Correlation of phenotypic tests with the presence of the blaZ gene for detection of beta-lactamase

Discrepancies between phenotypic and genotypic identification methods of antibiotic resistant genes harboring Staphylococcusaureus

Antimicrobial resistance is a global issue that limits therapeutic options for infections. S. aureus being a member of the ESKAPE group is capable of "escaping" the biocidal action of antimicrobial agents. There are phenotypic and genotypic methods used for the identification of antibiotic resistant genes harboring S. aureus but these methods do not always show concordant results. To address these discrepancies, a total of 335 equine nasal swab samples from four districts of Punjab were collected using a convenient sampling technique. These samples were first subjected to common microbial techniques to identify S. aureus. The disc diffusion assay was performed for the phenotypic identification of antibiotic resistant S. aureus by using discs of oxacillin, penicillin, vancomycin, gentamycin, and tetracycline. After this, PCR was performed by targeting mecA, blaZ, vanB, aaca-aphd, and tetK genes for genotypic identification of respective antibiotic-resistant S. aureus. Phenotypic discrepancies (number of antibiotic resistant isolates found from disc diffusion who appeared to be negative for the resistant gene), and genotypic discrepancies (number of antibiotic sensitive isolates found from disc diffusion who appeared to be positive for the resistant gene) were calculated. The discrepancy ratio for mecA, blaZ, vanB, aaca-aphd, and tetK genes were 3.09, 1.96, 2.67, 1.93, and 1.67 respectively. These discrepant results indicate that the absence or presence of only one gene is not a true marker of resistant or sensitive isolates. There are multiple resistance determinants and resistance mechanisms. This study also highlighted the phenomenon of silencing of antibiotic resistance determinants.

Antimicrobial susceptibility of staphylococci from bovine milk samples in routine microbiological mastitis analysis in Finland

The most frequent reason for antimicrobial use in dairy herds is mastitis and knowledge about mastitis-causing pathogens and their antimicrobial susceptibility should guide treatment decisions. The overall objective of this study was to assess antimicrobial resistance (AMR) of staphylococci in mastitic milk samples in Finland. MALDI-ToF MS identified a total of 504 Staphylococcus isolates (260 S. aureus and 244 non-aureus staphylococci, NAS) originating from bovine mastitic milk samples. Phenotypic susceptibility against cefoxitin, ceftiofur, enrofloxacin, gentamycin, oxacillin, penicillin, and tetracycline was evaluated by disk diffusion method and the presence of blaZ, mecA, and mecC genes investigated by PCR. Nitrocefin test assessed these isolates' beta-lactamase production. The most common NAS species were S. simulans, S. epidermidis, S. chromogenes, and S. haemolyticus. In total, 26.6% of the isolates (18.5% of S. aureus and 35.2% of all NAS) carried the blaZ gene. Penicillin resistance, based on disk diffusion, was lower: 18.8% of all the isolates (9.3% of S. aureus and 28.9% of all NAS) were resistant. Based on the nitrocefin test, 21.5% of the isolates produced beta-lactamase (11.6% of S. aureus and 32.0% of all NAS). Between the Staphylococcus species, the proportion of penicillin-resistant isolates varied, being lowest in S. simulans and highest in S. epidermidis. Resistance to antimicrobials other than penicillin was rare. Of the eight NAS isolates carrying the mecA gene, six were S. epidermidis. One S. aureus isolate carried the mecC gene. Agreement beyond chance, assessed by kappa coefficient, between phenotypic and genotypic resistance tests, was moderate to substantial. Some phenotypically penicillin-susceptible staphylococci carried the blaZ gene but isolates without blaZ or mec genes rarely exhibited resistance, suggesting that the more reliable treatment choice may depend upon genotypic AMR testing. Our results support earlier findings that penicillin resistance is the only significant form of antimicrobial resistance among mastitis-causing staphylococci in Finland.

Staphylococcal Resistance Patterns, blaZ and SCCmec Cassette Genes in the Nasopharyngeal Microbiota of Pregnant Women

Antimicrobial resistance in Staphylococcus spp. colonising the nasopharynx can create risk factors of therapeutic treatment failure or prophylaxis in pregnant women. Resistance is mostly encoded on plasmids (e.g., blaZ gene for penicillinase synthesis) or chromosomes (e.g., mecA and mecC for methicillin resistance). The mecA gene is part of the chromosomal mec gene cassette (SCCmec), which is also located on the plasmid. The disc diffusion method for the selected drugs (beta-lactams, fluoroquinolones, streptogramins, aminoglicosides, macrolides, oxasolidinones, tetracyclines and other groups) was used. PCR for blaZ, mecA and mecC genes and SCCmec cassette detection and typing were performed. S. aureus (54.4%) and S. epidermidis (27.9%) were the most prevalent and showed the highest diversity of resistance profiles. The blaZ, mecA and mecC genes were reported in 95.6%, 20.6% and 1.5% of isolates, respectively. The highest resistance was found to beta-lactams, commonly used during pregnancy. Resistance to a variety of antimicrobials, including benzylpenicillin resistance in blaZ-positive isolates, and the existence of a very high diversity of SCCmec cassette structures in all staphylococci selected from the nasopharyngeal microbiota of pregnant women were observed for the first time. Knowledge of the prevalence of antimicrobial-resistant staphylococci in the nasopharynx of pregnant women may be important for the appropriate treatment or prophylaxis of this group of patients.

The Characterization and Beta-Lactam Resistance of Staphylococcal Community Recovered from Raw Bovine Milk

Staphylococci is an opportunistic bacterial population that is permanent in the normal flora of milk and poses a serious threat to animal and human health with some virulence factors and antibiotic-resistance genes. This study was aimed at identifying staphylococcal species isolated from raw milk and to determine hemolysis, biofilm, coagulase activities, and beta-lactam resistance. The raw milk samples were collected from the Düzce (Türkiye) region, and the study data represent a first for this region. The characterization of the bacteria was performed with MALDI-TOF MS and 16S rRNA sequence analysis. The presence of coa, icaB, blaZ, and mecA was investigated with PCR. A nitrocefin chromogenic assay was used for beta-lactamase screening. In this context, 84 staphylococci were isolated from 10 different species, and the dominant species was determined as S. aureus (32.14%). Although 32.14% of all staphylococci were positive for beta hemolysis, the icaB gene was found in 57.14%, coa in 46.42%, mecA in 15.47%, and blaZ in 8.33%. As a result, Staphylococcus spp. strains that were isolated from raw milk in this study contained some virulence factors at a high level, but also contained a relatively low level of beta-lactam resistance genes. However, considering the animal–environment–human interaction, it is considered that the current situation must be monitored constantly in terms of resistance concerns. It must not be forgotten that the development of resistance is in constant change among bacteria.

Analysis of Whole-Genome Sequences of Pathogenic Gram-Positive and Gram-Negative Isolates from the Same Hospital Environment to Investigate Common Evolutionary Trends Associated with Horizontal Gene Exchange, Mutations and DNA Methylation Patterning

Hospital-acquired infections are a generally recognized problem for healthcare professionals. Clinical variants of Gram-negative and Gram-positive pathogens are characterized with enhanced antibiotic resistance and virulence due to mutations and the horizontal acquisition of respective genetic determinants. In this study, two Escherichia coli, two Klebsiella pneumoniae, three Pseudomonas aeruginosa, two Staphylococcus aureus, one Staphylococcus epidermidis and one Streptococcus pneumoniae showing broad spectra of antibiotic resistance were isolated from patients suffering from nosocomial infections in a local hospital in Almaty, Kazakhstan. The aim of the study was to compare general and species-specific pathways of the development of virulence and antibiotic resistance through opportunistic pathogens causing hospital-acquired infections. The whole-genome PacBio sequencing of the isolates allowed for the genotyping and identification of antibiotic resistance and virulence genetic determinants located in the chromosomes, plasmids and genomic islands. It was concluded that long-read sequencing is a useful tool for monitoring the epidemiological situation in hospitals. Marker antibiotic resistance mutations common for different microorganisms were identified, which were acquired due to antibiotic-selective pressure in the same clinical environment. The genotyping and identification of strain-specific DNA methylation motifs were found to be promising in estimating the risks associated with hospital infection outbreaks and monitoring the distribution and evolution of nosocomial pathogens.

Risk Factors for Antimicrobial Resistance of Staphylococcus Species Isolated from Dogs with Superficial Pyoderma and Their Owners

The microbial communities on the skin of dogs include several species of bacteria, which contribute to skin health and disease. Staphylococcus pseudintermedius, cultured at high frequency from the skin of dogs, is an opportunistic pathogen causing superficial pyoderma. Effective treatment against S. pseudintermedius infections is an important issue in veterinary medicine. However, multiple antibiotic-resistant mechanisms gradually developed by bacteria make treatment more challenging nowadays. Drug-resistant genes may have the chance to be transferred from infected dogs to other staphylococci in humans. The objective of this survey is to investigate the bacterial species that cause canine superficial pyoderma and characterize the antibiotic-resistant profiles and drug-resistant genes of isolated S. pseudintermedius. In addition, the possible risk factors causing S. pseudintermedius colonizing owners were also evaluated by a questionnaire survey. Sixty-five bacteria were isolated from dogs with superficial pyoderma, which included 47 S. pseudintermedius (72.3%), 12 other staphylococci (18.5%), 4 other Gram-positive bacteria (6.2%) and 2 Gram-negative bacteria (3.1%). Strains containing mecA and blaZ genes showed multiple-drug resistance characteristics. Dogs that received antimicrobial treatment within a recent month were at significantly higher risk of MRSP infections. Only five S. pseudintermedius strains (8.33%) were isolated from 60 samples of owners. Risk factor analysis indicated there was no significant association between S. pseudintermedius isolated from dogs and owners, but the “Keeping three or more dogs” and “Dogs can lick the owner’s face” have high odds ratios of 3.503 and 5.712, respectively. MRSP isolates belonged to three different dru types, including dt11y (29.41%), dt11a (47.06%) and dt10cp (23.53%). In conclusion, the major pathogen of canine superficial pyoderma is found to be S. pseudintermedius in Taiwan, and isolates which are mecA- or blaZ-positive are generally more resistant to commonly used antibiotics. Although S. pseudintermedius isolated from the owners might be transferred from their dogs, definite risk factors should be examined in the future study.

Impact of polymorphisms in blaZ, blaR1 and blaI genes and their relationship with β-lactam resistance in S. aureus strains isolated from bovine mastitis

There is not a consensus between the presence of the genotypic resistance marker gene and the phenotypic resistance to β-lactams in Staphylococcus aureus, which means, positive S. aureus blaZ isolates demonstrating sensitivity to β-lactams. The present study aimed to characterize the blaZ, blaR1 and blaI genes, identify and evaluate single nucleotide polymorphisms (SNPs) and their relationship with β-lactam resistance in samples of Staphylococcus aureus obtained from cases of bovine mastitis. Five isolates (two resistant and three sensitive to oxacillin) of Staphylococcus aureus with detected production of beta-lactamase, previously evaluated as containing the blaZ gene and negative for the mecA and mecC genes, had the bla operon completely sequenced. Impacts on the protein sequence due to the detected polymorphisms were evaluated by modeling the proteins encoded by the blaZ, blaR1 and blaI genes using a three-dimensional model structure obtained from the Protein Data Bank (PDB) database. Fifteen SNPs were detected in the blaZ gene, 30 in the blaR1 gene and three in the blaI gene. These SNPs caused alterations in amino acid sites. Deleterious mutations were detected in the blaZ gene (E146G, P218S, Y221C) and the blaR1 gene (K481E). Molecular docking analysis revealed that polymorphisms in the blaZ gene may explain the phenotypic sensitivity in isolates that contain the resistance marker gene. Although sensitive and resistant isolates encode beta-lactamase, these proteins are functionally altered due to a change in the binding site with the antibiotic.

Characteristics of Staphylococcus aureus small colony variants isolated from wound specimen of a tertiary care hospital in China

BACKGROUND

Small colony variants (SCVs) of Staphylococcus aureus (S. aureus) frequently lead to chronic and recurrent infections, but they are always ignored and there are few researches on their clinical isolates. We intended to investigate the prevalence and characteristics of S. aureus SCVs.

METHODS

None-duplicated S. aureus strains isolated from wound samples were collected from January 2018 to December 2020. The characteristics (i.e. colony morphology, growth rate, coagulase, biofilm formation, and pathogenic characteristics), antimicrobial susceptibilities, and resistance mechanisms of SCVs were also investigated. The genetic background of SCVs was analyzed through staphylococcal protein A (SPA) typing, sequence typing, and pulse field gel electrophoresis (PFGE).

RESULTS

Three SCVs were screened from 278 S. aureus strains (1.1%). They formed pinpoint white colonies on blood agar plates with weak hemolysis. The reproduction speed in liquid medium was very slow for SCVs strains. The coagulase weakened or disappeared, and the ability to form biofilm varied greatly. Only slight inflammation was triggered when wound infected. The SPA typing was t2592, t233, and t023, and the sequence typing was ST88, ST239, and ST965, respectively. The PFGE revealed three SCVs were singletons.

CONCLUSIONS

The rate of SCVs in wound sample is low in our hospital, and the formation is associated with the usage of antimicrobial. SCVs grow slowly, and their colony morphology and biochemical characteristics are significantly different from classic S. aureus. SCVs may cause chronic infection and weak inflammation. SCVs form in resistant or susceptible strains, and there is no clonal epidemic in this hospital.

Virulence Factors in Staphylococcus Associated with Small Ruminant Mastitis: Biofilm Production and Antimicrobial Resistance Genes

Small ruminant mastitis is a serious problem, mainly caused by Staphylococcus spp. Different virulence factors affect mastitis pathogenesis. The aim of this study was to investigate virulence factors genes for biofilm production and antimicrobial resistance to β-lactams and tetracyclines in 137 staphylococcal isolates from goats (86) and sheep (51). The presence of coa, nuc, bap, icaA, icaD, blaZ, mecA, mecC, tetK, and tetM genes was investigated. The nuc gene was detected in all S. aureus isolates and in some coagulase-negative staphylococci (CNS). None of the S. aureus isolates carried the bap gene, while 8 out of 18 CNS harbored this gene. The icaA gene was detected in S. aureus and S. warneri, while icaD only in S. aureus. None of the isolates carrying the bap gene harbored the ica genes. None of the biofilm-associated genes were detected in 14 isolates (six S. aureus and eight CNS). An association was found between Staphylococcus species and resistance to some antibiotics and between antimicrobial resistance and animal species. Nine penicillin-susceptible isolates exhibited the blaZ gene, questioning the reliability of susceptibility testing. Most S. aureus isolates were susceptible to tetracycline, and no cefazolin or gentamycin resistance was detected. These should replace other currently used antimicrobials.

Performance of penicillinase detection tests in Staphylococcus epidermidis: comparison of different phenotypic methods

Background

Staphylococcus epidermidis is the leading coagulase negative staphylococci (CoNS) species associated with healthcare associated infections. In order to de-escalate antimicrobial therapy, isolates of S. epidermidis lacking the blaZ gene should be eligible for targeted antimicrobial therapy. However, testing the susceptibility of coagulase negative staphylococci (CoNS) to penicillin G is no longer recommended by EUCAST, given the low performances for penicillinase detection in CoNS. The objective of this work was to determine a phenotypic method with high performance for detecting penicillinase production in S. epidermidis.

Results

Four techniques for the detection of penicillinase production (disk diffusion, zone edge test, nitrocefin test, Minimal Inhibitory Concentration (MIC) by automated system Vitek2®) were evaluated on 182 S. epidermidis isolates, using identification of blaZ gene by PCR as the reference method. The performance of the methods for penicillinase detection was compared by the sensitivity, the specificity, the negative predictive value and the positive predictive value, and with Cohen’s kappa statistical test. Among the 182 S. epidermidis included in this study, 55 carried the blaZ gene. The nitrocefin test, characterized by a poor sensitivity (91%), was therefore excluded from S. epidermidis penicillinase detection. The algorithm proposed here for the penicillinase detection in S. epidermidis involved two common antimicrobial susceptibility techniques: disk diffusion method and MIC by Vitek2® system. Disk diffusion method, interpreted with a 26 mm breakpoint for penicillin G, was associated with a high sensitivity (98%) and specificity (100%). This method was completed with zone edge test for S. epidermidis with penicillin G diameter from 26 to 35 mm (sensitivity of 98%). The Vitek2® system is associated with a low sensitivity (93%) and a high specificity (99%) This low sensitivity is associated with false negative results, in isolates with 0.12 mg/L Penicillin G MIC values and blaZ positive. Thus for penicillin G MIC of 0.06 mg/L or 0.12 mg/L, a second step with disc diffusion method is suggested.

Conclusions

According to our results, the strategy proposed here allows the interpretation of penicillin G susceptibility in S. epidermidis isolates, with an efficient detection of penicillin G resistance.

Employing MIC Data for Mink Pathogens to Propose Tentative Epidemiological Cut-Off Values: A Step Toward Rationalizing Antimicrobial Use in Mink

Optimizing antimicrobial dosage regimens and development of breakpoints for antimicrobial susceptibility testing are important prerequisites for rational antimicrobial use. The objectives of the study were (1) to produce MIC data for four mink pathogens and (2) to employ these MIC data to support the development of tentative epidemiological cut-off values (TECOFFs), which may be used for future development of mink-specific antimicrobial dosages and breakpoints. Broth microdilution was used to establish MIC distributions for 322 mink bacterial isolates of clinical origin from six European mink-producing countries. The included species were E. coli (n = 162), S. delphini (n = 63), S. canis (n = 42), and P. aeruginosa (n = 55). Sixty-four E. coli isolates and 34 S. delphini isolates were whole-genome sequenced and analyzed for antimicrobial resistance genes. No EUCAST MIC data are available on S. delphini and S. canis, hence tentative ECOFFs were suggested for the majority of the tested antimicrobials. For E. coli and P. aeruginosa, the wildtype distributions were in accordance with EUCAST data. Overall, the genotypes of the sequenced isolates were in concordance with the phenotypes. These data constitute an important piece in the puzzle of developing antimicrobial dosages and clinical breakpoints for mink. Until pharmacokinetic and clinical data become available, the (tentative) ECOFFs can be used for monitoring resistance development and as surrogates for clinical breakpoints.

Analysis of virulence traits of Staphylococcus aureus isolated from bovine mastitis in semi-intensive and family dairy farms

BACKGROUND

Staphylococcus aureus is one of the main microorganisms that causes bovine mastitis, and its well-known virulence characteristics and interactions with the environment are used to aid the design of more efficient therapies.

OBJECTIVES

To determine whether the virulence traits, such as antibiotic resistance and biofilm-forming and internalization abilities, of S. aureus isolated from bovine mastitis are related to dairy production system types.

METHODS

The study was performed in the Mexican states of Guanajuato and Michoacan. Semi-intensive dairy farms (SIDFs) and family dairy farms (FDFs) (454 and 363 cows, respectively) were included. The 194 milk samples from mastitis affected quarters were collected and 92 strains of S. aureus were isolated and identified by biochemical and molecular tests. Antibiotic resistance, biofilm and internalization assays were performed on 30 randomly selected isolated strains to determine virulence traits, and these strains were equally allocated to the 2 dairy production systems.

RESULTS

All 30 selected strains displayed a high degree of resistance (50%-91.7%) to the antibiotics tested, but no significant difference was found between SIDF and FDF isolates. S. aureus strains from SIDFs had an average biofilm forming capacity of up to 36% (18.9%-53.1%), while S. aureus strains from FDFs registered an average of up to 53% (31.5%-77.8%) (p > 0.05). Internalization assays revealed a higher frequency of internalization capacity for strains isolated from FDFs (33.3%) than for those isolated from SIDFs (6.7%) (p > 0.05). fnbpA gen was detected in 46.6% of FDF strains and 33.3% of SIDF strains, and this difference was significant (p < 0.05).

CONCLUSIONS

Our findings show that the virulence traits of S. aureus isolates analyzed in this study, depend significantly on several factors, such as phenotype, genotype, and environmental conditions, which are significantly related to dairy production system type and daily management practices.

Genotypic and Phenotypic Evaluation of Biofilm Production and Antimicrobial Resistance in Staphylococcus aureus Isolated from Milk, North West Province, South Africa

Background: Biofilm formation in S. aureus may reduce the rate of penetration of antibiotics, thereby complicating treatment of infections caused by these bacteria. The aim of this study was to correlate biofilm-forming potentials, antimicrobial resistance, and genes in S. aureus isolates. Methods: A total of 64 milk samples were analysed, and 77 S. aureus were isolated. Results: Seventy (90.9%) isolates were biofilm producers. The ica biofilm-forming genes were detected among 75.3% of the isolates, with icaA being the most prevalent (49, 63.6%). The icaB gene was significantly (P = 0.027) higher in isolates with strong biofilm formation potentials. High resistance (60%-90%) of the isolates was observed against ceftriaxone, vancomycin, and penicillin, and 25 (32.5%) of S. aureus showed multidrug resistance (MDR) to at least three antibiotics. Five resistance genes, namely blaZ (29, 37.7%), vanC (29, 37.7%), tetK (24, 31.2%), tetL (21, 27.3%), and msrA/B (16, 20.8%) were detected. Most MDR phenotypes possessed at least one resistance gene alongside the biofilm genes. However, no distinct pattern was identified among the resistance and biofilm phenotypes. Conclusions: The high frequency of potentially pathogenic MDR S. aureus in milk samples intended for human consumption, demonstrates the public health relevance of this pathogen in the region.

Different distribution of antimicrobial resistance genes and virulence profiles of Staphylococcus aureus strains isolated from clinical mastitis in six countries

Staphylococcus aureus is recognized worldwide as one of the main contagious mastitis agents in cattle and can express a set of antimicrobial resistance genes and virulence-associated genes that explain the wide range of outcomes of intramammary infections. Staphylococcus aureus strains are heterogeneous: their different resistance and virulence patterns, associated with host-level factors and treatment factors, are related to the severity of infection. The aim of this study was to determine phenotypic antibiotic susceptibility, occurrence of selected antimicrobial resistance genes and other virulence genes in 93 S. aureus strains isolated from clinical mastitis in 6 countries: Argentina, Brazil, Germany, Italy, the United States (New York State), and South Africa. These isolates were tested against a total of 16 drugs (amoxicillin-clavulanate, ampicillin, cefazolin, cefoperazone, cefquinome, enrofloxacin, erythromycin, gentamicin, kanamycin, lincomycin, oxacillin, penicillin, rifampin, spiramycin, sulfamethoxazole/trimethoprim, tylosin) by minimum inhibitory concentration (MIC) assay, and examined for the presence of 6 antibiotic-resistance genes (blaZ, mecA, mecC, ermA, ermB, ermC) and 6 virulence-associated genes (scn, chp, sak, hla, hlb, sea) via PCR analysis. The phenotypic results of this study revealed the presence of 19.4% penicillin-resistant strains, whereas 22.6% of the strains were classified as having resistance (5.4%) or intermediate resistance (17.2%) to erythromycin. Most (96.8%) of the isolates were inhibited by cephalosporins, and all were susceptible to amoxicillin-clavulanate. Two strains (1 from Germany, 1 from Italy) were resistant to oxacillin and were positive for mecA. Among the other antimicrobial resistance genes, the most frequently detected was blaZ (46.2%), and 32.3% of the isolates were positive for erm genes: ermC (21.5%) and ermB (10.8%). The most prevalent virulence gene was hla (100%), followed by hlb (84.9%) and sea (65.6%). These results show a low prevalence of antibiotic multidrug resistance in S. aureus isolates, even if the detection of selected antimicrobial resistance genes did not always correspond with the occurrence of phenotypic antibiotic resistance; the immune evasion cluster gene prevalence was quite low in the samples analyzed.

Characterization of Antibiotic and Biocide Resistance Genes and Virulence Factors of Staphylococcus Species Associated with Bovine Mastitis in Rwanda

The present study was conducted from July to August 2018 on milk samples taken at dairy farms in the Northern Province and Kigali District of Rwanda in order to identify Staphylococcus spp. associated with bovine intramammary infection. A total of 161 staphylococcal isolates originating from quarter milk samples of 112 crossbred dairy cattle were included in the study. Antimicrobial susceptibility testing was performed and isolates were examined for the presence of various resistance genes. Staphylococcus aureus isolates were also analyzed for the presence of virulence factors, genotyped by spa typing and further phenotypically subtyped for capsule expression using Fourier Transform Infrared (FTIR) spectroscopy. Selected S. aureus were characterized using DNA microarray technology, multi-locus sequence typing (MLST) and whole-genome sequencing. All mecA-positive staphylococci were further genotyped using dru typing. In total, 14 different staphylococcal species were detected, with S. aureus being most prevalent (26.7%), followed by S. xylosus (22.4%) and S. haemolyticus (14.9%). A high number of isolates was resistant to penicillin and tetracycline. Various antimicrobial and biocide resistance genes were detected. Among S. aureus, the Panton-Valentine leukocidin (PVL) genes, as well as bovine leukocidin (LukM/LukF-P83) genes, were detected in two and three isolates, respectively, of which two also carried the toxic shock syndrome toxin gene tsst-1 bovine variant. t1236 was the predominant spa type. FTIR-based capsule serotyping revealed a high prevalence of non-encapsulated S. aureus isolates (89.5%). The majority of the selected S. aureus isolates belonged to clonal complex (CC) 97 which was determined using DNA microarray based assignment. Three new MLST sequence types were detected.

Prevalence of Methicillin-Resistant Staphylococcus sp. (MRS) in Different Companion Animals and Determination of Risk Factors for Colonization with MRS

The aim of this study was to detect the prevalence of methicillin-resistant Staphylococcus sp. (MRS) in populations of companion animals that either have previously been exposed or have not been exposed to antibiotic therapy or veterinary facilities, and if owners' healthcare profession had an influence on colonization with MRS. In addition, the antimicrobial resistance pheno- and genotype were investigated and risks for colonization with MRS were assessed. During this study, 347 nasal swabs (dogs n = 152; cats n = 107; rabbits n = 88) were investigated for the presence of methicillin-resistant Staphylococcus aureus (MRSA). In addition, 131 nasal swabs (dogs n = 79; cats n = 47; rabbits = 3; guinea pigs = 2) were examined for the presence of MRSA but also other MRS. In total, 23 MRS isolates belonged to nine staphylococcal species: Staphylococcus epidermidis (n = 11), Staphylococcus warneri (n = 3), Staphylococcus hominis (n = 2), Staphylococcus pseudintermedius (n = 2), and singletons Staphylococcus cohnii, Staphylococcus sciuri, Staphylococcus fleurettii, Staphylococcus lentus, and Staphylococcus haemolyticus. Twenty isolates displayed a multidrug-resistant phenotype. Various resistance and biocide resistance genes were detected among the examined staphylococci. Risk assessment for MRS colonization was conducted using a number of factors, including animal species, breed, age, gender, recent veterinary health care hospitalization, and antibiotic prescription, resulting in recent veterinary health care hospitalization being a significant risk factor. The detection of multidrug-resistant MRS in healthy animals is of importance due to their zoonotic potential.

Biochemical and genetic characterization of a novel metallo-β-lactamase from marine bacterium Erythrobacter litoralis HTCC 2594

Metallo-β-lactamases (MBLs) are a group of enzymes that can inactivate most commonly used β-lactam-based antibiotics. Among MBLs, New Delhi metallo-β-lactamase-1 (NDM-1) constitutes an urgent threat to public health as evidenced by its success in rapidly disseminating worldwide since its first discovery. Here we report the biochemical and genetic characteristics of a novel MBL, ElBla2, from the marine bacterium Erythrobacter litoralis HTCC 2594. This enzyme has a higher amino acid sequence similarity to NDM-1 (56%) than any previously reported MBL. Enzymatic assays and secondary structure alignment also confirmed the high similarity between these two enzymes. Whole genome comparison of four Erythrobacter species showed that genes located upstream and downstream of elbla2 were highly conserved, which may indicate that elbla2 was lost during evolution. Furthermore, we predicted two prophages, 13 genomic islands and 25 open reading frames related to insertion sequences in the genome of E. litoralis HTCC 2594. However, unlike NDM-1, the chromosome encoded ElBla2 did not locate in or near these mobile genetic elements, indicating that it cannot transfer between strains. Finally, following our phylogenetic analysis, we suggest a reclassification of E. litoralis HTCC 2594 as a novel species: Erythrobacter sp. HTCC 2594.