistance and the long-lasting and potentially disabling side effects of these drugs. The favoured drug to replace fluoroquinolones is fosfomycin trometamol (FT), a well-known derivate of phosphonic acid with broad-spectrum activity against Gram-negative and Gram-positive bacteria, including multidrug-resistant (MDR) strains. The European Committee on Antimicrobial Susceptibility Testing (EUCAST) recently reduced the susceptibility breakpoint for E. coli from 32 mg/L to 8 mg/L regarding FT used for uUTIs. This might lead to increased appropriate use of oral fosfomycin target therapy against E. coli and other microorganisms, and may be associated with a high likelihood of success. For species such as Klebsiella spp, particularly MDR strains, the absence of clinical breakpoints might lead to reduced use of oral fosfomycin, particularly if minimum inhibitory concentration is not available. To address this issue, this review presents an overview of the preclinical evidence on the activity of FT, and a systematic review of the clinical activity of FT in uUTIs in women, and in the prevention of infectious complications after prostate biopsy. The findings indicate that the safety and microbiological and clinical effectiveness of a single oral dose of FT are similar to that for comparator regimens with longer treatment schedules in women with uUTI, and FT can be considered a viable alternative to fluoroquinolones for antimicrobial prophylaxis in prostate biopsy. These observations and a broad clinical experience support the empirical use of FT for treating uUTI and indicate that FT is a promising candidate to effectively counteract antibiotic-resistant uUTIs throughout Europe. [ABSTRACT FROM AUTHOR]

An alarming increase of vancomycin-resistant Enterococcus faecium (VREfm) isolates was detected in an Italian referral hospital subjected to policies of infection control validated by the Joint Commission International. Analysis of the population structure of 122 consecutive, nonreplicate VREfm isolates collected over an 18-month period identified a single major clone that spread around the whole hospital, rapidly establishing an endemic state. It belonged to sequence type (ST) 17 and showed a highly multidrug-resistant phenotype, being resistant to all antimicrobial classes for the carriage of several resistance determinants. Furthermore, some strains with decreased susceptibility to daptomycin were detected. Eighteen out of the 122 isolates did not group in the major clone. They showed a low spreading potential inside the hospital wards, even if most of them displayed a multidrug-resistant phenotype and belonged to a hospital-adapted lineage. Causes that led to the VREfm endemic state have not been fully elucidated. However, it is conceivable that the increase in systemic antibiotic consumption and the use of selective digestive tract decontamination, including vancomycin in critically ill patients during the period before 2014, may have played a role in the ST17 clone dissemination, but additional traits conferring high fitness in hospital environment cannot be excluded. [ABSTRACT FROM AUTHOR]