A real-time PCR assay to detect the Panton Valentine Leukocidin toxin in staphylococci: screening Staphylococcus schleiferi subspecies coagulans strains from companion animals

Methicillin-resistant staphylococci in clinical bovine mastitis: occurrence, molecular analysis, and biofilm production

Staphylococcus aureus is an important pathogen that causes mastitis in cattle, and the emergence of methicillin-resistant S. aureus (MRSA) poses a threat to veterinary and human medicine. The aims of the study were to investigate the prevalence of MRSA and methicillin-resistant coagulase-negative staphylococci (MR-CoNS) isolated from clinical mastitis, their ability to form biofilms, and the antimicrobial susceptibility of S. aureus strains. In addition, the Staphylococcal Cassette Chromosome mec (SCCmec) type, spa type and the presence of Panton-Valentine Leucocidin in MRSA were evaluated. A total of 326 staphylococcal strains were screened by multiplex-PCR for S. aureus and Staphylococcus intermedius group (SIG) identification. The S. aureus strains (n = 163) were subjected to phenotypic testing for antimicrobial susceptibility and biofilm formation. Molecular analysis was performed on MRSA mecA-positive strains. Of 163 S. aureus isolates, 142 strains (87.1%) were resistant to at least one antibiotic, and all 19 MRSA strains were resistant to at least four out of five antibiotics tested. All S. aureus strains harboured the icaA gene and were biofilm producers. Nineteen MR-CoNS strains were also isolated. The most prevalent spa types among MRSA were t001 (57.9%) and t037 (31.6%), while one MRSA was type t008 and one was type t041. Most MRSA were SCCmec type I (63.2%) and III (31.6%) and only one strain was type IV. None of the MRSA isolates had the PVL gene. The prevalence of multidrug-resistant S. aureus in bovine mastitis is a serious concern. The finding of MRSA with spa types predominant in humans and infrequent in Italian cows and with SCCmec infrequently found in bovine milk or cheese suggest a human origin of these strains. The ability of MRSA and MR-CoNS involved in bovine mastitis to be transferred to humans and vice versa poses a public health concern.

Whole Genome Sequencing and Comparative Genomics of Six Staphylococcus schleiferi and Staphylococcus coagulans Isolates

Staphylococcus schleiferi and Staphylococcus coagulans, closely related bacterial species within the Staphylococcus genus, present a challenge in classification and diagnosis due to their close genetic proximity and overlapping phenotypic features. Moreover, our understanding of the virulence mechanisms in staphylococcal species, beyond the extensively studied Staphylococcus aureus, remains limited, underscoring the importance of using comparative data to enhance our insights into virulence within these bacterial species. This study employed a comprehensive approach, utilizing comparative genomics, to identify genomic distinctions between S. schleiferi and S. coagulans, aiming to address the challenges in the accurate classification and diagnosis of these organisms and identify unique features. Whole genome sequencing was performed on six clinical isolates, and their genomes were compared to identify variations in gene content and virulence factors. De novo assembly and annotation revealed two samples as S. coagulans and four samples as S. schleiferi. Analysis of the core genomes revealed conserved regions crucial for defining species identity, while accessory genomic elements contained unique genes, possibly impacting the pathogenicity of the species.

High prevalence of Panton-Valentine Leucocidin among Staphylococcus coagulans isolated from dogs in Rio de Janeiro

AIMS

The purpose of this study was to characterize the capacity for biofilm formation, antimicrobial resistance rates, and search for genetic determinants of resistance and virulence in the species.

METHODS AND RESULTS

Strains were collected from asymptomatic and infected dogs. Identification was conducted using matrix-assisted laser desorption ionization-time of flight (MALDI-TOF), antimicrobial susceptibility using disk diffusion and PCR targeting mecA. Biofilm formation was evaluated on a microtiter plate assay. A total of 27 strains were selected for whole-genome sequencing. We identified 111 Staphylococcus coagulans. The highest number was obtained from infected dogs. The highest resistance rates were observed for penicillin, gentamicin, and ciprofloxacin/erythromycin. Twelve strains were characterized as resistant to methicillin. All isolates had the ability to form biofilm and were strong producers. Among Methicillin Resistant Staphylococcus coagulans (MRSC), SCCmec types IIIA, and Vc were identified. Acquired resistance genes, such as aac(6')-aph(2''), tet(K), blaZ, qacG, qacJ, and erm(C) were found. Different virulence genes were identified. Of note, Panton-Valentine Leucocidin was highly prevalent among the isolates.

CONCLUSION

Staphylococcus coagulans had a high isolation rate among infected dogs and demonstrated significant resistance to commonly used antibiotics such as penicillin and gentamicin.

Virulence Potential of Biofilm-Producing Staphylococcus pseudintermedius, Staphylococcus aureus and Staphylococcus coagulans Causing Skin Infections in Companion Animals

Coagulase-positive staphylococci (CoPS) account for most bacteria-related pyoderma in companion animals. Emergence of methicillin-resistant strains of Staphylococcus pseudintermedius (MRSP), Staphylococcus aureus (MRSA) or Staphylococcus coagulans (MRSC), often with multidrug-resistant (MDR) phenotypes, is a public health concern. The study collection comprised 237 staphylococci (S. pseudintermedius (n = 155), S. aureus (n = 55) and S. coagulans (n = 27)) collected from companion animals, previously characterized regarding resistance patterns and clonal lineages. Biofilm production was detected for 51.0% (79/155), 94.6% (52/55) and 88.9% (24/27) of the S. pseudintermedius, S. aureus and S. coagulans, respectively, and was a frequent trait of the predominant S. pseudintermedius and S. aureus clonal lineages. The production of biofilm varied with NaCl supplementation of the growth media. All S. pseudintermedius and S. aureus strains carried icaADB. Kaplan–Meier survival analysis of Galleria mellonella infected with different CoPS revealed a higher virulence potential of S. aureus when compared with other CoPS. Our study highlights a high frequency of biofilm production by prevalent antimicrobial-resistant clonal lineages of CoPS associated with animal pyoderma, potentially related with a higher virulence potential and persistent or recurrent infections.

Genomic epidemiology of the opportunistic pathogen Staphylococcus coagulans from companion dogs

Introduction

Staphylococcus coagulans (formerly Staphylococcus schleiferi subsp. coagulans) is a common commensal and opportunistic pathogen of companion dogs. It carries a range of antimicrobial resistance genes and is an occasional zoonotic pathogen.

Hypothesis/Gap Statement

Despite the potential insight offered by genome sequencing into the biology of S. coagulans, few genomes are currently available for study.

Aim

To sequence and analyse S. coagulans genomes to improve understanding of this organism’s molecular epidemiology, antimicrobial resistance and bacterium–host interactions.

Methodology

Twenty-five genomes of clinical isolates collected at a veterinary referral hospital in Scotland, UK, were sequenced with Illumina technology. These genomes were analysed by a series of bioinformatics tools along with 16 previously sequenced genomes.

Results

Phylogenetic comparison of the 41 genomes shows that the current S. coagulans phylogeny is dominated by clades of closely related isolates, at least one of which has spread internationally. Ten of the 11 methicillin-resistant S. coagulans genomes in this collection of 41 encoded the mecA promoter and gene mutations that are predicted to render the isolates susceptible to penicillins in the presence of clavulanic acid, a feature only described to date in methicillin-resistant Staphylococcus aureus. Seven such isolates were from the current study and, in line with the genome-based prediction, all were susceptible to amoxicillin/clavulanic acid in vitro. S. coagulans shared very few highly conserved virulence-associated genes with Staphylococcus pseudintermedius, another common commensal and opportunistic canine pathogen.

Conclusion

The availability of a further 25 genome sequences from clinical S. coagulans isolates will aid in better understanding the epidemiology, bacterial–host interactions and antimicrobial resistance of this opportunistic pathogen.

Phenotypic and Molecular Traits of Staphylococcus coagulans Associated with Canine Skin Infections in Portugal

Staphylococcus coagulans is among the three most frequent pathogens of canine pyoderma. Yet, studies on this species are scarce. Twenty-seven S. coagulans and one S. schleiferi, corresponding to all pyoderma-related isolations from these two species at two veterinary laboratories in Lisbon, Portugal, between 1999 and 2018 (Lab 1) or 2018 (Lab 2), were analyzed. Isolates were identified by the analysis of the nuc gene and urease production. Antibiotic susceptibility towards 27 antibiotics was evaluated by disk diffusion. Fourteen antibiotic resistance genes were screened by PCR. Isolates were typed by SmaI-PFGE. Two S. coagulans isolates (2/27, 7.4%) were methicillin-resistant (MRSC, mecA+) and four (4/27, 14.8%) displayed a multidrug-resistant (MDR) phenotype. We observed resistance to penicillin (17/27, 63.0%), fluoroquinolones (11/27, 40.7%), erythromycin and clindamycin (3/27, 11.1%), fusidic acid (3/27, 11.1%) and tetracycline (1/27, 3.7%). The blaZ and erm(B) genes were carried by 16 and 1 isolates resistant to penicillin and erythromycin/clindamycin, respectively. Only three S. coagulans carried plasmids. The single S. schleiferi isolate presented an MDR phenotype. SmaI-PFGE revealed a limited genetic diversity of S. coagulans, with a predominant lineage present from 2001 to 2018. This study describes the first MRSC causing canine infection in Portugal and reveals a high burden of antimicrobial resistance, with the emergence of MDR phenotypes within the main lineages.

Isolation and genome sequencing of Staphylococcus schleiferi subspecies coagulans from Antarctic and North Sea seals

Reports on the commensal organism and opportunistic pathogen Staphylococcus schleiferi have largely considered isolates from humans and companion dogs. Two subspecies are recognized: the coagulase-negative S. schleiferi ssp. schleiferi, typically seen in humans, and the coagulase-positive S. schleiferi ssp. coagulans, typically seen in dogs. In this study, we report the isolation, genome sequencing and comparative genomics of three S. schleiferi ssp. coagulans isolates from mouth samples from two species of healthy, free-living Antarctic seals, southern elephant seals (Mirounga leonina) and Antarctic fur seals (Arctocephalus gazella), in the South Orkney Islands, Antarctica, and three isolates from post-mortem samples from grey seals (Halichoerus grypus) in Scotland, UK. This is the first report of S. schleiferi ssp. coagulans isolation from Antarctic fur seal and grey seal. The Antarctic fur seal represents the first isolation of S. schleiferi ssp. coagulans from the family Otariidae, while the grey seal represents the first isolation from a pinniped in the Northern Hemisphere. We compare seal, dog and human isolates from both S. schleiferi subspecies in the first genome-based phylogenetic analysis of the species.

Evaluation of Oxacillin and Cefoxitin Disk Diffusion and MIC Breakpoints Established by the Clinical and Laboratory Standards Institute for Detection of mecA-Mediated Oxacillin Resistance in Staphylococcus schleiferi

Staphylococcus schleiferi is a beta-hemolytic, coagulase-variable colonizer of small animals that can cause opportunistic infections in humans. In veterinary isolates, the rate of mecA-mediated oxacillin resistance is significant, with reported resistance rates of >39%. The goal of this study was to evaluate oxacillin and cefoxitin disk diffusion (DD) and MIC breakpoints for detection of mecA-mediated oxacillin resistance in 52 human and 38 veterinary isolates of S. schleiferi Isolates were tested on multiple brands of commercial media and according to Clinical and Laboratory Standards Institute (CLSI) methods. Zone diameters and MIC values were interpreted using CLSI breakpoints (CLSI, Performance Standards for Antimicrobial Susceptibility Testing. M100-S27, 2017) for Staphylococcus aureus/Staphylococcus lugdunensis, coagulase-negative staphylococci (CoNS), and Staphylococcus pseudintermedius Results were compared to those of mecA PCR. Twenty-nine of 90 (32%) isolates were mecA positive. Oxacillin inhibition zone sizes and MICs interpreted by S. pseudintermedius breakpoints reliably differentiated mecA-positive and mecA-negative isolates, with a categorical agreement (CA) of 100% and no very major errors (VMEs) or major errors (MEs) for all media. For cefoxitin DD results interpreted using S. aureus/S. lugdunensis and CoNS breakpoints, CA values were 85% and 75%, respectively, and there were 72% and 64% VMEs, respectively, and 0 MEs. For cefoxitin MICs interpreted using S. aureus/S. lugdunensis breakpoints, CA was 81%, and there were 60% VMEs and no MEs. Our data demonstrate that oxacillin DD or MIC testing methods using the current S. pseudintermedius breakpoints reliably identify mecA-mediated oxacillin resistance in S. schleiferi, while cefoxitin DD and MIC testing methods perform poorly.

A Glance at the Role of Exotoxins in Opportunistic Bacterial Infections

The production and the mechanism of action of exotoxins from Staphylococcus aureus, Staphylococcus epidermidis and Pseudomonas aeruginosa are presented. The attack to the immune host's defenses is the main virulence factor of opportunistic bacteria in implant infections, favoring the invasion and colonization of compromised periprosthesis tissues.

Genotypic relatedness and antimicrobial resistance of Staphylococcus schleiferi in clinical samples from dogs in different geographic regions of the United States

BACKGROUND

Staphylococcus schleiferi is a known pathogen that can cause canine skin and ear infections. The aim of this study was to determine the molecular epidemiology and antimicrobial susceptibility of clinical veterinary isolates from different geographic regions in the United States.

HYPOTHESIS

It was hypothesized that S. schleiferi would maintain genotypic homogeneity across the different geographic regions and that meticillin-resistant (MR) isolates of S. schleiferi would predominate.

METHODS

Isolates were identified as S. schleiferi by a commercial microbiology identification system and confirmed by nuc gene PCR. Antibiotic susceptibility data were collected and PBP2a latex agglutination testing was performed on MR isolates. Pulsed-field gel electrophoresis (PFGE) was performed and clonal clusters were identified with a Dice coefficient similarity of >80%.

RESULTS

There were 116 isolates from the Mid-Atlantic region and 101 from across the United States. Of these 217 isolates, 209 (96%) were obtained from cutaneous sites. Of the Mid-Atlantic isolates, 62% (72 of 116) were MR and 16% (18 of 116) were multidrug-resistant (MDR). Of the isolates from the other geographic regions, 73% (74 of 101) were MR and 24% (24 of 101) were MDR. All MR isolates were positive by PBP2a latex agglutination. PFGE identified 155 individual pulsed-field profiles and three major pulsed-field types (PFT) that contained 61% (133 of 217) of the isolates. These pulsed-field types were geographically heterogeneous.

CONCLUSIONS

This study demonstrates the dissemination of successful MR pulsed-field types of S. schleiferi across the United States.

Methicillin-resistant Staphylococcus aureus in commercial swine herds is associated with disinfectant and zinc usage

Methicillin-resistant Staphylococcus aureus (MRSA) originating from swine is concerning for public health, but an understanding of the emergence and persistence of MRSA in nursery herds is lacking. The aim of this study was to determine whether MRSA in nursery pigs is associated with particular herd-level parameters, including the use of antimicrobials, disinfectants, and heavy metals, which may be driving the selection and persistence of antimicrobial resistance. Nasal cultures for MRSA were completed for 390 pigs from 26 farms at the end of the suckling phase and again at 3 weeks postweaning. Herd-level information was collected, and a random subset of MRSA isolates was screened for resistance to zinc and quaternary ammonium compounds (QACs). Multivariate analysis revealed that in-feed concentrations of zinc (P < 0.001) and frequent disinfection of nursery pens (P < 0.001) are associated with MRSA shedding in nursery pigs. Furthermore, 62.5% (25/40) of MRSA isolates carried the zinc resistance gene czrC and demonstrated decreased susceptibility to zinc. All MRSA isolates carried at least 1 QAC resistance gene. The most common genotype was qacG qacH smr, which occurred in 32.5% (13/40) of isolates. Seven isolates (17.5%) demonstrated a significant tolerance to benzalkonium chloride, indicating a potential to survive commercial QAC exposure in the presence of organic matter. Overall, these findings indicate that high levels of in-feed zinc and QAC-based disinfectants are important drivers in the selection and persistence of MRSA in commercial swine herds, and these agents may be coselecting for other antimicrobial resistance genes.

Strain typing and antimicrobial susceptibility of methicillin-resistant coagulase-positive staphylococcal species in dogs and people associated with dogs in Thailand

AIMS

This study was to investigate and to characterize methicillin-resistant coagulase-positive staphylococci (MRCoPS) harboring in dogs and people associated with dogs in Thailand.

METHODS AND RESULTS

Staphylococci were collected from 100 dogs, 100 dog owners, 200 small animal veterinarians and 100 people without pet association. Species of MRCoPS were identified phenotypically and genotypically. Molecular characteristics were determined by multilocus sequence typing (MLST), pulsed-field gel electrophoresis (PFGE) and SCCmec typing, and antimicrobial susceptibility was assayed by broth microdilution and by microarray analysis for resistance genes. Methicillin-resistant Staphylococcus pseudintermedius (MRSP), methicillin-resistant Staphylococcus schleiferi subsp. coagulans (MRSSc) and methicillin-resistant Staphylococcus aureus (MRSA) were isolated from dogs (45, 17 and 1%, respectively), veterinarians (8, 2 and 1·5%, respectively) and dog owners (3, 2 and 0%, respectively). Seventeen sequence types (STs) were identified among 83 MRSP isolates which specifically carried SCCmec V, II-III, ΨSCCmec57395 and three uncharacterized SCCmec types. MRSP ST 45, 68 and novel STs including 169, 178, 181 and 183 were shared among canine and human isolates. Most of MRSA ST398 and MRSSc carried SCCmec type V. The MRCoPS commonly displayed multiple resistances to tested antimicrobials and carried various resistance genes.

CONCLUSION

Variety of MRCoPS, especially new MRSP clones, distributed in dogs and people in Thailand.

SIGNIFICANCE AND IMPACT OF THE STUDY

The existence of MRCoPS circulating between dogs and humans in Thailand provides indirect evidence of interspecies transmission and represents a potential public health hazard.

[Staphylococcus aureus broncho-pulmonary infections]

Staphylococcus aureus accounts for 2-5% of the etiologies of community-acquired pneumonia. These infections occur mainly in elderly patients with comorbidity, after a respiratory viral infection. S. aureus could also be responsible for necrotizing pneumonia, which occurs in young subjects, also after flu. Necrotizing pneumonia are associated with the production of a particular staphylococcal toxin called Panton-Valentine leukocidin, responsible for pulmonary focal necrosis, occurrence haemoptysis, leucopenia, and death. In Europe, these strains are still predominantly sensitive to anti-staphylococcal penicillin, which must be used at high dosage intravenously in combination with an antibiotic that reduces toxin production such as clindamycin, and intravenous immunoglobulin in severe cases. The mortality rate is estimated at 50%. In addition, S. aureus is one of the pathogens involved in early respiratory infections in cystic fibrosis patients, in whom methicillin resistance plays an important prognostic role. However, the involvement of S. aureus in COPD exacerbations is rare. Finally, S. aureus represents 20 to 30% of cases of hospital-acquired pneumonia, including ventilator-associated pneumonia. In these cases, methicillin-resistance is common and requires the use of glycopeptides or linezolid. The place of new anti-staphylococcal antibiotics such as new generation cephalosporins or tigecyclin remains to be defined.

Pragmatic management of Panton-Valentine leukocidin-associated staphylococcal diseases

Panton-Valentine leukocidin (PVL)-producing Staphylococcus aureus is associated with a broad spectrum of diseases, ranging from common uncomplicated soft tissue infections to severe diseases such as complicated soft tissue infections, extensive bone and joint infections, and necrotising pneumonia. Specialised management of infection based on the presence of PVL may not be required for mild infections, whereas it could be lifesaving in other settings. Moreover, most severe PVL diseases are recently identified entities and a 'gold standard' treatment from comparatives studies of different therapeutic options is lacking. Thus, recommendations are based on expert opinions, which are elaborated based on theory, in vitro data and analogies with other toxin-mediated diseases. In this review, we consider the potential need for specialised PVL-based management and, if required, which tools should be used to achieve optimal management.

Genotypic relatedness and phenotypic characterization of Staphylococcus schleiferi subspecies in clinical samples from dogs

OBJECTIVE

To assess the degree of biological similarity (on the basis of genotype determined via pulsed-field gel electrophoresis [PFGE]) between isolates of 2 Staphylococcus schleiferi subspecies (S schleiferi subsp coagulans and S schleiferi subsp schleiferi) in clinical samples obtained from dogs.

SAMPLE POPULATION

161 S schleiferi isolates from 160 canine patients.

PROCEDURES

A commercial microbiology identification system was used to identify each isolate as S schleiferi. Isolates underwent slide and tube coagulase testing and antimicrobial susceptibility testing. A mecA PCR assay and a latex agglutination test for penicillin-binding protein 2a (PBP2a) were also performed on each isolate. Clonal clusters with a similarity cutoff value of 80% were identified via PFGE.

RESULTS

Of the 161 isolates, 61 (38%), 79 (49%), and 21 (13%) were obtained from cutaneous sites, ears, and other sites, respectively; 110 (68%) were coagulase negative, and 51 (32%) were coagulase positive. Among the coagulase-negative and coagulase-positive isolates, 65% (71/110) and 39% (20/51) were oxacillin resistant, respectively. All oxacillin-resistant isolates yielded positive results via mecA PCR assay and PBP2a latex agglutination testing. Via PFGE, 15 major clusters and 108 individual pulsed-field profiles were identified. Oxacillin-resistant and oxacillin-susceptible isolates clustered separately. Clonal clusters were heterogeneous and contained representatives of both subspecies.

CONCLUSIONS AND CLINICAL RELEVANCE

Coagulase-positive and coagulase-negative isolates were not genotypically distinct and may represent a single S schleiferi sp with variable coagulase production, rather than 2 biologically distinct subspecies. Further studies are needed to characterize clinical or epidemiological differences associated with infections with coagulase-positive and coagulase-negative S schleiferi in dogs.

Prevalence of Staphylococcus aureus and methicillin-resistant Staphylococcus aureus carriage in three populations

BACKGROUND

A higher prevalence of methicillin-resistant Staphylococcus aureus (MRSA) colonization is reported in healthcare workers compared with nonhealthcare workers.

HYPOTHESIS

The prevalence of MRSA colonization differed in people and pets in households with healthcare workers as compared with households without healthcare workers.

SUBJECTS

A person and 1 dog or cat from 586 households defined as either a nonhealthcare (n = 213), veterinary healthcare (n = 211), or human healthcare (n = 162) worker household.

METHODS

Prospective cross-sectional study. Samples from humans and pets were cultured in vitro. Staphylococcus aureus was identified as methicillin sensitive (MSSA) or MRSA with mecA polymerase chain reaction. Pulsed-field gel electrophoresis and spa-typing were used to characterize relatedness of S. aureus and MRSA and assign USA types.

RESULTS

The prevalence of MSSA and MRSA in humans was 21.5% (126/586) and 5.63% (33/586), respectively, and 7.85% (46/586) and 3.41% (20/586), respectively, in pets. There were no differences in prevalences of either MSSA or MRSA between household types. The proportion of MRSA among all S. aureus isolates in humans and pets was 20.8% (33/159) and 30.3% (20/66), respectively. In < 1.0% (4/586) of households, the same strain of MRSA was found in both a person and a pet.

CONCLUSIONS AND CLINICAL IMPORTANCE

There were no differences in the prevalences of MSSA or MRSA between healthcare worker and nonhealthcare worker households. Pets and people colonized with S. aureus were as likely to be colonized with MRSA. Colonization of a person and their pet with the same strain of MRSA was rare.

Multiplex-PCR method for species identification of coagulase-positive staphylococci

In veterinary medicine, coagulase-positive staphylococci (CoPS) other than Staphylococcus aureus have frequently been misidentified as being S. aureus strains, as they have several phenotypic traits in common. There has been no reliable method to distinguish among CoPS species in veterinary clinical laboratories. In the present study, we sequenced the thermonuclease (nuc) genes of staphylococcal species and devised a multiplex-PCR (M-PCR) method for species identification of CoPS by targeting the nuc gene locus. To evaluate sensitivity and specificity, we used this M-PCR method on 374 staphylococcal strains that had been previously identified to the species level by an hsp60 sequencing approach. We could successfully distinguish between S. aureus, S. hyicus, S. schleiferi, S. intermedius, S. pseudintermedius, and S. delphini groups A and B. The present method was both sensitive (99.8%) and specific (100%). Our M-PCR assay will allow the routine species identification of CoPS isolates from various animal species for clinical veterinary diagnosis.

Surveillance of healthy cats and cats with inflammatory skin disease for colonization of the skin by methicillin-resistant coagulase-positive staphylococci and Staphylococcus schleiferi ssp. schleiferi

In this study, bacterial cultures were collected from five sites on each of 50 healthy cats and 48 cats with inflammatory skin disease (ISD), to determine prevalence of carriage and relative frequency of methicillin resistance in coagulase-positive staphylococci and Staphylococcus schleiferi ssp. schleiferi. Latex agglutination testing for penicillin-binding protein 2a (PBP2a) and pulsed field gel electrophoresis (PFGE) were performed on all methicillin-resistant (MR) isolates. Polymerase chain reaction (PCR) for the mecA gene was performed on MR S. intermedius and S. schleiferi isolates. Staphylococcal chromosomal cassette (SCCmec) typing was performed on all MR S. aureus isolates. Coagulase-positive staphylococci and S. schleiferi ssp. schleiferi were isolated from 24 of 48 cats with ISD: Staphylococcus aureus (14 of 24, 58%), Staphylococcus intermedius (11 of 24, 46%), Staphylococcus schleiferi ssp. schleiferi (1 of 24, 4%), and Staphylococcus hyicus (1 of 24, 4%). Prevalence of MR was 7% for S. aureus, 0% for S. intermedius, 100% for S. schleiferi ssp. schleiferi, and 0% for S. hyicus. Coagulase-positive staphylococci were isolated from 17 of 50 healthy cats: S. aureus (10 of 17, 59%), S. intermedius (11 of 17, 65%), and S. schleiferi ssp. coagulans (1 of 17, 6%). Prevalence of MR was 20% for S. aureus, 18% for S. intermedius, and 0% for S. schleiferi ssp. coagulans. All MR isolates were positive for PBP2a via latex agglutination. Methicillin-resistant S. intermedius and S. schleiferi ssp. schleiferi isolates were also positive for the mecA gene via PCR. Methicillin-resistant S. aureus isolates were identified as SCCmec type II. Results of PFGE indicated heterogeneity among isolates. There was no significant difference in staphylococcal isolation or methicillin resistance between study groups. While present, MR coagulase-positive staphylococci are significantly less common in these study populations.

Screening of Staphylococcus aureus, Staphylococcus intermedius, and Staphylococcus schleiferi isolates obtained from small companion animals for antimicrobial resistance: a retrospective review of 749 isolates (2003?04)

Companion animal staphylococcal isolate antibiograms were screened retrospectively to determine the frequency of methicillin-resistant (MR) infection by Staphylococcus aureus, Staphylococcus intermedius, and Staphylococcus schleiferi. Rates of MR were: S. aureus 35%, S. intermedius 17%, and S. schleiferi 40%. Frequency of isolation of methicillin-resistant S. aureus (MRSA) from dogs and cats was similar, whereas methicillin-resistant S. intermedius (MRSI) and methicillin-resistant S. schleiferi (MRSS) were significantly more common in dogs. MRSS was more commonly associated with superficial (skin and ear canal) infections, whereas MRSA was more commonly associated with deep infections. The MR strain resistance pattern to other classes of antibiotics was also investigated. MRSA was resistant to the most classes of antibiotics, followed by MRSI, while MRSS maintained the most favourable susceptibility profile. MR staphylococci may pose a significant risk to animal and public health. Therefore, to avoid selecting for resistant strains in cases of suspected staphylococcal infection, clinicians should consider culture and susceptibility testing early in the course of treatment.

Clinical, microbiological, and molecular characterization of methicillin-resistantStaphylococcus aureusinfections of cats

OBJECTIVE

To compare clinical information obtained from medical records of cats with methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-susceptible S aureus (MSSA) infections, evaluate antibiograms of MRSA and MSSA for multiple-drug resistance (MDR), and characterize the strain type and staphylococcal chromosome cassette (SCC)mec type of each MRSA.

SAMPLE POPULATION

70 S aureus isolates obtained from 46 cats.

PROCEDURES

Clinical information obtained from medical records, including signalment, clinical signs, histologic examination of affected tissues, and outcomes, was compared between the 2 groups. Composite antibiograms of MRSA and MSSA were compared statistically. The MRSA strains were characterized by use of pulsed-field gel electrophoresis and SCCmec typing.

RESULTS

No statistical differences in signalment or subjective differences in clinical signs or outcomes were detected between groups with MRSA or MSSA infection. Significant differences in antimicrobial resistance were detected, with MRSA having complete resistance to fluoroquinolone and macrolide antimicrobials, whereas MSSA maintained a high frequency of susceptibility. Seven pulsed-field patterns were observed in 15 MRSA strains; all but 1 were highly related. All MRSA isolates contained a type II SCCmec element.

CONCLUSIONS AND CLINICAL RELEVANCE

Because MDR cannot be predicted in staphylococcal infections in cats on the basis of clinical signalment, culture and susceptibility testing are recommended whenever initial empirical treatment is unsuccessful. Molecular characterization of MRSA strains suggests that there has been reverse-zoonotic transmission from humans.

IMPACT FOR HUMAN MEDICINE

The SCCmec type II element is typically associated with nosocomial MRSA infections of people. Cats may serve as reservoirs for MRSA infections in humans.

Novel multiplex PCR assay for detection of the staphylococcal virulence marker Panton-Valentine leukocidin genes and simultaneous discrimination of methicillin-susceptible from -resistant staphylococci

We developed a new multiplex PCR assay for detection of Panton-Valentine leukocidin virulence genes and simultaneous discrimination of methicillin-susceptible from -resistant staphylococci. This assay is simple, rapid, and accurate and offers the potential for prompt detection of newly emerging community-associated methicillin-resistant Staphylococcus aureus.

Panton valentine leukocidin (PVL) toxin positive MRSA strains isolated from companion animals

Methicillin-resistant Staphylococcus aureus (MRSA) is a highly pathogenic multiple-drug resistant (MDR) microorganism that has recently become more prevalent in the community. It has been found that MRSA strains can also contain genes that encode the panton valentine leukocidin toxin (PVL). The PVL toxin has been shown to be responsible for many of the severe clinical symptoms of infection with MRSA, such as furunculosis, severe necrotizing pneumonia, and necrotic lesions of the skin and soft tissues. The aim of this study was to determine the presence of the S. aureus PVL toxin genes (lukS-PV and lukF-PV) in MRSA strains isolated from companion animals. Eleven MRSA isolates, from a total of 23 tested, were shown to possess the mecA gene and the PVL toxin genes. Pulsed-field gel electrophoresis showed that the 11 PVL toxin positive MRSA strains were highly clonal.