Methicillin-resistant Coagulase-negative Staphylococci Isolates Research Articles

Phenotypic and Genotypic Study of Staphylococcus Haemolyticus and Staphylococcus Warneri Clinically Isolated from the Bloodstream

Background: The Staphylococcus haemolyticus and Staphylococcus warneri are coagulase-negative staphylococci (CoNS) as part of human skin’s natural flora. In recent years, CoNS has increased its visibility as opportunistic pathogens acquired in hospital patients. This study aims to isolate S. haemolyticus and S. warneri strains from patients with bloodstream infections and to analyze the antimicrobial profile of these bacteria by molecular detection of the mecA gene. Materials and Methods: Four hundred and twenty-three clinical blood samples were collected from patients admitted to general three hospitals in Hilla city, Iraq, during the period from September 2021 to July 2022. Blood samples were inoculated immediately into blood bottles containing 70 ml of Brain-Heart Infusion Broth. All isolates were identified by morphology, biochemical tests, and VITEK 2 automated system (bioMerieux, France). The Congo red agar plate test was used to detect biofilm production. The mecA gene was detected by conventional polymerase chain reaction. Results: S. haem olyticus (nine isolates) and S. warneri (six isolates) were detected out of 423 clinical blood samples. Molecular detection of the mecA gene was detected in all 15 isolates. As well 11 (73.3%) isolates were β-lactam resistant and biofilm production. The results of oxacillin-resistance minimum inhibitory concentration (MIC) (≥4 mg/ml) showed that 11 (73.3%) of the 15 isolates were oxacillin and methicillin-resistant CoNS (MR-CoNS). Susceptibility to various isolates (MICs µg/ml) using VITEK 2 system showed erythromycin (≥8 µg/ml), rifampin (≥4 µg/ml), clindamycin (≥4 µg/ml), and trimethoprim-sulfamethoxazole (≥4 µg/ml) resistance were (80%), (13.3%), (20%), and (53.3%), respectively. All isolates were (100%) sensitive to linezolid (≥8 µg/ml) and teicoplanin (≥32 µg/ml). Conclusions: The S. haemolyticus and S. warneri are serious infections associated with bacteremia and septicemia infections. Linezolid, teicoplanin, and rifampin are the drug of choice for the treatment of infections caused by MR-CoNS isolates. A high rate of the mecA gene and biofilm production is present in these bacteria.

Identification and characterization of SCCmec typing with psm-mec positivity in staphylococci from patients with coagulase-negative staphylococci peritoneal dialysis-related peritonitis

BackgroundPeritonitis is the most important complication of peritoneal dialysis (PD) and coagulase-negative staphylococci (CNS) are a frequent cause of dialysis-related infections. The association between SCCmec typing with psm-mec positivity in staphylococci and PD-related infections has not been identified. We aim to investigate the molecular epidemiology of CNS isolated from PD-peritonitis in a single Chinese center, focusing on the genetic determinants conferring methicillin resistance.MethodsWe collected 10 genetically unrelated CNS isolates from 10 patients with CNS PD-related peritonitis. The patients were divided into two groups based on the results of MIC to oxacillin: the methicillin-resistant CNS (MRCNS) and methicillin-sensitive CNS (MSCNS) groups. The biofilm formation group (BFG) and the non-biofilm formation group (NBFG) were used as the control groups. Phenotypic and molecular methods were used to analyze SCCmec types I, II and III, associated genes and biofilm formation and the existence of psm-mec. The demographic data and clinical indicators were collected.ResultsTen CNS PD-related peritonitis patients were enrolled for this study. There were 6 MRCNS and 4 MRCNS isolates. SCCmec types were fully determined in 10 isolates. Seven staphylococci (70%) carried SCCmec, of which 4 isolates carried single SCCmec type I (40%) and 3 isolates had multiple SCCmec elements (I + III). Of the 6 MRCNS isolates, 3 carried SCCmec type I (50%) and 2 isolates carried SCCmec type I + III (33.3%). A high diversity of ccr types, mec complexes and ccr-mec complex combinations was identified among the 10 CNS isolates. The psm-mec gene was detected in 2/10 (20%) CNS isolates. There was no mutation in the psm-mec gene.ConclusionsThe majority of isolates were hospital-associated isolates. Furthermore, 2 psm-mec positive isolates were MRCNS in the NBFG. The PD patients frequent exposure to hospital would be the main risk factor. The presence of the psm-mec signal in the spectra of the MRCNS tested here demonstrates the presence of certain SCCmec cassettes that convey methicillin resistance.

Clonality and Persistence of Multiresistant Methicillin-Resistant Coagulase-Negative Staphylococci Isolated from the Staff of a University Veterinary Hospital.

The aim of this study was to characterize methicillin-resistant coagulase-negative staphylococci (MRCoNS) isolates from the healthy staff of a university veterinary hospital in order to assess their importance as a reservoir of antimicrobial resistance and to determine their population structure and evolution. The study duration was over two years (2020–2021), 94 individuals were analyzed in duplicate, and 78 strains were obtained. The overall prevalence of methicillin-resistant strains detected throughout the study was 61.7%, with point prevalence values of 53.2% in 2020 and 31.5% in 2021. A total of 19.1% of the individuals analyzed were carriers throughout the study. The most frequently identified MRCoNs were Staphylococcus epidermidis (92.3%) and S. warneri (3.8%). A total of 75.6% of the isolates obtained showed the development of multi-resistance, preferentially against erythromycin, gentamicin, and tetracycline, and to a lesser extent against fusidic acid, norfloxacin, and clindamycin; these antimicrobials are frequently used in the veterinary field. Although most of the S. epidermidis isolates obtained showed wide genetic variability and low dispersion, which are characteristic of community-associated isolates, a small number of strains spread between individuals in close physical proximity and were maintained over time, forming stable clones. These clones generally maintained the same type of staphylococcal cassette chromosome mec (SCCmec) and had a similar antimicrobial resistance pattern.

Antibiotic Susceptibility Pattern of Canine Coagulase Positive and Coagulase Negative Staphylococcus spp. in a Hot and Dry Region of India

The emergence of antimicrobial resistance among Staphylococcus spp. isolated from clinical cases of canines should be continuously monitored hence the present study was formulated to ascertain the antibiotypes and methicillin resistance in coagulase positive and coagulase negative staphylococci of canine skin and associated mucous membrane affections from a hot and dry region of India. A total of 165 clinical samples were collected and Staphylococcus aureus was identified by conventional bacteriological methods and PCR. Antibiotic susceptibility test was done against commercially available antibiotic impregnated discs as per Clinical and Laboratory Standards Institute (CLSI) method. Methicillin resistance was determined by plate methods and then via PCR of mecA gene. These 165 samples yielded, 88 (53.33%) isolates of genus Staphylococcus and 46 S. aureus and 51/88 (57.95%) isolates were coagulase positive staphylococci. Total 55 (62.5%) isolates showed susceptibility to Ceftriaxone/Sulbactum, 37 (42.05%) to Ciprofloxacin, 26 (29.55%) to Oxacillin, 24 (27.27%) to Penicillin, and 10 (11.36%) to Gentamicin. Total 21 methicillin-resistant S. aureus (MRSA) and 12 methicillin-resistant coagulase negative staphylococci (MRCoNS) were found on phenotypic basis whereas the mecA gene was detected in 6/21 MRSA and 2/12 MRCoNS isolates. Staphylococcus spp. showed increased level of resistance against commonly used antibiotics. The higher prevalence of methicillin resistance found with phenotypic methods than to mecA PCR indicates toward additional mechanisms responsible for emergence of MRS, especially in CoNS.

In vitro activity of dalbavancin and other anti-staphylococcal agents against infecting isolates of methicillin-resistant coagulase-negative staphylococci.

Introduction. Dalbavancin was approved in Europe in 2015 for skin and soft tissue infections.Hypothesis/Gap Statement. Data on methicillin-resistant coagulase-negative staphylococci (MR-CNS) dalbavancin susceptibility are scarce.Aim. To assess the susceptibility of MR-CNS to dalbavancin and other anti-staphylococcal agents.Methodology. A total of 443 MR-CNS clinical isolates from patients hospitalized in a Greek university hospital during a 2.5-year period (January 2018 to June 2020) were included. The MICs for vancomycin, teicoplanin, linezolid and daptomycin were investigated by Etest and the MIC for dalbavancin was determined according to European Committee on Antimicrobial Susceptibility Testing (EUCAST) guidelines in 196 isolates. The consumption of the aforementioned antimicrobials was calculated.Results. In total, 51 isolates were resistant to teicoplanin (11.5 %) and 211 (47.6 %) to linezolid; all were susceptible to vancomycin and daptomycin. Among 196 isolates tested, 32 (16.3 %) were resistant to dalbavancin. A significant increase of MIC during the study period was found for vancomycin, teicoplanin and daptomycin, while a decrease in linezolid's MIC was observed. Dalbavancin's MIC remained stable. No difference in consumption was observed among the studied anti-staphylococcal agents.Conclusion. An increase of vancomycin, teicoplanin and daptomycin MICs among MR-CNS was observed, whereas 47.6 % of isolates were non-susceptible to linezolid. Dalbavancin retains excellent potency against MR-CNS, even in the presence of non-susceptibility to other anti-staphylococcal antibiotics.

Methicillin-Resistant Coagulase-Negative Staphylococci Carriage is a Protective Factor of Methicillin-Resistant Staphylococcus Aureus Nasal Colonization in HIV-Infected Patients: A Cross-Sectional Study.

Background Methicillin-resistant coagulase-negative Staphylococci (MRCoNS) is regarded as the repository of mecA gene for methicillin-resistant Staphylococcus aureus (MRSA) and may develop methicillin-susceptible Staphylococcus aureus (MSSA) to MRSA. Therefore, we aimed to explore whether MRCoNS carriage is a risk factor of MRSA colonization. Phenotypic characteristics were performed to further assess the associations between MRSA and MRCoNS. Methods This cross-sectional study was conducted in Guangzhou, China. Participants completed a questionnaire and provided a nasal swab for further analysis. The risk factors of MRSA colonization were analyzed using nonconditional logistic regression models. The phenotypic characteristics between MRSA and MRCoNS were compared by Chi-square test. Results Among the 1001 HIV-infected patients, a total of 119 (11.89%) participants were positive for MRSA, and 34.45% (41/119) of all MRSA carriers were positive for MRCoNS. We found MRCoNS carriage was a protective factor of MRSA colonization (adjusted odds ratio = 0.59, 95% confidence interval: 0.38–0.91). A significant difference in the proportions of antibiotic resistance between MRSA and MRCoNS isolates was found except for penicillin, clindamycin, tetracycline, and teicoplanin. The main STs and CC types of MRSA isolates in this population were ST188 (15.1%) and CC59 (17.6%), respectively. Conclusions HIV-infected patients remain a highly vulnerable population for MRSA colonization. Though who carried MRCoNS is less likely to have MRSA colonization, similarity of some antibiotic resistance between MRSA and MRCoNS was found in this study. Regular surveillance on the colonization and antibiotic patterns of MRSA and MRCoNS is still necessary.

Investigation of SCCmec types I-IV in clinical isolates of methicillin-resistant coagulase-negative staphylococci in Ahvaz, Southwest Iran.

Today methicillin resistant coagulase-negative staphylococci (MR-CoNS) are important in terms of causing significant nosocomial infections. Besides, MR-CoNS are confirmed as the reservoir of SCCmec elements that carry mecA (methicillin-resistant) gene. Hence, the present study was designed to evaluate the susceptibility pattern, prevalence and diversity of SCCmec types I, II, III, and IV in MR-CoNS strains. In this cross-sectional study, 44 clinical isolates of MR-CoNS were identified using the cefoxitin disc method and further confirmation by polymerase chain reaction (PCR) amplification of the mecA gene. Antimicrobial susceptibility of isolates was investigated by disc diffusion. The identification of CoNS was done by amplification and sequencing of the tuf gene. Multiplex PCR method was done for the determination of SCCmec types. In the present study, the Staphylococcus epidermidis and Staphylococcus haemolyticus were the most predominant isolates with a prevalence of 45.4%. The highest resistance rates were observed against erythromycin (84.1%) and clindamycin (75%). Multiplex PCR revealed the SCCmec type I as the predominant type in the present study. Our study showed that there was no significant relationship between the presence of different types of SCCmec elements and resistance to antibiotics. The present study highlighted a frequent prevalence of MR-CoNS harboring SCCmec type genes in Ahvaz, southwest of Iran. Thus, the molecular typing and periodical monitoring of their drug resistance pattern should be considered in national stewardship programs to designing useful antibiotic prescription strategies.

Molecular Characteristics of Methicillin-Resistant Staphylococci Clinical Isolates from a Tertiary Hospital in Northern Thailand.

Methicillin-resistant staphylococci are now recognized as a major cause of infectious diseases, particularly in hospitals. Molecular epidemiology is important for prevention and control of infection, but little information is available regarding staphylococcal infections in Northern Thailand. In the present study, we examined antimicrobial susceptibility patterns, detection of antimicrobial resistance genes, and SCCmec types of methicillin-resistant S. aureus (MRSA) and methicillin-resistant coagulase-negative staphylococci (MR-CoNS) isolated from patients in a hospital in Northern Thailand. The species of MRSA and MR-CoNS were identified using combination methods, including PCR, MALDI-TOF-MS, and tuf gene sequencing. The susceptibility pattern of all isolates was determined by the disk diffusion method. Antimicrobial resistance genes, SCCmec types, and ST239 were characterized using single and multiplex PCR. ST239 was predominant in MRSA isolates (10/23). All MR-CoNS (N=31) were identified as S. haemolyticus (N=18), S. epidermidis (N=3), S. cohnii (N=3), S. capitis (N=6), and S. hominis (N=1). More than 70% of MRSA and MR-CoNS were resistant to cefoxitin, penicillin, oxacillin, erythromycin, clindamycin, gentamicin, and ciprofloxacin. In MRSA isolates, the prevalence of ermA (78.3%) and ermB (73.9%) genes was high compared to that of the ermC gene (4.3%). In contrast, ermC (87.1%) and qacA/B genes (70.9%) were predominant in MR-CoNS isolates. SCCmec type III was the dominant type of MRSA (13/23), whereas SCCmec type II was more present in S. haemolyticus (10/18). Ten MRSA isolates with SCCmec type III were ST239, which is the common type of MRSA in Asia. This finding provides useful information for a preventive health strategy directed against methicillin-resistant staphylococcal infections.

Antibiotic resistance among bacterial conjunctival pathogens collected in the Antibiotic Resistance Monitoring in Ocular Microorganisms (ARMOR) surveillance study.

The Antibiotic Resistance Monitoring in Ocular Microorganisms (ARMOR) surveillance study evaluates in vitro antibiotic resistance among Staphylococcus aureus, coagulase-negative staphylococci (CoNS), Streptococcus pneumoniae, Pseudomonas aeruginosa, and Haemophilus influenzae isolates from ocular infections. Here we report resistance rates and trends among conjunctival-sourced ocular isolates collected across the US from 2009 through 2016. A total of 1198 conjunctival isolates (483 S. aureus, 305 CoNS, 208 H. influenzae, 118 S. pneumoniae, and 84 P. aeruginosa) were collected from patients with presumed bacterial conjunctivitis from 57 sites across 40 states. A large proportion of staphylococci demonstrated resistance to oxacillin and azithromycin, while resistance was low against the majority of antibiotics tested for S. pneumoniae, P. aeruginosa, and H. influenzae. Multidrug resistance (≥3 antibiotic classes) was found in 30.2% of S. aureus and 39.0% of CoNS isolates, and methicillin resistance more than doubled the rate of multi-drug resistance (methicillin-resistant S. aureus [MRSA], 76.5%; methicillin-resistant CoNS isolates, 72.8%). There was a pattern of increasing mean percent resistance with increasing age by decade of life among S. aureus, MRSA, and CoNS (P≤0.038). Over the eight-year study period, there were small yet significant decreases in resistance rates among S. aureus to azithromycin, ciprofloxacin, tobramycin, trimethoprim, and oxacillin (P≤0.003), and among CoNS and P. aeruginosa (both P<0.05) to ciprofloxacin. These data indicate that antibiotic resistance is high, but did not increase, among conjunctival-sourced isolates collected in the US from 2009 through 2016. For certain antibiotic/pathogen combinations, there was a trend of decreased resistance, including a decrease in oxacillin resistance among S. aureus.

Genotyping of Antimicrobial Resistance and Virulence in Staphylococcus Isolated from Food of Animal Origin in Mexico.

Ninety-six methicillin-susceptible Staphylococcus aureus (MSSA) and 11 methicillin-resistant coagulase-negative staphylococci (MRCNS) were recovered from food of animal origin. Multi-drug resistance was detected in 34.1% of isolates. Tetracycline-resistant staphylococci harbored tetK gene (68.8%). Erythromycin/clindamycin-resistant staphylococci carried lnuA/lnuB genes frequently alone or combined with msrA gene. The sec gene was detected in 15.6% of MSSA and two isolates harbored the immune evasion cluster. The spa t337 predominated among MSSA strains. Two ermC-positive MRCNS isolates were observed, five mecA-positive carried SCCmec IVa and 6 were non-typeable by the IWG-SCC classification. These results demonstrate that food of animal origin can be a potential source for spreading of multidrug-resistance gene.

Biofilm formation of methicillin-resistant coagulase negative staphylococci (MR-CoNS) isolated from community and hospital environments.

Methicillin-resistant coagulase negative staphylococci (MR-CoNS) are the major cause of infectious diseases because of their potential ability to form biofilm and colonize the community or hospital environments. This study was designed to investigate the biofilm producing ability, and the presence of mecA, icaAD, bap and fnbA genes in MR-CoNS isolates. The MR-CoNS used in this study were isolated from various samples of community environment and five wards of hospital environments, using mannitol salt agar (MSA) supplemented with 4 μg/ml of oxacillin. The specie level of Staphylococcus haemolyticus, Staphylococcus epidermidis, Staphylococcus hominis and Staphylococcus warneri was identified by specific primers of groESL (S. haemolyticus), rdr (S. epidermidis) and nuc (S. hominis and S. warneri). The remainder isolates were identified by tuf gene sequencing. Biofilm production was determined using Congo red agar (CRA) and Microtiter plate (MTP) assay. The mecA and biofilm associated genes (icaAD, fnbA and bap) were detected using PCR method. From the 558 samples from community and hospital environments, 292 MR-CoNS were isolated (41 from community environments, and 251 from hospital environments). S. haemolyticus (41.1%) and S. epidermidis (30.1%) were the predominant species in this study. Biofilm production was detected in 265 (90.7%) isolates by CRA, and 260 (88.6%) isolates were detected by MTP assay. The staphylococci isolates derived from hospital environments were more associated with biofilm production than the community-derived isolates. Overall, the icaAD and bap genes were detected in 74 (29.5%) and 14 (5.6%) of all isolates from hospital environments. When tested by MTP, the icaAD gene from hospital environment isolates was associated with biofilm biomass. No association was found between bap gene and biofilm formation. The MR-CoNS isolates obtained from community environments did not harbor the icaAD and bap genes. Conversely, fnbA gene presented in MR-CoNS isolated from both community and hospital environments. The high prevalence of biofilm producing MR-CoNS strains demonstrated in this study indicates the persisting ability in environments, and is useful in developing prevention strategies countering the spread of MR-CoNS.

Antimicrobial resistance profile and molecular characterization of methicillin-resistant staphylococcus isolates in Tripoli Central Hospital, Libya

Abstract Background: Nosocomial infections caused by methicillin-resistant Staphylococci could lead to increased morbidity and mortality, but little is known about the prevalence of infections with these organisms in healthcare facilities and in the community in Tripoli. This study investigated the in vitro susceptibility of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase negative staphylococci (MRCNS) to antimicrobial agents, and determined the molecular characteristics of MRSA. Methods: This is a retrospective observational study aiming at determining the prevalence and antibiotic resistance pattern of (MRSA) and (MRCNS) isolated from non-duplicated clinical specimens in Tripoli Central Hospital (TCH) between June 2013 and June 2014. Isolates were identified using standard laboratory procedures. Antimicrobial susceptibility tests were carried out by disk diffusion method and automated systems. DNA of the MRSA isolates was used for PCR to determine the molecular analysis. Results: 218 isolates of Staphylococci were obtained, 71.6% were coagulase positive staphylococci (CPS) and 28.4% were coagulase negative staphylococci (CNS). 39.7% of CPS were MRSA, while 75.8% of CNS were MRCNS. The rates of hospital-acquired MRSA (HA-MRSA) and community-acquired MRSA (CA-MRSA) among MRSA isolates were 61.3% and 38.7% respectively. A similar trend was detected among MRCNS isolates, where 74.5% were HA-MRCNS and 25.5% were CA-MRCNS. All the MRSA and MRCNS isolates were susceptible (100%) to vancomycin, tigecycline, linezolid, quinupristin/dalfopristin, daptomycin and moxifloxacin. Generally, hospital-acquired strains showed higher resistance rates than community-acquired ones to the most commonly tested non-beta-lactam antibiotics. 35.5% of all staphylococcal isolates exhibited mecA+ gene and 12.9% expressed mecC+. Meanwhile, 38.7% of MRSA isolates harbored both mecA and mecC. However, 12.9% of MSSA isolates were negative for both mecA and mecC. The mecA gene was detectable in 59.1% and 40.9 % of HA-MRSA and CA-MRSA isolates respectively. Conclusion: Hospital-acquired MRSA and MRCNS isolates had higher resistance rates to non-beta lactam antimicrobial drugs than the respective community-acquired isolates. This was shown by early detection of mecC gene among MRSA isolates.

Cfr-mediated linezolid-resistant clinical isolates of methicillin-resistant coagulase-negative staphylococci from China.

Three linezolid-resistant coagulase-negative staphylococci (LR-CoNS), including two Staphylococcus cohnii and one Staphylococcus capitis, were isolated from 1104 clinical staphylococcal isolates across China in 2013-2014. Antibiotic susceptibilities of the bacteria were determined by the agar dilution method. PCR and DNA sequencing were performed to determine the potential molecular mechanism of linezolid resistance. The two linezolid-resistant S. cohnii isolates were subjected to pulsed-field gel electrophoresis (PFGE) to investigate their genetic relatedness. Primer walking, S1 nuclease PFGE and Southern blot hybridisation were conducted to ascertain the location and environment of the cfr gene. All three isolates were positive for the cfr gene. Amino acid mutations S158F and S158Y in the ribosomal protein L3 were identified in S. cohnii 13B289 and 13L105, respectively, both of which also had an additional substitution (D159Y) in L3. PFGE indicated that the two S. cohnii isolates belonged to diverse clonal strains. S1 nuclease PFGE and Southern blotting experiments indicated that the cfr gene of the three isolates resided on plasmids of similar size (ca. 35.4kb). The cfr-harbouring segments of S. capitis 13G350 and S. cohnii 13L105 were identical to plasmid pSS-01 reported previously. The cfr-carrying fragment of S. cohnii 13B289 was indistinguishable from the formerly described plasmid pSS-02. In conclusion, the presence of the cfr gene located on a plasmid was the main mechanism contributing to resistance to linezolid in the three staphylococcal isolates. Hence, timely detection and judicious use of antibiotics are essential to prevent further transmission of this resistance mechanism.

Characterization of methicillin-resistant and -susceptible staphylococcal isolates from bovine milk in northwestern china.

Emergence of methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant coagulase-negative staphylococci (MR-CoNS) in bovine milk is a major public health concern. The primary purpose of this research was to determine molecular genetic characteristics and antibiotic resistance of staphylococcal isolates recovered from milk of mastitic cows in the Shaanxi Province in Northwestern China. One hundred and thirteen methicillin-susceptible Staphylococcus aureus (MSSA), one mecA-positive and phenotype-positive MRSA, seven mecA- and mecC- negative but phenotype-positive MRSA and two MR-CoNS including one oxacillin-susceptible mecA-positive Staphylococcus haemolyticus (OS-MRSH) and one mecA-positive and methicillin-resistant Staphylococcus epidermidis (MRSE) isolates were recovered from 214 quarter milk samples on 4 dairy farms. All above 123 isolates were subjected to antibiotic resistance profiling. S. aureus isolates were also genotyped using the spa typing and the multilocus sequence typing (MLST). Eight MRSA and 2 MR-CoNS isolates were additionally tested for SCCmec types. Resistance was common among isolates against ampicillin or penicillin (80.5%), kanamycin (68.3%), gentamicin (67.5%), tetracycline (43.9%) and chloramphenicol (30.1%). However, no isolate was resistant to vancomycin or teicoplanin. Twenty, 29 and 58 isolates showed resistance to 1, 2 or more than 2 antibiotics, respectively. The predominant multidrug resistance profile was penicillin/ampicillin/kanamycin/gentamicin/tetracycline (46 isolates). Most S. aureus isolates belonged to spa types t524 (n = 63), t11772 (a new type, n = 31) and t4207 (n = 15). At the same time, MLST types ST71 (n = 67) and ST2738 (a new type, n = 45) were identified as dominant sequence types. The mecA-positive and phenotype-positive MRSA isolate had a composite genotype t524-ST71-SCCmecIVa, while 7 mecA-negative but phenotype-positive MRSA isolates were all t524-ST71. The OS-MRSH isolate contained a type V SCCmec cassette, while the MRSE isolate possessed a non-typeable SCCmec. The spa-MLST types t11772-ST2738 (n = 27), t11807-ST2683 (n = 4) and t11771-ST2738 (n = 3) were newly identified genotypes of S. aureus. These new genotypes and multidrug-resistant staphylococci could pose additional threat to animal and human health.

Prevalence of SCCmec types among Methicillin resistant Coagulase negative Staphylococci isolated from HIV patients in Chennai, South India

Background Methicillin resistant Coagulase negative staphylococci (MRCoNS) are opportunistic pathogens among HIVAIDS patients and serve as a large reservoir of Staphylococcal Cassette Chromosome mec (SCCmec) that carries mecA. Very little is known about the prevalent SCCmec types among MRCoNS from HIV patients and its molecular epidemiology. Hence, this study was aimed at determining the distribution of SCCmec elements amongst MRCoNS isolates from HIV infected patients from Chennai, South India. Methods 52 clinically significan tM RCoNS isolates from HIV patients were included in this study. Following speciation, isolates were subjected to antibiotic susceptibility testing and screening for methicillin resistance using cefoxitin disc (30µg) and confirmed by mecA gene PCR. The presence of SCCmec types (I - V) was determined using multiplex PCR. Results Of the 52 isolates, S. haemolyticus (n =29, 56%) was predominant followed by S. epidermidis (n =13, 25%), S. capitis (n=4, 7%), S. lugdunensis (n =3, 6%) and S. hominis, (n =3, 6%). Highest resistance was shown towards ciprofloxacin (44%) followed by erythromycin (42%) and ofloxacin (39%). SCCmec typing revealed type I (n=26, 50%) to be predominant followed by type V (n=10, 19%), type III (n=7, 14%), type IV (n=4, 7%) and type I & V (n=2, 4%). Three (6%) isolates were nontypeable and type II was absent. Conclusion The MRCoNS isolates carried genetically diverse SCCmec elements including types I, V, III, IV and I and V in combination with SCCmec type I being predominant among HIV patients, which may be attributed to majority of patients being hospitalized.

Investigation of Biofilm-Associated Antibiotic Susceptibilities of Methicillin-Resistant Staphylococci Isolated from Catheter-Related Nosocomial Infections

Risks for development of local and/or systemic infections are the most important complications of catheters that are widely used during hospitalization process. The aims of this study were to investigate and compare the antibiotic susceptibilities of methicillin-resistant staphylococci isolated from catheters, in planktonic and biofilm forms, and to evaluate the antimicrobial effects of antibiotics on those forms alone and in combinations. A total of 30 strains [15 methicillin-resistant Staphylococcus aureus (MRSA) and 15 methicillin-resistant coagulase-negative staphylococci (MR-CNS)] isolated from catheter cultures of patients hospitalized in different clinics and intensive care units in Baskent University Medical School Hospital between 2006-2009, were included in the study. The antibiotic sensitivities of MRSA and MR-CNS isolates were investigated in vitro in planktonic phase and on sessile cells after biofilm was formed. Vancomycin, ciprofloxacin, rifampicin, gentamicin, meropenem, tigecycline, linezolid, ceftazidime and cephazolin were used for antibiotic susceptibility testing. The sensitivity of planktonic cells to antibiotics was primarily investigated, so that minimal inhibitor concentration (MIC) and minimal bactericidal concentration (MBC) values were determined by broth microdilution method. Afterwards, each strain was transformed to sessile cell in a biofilm environment, and MIC and MBC values were also determined for sessile cells. Double and triple antibiotic combinations were prepared, the effectiveness of combinations were studied on both planktonic and biofilm cells with multiple-combination bactericidal testing (MCBT) method. The data set obtained from planktonic and biofilm cells for each antibiotic analyzed via two proportion z test. Statistically significant decreases were found in the sensitivities of sessile cells when compared to planktonic cells (p< 0.01). The tests performed with the use of double and triple antibiotic combinations also showed the susceptibility decrease between planktonic and biofilm forms to be significant in most of the combinations (p< 0.01). The comparison of double and triple antibiotic combinations against planktonic and sessile cells as determined by the inhibition of more than 90% of the strains, revealed no significant difference . Vancomycin and tigecycline were the most effective antibiotics for all isolates in planktonic and sessile cells. Combinations containing vancomycin and rifampicin showed the best activity both double and triple antibiotic combinations against biofilm. In conclusion, our data indicated that combination therapy, especially double combinations of antibiotics seem to be a rational approach for biofilm-related infections.

Clonal Dynamics of Nasal Staphylococcus aureus and Staphylococcus pseudintermedius in Dog-Owning Household Members. Detection of MSSA ST398

The objective of this study was to investigate the dynamics of nasal carriage by Staphylococcus aureus (SA) and Staphylococcus pseudintermedius (SP) among healthy dog-owning household members involved in 7 previous index cases of suspected anthropozoonotic (n = 4) and zoonotic (n = 3) interspecies transmission [4 direct cases, identical SA (n = 3) or SP (n = 1) in owner and dog; three indirect, SP in owner (n = 2) or SA in dog (n = 1)]. Co-carriage with methicillin-resistant coagulase-negative staphylococci (MRCoNS) was also evaluated. Sixteen owners and 10 dogs were sampled once every three months for one year. In total, 50 SA and 31 SP were analysed by MLST, and SA also by spa typing. All isolates were subjected to ApaI/SmaI-PFGE and antimicrobial resistance and virulence profiles were determined. All index owners were persistent SA carriers in all direct-anthropozoonotic transmission cases, while only one dog was persistent SA carrier. Owner and dog exhibited a persistent SP carriage status in the direct-zoonotic transmission case. SP was maintained in the index human over time in one indirect-zoonotic transmission case. Only one SP was methicillin-resistant. SA belonged to genetic backgrounds of MRSA pandemic clones: CC45, CC121, CC30, CC5 and CC398. Three individuals carried a MSSA t1451-ST398 clone with the erm(T)-cadD/cadX resistance genes. SA or SP were persistently detected in the nasal cavity of 7 (43.8%) and 2 (12.5%) owners, and in one and 2 dogs, respectively. SA was recovered as the single species in 10 owners and in one dog; SP in 3 owners and 4 dogs; and both bacterial species in one owner and 4 dogs. Co-carriage of SA or SP with MRCoNS isolates was common (30.7%). This is the first study on the dynamics of nasal carriage of SA and SP in healthy pet-owning household members. Dog-contact may play a role in the staphylococcal species distribution of in-contact individuals.

Prevalence and Antimicrobial Susceptibility Pattern of Methicillin-Resistant Staphylococcus aureus and Coagulase-Negative Staphylococci in Rawalpindi, Pakistan

Methicillin resistant Staphylococcus aureus(MRSA) and methicillin resistant coagulase negative staphylococci (MRCoNS) are the important nosocomial infectious agents. There is a growing concern about the rapid rise in the resistance of Staphylococcus aureusto presently available antimicrobial agents. The aim of this study was to evaluate the prevalence rate of MRSA and MRCoNS and their rate of resistance to different antistaphylococcal antibiotics used broadly for treatment. Out of the total 350 staphylococcal isolates from different clinical specimens 148 isolates (60.40%) were identified as MRSA by oxacillin screen agar method, and 46 isolates (43.80%) were screened as MRCoNS. All the MRSA and MRCoNS isolates were tested for antibiotic resistance pattern by disc diffusion method for 16 different antibiotics. All the isolates of

Linezolid resistance mechanisms and molecular epidemiology of clinical isolates of methicillin-resistant coagulase-negative staphylococci

Objective To investigate the linezolid resistance mechanisms and molecular epidemiology of clinical isolates of methicillin-resistant coagulase-negative staphylococci (MRCoNS).Methods Seventeen MRCoNS,including 10 S.capitis,4 S.cohnii,2 S.haemolyticus,and 1 S.sciuri with various levels of linezolid resistance were isolated from intensive care units in our hospital from March to August 2011. Minimal inhibitory concentration (MIC) was determined by E-test method. Pulsed-field gel electrophoresis was performed to analyze the molecular epidemiology.PCRs and DNA sequencing were preformed to investigate the mechanisms of linezolid resistance in MRCoNS.Results Nine S.capitis with linezolid MIC of ＞256 μg/ml were indistinguishable,and another S.capitis with linezolid MIC of 4 μg/ml was closely related.Four S.cohnii with linezolid MIC of ＞256 μg/ml were belonged to the same clonal strain.MIC of linezolid for S.sciuri was 64 μg/ml,and were 4 μg/ml and 6 μg/ml for 2 S.haemolyticus,respectively.A commom G2576T mutation and a novel C2104T mutation were identified in 9 S.capitis with linezolid MIC of ＞256 μg/ml by DNA sequence analysis of domain V of the 23S rRNA gene.cfr gene was deteeted in all staphylococci except a S.sciuri whose 23S rRNA gene contained the G2576T mutation.Conclusion It is the first report of linezolid-resistant clinical isolates of staphylococci in China.Linezolid resistance in MRCoNS is related to the presence of DNA mutation in domain V of the 23S rRNA gene and cfr gene.It's a clonally dissemination of linezolid-resistant MRCoNS in intensive care units of our hospital. Key words: Staphylococci; Linezolid; Antibiotic resistance; 23S rRNA; cfr

DMolecular detection of methicillin resistant Staphylococcus aureus (MRSA) and methicillin resistant coagulase-negative Staphylococcus (CoNS) in Iran

The incidence of methicillin resistance has risen among nosocomial isolates ofStaphylococcus aureus and coagulase negative staphylococci. The present study was carried out to investigate the prevalence of methicillin-resistant Staphylococcus aureus(MRSA) and methicillin-resistant coagulase negative staphylococci (MRCoNS) and to determine their antibiotic susceptibility pattern. A total of one hundred and thirty clinical staphylococcal isolates recovered from blood, tracheal aspirate, urine and wound specimens were evaluated for susceptibility to penicillin, amikacin, ciprofloxacin, vancomycin, erythromycin, ceftriaxone, methicillin, rifampin and gentamicin by Disk diffusion method and molecular detection of mecA gene. The results showed that MRCoNS were more resistant to these antibiotics as compared to MRSA and the most effective antibiotic to use for staphylocoocal isolates is vancomycin showing (100% of S. aureus and 90% of CoNS) efficacy. The mecA gene was detected in 56% of the isolatedS. aureus and 70% of the CONS isolates. The prevalence of methicillin resistant staphylococci in Iran was very high and 45.4% of MRSA and MRCoNS isolates were at least resistance to 3 or more classes of antibiotics. The high prevalence of MRSA immerged in Iran could be originated due to antibiotic pressure and poor control measures on the application of antibiotics such as methicillin. Key words: Staphylococcus aureus (S. aureus), coagulase-negative staphylococci (CoNS), mecA gene, methicillin-resistance