Presence Of mecA Gene Research Articles

Differences in distribution of MLS antibiotics resistance genes in clinical isolates of staphylococci belonging to species: S. epidermidis, S. hominis, S. haemolyticus, S. simulans and S. warneri

BackgroundMacrolides and lincosamides are two leading types of antibiotics commonly used in therapies. The study examines the differences in resistance to these antibiotics and their molecular bases in S. epidermidis as well as in rarely isolated species of coagulase-negative staphylococci such as S. hominis, S. haemolyticus, S. warneri and S. simulans. The isolates were tested for the presence of the erm(A), erm(B), erm(C), lnu(A), msr(A), msr(B), mph(C), ere(A) and ere(B) genes. Phenotypic resistance to methicillin and mecA presence were also determined.ResultsThe MLSB resistance mechanism was phenotypically found in isolates of species included in the study. The most prevalent MLSB resistance mechanism was observed in S. hominis, S. haemolyticus and S. epidermidis isolates mainly of the MLSB resistance constitutive type. Macrolide, lincosamide and streptogramin B resistance genes were rarely detected in isolates individually. The erm(B), ere(A) and ere(B) genes were not found in any of the strains. The erm(A) gene was determined only in four strains of S. epidermidis and S. hominis while lnu(A) was seen in eight strains (mainly in S. hominis). The erm(C) gene was present in most of S. epidermidis strains and predominant in S. hominis and S. simulans isolates. The examined species clearly differed between one another in the repertoire of accumulated genes.ConclusionsThe presence of genes encoding the MLSB resistance among CoNS strains demonstrates these genes’ widespread prevalence and accumulation in opportunistic pathogens that might become gene reservoir for bacteria with superior pathogenic potential.

Frequency of icaA and icaD determinants and biofilm formation among coagulase-negative staphylococci associated with nasal carriage in neonatal intensive care units.

Nasal colonization with coagulase-negative staphylococci (CoNS) may be a preliminary risk factor for systemic infection. The aim of this study was to assess the frequency of ica A and D genes and biofilm formation among hospital-acquired nasal colonizing CoNS strains isolated from neonates in the neonatal intensive care units (NICUs). Antibiotic sensitivity patterns and some relevant risk factors were estimated. This study assessed nasal colonization with CoNS among neonates at days one and three of admission to NICUs of Beni-Suef University Hospital and Beni-Suef General Hospital from November 2015 to May 2016. The isolates were screened and identified; susceptibility testing was performed. Biofilm formation was examined using the Congo red agar method. Isolates identified as CoNS were tested by polymerase chain reaction (PCR) for the presence of mecA and icaA and icaD genes. A total of 340 nasal swabs were collected from 170 neonates. The incidence of nasal colonization with CoNS was 50%. The species most frequently isolated were S. haemolyticus and S. epidermidis. Multidrug resistance (MDR) was detected in 86% of isolates. It was found that there was a strong association between the presence of mecA gene and phenotypic resistance to methicillin and also the presence of the icaA gene and biofilm formation. Neonates admitted to NICUs can become reservoirs for CoNS strains, leading to potential dissemination of MDR strains into the community.

DETECTION FOR MECA GENE IN EGYPTIAN CLINICAL Staphylococcus aureus SAMPLES AND STUDY THEIR GENOTOXIC ACTIVITY

Staphylococcus aureus isolates were isolated from fifty clinical samples collected from Ain Shams University Hospitals (March - July 2016) and identified using biochemical and microbiological tests. PCR was performed using specific primers to determine the isolates of Methicillin - Resistant Staphylococcus aureus (MRSA) based on the presence of mecA gene. Thirty-four isolates from total fifty isolates (68%) were identified as MRSA isolates. To study the genotoxicity for this isolates, forty-five mice were injected with these MRSA isolates and comet and micronuclei assays were performed on mice liver tissues and bone marrow respectively. These assays revealed 24% - 22% DNA damage as an indicator for chromosomal breakage by comet and micronucleus assays respectively which indicate that infection with these isolates leads to mutations. Studying these isolate furthermore will give an insight on how critical maintaining high standard hygiene in Egyptian hospitals and attention to infection control system can prevent occur of outbreaks

Detection of vancomycin nonsusceptible strains in clinical isolates of Staphylococcus aureus in northern Iran.

Glycopeptides, particularly the cell wall-acting antibiotic vancomycin, are the safest cure for methicillin-resistant Staphylococcus aureus. The aim of this study was to evaluate nonsusceptibility of clinical isolates of S. aureus to vancomycin and investigate mutations in vraSR, a cell wall synthesis regulator gene, in vancomycin-resistant strains. Susceptibility of 110 clinical strains of S. aureus to methicillin and vancomycin were determined using disc diffusion method and determination of minimum inhibitory concentration, respectively. Presence of mecA and vanA genes was determined by PCR. Determination of spa types and mutations of the vraSR gene in vancomycin nonsusceptible isolates were assessed by PCR-sequencing analyses. In total, 47 isolates (42.73%) were recognized as MRSA, three (2.73%) strains were resistant to vancomycin, and eight (7.27%) strains were vancomycin intermediates. The MIC of vancomycin was 4-64μg/ml in these isolates. All vancomycin nonsusceptible S. aureus strains were mecA positive and one isolate was positive for the vanA gene. Spa type t030 was found as the most common type. In vraSR sequence analysis, all 11 vancomycin nonsusceptible isolates had the D59E mutation in the vraR and E45G in vraS genes. R117H, R121S, and R121I are the other identified missense mutations in the vraR gene. The identification of a high percentage of MRSA and presence of VRSA and VISA isolates is a serious warning about the treatment of future MRSA infections and reveals the need for new and effective therapeutic agents.

Prevalence and Genetic Characteristics of Methicillin-Resistant Staphylococcus aureus and Coagulase-Negative Staphylococci Isolated from Oral Cavity of Healthy Children in Japan.

Prevalence and genetic characteristics of methicillin-resistant Staphylococcus aureus (MRSA) and coagulase-negative staphylococci in oral cavity of healthy children were studied in Hokkaido, northern main island of Japan. From saliva of 526 children, a total of 248 staphylococcal isolates comprising S. aureus (n = 143), S. epidermidis (n = 84), S. warneri (n = 13), S. haemolyticus (n = 5), S. hominis (n = 2), and S. intermedius (n = 1) were recovered. Presence of mecA was confirmed in 6.3% of S. aureus, 50% of S. epidermidis, and 7.7% in S. warneri. SCCmec was mostly classified into type IV, and ACME (arginine catabolic mobile element)-arcA was detected in S. epidermidis (23.8%) and S. intermedius. Nine MRSA isolates belonged to staphylocoagulase gene (coa) type Ia, IIa, IIIa, VIIb/sequence type 1 (ST1), ST5, ST8, ST89, ST120, and were negative for PVL (Panton-Valentine leukocidin) genes. These isolates included two clones of emerging community-acquired MRSA (CA-MRSA) that had been described recently in Japan: ST5/SCCmec IVc, which resembles the "Pediatric clone," and ST8/SCCmec IVl belonging to coa-IIIa/agr-I with sasL gene, designated "CA-MRSA/J" clone. Various enterotoxin genes were found in all the MRSA and some methicillin-susceptible S. aureus (MSSA) isolates examined, while tst-1 was detected in four MRSA isolates. Notably, a variant of elastin-binding protein gene (ebpS-v) was identified in ST120 MRSA and ST45 MSSA isolates, and exfoliative toxin D gene (etd) was detected in an MSSA isolate. The present study revealed the presence of MRSA, including the novel CA-MRSA clones, and high prevalence of methicillin-resistant S. epidermidis in oral cavity of healthy children in Japan.

Methicillin-Resistant Staphylococcus aureus ST80 Induce Lower Cytokine Production by Monocytes as Compared to Other Sequence Types.

Methicillin-resistant Staphylococcus aureus (MRSA) remains an important cause of nosocomial and community-associated infections due to its ability to produce toxins and evade host’s immune responses. The aim of the present study was to investigate the association of monocytes immune response in terms of cytokines produced after inoculation with different MRSA clones. Thirty-one clinical MRSA strains were selected on the basis of clonal types, accessory gene regulator (agr) groups and toxin genes carriage. Isolates were identified as S. aureus by Gram stain, catalase, coagulase production and PCR for nuc gene. The presence of mecA, lukS/lukF-PV (Panton-Valentine Leukocidin) and tst (Toxic Shock Syndrome Toxin-1) genes, as well as, the determination of agr groups was performed by PCR. Clonality was investigated by means of multi-locus sequence typing (MLST). Peripheral blood mononuclear cells were stimulated with live bacterial cells for 45 min at a ratio of 1:10. Cells were incubated for 10 h and supernatants were collected. The levels of Tumor Necrosis Factor alpha (TNFa), IL-1b, IL-8, IL-6, IL-12p40, IL-10, interferon-gamma (IFN-γ) and IL-2, were measured by Human Cytokine Multiplex Immunoassay kit. Thirteen strains were tst and 12 lukS/lukF-PV-positive. Seven strains belonged to ST80 and ST225, five to ST30 and ST239, while the remaining seven isolates were grouped together as “other.” Strains belonging to ST80 induced statistically lower levels of TNFa, IL-1b, IL-8, IL-6, IL-10, IFN-γ, and IL-2. PVL-positive strains classified into ST80 clone induced statistically lower concentrations of most cytokines as compared to PVL-positive strains belonging to other clones, tst-positive strains and toxin-negative ones. Strains of agr3 group belonging to ST80 induced statistically lower concentrations of most tested cytokines as compared to agr3 strains not-belonging to ST80, agr2 or agr1. This low induction of immune response by MRSA ST80 cannot be attributed to the presence of neither lukS/lukF-PV nor agr3.

Phenotypic Antibiotic Resistance Pattern and Presence of mecA in Staphylococcus aureus Isolated from Bovine Mastitis

Phenotypic Antibiotic Resistance Pattern and Presence of mecA in Staphylococcus aureus Isolated from Bovine Mastitis

Superantigenic Toxin Genes in Some Methicillin Resistant Coagulase Negative Staphylococci

Coagulase-negative staphylococci (CNS) exemplify common skin commensals. They are opportunistic microorganisms. It has been recently confirmed that CNS can produce superantigens of Staphylococcus aureus. Different clinical samples (251) were collected from Al-Musayyib General Hospital in Babylon, Iraq. Sixty isolates were CNS, identified by conventional methods and Vitek2 system. The isolates were Staphylococcussciuri (31.66%), Staphylococcus haemolyticus (25%), Staphylococcussaprophyticus (23.33%) and Staphylococcus lentus (20%), the isolate obtained from seminal fluid, blood, tonsil and wound infections. All isolates showed resistant to methicillin antibiotic. Multiplex PCR was used to detect the presence of mecA, sea, seb, seg, seh, sei, selpand tst1 in Methicillin resistant CNS. This study suggested that MRCNS isolates from patient carried sea, seb, seg, seh, sei, and tst1superantigenic toxin genes.

1219. Increasing Methicillin Resistance of Staphylococcus lugdunensis in a Tertiary Care Community Hospital in Japan

Background Staphylococcus lugdunensis, a coagulase-negative staphylococcus, has virulence and pathogenicity similar to that of Staphylococcus aureus. Methicillin resistance and presence of mecA gene are not common in S. lugdunensis in many parts of the world. Recently, higher prevalence of methicillin-resistant S. lugdunensis is reported from Taiwan and Japan. We describe the change in methicillin resistance of S. lugdunensis in a tertiary care community hospital in Sapporo, Japan.MethodsWe performed a retrospective study of S. lugdunensis, isolated from inpatients and outpatients at our hospital from 2008 to 2017. Rate of methicillin resistance of the first 5 years from 2008 to 2012, and that of the second 5 years from 2013 to 2017 were compared. Risk factors of methicillin resistance were also evaluated. Phenotypic detection of methicillin resistance was identified using broth microdilution by VITEK two system (bioMérieux).ResultsA total of 369 cases of S. lugdunensis were detected during the study period. Of all cases, 228 (61.8%) were men, and 177 (48.0%) were hospitalized. Twenty-one isolates (5.7%) were positive in blood culture, 216 (58.5%) were positive in cultures of skin and soft tissue. Methicillin-resistant strains were found in 43 (31.6%) of 136 isolates from 2008 to 2012, and in 108 (46.4%) of 233 from 2013 to 2017 (OR 1.87; 95% CI 1.20–2.91; P = 0.006). Of patients with methicillin-resistant S. lugdunensis, 105 cases (69.5%) were hospitalized (P < 0.001).ConclusionIn our hospital, methicillin-resistant S. lugdunensis is increasing over the 10 years. Further research is needed to assess trend of methicillin resistance of S. lugdunensis in other healthcare facilities and countries.Disclosures All authors: No reported disclosures.

1221. Genetic Characteristics of Healthcare-Associated Methicillin-Resistant Staphylococcus aureus (HA-MRSA) Belonging to Clonal Complex 5 (CC5) in Latin-America

BackgroundMRSA are responsible for a high proportion of healthcare-associated infections. HA-MRSA is multidrug resistant, and infections occur most frequently among inpatients, for example, those who have undergone invasive medical procedures or those aged 50 to 60 years and older. Dominance of multidrug-resistant CC5 (Chilean and New York/Japan clones) was prevalent in infections in Latin America with the notable exception of Colombia and Ecuador where USA300-LV isolates dominate. We performed genetic characterization of HA-MRSA-CC5 isolates recovered from infections in nine countries (12 hospitals).MethodsSpecies identification of S. aureus and presence of mecA were performed by PCR. We determined MICs to common anti-MRSA antibiotics and performed screening for VISA phenotype. Molecular characterization included detection of lukSF-PV and SCCmec typing. PFGE and MLST were performed in selected MRSA isolates with susceptibility patterns typical of the Chilean (ST5-MRSA-I) and USA300-LV (ST8-MRSA-IV) lineages.ResultsA total of 665 S. aureus isolates were prospectively recovered from 592 patients. A high frequency of methicillin resistance (>40%) was observed in all countries (62%, 55%, 44%, and 40% in BRA, PER, CHI and ARG, respectively). Decreased susceptibility to VAN was not observed and VAN MIC90 was 1 µg/mL. In PER and CHI, the overwhelming majority of isolates (89%) belonged to the Chilean/Cordobes clone (CC5) with susceptibility patterns typical of this lineage (Resistance to β-lactams, MLSB-type, quinolones, and aminoglycosides). The New York/Japan clone (ST5-MRSA-II) was predominant in Brazil, replacing the prevalent hospital-associated Brazilian (ST239-MRSA-III) lineage. Most Argentinian MRSA isolates exhibiting a CA (ST5-IV) pattern, previously described in this country.ConclusionA variety of MRSA genetic lineages are circulating in Latin America with geographic clustering and clonal replacement. Dissemination of the CA-USA300-LV has not occurred beyond the northern region of the subcontinent.Disclosures J. M. Munita, Pfizer: Grant Investigator, Research grant. C. Arias, Merck & Co., Inc.: Grant Investigator, Research support. MeMed: Grant Investigator, Research support. Allergan: Grant Investigator, Research support.

Cationic Branched Polyethylenimine (BPEI) Disables Antibiotic Resistance in Methicillin-Resistant Staphylococcus epidermidis (MRSE).

Staphylococcus epidermidis is one of the most prevalent prokaryotic species on human skin and mucosal membranes that constitute the commensal flora. S. epidermidis has become one of the most common causes of primary bacteremia. Infections are difficult to diagnose because the pathogen has natural niches on human skin and the ability to adhere to inanimate surfaces via biofilms. Alarmingly, S. epidermidis has acquired resistance to many antibiotics, which presents a danger to human health. Known as methicillin-resistant S. epidermidis (MRSE), most clinical isolates of MRSE in North America exhibit β-lactam resistance primarily due to the presence of mecA, a gene that bestows β-lactam antibiotic resistance in a manner similar to methicillin-resistant Staphylococcus aureus (MRSA). MecA encodes for expression of penicillin-binding protein 2a (PBP2a), which is absent in β-lactam susceptible strains of S. epidermidis. We can disable this resistance factor in MRSE with 600-Da branched polyethylenimine (BPEI). Cationic BPEI targets anionic wall teichoic acid (WTA), an essential cofactor for proper functioning of PBP2a. We found that BPEI synergizes the activity of β-lactam antibiotics against MRSE. Growth curves suggest that the combination of BPEI and oxacillin is bactericidal. Electron micrographs indicate abnormalities in the cellular septa and cell walls of treated samples. Therefore, first-line clinical treatments can be effective against MRSE when used in combination with BPEI.

Prevalence, Molecular Characterization, and Antimicrobial Susceptibility of Methicillin-Resistant Staphylococcus aureus from Different Origins in Sichuan Province, China, 2007-2015.

Methicillin-resistant Staphylococcus aureus (MRSA) is a major multidrug-resistant (MDR) opportunistic pathogen that is responsible for nosocomial infections worldwide. The emergence of MRSA in food-producing animals has heightened concerns regarding the presence of MRSA in foods having an animal origin. The objectives of this study were to determine the prevalence of MRSA in different sources, including retail food, food-producing animals, and food handlers in Sichuan province. During 2007-2015, S. aureus was isolated from samples having different origins. Susceptibilities of MRSA to a panel of 12 antimicrobial agents were determined according to Clinical and Laboratory Standards Institute (CSLI) procedures. Pulsed-field gel electrophoresis, spa typing, staphylococcal chromosomal cassette (SCC) mec typing, and multilocus sequence typing (MLST) were used to characterize the relationship between these isolates. A total of 756 S. aureus were isolated from 11,067 samples. Of these, 52 isolates were classified as MRSA based on the presence of mecA genes. An antimicrobial susceptibility assay indicated that CHL-CLI-ERY-FOX-OXA-PEN-TET (n = 10) and CHL-CIP-CLI-ERY-FOX-OXA-PEN-TET (n = 8) were the two predominant MDR profiles in the isolates. Using 60% genetic similarity as a cutoff, the 52 MRSA isolates were grouped into 6 clusters having 34 pulsotypes. MLST typing showed seven multilocus sequence types (STs) with ST59 and ST9 being the most common. Six SCCmec types were identified in all MRSA isolates. The MRSA isolates had relatively low prevalence in Sichuan province. Clonal expansion is not involved in the dissemination of MRSA from food origins. Considering the threat of MRSA to public health, further surveillance is required to monitor the prevalence of food-related MRSA.

Staphylococcus spp. isolated from wild birds apprehended in the local illegal trade in Rio de Janeiro, Brazil, and relevance in public health.

The isolation of Staphylococcus species that are not commonly isolated from wild bird faeces, the relatively high proportion of strains showing degrees of resistance to β-lactamics, lincosamides and tetracycline, and also the presence of mecA and blaZ genes that has been associated with multidrug phenotype reveal its public health relevance and zoonotic potential. Consequently, this represents an important route to transmission of this pathogen and its antimicrobial resistance mechanisms throughout national and international frontiers fostered by the illegal trade of wild animals and close contact with humans.

Biofilm-forming ability and virulence factors of methicillin-resistant Staphylococcus pseudintermedius from canine pyoderma

Staphylococcus pseudintermedius (SP) has been associated with high antibiotic-resistance rates (e.g. methicillin) in European countries [1,3]. This condition could be also related to the ability to produce biofilm [2]. The aim of this study was to investigate the presence of methicillin-resistant SP strains and determine their ability to produce biofilm and some crucial virulence factors.Forty-two SP strains, previously determined as multi drug resistant (MDR) by the disk diffusion method using a panel of 17 antimicrobial agents, were selected from our collection and tested phenotypically for the minimum inhibitory concentration (MIC) of methicillin and genotypically for the presence of mecA and blaZ genes. The ability to produce biofilm was assessed phenotypically by two different assays: the Congo Red Agar plates (CRA) and the Microtitre Plate test (MtP) and genetically by the amplification of icaA and icaD genes. Three virulence factors genes coding for bicomponent leukocidin and enterotoxins (luk-I, seC, se-int) were searched.Twenty-three strains revealed a value of MIC for the methicillin greater than 128 µg/mL. The 83% were mecA-positive and 86% resulted blaZ-positive; all the strains positive for mecA were also positive for blaZ. All SP strains resulted biofilm-producers by MtP assay and classified as weakly producers (4.7%), moderate producers (47.6 %) and strongly producers (47.6 %). In contrast, only 35.7% of all strains were considered biofilm-producers by CRA method. The amplification of icaA and icaD gene occurred respectively in 66.6% and 97.6%; only one strain was negative for both genes. Almost all strains were positive for luk-I (95%), seC (74%) and se-int (84%).Our data reveal the pathogenicity potential of SP strains from dogs, suggesting that they could be considered zoonotic potential agents and confirming other previous studies [3-5]. Moreover could be observed a clear linkage between antibiotic-resistance and ability to produce biofilm.

Validity of Cefoxitin Disc Diffusion Test for the Detection of Methicillin-resistant Staphylococcus Aureus

Definite detection of MRSA is important for proper treatment. The purpose of the present study was to measure the validity of cefoxitin disc diffusion test for the detection of methicillin-resistant Staphylococcus aureus. This cross-sectional study was carried out in the Department of Microbiology and Immunology at Bangabandhu Sheikh Mujib Medical University, Dhaka from January 2010 to December 2010 for a period of one (01) year. S. aureus isolates were collected from different clinical samples including wound swab, pus, blood, urine, tracheal aspirate, throat swab, aural swab etc. Staphylococcus aureus (S.aureus) were isolated and confirmed by staining, biochemical tests. Routine antimicrobial susceptibility testing was performed cefoxitin discs diffusion test. PCR was performed for detection of the mecA gene for MRSA. Out of the 22 suspected MRSA isolates 19 were mecA positive by PCR and all of them 19(100.0%) were resistant to cefoxitin disc diffusion. The comparison of oxacillin and cefoxitin resistance and presence of mecA gene by PCR showed that out of 22 suspected MRSA isolates 19 were mecA positive by PCR and all the 19 (100.0%) showed resistance to cefoxitin disc diffusion. The sensitivity and specificity of cefoxitin disc diffusion were 100.0% and 100.0% respectively. Cefoxitin disc diffusion test has high sensitivity and specificity for the detection of MRSA.

The coa, mec, and spa genes diversity among methicillin-resistant Staphylococcus aureus Strains from health-care workers and patients

Methicillin-resistant Staphylococcus aureus (MRSA) is a bacterial pathogen that is frequently isolated in both hospital and community environments. MRSA is considered a major nosocomial pathogen that causes severe morbidity and mortality. Two hundred and twenty-five nasal swabs were collected (100 from health-care workers and 125 from patients). S. aureus was identified by colony morphology in both blood and mannitol salt agars, catalase and coagulase productions, and also by standard biochemical tests. Susceptibility test to several antimicrobial agents was performed by disc diffusion agar according to the Clinical and Laboratory Standards Institute guidelines. The polymerase chain reaction amplification of the coa, mecA, and spa gene was carried out in the clinical isolates showed resistant to oxacillin. Among 225 isolates of bacteria, 76 were confirmed to be S. aureus by phenotypic characteristics. Thirty isolates were considered MRSA by susceptibility antimicrobial test. Twenty-four were confirmed to be S. aureus by the presence of coa gene bands. Twenty-one S. aureus isolates were confirmed to be MRSA by the presence of mecA gene. The spa gene in health-care workers was present in 88.88% and for patients was 41.66%. This study is suggestive that the PCR for the detection of coa, mecA, and spa gene is a fast, accurate, and valuable diagnostic tool.

Detection of New Virulence Genes in mecA-positive Staphylococcus aureus Isolated From Clinical Samples

Background Methicillin-resistant Staphylococcus aureus (MRSA) has become a main clinical and epidemiological concern for the past decades. These isolates have spread worldwide, causing health care– and community-associated infections. The aim of the present work was the determination of antibiotic resistance profile and simultaneous detection of psm-α and sasX genes in the clinical MRSA strains isolated from Tehran—the first report from Iran. Methods This descriptive study was performed on hospitalized patients during August to February 2015. Antibiotic susceptibility test for all S. aureus isolates was conducted on Mueller-Hinton agar. The presence of mecA, sasX, and psm genes was detected by multiplex polymerase chain reaction method. Results Of 153 S. aureus, 79 (51.6%) of the strains carried the mecA gene. Molecular analysis of mecA-positive S. aureus showed that the prevalence of sasX and psm genes was 13.9% (11/79) and 7.6% (6/79), respectively. Conclusions This is the first report of sasX and psm genes among S. aureus isolates from Iran. Phenol-soluble modulins have recently appeared as a novel toxin family describing the virulence potential of vastly aggressive S. aureus. Current understanding is needed on S. aureus surface protein-encoding gene sasX, which plays a vital role in colonization and pathogenesis of MRSA.

Toxin production and drug resistance profiles of pediatric methicillin-resistant Staphylococcus aureus isolates in Tehran.

Staphylococcus aureus is known to be a major cause of skin and soft tissue infections, pneumonia and invasive diseases. In this study, attempts were made to examine the prevalence of tsst-1, eta, etb, and luk-PV genes among methicillin-resistant S. aureus (MRSA) isolated from children in Tehran. In the present cross-sectional study, a total of 100 MRSA were isolated from children who were referred to a pediatric hospital during 11-month period of September 2014 to August 2015. Isolates were identified using biochemical tests and then, using PCR, the isolates were tested for the presence of mecA, tsst-1, eta, etb, and luk-PV genes. Susceptibility of isolates to cefoxitin, penicillin, erythromycin, clindamycin, gentamicin, rifampin, minocycline, co-trimoxazole, linezolid, and vancomycin were evaluated using standard methods. It was found that the MRSA isolates had the greatest resistance to clindamycin (72%) and erythromycin (59%), while the lowest rates of resistance were observed to be related to minocycline (6%) and rifampin (12%). All of isolates were sensitive to vancomycin and linezolid. The mecA gene was detected in all the isolates. Moreover, luk-PV and tsst-1 were detected in 18% and 17% of the isolates, respectively. None of the isolates harbored eta and etb genes. Our data provide specifications about the toxin production status of S. aureus isolates from pediatric children. The current study showed increased resistance to different antibiotics in S. aureus isolates. Therefore, to prevent multi-resistance to other antibiotic classes, it is essential to withhold prescriptions and stop unessential use of available antibiotics.

Frequency, antimicrobial susceptibility and clonal distribution of methicillin-resistant Staphylococcus pseudintermedius in canine clinical samples submitted to a veterinary diagnostic laboratory in Italy: A 3-year retrospective investigation

In the last decade there has been a rapid global spread of methicillin-resistant Staphylococcus pseudintermedius (MRSP) clones displaying multidrug resistance in dogs. We investigated prevalence, antimicrobial susceptibility and clonal distribution of MRSP isolated from clinical canine samples between during 2011–2014. Following species identification by nuc PCR, MRSP were confirmed by the presence of mecA and characterized by antimicrobial susceptibility testing, Pulsed Field Gel Electrophoresis (PFGE), SCCmec typing, and Multi-Locus Sequence Typing (MLST) of a few isolates having distinct PFGE profiles. Both the MRSP isolation frequency in the 175 samples tested (12%) and the prevalence of methicillin resistance amongst the 63S. pseudintermedius isolates (33%) were high compared to a previous study in Italy. Sequence type (ST)71 carrying SCCmec type II–III, described as the epidemic European MRSP clone, accounted for approximately half of the isolates. The remaining isolates belonged to ST410-SCCmec type II–III, ST258-SCCmec type IV and other three clones associated with SCCmec type IV (ST261, ST290 and ST477). MRSP were consistently resistant to potentiated sulfonamides, and more frequently to clindamycin, ciprofloxacin and doxycycline than methicillin-susceptible isolates. Gentamicin was the only antibiotic showing good in vitro activity on all MRSP with 20 of the 21 isolates being susceptible. Results confirm a high prevalence of MRSP amongst clinical samples in Italy, revealing the emergence of new clones other than ST71, such as ST258, ST410, ST261, ST290 and ST477, here describe for the first time. Implementation of antimicrobial stewardship and surveillance programmes are required to prevent the emergence of new MRSP clones and reducing transmission in small animal practice.

Molecular Level Investigation of Staphylococci’s Resistance Mechanisms to Antibiotics

Polymerase chain reaction (PCR ) techniques development allows elaboration of many assays for identification of bacteria’s resistance mechanisms to antibiotics. Following this idea, the results of molecular level investigation of bacteria’s resistance mechanisms to antibiotics may give many opportunities to find more rapid methods for identifying the genes which are responsible for antibiotic resistance induction. The aim of this study was to investigate antibiotic resistance genes in Staphylococcus bacteria on molecular level. As classes of antibiotics it was used macrolides-lincosamides-streptogramin B (MLSB) and beta-lactams. In the proposed study the bacterial strains are represented by 50 isolates of Staphylococcus. The bacterial strains were analyzed using polymerase chain reaction to identify the nuc, tuf, tst, sea, pathogenic activity genes. After this, the bacteria were tested for ermA, ermB, ermC genes and for mecA, femA which are involved in resistance to macrolides, lincosamides, streptogramin B and to beta-lactams, respectively. The presence or the absence of these genes confirms that tested strains are resistant to specific antibiotic or not. Bacteria pathogenic activity was emphasized by genes as follows: sea (enterotoxin) which was found at all isolates, tst (toxic shock toxin) gene was not detected in any of isolates and tuf gene (elongation factor) was obtained with one pair of primers. Resistance to beta-lactams was evidenced by the presence of mecA in all isolates and femA in some strains. Each of ermC, ermA and ermB, macrolides-lincosamides-streptogramin B resistance genes, were detected.