Comparison of mecA polymerase chain reaction with phenotypic methods for the detection of methicillin-resistant Staphylococcus aureus

Antimicrobial resistance profiles of salmonella spp. and escherichia coli isolated from fresh nile tilapia (oreochromis niloticus) fish marketed for human consumption

BACKGROUND

Salmonella spp. and pathogenic strains of Escherichia coli are among the major foodborne zoonotic pathogens. These bacterial pathogens cause human illnesses characterized by hemorrhagic colitis, vomiting, nausea, and other agent-related symptoms. The increasing occurrence of antimicrobial resistance in these pathogens is also a serious public health concern globally. Regular surveillance of phenotypes and genotypes of Salmonella spp. and Escherichia coli from animal-derived foods is necessary for effective reduction and control of these foodborne pathogens. This study was conducted to assess the occurrence, antimicrobial resistance, virulence genes and genetic diversity of Salmonella spp. and E. coli isolates from fresh Nile tilapia obtained from retail markets in Nairobi, Kenya.

METHODS

A total of 68 fresh Nile tilapia fish samples were collected from retail markets and used for isolation of Salmonella spp. and E. coli. Antimicrobial susceptibilities of the isolates weretested by Kirby-Bauer agar disc diffusion method. According to the antimicrobial resistance profiles, the multi-drug resistant isolates were identified by 16 S rRNA sequencing and phylogenetic analysis using the Bayesian inference method. The MDR Salmonella spp. and E. coli isolates were subjected to PCR-based screening for the detection virulence and antibiotic resistance genes.

RESULTS

The prevalence of contamination of the fish samples with Salmonella spp. and E.coli was 26.47% and 35.29% respectively. Overall phenotypic resistance among the Salmonella spp. ranged from 5.5% for ceftazidime, chloramphenicol, meropenem, nitrofurantoin and streptomycin and 22.2% for penicillin-G. For E. coli phenotypic resistance ranged from 4.2% for ceftazidime and chloramphenicol and 25% for rifampicin. Multi-drug resistance was observed in three Salmonella spp. and two E. coli isolates. Results of 16 S rRNA sequences, sequence alignment and phylogenic trees confirmed the identified MDR isolates as S. typhymurium WES-09, S. typhymurium MAK-22, S. typhimurium EMB-32 and E. coli MAK-26 and E. coli LAN-35. The presence of antibiotic-resistance genes belonging to β-lactamases, tetracycline, sulfonamide, trimethoprim and aminoglycosides-resistant genes were detected in all the identified MDR isolates.

CONCLUSIONS

The findings from this study indicate that Nile tilapia (Oreochromis niloticus) sold in retail markets can acts as reservoirs of Salmonella spp. and E. coli pathogens linked to human disease, some of which were multidrug resistance to critically important antimicrobials. Both microorganisms are of zoonotic significance and represent a significant public health risk to the society.

ARGs Detection in Listeria Monocytogenes Strains Isolated from the Atlantic Salmon (Salmo salar) Food Industry: A Retrospective Study

Among bacterial foodborne pathogens, Listeria monocytogenes represents one of the most important public health concerns in seafood industries. This study was designed as a retrospective study which aimed to investigate the trend of antibiotic resistance genes (ARGs) circulation in L. monocytogenes isolates identified (in the last 15 years) from Atlantic salmon (Salmo salar) fresh and smoked fillets and environmental samples. For these purposes, biomolecular assays were performed on 120 L. monocytogenes strains collected in certain years and compared to the contemporary scientific literature. A total of 52.50% (95% CI: 43.57-61.43%) of these samples were resistant to at least one antibiotic class, and 20.83% (95% CI: 13.57-28.09%) were classified as multidrug resistant. Concerning ARGs circulation, tetracycline (tetC, tetD, tetK, tetL, tetS), aminoglycoside (aadA, strA, aacC2, aphA1, aphA2), macrolide (cmlA1, catI, catII), and oxazolidinone (cfr, optrA, poxtA) gene determinants were majorly amplified. This study highlights the consistent ARGs circulation from fresh and processed finfish products and environmental samples, discovering resistance to the so-called critical important antimicrobials (CIA) since 2007. The obtained ARGs circulation data highlight the consistent increase in their diffusion when compared to similar contemporary investigations. This scenario emerges as the result of decades of improper antimicrobial administration in human and veterinary medicine.

A survey of prevalence and phenotypic and genotypic assessment of antibiotic resistance in Staphylococcus aureus bacteria isolated from ready-to-eat food samples collected from Tehran Province, Iran

BACKGROUND

Resistant Staphylococcus aureus (S. aureus) bacteria are considered among the major causes of foodborne diseases. This survey aims to assess genotypic and phenotypic profiles of antibiotic resistance in S. aureus bacteria isolated from ready-to-eat food samples.

METHODS

According to the previously reported prevalence of S. aureus in ready-to-eat food samples, a total of 415 ready-to-eat food samples were collected from Tehran province, Iran. S. aureus bacteria were identified using culture and biochemical tests. Besides, the phenotypic antibiotic resistance profile was determined by disk diffusion. In addition, the genotypic pattern of antibiotic resistance was determined using the PCR.

RESULTS

A total of 64 out of 415 (15.42%) ready-to-eat food samples were contaminated with S. aureus. Grilled mushrooms and salad olivieh harbored the highest contamination rate of (30%), while salami samples harbored the lowest contamination rate of 3.33%. In addition, S. aureus bacteria harbored the highest prevalence of resistance to penicillin (85.93%), tetracycline (85.93%), gentamicin (73.43%), erythromycin (53.12%), trimethoprim-sulfamethoxazole (51.56%), and ciprofloxacin (50%). However, all isolates were resistant to at least four antibiotic agents. Accordingly, the prevalence of tetK (70.31%), blaZ (64.06%), aacA-D (57.81%), gyrA (50%), and ermA (39.06%) was higher than that of other detected antibiotic resistance genes. Besides, AacA-D + blaZ (48.43%), tetK + blaZ (46.87%), aacA-D + tetK (39.06%), aacA-D + gyrA (20.31%), and ermA + blaZ (20.31%) were the most frequently identified combined genotypic patterns of antibiotic resistance.

CONCLUSION

Ready-to-eat food samples may be sources of resistant S. aureus, which pose a hygienic threat in case of their consumption. However, further investigations are required to identify additional epidemiological features of S. aureus in ready-to-eat foods.

Comparison of PCR and phenotypic methods for the detection of methicillin resistant Staphylococcus aureus

Background and Objectives:

Resistance to methicillin in methicillin resistant strains of Staphylococcus aureus (MRSA) is due to the presence of mec-A gene, which encodes a low affinity penicillin binding protein (PBP)-2a or PBP2. Accurate and rapid identification of MRSA in clinical specimens is essential for timely decision on effective treatment. The aim of the study was to compare three different methods for detection of MRSA namely cefoxitin disc diffusion, CHROM agar MRSA and VITEK-2 susceptibility with PCR which is the gold standard reference method and to find the antibiotic susceptibility pattern of these isolates by VITEK-2.

Materials and Methods:

A Total of 100 non-duplicate S. aureus isolates were collected from different clinical samples among both outpatient and inpatients. Detection of MRSA among these isolates was done by cefoxitin disc diffusion, VITEK-2, CHROM agar MRSA and PCR.

Results:

The sensitivity and specificity of cefoxitin disc diffusion and Vitek was found to be 97.2% and 100%, while that of CHROM agar was found to be 100% and 78.6%. The overall prevalence of MRSA in our study by PCR was 72%.

Conclusion:

Based on the findings in our study, isolates which show cefoxitin zone diameter < 22 mm can be reported as MRSA. However, those isolates which have a zone diameter between 22–24 mm, should ideally be confirmed by PCR.

Antimicrobial Susceptibility Testing and Phenotypic Detection of MRSA Isolated from Diabetic Foot Infection

Background

Diabetic foot infection (DFI) is a common and costly complication of diabetes that may be caused by various bacteria with multi-resistant genes. The aim of this study is to evaluate the efficacy of phenotypic methods for identification of methicillin-resistant Staphylococcus aureus (MRSA) with genotypic detection of MRSA-related genes.

Methods

In this cross-sectional study, swab samples were collected from patients with DFI from hospitals in Sulaimani/Iraq in April–July 2019. All the samples were processed for microbiological assessment and further MRSA phenotypic and genotypic testing.

Results

A total of 46 swab samples were collected from diabetic foot ulcers of 29 males and 17 females. Most samples (93.5%) showed positive growth, with higher proportions of monomicrobial (23; 53.5%) than mixed-bacterial infections (20; 46.5%) and S. aureus as the predominant pathogen. Conventional methods of MRSA detection, such as cefoxitin disc diffusion, can predict methicillin resistance in 45.8% of the cases. Real-time/conventional PCR showed that 41.6% of Staphylococcus aureus were positive for the mecA gene, while none of the isolates was positive for PVL.

Conclusion

Staphylococcus aureus was the predominant pathogen in DFI. Although cefoxitin and oxacillin disc diffusion methods can help in the prediction of MRSA, real-time PCR is a reliable method for MRSA detection and confirmation.

Phenotypic and Genotypic Assessment of Antibiotic Resistance of Staphylococcus aureus Bacteria Isolated from Retail Meat

BACKGROUND

Resistant Staphylococcus aureus (S. aureus) bacteria are determined to be one of the main causes of foodborne diseases.

PURPOSE

This survey was done to assess the genotypic and phenotypic profiles of antibiotic resistance of S. aureus bacteria isolated from retail meat.

METHODS

Four-hundred and eighty-five retail meat samples were collected and examined. S. aureus bacteria were identified using culture and biochemical tests. The phenotypic profile of antibiotic resistance was examined using the disk diffusion method. The genotypic pattern of antibiotic resistance was determined using the polymerase chain reaction.

RESULTS

Forty-eight out of 485 (9.89%) raw retail meat samples were contaminated with S. aureus. Raw retail buffalo meat (16%) had the highest incidence of S. aureus, while raw camel meat (4%) had the lowest. S. aureus bacteria exhibited the uppermost incidence of resistance toward tetracycline (79.16%), penicillin (72.91%), gentamicin (60.41%), and doxycycline (41.666%). The incidence of resistance toward chloramphenicol (8.33%), levofloxacin (22.91%), rifampin (22.91%), and azithromycin (25%) was lower than other examined antibiotics. The most routinely detected antibiotic resistance genes were blaZ (58.33%), tetK (52.08%), aacA-D (33.33%), and ermA (27.08%). Cat1 (4.16%), rpoB (10.41%), msrA (12.50%), grlA (12.50%), linA (14.58%), and dfrA1 (16.66%) had the lower incidence rate.

CONCLUSION

Raw meat of animals may be sources of resistant S. aureus which pose a hygienic threat about the consumption of raw meat. Nevertheless, further investigations are essential to understand supplementary epidemiological features of S. aureus in retail meat.

Phenotypic and genotypic characterization of antibiotic resistance in the methicillin-resistant Staphylococcus aureus strains isolated from hospital cockroaches

Background

Cockroaches are one of the most important and frequent insects responsible for harboring, transmission and dissemination of human pathogens in the hospital environment. The present research was done to study the phenotypic and genotypic characterization of antibiotic resistance in the Methicillin-resistant Staphylococcus aureus strains isolated from hospital cockroaches.

Methods

Five-hundred and thirty Periplanets americana and Blattella germanica cockroaches were collected and their gut content and external washing samples were subjected to bacterial isolation. MRSA strains were subjected to disk diffusion and PCR amplification of antibiotic resistance genes.

Results

Prevalence of MRSA strains in P. americana and B. germanica cockroaches were 52.77 and 43.33%, respectively. External washing samples of P. americana cockroaches had the highest prevalence of MRSA strains (59.57%). MRSA isolates of external washing samples harbored the highest prevalence of resistance against penicillin (100%), ceftaroline (100%), tetracycline (100%), gentamicin (83.33%) and trimethoprim-sulfamethoxazole (80.55%). MRSA strains isolated from gut content samples harbored the highest prevalence of resistance against penicillin (100%), ceftaroline (100%), tetracycline (100%), trimethoprim-sulfamethoxazole (80%) and gentamicin (73.33%). BlaZ, aacA-D, tetK, msrA, dfrA, ermA, gyrA, grlA and rpoB were the most commonly detected antibiotic resistance genes amongst the MRSA strains.

Conclusions

The present investigation is the first report of the phenotypic and genotypic evaluation of antibiotic resistance in the MRSA strains isolated from P. americana and B. germanica hospital cockroaches. Hospital cockroaches are considered as a potential mechanical vector for MRSA strains.

Biofilm-Forming Clinical Staphylococcus Isolates Harbor Horizontal Transfer and Antibiotic Resistance Genes

Infections caused by staphylococci represent a medical concern, especially when related to biofilms located in implanted medical devices, such as prostheses and catheters. Unfortunately, their frequent resistance to high doses of antibiotics makes the treatment of these infections a difficult task. Moreover, biofilms represent a hot spot for horizontal gene transfer (HGT) by bacterial conjugation. In this work, 25 biofilm-forming clinical staphylococcal isolates were studied. We found that Staphylococcus epidermidis isolates showed a higher biofilm-forming capacity than Staphylococcus aureus isolates. Additionally, horizontal transfer and relaxase genes of two common staphylococcal plasmids, pSK41 and pT181, were detected in all isolates. In terms of antibiotic resistance genes, aac6-aph2a, ermC, and tetK genes, which confer resistance to gentamicin, erythromycin, and tetracycline, respectively, were the most prevalent. The horizontal transfer and antibiotic resistance genes harbored on these staphylococcal clinical strains isolated from biofilms located in implanted medical devices points to the potential risk of the development and dissemination of multiresistant bacteria.

A Meta-Analysis of the Global Prevalence Rates of Staphylococcus aureus and Methicillin-Resistant S. aureus Contamination of Different Raw Meat Products

Previous research has indicated that raw meats are frequently contaminated with Staphylococcus aureus, but data regarding the pooled prevalence rates of S. aureus and methicillin-resistant S. aureus (MRSA) contamination in different types of raw meat products (beef, chicken, and pork) and across different periods, regions, and purchase locations remain inconsistent. We systematically searched the PubMed, EMBASE, Ovid, Web of Science, and HighWire databases to identify studies published up to June 2016. The STROBE guidelines were used to assess the quality of the 39 studies included in this meta-analysis. We observed no significant differences in the pooled prevalence rates of S. aureus and MRSA contamination identified in various raw meat products, with overall pooled prevalence rates of 29.2% (95% confidence interval [CI], 22.8 to 35.9%) and 3.2% (95% CI, 1.8 to 4.9%) identified for the two contaminants, respectively. In the subgroup analyses, the prevalence of S. aureus contamination in chicken products was highest in Asian studies and significantly decreased over time worldwide. In European studies, the prevalence rates of S. aureus contamination in chicken and pork products were lower than those reported on other continents. The pooled prevalence rates of S. aureus contamination in chicken and pork products and MRSA contamination in beef and pork products were significantly higher in samples collected from retail sources than in samples collected from slaughterhouses and processing plants. These results highlight the need for good hygiene during transportation to and manipulation at retail outlets to reduce the risk of transmission of S. aureus and MRSA from meat products to humans.

Distribution of high-level mupirocin resistance among clinical MRSA

Mupirocin is a topical antibiotic for methicillin-resistant Staphylococcus aureus (MRSA) decolonization in hospital settings and nursing homes and is used as a highly effective antibiotic against MRSA. In this study, we aimed to evaluate the frequency of high-level mupirocin-resistant (HLMR) strains among the MRSA subtypes. A total of 188 clinical MRSA isolates were collected from 2011 to 2014, and their susceptibility to antimicrobial agents and vancomycin resistance was evaluated using disc diffusion method and micro-dilution method, respectively. Furthermore, the presence of mecA, SSCmec, mupA and mupB was assessed by PCR. All isolates were multi-drug resistant (MDR) but 2 strains (1.06%) were resistant to mupirocin. Minimum inhibitory concentration (MIC) of vancomycin for 8 strains (4.7%) was higher than 2 μg/ml. Of 188 isolates, 188 (100%), 64 (34.04%), 8 (4.3%), 150 (79.8%), 26 (13.8%), 2 (1.06) and 2 (1.06%) isolates possessed mecA, SCCmec types I, II, III, IV, mupA and mupB genes, respectively. Our data showed that despite infection control policy enforced by health care committee, the rate of mupirocin resistance among MRSA strains is continuously rising.

Hemoculture and Direct Sputum Detection of mecA-Mediated Methicillin-Resistant Staphylococcus aureus by Loop-Mediated Isothermal Amplification in Combination With a Lateral-Flow Dipstick

This study reports loop-mediated isothermal amplification (LAMP) for rapid detection of methicillin-resistant Staphylococcus aureus from direct clinical specimens. Four primers including outer and inner primers were specifically designed on the two target sequences-femB to identify S. aureus and mecA to identify antibiotic-resistant gene. Reference strains including various species of gram-positive/gram-negative isolates were used to evaluate and optimize LAMP assays. The optimum LAMP condition was found at 63°C within 70 min assay time (include hybridization with FITC probe for 5 min and further 5 min for reading the results on the lateral flow dipstick). The detection limits of LAMP for mecA was 10 pg of total DNA or 100 CFU/ml. The LAMP assays were applied to a total of 155 samples of direct DNA extraction from sputum and hemoculture bottles. The sensitivity of LAMP for mecA detection in sputum and hemoculture bottles was 93.3% (28/30) and 100% (52/52), respectively. In conclusion, LAMP assay is an alternative technique for rapid detection of MRSA infection with a technical simplicity and cost-effective method in a routine diagnostic laboratory.

Identification and antimicrobial resistance prevalence of pathogenic Escherichia coli strains from treated wastewater effluents in Eastern Cape, South Africa

Antimicrobial resistance (AMR) is a global problem impeding the effective prevention/treatment of an ever-growing array of infections caused by pathogens; a huge challenge threatening the achievements of modern medicine. In this paper, we report the occurrence of multidrug resistance (MDR) in Escherichia coli strains isolated from discharged final effluents of two wastewater treatment facilities in the Eastern Cape Province of South Africa. Standard disk diffusion method was employed to determine the antibiotic susceptibility profile of 223 polymerase chain reaction (PCR)-confirmed E. coli isolates against 17 common antibiotics in human therapy and veterinary medicine. Seven virulence associated and fourteen antibiotic resistance genes were also evaluated by molecular methods. Molecular characterization revealed five pathotypes of E. coli in the following proportions: enterotoxigenic ETEC (1.4%), enteropathogenic EPEC (7.6%), enteroaggregative EAEC (7.6%), neonatal meningitis (NMEC) (14.8%), uropathogenic (41.7%), and others (26.9%). Isolates showed varying (1.7-70.6%) degrees of resistance to 15 of the test antibiotics. Multidrug resistance was exhibited by 32.7% of the isolates, with the commonest multiple antibiotic-resistant phenotype (MARP) being AP-T-CFX (12 isolates), while multiple antibiotic-resistant indices (MARI) estimated are 0.23 (Site 1) and 0.24 (Site 2). Associated antibiotic resistance genes detected in the isolates include: strA (88.2%), aadA (52.9%), cat I (15%), cmlA1 (4.6%), blaTEM (56.4%), tetA (30.4%), tetB (28.4%), tetC (42.2%), tetD (50%), tetK (11.8%), and tetM (68.6%). We conclude that municipal wastewater effluents are important reservoirs for the dissemination of potentially pathogenic E. coli (and possibly other pathogens) and antibiotic resistance genes in the aquatic milieu of the Eastern Cape and a risk to public health.

Antimicrobial resistance determinants of Escherichia coli isolates recovered from some rivers in Osun State, South-Western Nigeria: Implications for public health

The inevitable development of resistance has sunk the great success achieved in the discovery of antimicrobial agents and dashed the hope of man in the recovery from infections and illnesses, as diseases and disease agents that were once thought to be controlled by antimicrobials are now re-emerging in new leagues resistance to therapy. A total of 300 PCR confirmed Escherichia coli isolates recovered from different river sources in Osun State, Nigeria were evaluated for their antibiogram profiling by the disc diffusion method and the resistant isolates were further profiled for their genotypic antimicrobial resistance determinants by polymerase chain reaction assays. Among the 20 antimicrobials selected from 10 families, resistance among sulfonamides, β-lactams and tetracyclines were found to be most frequent than phenicols and aminoglycosides with a noticeable increase in the number of multi-drug resistance ranging from three to nine antimicrobials. A total of 19 resistance determinants were assessed with their prevalence and distributions obtained as follows; [sulfonamides sulI (8%), sulII (41%)], [β-lactams; ampC 22%; blaTEM, (21%), and blaZ (18%),], [tetracyclines tetA (24%), tetB (23%), tetC (18%), tetD (78%), tetK (15%), and tetM, (10%)], [phenicols; catI (37%), catII (28%), and cmIA1 (19%)] and [aminoglycosides; aacC2 (8%), aphA1 (80%), aphA2 (80%), aadA (79%) and strA (38%)]. The Pearson chi-square exact test revealed many strong significant associations among ampC, blaTEM, blaZ and tetA genes with some determinants screened. The findings signify high increase in the prevalence of multidrug resistant E. coli isolates and resistance determinants indicating increased public health risks associated with the ingestion of waters from untreated sources. Hence, a necessity for safe water supply, provision of proper sanitation facilities and good surveillance programmes to monitor antimicrobial resistance patterns in water bodies.

The distribution of pathogenic and toxigenic genes among MRSA and MSSA clinical isolates

Staphylococcus aureus (S. aureus) is considered as a notorious nosocomial pathogen among hospitalized patients and community-dwelling subjects. Its increasing morbidity and mortality is believed to be due to antibiotic resistance. However, the data concerning molecular properties of infecting strains are few. In this study, a total of 192 S. aureus strains, including 88 (45.8%) meticillin-sensitive S. aureus (MSSA) and 104 (54.2%) meticillin-resistant S. aureus (MRSA) were recovered from clinical samples. The prevalence of subtypes containing staphylococcal cassette chromosome mec (SSCmec), staphylococcal enterotoxins (SEs), toxic shock syndrome toxin (TSST) and exfoliative toxin was assessed by PCR. Antibiotic susceptibility pattern and vancomycin resistance of each isolate were evaluated by disk diffusion method and micro-dilution method, respectively. 9 (2.3%) strains required MIC > 2 mg/l of vancomycin, which significantly increased among multi drug resistant (MDR), MRSA and SCCmec type III strains (p < 0.05). 171 (89%), 140 (72.91%), 7 (3.6), 78 (48.6%), 5 (2.6%), 151 (78.64%), 129 (67.18%), 178 (92.7%) and 15 (7.8%) of 192 isolates harbored mecA, entA, entB, entC, entD, entE, eta, etb and tsst-1 genes, respectively. 31 (16.14%), 5 (2.6%), 95 (49.48%) and 7 (3.64%) of 192 isolates carried SCCmec type I, II, III and IV, respectively. We found a significantly higher rate of MRSA and resistance to all tested antibiotics, except to penicillin G, kanamycin and linezolide among the SCCmec type III class (p < 0.05). According to our findings, MSSA isolates should be taken as seriously as MRSA strains due to the potential presence of broad spectrum virulence factor genes.

Impairments of mecA gene detection in bovine Staphylococcus spp

Staphylococcus aureus antimicrobial resistance, especially to beta-lactams, favors treatment failures and its persistence in herd environment. This work aimed to develop a more specific primer for mecA gene detection based on the comparison of the conserved regions from distinct host origins and also investigated the presence of homologue mecA(LGA251) in bovine strains. A total of 43 Staphylococcus spp. were included in this study, comprising 38 bovine S. aureus, two human and three equine coagulase-negative staphylococci (CNS). Phenotypical methicillin-resistance detection was performed through oxacillin agar-screening and cefoxitin disk-diffusion test. None isolate tested positive for mecA(LGA251) gene. For mecA gene PCR, new primers were designed based on the sequences of human S. aureus (HE681097) and bovine S. sciuri (AY820253) mecA. The new primers based on the S. aureus mecA sequence amplified fragments of human and equine CNS and the ones based on S. sciuri mecA sequence only yielded fragments for S. aureus bovine strains. Multiples alignments of mecA gene sequences from bovine, human and equine revealed punctual but significant differences in bovine strains that can lead to the mecA gene detection impairment. The observed divergences of mecA gene sequences are not a matter of animal or human origin, it is a specificity of bovine samples.

Genotyping of methicillin-resistant Staphylococcus aureus in the Sultan Qaboos University Hospital, Oman reveals the dominance of Panton-Valentine leucocidin-negative ST6-IV/t304 clone

The objective of this study was to determine the prevalence and distribution of methicillin-resistant Staphylococcus aureus (MRSA) genotypes circulating at a tertiary hospital in the Sultanate of Oman. A total of 79 MRSA isolates were obtained from different clinical samples and investigated using antibiogram, pulsed-field gel electrophoresis (PFGE), staphylococcal chromosome cassette mec (SCCmec), Spa typing and multilocus sequence typing (MLST). The isolates were susceptible to linezolid, vancomycin, teicoplanin, tigecycline and mupirocin but were resistant to tetracycline (30.4%), erythromycin (26.6%), clindamycin (24.1%), trimethoprim (19.0%), ciprofloxacin (17.7%), fusidic acid (15.2%) and gentamicin (12.7%). Molecular typing revealed 19 PFGE patterns, 26 Spa types and 21 sequence types. SCCmec-IV (86.0%) was the dominant SCCmec type, followed by SCCmec-V (10.1%). SCCmec-III (2.5%) and SCCmec-II (1.3%) were less common. ST6-IV/t304 (n = 30) and ST1295-IV/t690 (n = 12) were the dominant genotypes followed by ST772-V/t657 (n = 5), ST30-IV/t019/t021 (n = 5), ST22-IV/t852 (n = 4), ST80-IV/t044 (n = 3) and 18 single genotypes that were isolated sporadically. On the basis of SCCmec typing and MLST, 91.2% of the isolates were classified as community-associated MRSA and 8.8% of the isolates (consisting of four ST22-IV/t852, one ST239-III/t632, one ST5-III/t311 and one ST5-II/t003) were classified as healthcare-associated MRSA. The study has revealed the dominance of a Panton–Valentine leucocidin-negative ST6-IV/t304 clone and provided insights into the distribution of antibiotic resistance in MRSA at the tertiary hospital in Oman. It also highlights the importance of surveillance in detecting the emergence of new MRSA clones in a healthcare facility.

Antimicrobial resistance and characterisation of staphylococci isolated from healthy Labrador retrievers in the United Kingdom

BACKGROUND

Coagulase-positive (CoPS) and coagulase-negative (CoNS) staphylococci are normal commensals of the skin and mucosa, but are also opportunist pathogens. Meticillin-resistant (MR) and multidrug-resistant (MDR) isolates are increasing in human and veterinary healthcare. Healthy humans and other animals harbour a variety of staphylococci, including MR-CoPS and MR-CoNS. The main aims of the study were to characterise the population and antimicrobial resistance profiles of staphylococci from healthy non-vet visiting and non-antimicrobial treated Labrador retrievers in the UK.

RESULTS

Nasal and perineal samples were collected from 73 Labrador retrievers; staphylococci isolated and identified using phenotypic and biochemical methods. They were also confirmed by matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF-MS), PCR of the nuc gene and PCR and sequencing of the tuf gene. Disc diffusion and minimum inhibitory concentration (MIC) susceptibility tests were determined for a range of antimicrobials. In total, 102 CoPS (S. pseudintermedius n = 91, S. aureus n = 11) and 334 CoNS isolates were detected from 99% of dogs in this study. In 52% of dogs CoNS only were detected, with both CoNS and CoPS detected in 43% dogs and CoPS only detected in 4% of dogs. Antimicrobial resistance was not common among CoPS, but at least one MDR-CoNS isolate was detected in 34% of dogs. MR-CoNS were detected from 42% of dogs but no MR-CoPS were isolated. S. epidermidis (52% of dogs) was the most common CoNS found followed by S. warneri (30%) and S. equorum (27%), with another 15 CoNS species isolated from ≤ 15% of dogs. S. pseudintermedius and S. aureus were detected in 44% and 8% of dogs respectively.

CONCLUSIONS

MR- and MDR-CoPS were rare. However a high prevalence of MR- and MDR-CoNS were found in these dogs, even though they had no prior antimicrobial treatment or admission to veterinary premises. These findings are of concern due to the potential for opportunistic infections, zoonotic transmission and transmission of antimicrobial resistant determinants from these bacteria to coagulase positive staphylococci.

Methicillin-resistant Staphylococcus aureus in the western region of Saudi Arabia: prevalence and antibiotic susceptibility pattern

BACKGROUND AND OBJECTIVES

Methicillin-resistant Staphylococcus aureus (MRSA) emerged in 1960 and was a problem confined largely to the healthcare setting, or hospital-associated MRSA (HA-MRSA). In the 1990s, community-associated MRSA (CA-MRSA) infections appeared. In Saudi Arabia, the prevalence of MRSA has increased in the past ten years and severe community-acquired infection has been reported. Our objective was to investigate the prevalence of MRSA and their antibiotic susceptibilities in the western region of Saudi Arabia.

DESIGN AND SETTING

A retrospective review of the medical records of 186 S aureus infected patients diagnosed from November 2009 through October 2010.

METHODS

S aureus was Identified based on Gram stain, catalase and coagulase tests. Susceptibility testing was performed using antibiotic discs and the VITEK 2 system.

RESULTS

MRSA was isolated in 39.5% of the specimens. The isolates were commonly associated with wound, skin, and soft tissue infections (87.3%). The prevalence of MRSA was highest among patients who were 56 years old or older (52.2%). CA-MRSA infections represented 31.5% of community S aureus infections, while HA-MRSA accounted 52.6% of hospital S aureus (P=.0029). All MRSA isolates in our study were susceptible to vancomycin, linozolid and teicoplanin. However, multi-resistance was observed in 29.1% of the isolates and was significantly higher among HA-MRSA (P=.03).

CONCLUSIONS

The prevalence of MRSA was 39.5%, and infection was commonly associated with wound, skin, and soft tissue infections. MRSA was more prevalent in hospitals and among older patients. All MRSA susceptible to vancomycin, linozolid and teicoplanin.

Incidence and characterization of Staphylococcus aureus in fishery products marketed in Galicia (Northwest Spain)

A total of 298 fishery products purchased from retail outlets in Galicia (NW Spain) between January 2008 and May 2009 were analyzed for the presence of Staphylococcus aureus. S. aureus was detected in a significant proportion of products (~25%). Incidence was highest in fresh (43%) and frozen products (30%), but it was high in all other categories: salted fish (27%), smoked fish (26%), ready-to-cook products (25%), non-frozen surimis (20%), fish roes (17%) and other ready-to-eat products (10%). A significant proportion of smoked fish, surimis, fish roes and other ready-to-eat products did not comply with legal limits in force. RAPD-PCR of 125 S. aureus isolated from fishery products was carried out using three primers (AP-7, ERIC-2 and S). Isolates displayed 33 fingerprint patterns. Each pattern was attributed to a single bacterial clone. Cluster analysis based on similarity values between RAPD fingerprints did not find relationship between any RAPD pattern and any product category. Isolates were also tested for se genes and susceptibility to a range of antibiotics (cephalothin, clindamycin, chloramphenicol, erythromycin, gentamicin, oxacillin, penicillin G, tetracycline, vancomycin, methicillin, ciprofloxacin and trimethoprim-sulfamethoxazole). Most isolates (88%) were found to be sea positive. Putative enterotoxigenic strains counts reached high risk levels in 17 products. No relationship was found between the presence of se genes and RAPD patterns. All isolates were resistant to penicillin, chloramphenicol and ciprofloxacin, and most to tetracycline (82.4%), but none was methicillin-resistant. A revision of pre-requisite programs leading to improve hygienic practices in handling and processing operations from fishing or farming to retail is recommended to ensure fishery products safety.

Comparison of real-time PCR with disk diffusion, agar screen and E-test methods for detection of methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is a nosocomial pathogen. Our main objective was to compare oxacillin disk test, oxacillin E-test, and oxacillin agar screen for detection of methicillin resistance in S. aureus, using real-time PCR for mecA as the "gold standard" comparison assay. 196 S. aureus isolates were identified out of 284 Staphylococcus isolates. These isolates were screened for MRSA with several methods: disk diffusion, agar screen (6.0 μg/ml), oxacillin E-test, and real-time PCR for detection of mecA gene. Of the 196 S. aureus isolates tested, 96 isolates (49%) were mecA-positive and 100 isolates (51%) mecA-negative. All methods tested had a statistically significant agreement with real-time PCR. E-test was 100% sensitive and specific for mecA presence. The sensitivity and specificity of oxacillin agar screen method were 98 and 99%, respectively and sensitivity and specificity of oxacillin disk diffusion method were 95 and 93%, respectively. In the present study, oxacillin E-test is proposed as the best phenotypic method. For economic reasons, the oxacillin agar screen method (6.0 μg/ml), which is suitable for the detection of MRSA, is recommended due to its accuracy and low cost.

Evaluation of different methods for detecting methicillin resistance in Staphylococcus aureus isolates in a university hospital located in the Northeast of Brazil

Many methods have been described for the detection of methicillin-resistant Staphylococcus aureus (MRSA), but the heterogeneous expression of methicillin resistance affects the reliability of these methods. The aim of the present study was to evaluate some methods for detecting methicillin resistance in Staphylococcus aureus isolates in a university hospital located in the Northeast of Brazil. Among the isolates, 15 were methicillin-susceptible and 45 were methicillin-resistant, including low-level heterogeneous resistance strains. Both the 30 ηg-cefoxitin disk and PBP2a test had 100% sensibility/specificity and appear to be good options for the detection of MRSA in the clinical laboratory.

Current diagnostic tools for methicillin-resistant Staphylococcus aureus infections

Methicillin-resistant Staphylococcus aureus (MRSA) is a common pathogen responsible for a wide spectrum of healthcare-associated and community-acquired infections. Infections with MRSA strains that are resistant to beta-lactams and other types of antibiotics are a serious therapeutic problem - first, because in such cases only a limited spectrum of antibiotics can be used; and second, because such infections require prolonged hospitalization and result in economic losses. Therefore, in order to limit the overspread of pathogens, the development of diagnostic tools enabling rapid identification of carriers and infected patients, as well as proper identification of drug-resistance mechanisms to enable development of more targeted clinical treatment, are vital. This article reviews the current knowledge concerning prospective diagnostics of MRSA infections.

Evaluation of Clinical Laboratory Standards Institute interpretive criteria for methicillin-resistant Staphylococcus pseudintermedius isolated from dogs

The Clinical and Laboratory Standards Institute published in 2008 new interpretive criteria for the identification of methicillin resistance in staphylococci isolated from animals. The sensitivity of the 2008 interpretive criteria for mecA gene-positive Staphylococcus pseudintermedius, compared with the previous criteria of 2004, was investigated. Thirty clinical isolates of methicillin-resistant S. pseudintermedius from dogs were used. The presence of the mecA gene was determined by polymerase chain reaction. The minimum inhibitory concentration for oxacillin was determined by broth microdilution. The 2008 breakpoint of >or=4 microg/ml for methicillin resistance resulted in a diagnostic sensitivity of 73.3% (22/30). The 2004 breakpoint guideline of >or=0.5 microg/ml resulted in a diagnostic sensitivity of 97% (29/30). For oxacillin disk diffusion, the 2008 interpretive criterion of <or=10 mm for methicillin resistance resulted in a sensitivity of 70% (21/30). If intermediate isolates (11 or 12 mm) were considered resistant, the sensitivity was 93% (28/30). If intermediate isolates (11 or 12 mm) were considered resistant, the sensitivity was 93% (28/30). Application of the 2004 interpretive criterion of <or=17 mm resulted in a diagnostic sensitivity of 100% (30/30). For cefoxitin disk diffusion, the interpretive criterion of <or=21 mm for methicillin resistance (as used for Staphylococcus aureus) resulted in a diagnostic sensitivity of 6.7% (2/30). The interpretive criterion of <or=24 mm (as used for coagulase-negative staphylococci) resulted in a diagnostic sensitivity of 43.3% (13/30). With the use of 2008 interpretive criteria, all 3 tests produced what we consider to be an unacceptable level of false negative results. Our findings also suggest that cefoxitin disk diffusion is an inappropriate screening test for methicillin resistance of canine S. pseudintermedius.