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Staphylococcus aureus bacteremia is associated with high mortality and morbidity, requiring prompt and appropriate antimicrobial treatment. Therefore, it is important to detect methicillin-resistant S. aureus (MRSA) rapidly from blood cultures. Two immunochromatographic tests, BinaxNow S. aureus and BinaxNow PBP2a, were directly applied to 79 Bact/Alert bottles that were positive for Gram positive cocci in cluster aggregations. Sensitivity and specificity for the identification of S. aureus and determination of methicillin resistance were 94% and 87%, and 100% and 100%, respectively, with less than 30 min of performance time. These tests are efficient and rapid; these tests are valuable alternatives to more sophisticated and expensive methods used in the diagnosis of MRSA bacteremia.

Background: Panton-Valentine leukocidin (PVL)-positive methicillin-susceptible Staphylococcus aureus and methicillin-resistant S. aureus (MSSA and MRSA, respectively) are both associated with severe infections, such as necrotizing pneumonia. The epidemiological profile of PVL-positive community-acquired (CA) MRSA has been extensively studied, but few corresponding data on PVL-positive MSSA are available., Objectives: The objectives of the study were to investigate the global population structure of PVL-positive MSSA, to compare it with that reported for CA-MRSA, and thus to examine the phylogenetic relationship between these pathogens., Methods: We determined the agr types, multilocus sequence types, and toxin gene profiles of 211 PVL-positive MSSA clinical isolates collected in 19 countries throughout the world between 1981 and 2007., Results: The predominant lineages of PVL-positive MSSA were agr3/ST30, agr4/ST121, agr3/ST1, agr2/ST5, and agr3/ST80. Except for agr4/ST121, these lineages are also reported to be prevalent among CA-MRSA. PVL-positive MSSA lineages that are genetically related to CA-MRSA have gradually replaced other lineages (especially agr4/ST121) over the past 2 decades. Within a given sequence type, the toxin gene content of PVL-positive MSSA strains was very similar to that of PVL-positive CA-MRSA., Conclusions: The molecular epidemiological profiles of PVL-positive MSSA and CA-MRSA are dynamically interrelated, with the former appearing to constitute a reservoir for the latter.

The objective of this study was to characterize Staphylococcus aureus isolates recovered from the nasal samples of healthy pet cats in Algiers province. A total of 138 nasal swabs were collected. Antimicrobial susceptibility was conducted using the disk-diffusion method and the VITEK-2 susceptibility system. Whole genome sequencing was performed to identify multiple-locus sequence typing, antimicrobial and virulence genes. Staphylococcus aureus isolates were detected in 23 cats. Among these, 11 were methicillin-resistant S. aureus (MRSA) (one isolate/sample). Three sequence types (ST6, ST5, and ST1) were identified in MRSA, with the predominance of ST6 (n  = 7). Seven distinct STs [ST398, ST97, ST15, ST7, ST291, ST5043, and a new ST, (ST9219)] were detected in methicillin-sensitive S. aureus. All MRSA isolates harbored the mec A gene and SCC mec -type-IVa. MRSA exhibited resistance to tetracycline [ n  = 3/ tet (L) and tet (M); n  = 1/ tet (K)], kanamycin-tobramycin [ n  = 3/ ant (4′)- Ia), amikacin-kanamycin (n  = 1/ aph (3′)- IIIa ], and erythromycin-clindamycin [ n  = 1/ erm (C)]. Seven S. aureus isolates were multidrug resistant. All the isolates were negative for lukS/lukF -PV and tst- 1 genes, while 20 isolates were IEC-positive. This study revealed a diversity of genetic lineages in S. aureus strains isolated from nasal samples of pet cats, including multidrug-resistant and toxigenic strains. The presence of IEC-positive S. aureus suggests possible human–animal transmission. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the molecular features and the antibiotic resistance profile of 98 clinical Staphylococcus aureus isolates collected during 6 months in two hospitals of Kabul, Afghanistan. For all isolates, antimicrobial resistance patterns were determined by the disc diffusion method (including methicillin resistance which was detected using cefoxitin). The presence of the mecA/mecC genes was detected by PCR. Strains were then extensively characterized using microarray analysis. Of the 98 S. aureus isolates, methicillin-resistant S. aureus (MRSA) prevalence was high at 66.3%. Antibiotic susceptibility testing also revealed a high resistance rate to penicillin (100%), erythromycin (66.3%), ciprofloxacin (55.1%), and cotrimoxazole (40.8%). Resistance to tobramycin was detected in 25.5%, to gentamicin in 16.3%, to chloramphenicol in 34.7%, and to doxycycline in 23.5% of the isolates. All the MRSA isolates were mecA-positive and none of them harbored mecC. Isolates were grouped into twelve clonal complexes and twenty-seven distinct clones. The most frequently detected clones were the Southwest Pacific clone (CC30-MRSA-IV PVL+) (21/65 MRSA, 32.3%), the CC22-MRSA-IV TSST-1+ clone (11/65 MRSA, 16.9%), and the Bengal Bay clone (ST772-MRSA-V PVL+) (11/65 MRSA, 16.9%). The PVL genes were found in 59.2% (46/65 MRSA and 12/33 methicillin-susceptible S. aureus, MSSA) and tst1 gene in 16.3% of isolates. This molecular study highlights the high prevalence of MRSA and the large genetic diversity of the S. aureus isolates circulating and detected in two hospitals of Kabul, with the presence of multiple virulence and antibiotic resistance genes. [ABSTRACT FROM AUTHOR]

Staphylococcus aureus isolates from two prospective studies on infective endocarditis (IE) conducted in 1999 and 2008 and isolated from non-IE bacteremia collected in 2006 were spa-typed and their virulence factors were analyzed with a microarray. Both populations were genetically diverse, with no virulence factors or genotypes significantly more associated with the IE isolates compared with the non-IE isolates. The population structure of the IE isolates did not change much between 1999 and 2008, with the exception of the appearance of CC398 methicillin-susceptible Staphylococcus aureus (MSSA) isolates responsible for 5.6% of all cases in 2008. In 1999, this lineage was responsible for no cases. The increasing prevalence of S. aureus in IE is apparently not the result of a major change in staphylococcal population structure over time, with the exception of the emerging CC398 MSSA lineage. [ABSTRACT FROM AUTHOR]

The aim of the present study was to detect the Staphylococcus aureus delta-toxin using Whole-Cell (WC) Matrix Assisted Laser Desorption Ionization - Time-of-Flight (MALDI-TOF) mass spectrometry (MS), correlate delta-toxin expression with accessory gene regulator (agr) status, and assess the prevalence of agr deficiency in clinical isolates with and without resistance to methicillin and glycopeptides. The position of the delta-toxin peak in the mass spectrum was identified using purified delta-toxin and isogenic wild type and mutant strains for agr-rnaIII, which encodes delta-toxin. Correlation between delta-toxin production and agr RNAIII expression was assessed by northern blotting. A series of 168 consecutive clinical isolates and 23 unrelated glycopeptide-intermediate S. aureus strains (GISA/heterogeneous GISA) were then tested by WCMALDI- TOF MS. The delta-toxin peak was detected at 3005±5 Thomson, as expected for the naturally formylated delta toxin, or at 3035±5 Thomson for its G10S variant. Multivariate analysis showed that chronicity of S. aureus infection and glycopeptide resistance were significantly associated with delta-toxin deficiency (p = 0.048; CI 95%: 1.01-10.24; p = 0.023; CI 95%: 1.20-12.76, respectively). In conclusion, the S. aureus delta-toxin was identified in the WC-MALDI-TOF MS spectrum generated during routine identification procedures. Consequently, agr status can potentially predict infectious complications and rationalise application of novel virulence factor-based therapies. [ABSTRACT FROM AUTHOR]

Necrotizing pneumonia caused by Staphylococcus aureus strains carrying the Panton-Valentin leukocidin gene is a newly described disease entity. We report a new fatal case of necrotizing pneumonia. An S. aureus strain with an agr1 allele and of a new sequence type 377 was recovered, representing a new, emerging, community-acquired methicillin-resistant clone. [ABSTRACT FROM AUTHOR]

Background B-lactam resistance in Staphylococci is mediated by mec genes usually diagnosed by disc diffusion Cefoxitin test (DDFOX) and PCR testing. Here, we report methicillin-resistant Staphylococcus lugdunensis and Staphylococcus aureus strains lacking mec gene misdiagnosed by reference methods. Since the strains are not B-lactamase hyperproducers we investigated the molecular basis of the methicillin resistance. Methods We tested 2 S. lugdunensis isolates (SL1, SL2) collected from distinct blood cultures of the same patient and 2 S. aureus isolates (SA1, SA2): (i) by DDFOX, (ii) for Oxacillin MIC by agar dilution (AD), (iii) by VITEK®2 (bioMérieux) for Oxacillin MIC (V2 OXA) and Cefoxitin Screen Test (V2 OXSF), (iv) for mec A, B, C genes by PCR and (v) by whole-genome sequencing (WGS). Results The 4 isolates were methicillin susceptible by DD FOX and mec negative. However, all the isolates displayed variable results for V2 OXA MIC (0.5 to ≥4 mg/L) and for V2 OXSF (POSITIVE, NEGATIVE). For SL1 and SL2 isolates, the V2 OXSF growth curve atypical pattern has led to investigating the OXSF wells. The plates inoculated with the broth extracted from the OXSF well showed 2 colony morphotypes (small "P" and regular "G") for both isolates. The small colonies (SL1P, SL2P) were Oxacillin resistant (V2 OXA MIC≥4; AD MIC = 4) and V2 OXSF POSITIVE whereas the regular colonies (SL1G, SL2G) were Oxacillin susceptible (V2 OXA MIC = 2; AD MIC = 0.5) and V2 OXSF NEGATIVE. The 4 morphotypes were cefoxitin susceptible by DDFOX and mec negative. Interestingly, WGS revealed a GdpP truncation in the N-terminal domain only found in S. lugdunensis small colonies (SL1P, SL2P) phenotypically resistant to Oxacillin. GdpP is a cyclic diadenosine monophosphate phosphodiesterase enzyme which function is the hydrolysis of a signaling nucleotide. Conclusion We described mec negative S. lugdunensis and S. aureus strains expressing heterogeneous methicillin resistance detected by the VITEK2 OXSF test. S. lugdunensis subpopulation of small colonies resistant to oxacillin is associated with a truncation of GdpP protein previously described in S. aureus. Interestingly GdpP loss of function in Staphylococci is associated with a reduced growth and may arise as a result of the selective pressure of exposure to B Lactams. Disclosures All authors: No reported disclosures. [ABSTRACT FROM AUTHOR]