Identification and prevalence of an enterotoxin-related gene, se-int, in Staphylococcus intermedius isolates from dogs and pigeons

Susceptibility of emetic and enterotoxigenic Bacillus cereus grown at high temperature to disinfectants

The prevalence of emetic strains in food products is rare; however, infection with these may be fatal to the vulnerable population. Bacterial control of the emetic Bacillus cereus strains is still unclear. This study aimed to assess the influence of high temperature on the disinfection of emetic and enterotoxigenic B. cereus. Emetic B. cereus strains survived up to 50 °C; the lag time and maximum growth rate were higher at 42 °C than those at 30 °C. Compared to enterotoxigenic B. cereus, all emetic food strains showed higher minimum inhibitory concentrations and minimum bactericidal concentrations for sodium hypochlorite and citric acid. The disinfectant susceptibility of the emetic B. cereus OS-05 strain incubated at a higher temperature did not increase and was maintained at the highest MBC value. In all emetic B. cereus strains, enterotoxin gene expression was upregulated at 42 °C and 45 °C. Increased ces gene expression was also found in emetic B. cereus strains GP-15 and OS-05, with upregulation of 128- and 820-fold at 42 °C. Thus, emetic B. cereus grown at high temperatures may resist common disinfectants of the food industry. The findings may help control B. cereus in food or the food processing industry.

Prevalence of Staphylococcus spp. from human specimens submitted to diagnostic laboratories in South Africa, 2012-2017

Background

Although staphylococci are commensals of the skin and mucosa of humans and animals, they are also opportunistic pathogens. Some coagulase-negative Staphylococcus spp. (CoNS), such as S. haemolyticus and S. epidermidis, are reported to be zoonotic.

Objectives

The prevalence of coagulase positive (CoPS), CoNS and coagulase-variable Staphylococcus spp. isolated from human clinical cases in South Africa was investigated.

Method

Retrospective records of 404 217 diagnostic laboratory submissions from 2012 to 2017 were examined and analysed in terms of time, place and person.

Results

Of the 32 different species identified, CoPS were the most frequently isolated (74.7%), followed by CoNS (18.9%). Just over half (51.2%) of the Staphylococcus isolates were from males, while females contributed 44.8%. Patients aged 0-4 years contributed the most (21.5%) isolates, with the highest number coming from KwaZulu-Natal (32.8%). Urinary specimens accounted for 29.8% of the isolates reported. There was no variation in the number of Staphylococcus isolates reported in the autumn (25.2%), winter (25.2%), spring (25.1%) and summer (24.5%) seasons.

Conclusion

This study demonstrated the diversity of Staphylococcus spp. isolated from humans and the magnitude of infection, with the most predominant species being S. aureus and S. epidermidis.

Contribution

Although most isolates were CoPS, the isolation of CoNS seen in this study suggests a need to improve infection control measures in a South African context. More research is needed to investigate the determinants of the observed variations in the study.

Regulatory and Enterotoxin Gene Expression and Enterotoxins Production in Staphylococcus aureus FRI913 Cultures Exposed to a Rotating Magnetic Field and trans-Anethole

The study aimed to examine the influence of a rotating magnetic field (RMF) of two different frequencies (5 and 50 Hz) on the expression of regulatory (agrA, hld, rot) and staphylococcal enterotoxin (SE—sea, sec, sel) genes as well as the production of SEs (SEA, SEC, SEL) by the Staphylococcus aureus FRI913 strain cultured on a medium supplemented with a subinhibitory concentration of trans-anethole (TA). Furthermore, a theoretical model of interactions between the bacterial medium and bacterial cells exposed to RMF was proposed. Gene expression and SEs production were measured using quantitative real-time PCR and ELISA techniques, respectively. Based on the obtained results, it was found that there were no significant differences in the expression of regulatory and SE genes in bacteria simultaneously cultured on a medium supplemented with TA and exposed to RMF at the same time in comparison to the control (unexposed to TA and RMF). In contrast, when the bacteria were cultured on a medium supplemented with TA but were not exposed to RMF or when they were exposed to RMF of 50 Hz (but not to TA), a significant increase in agrA and sea transcripts as compared to the unexposed control was found. Moreover, the decreased level of sec transcripts in bacteria cultured without TA but exposed to RMF of 50 Hz was also revealed. In turn, a significant increase in SEA and decrease in SEC and SEL production was observed in bacteria cultured on a medium supplemented with TA and simultaneously exposed to RMFs. It can be concluded, that depending on SE and regulatory genes expression as well as production of SEs, the effect exerted by the RMF and TA may be positive (i.e., manifests as the increase in SEs and/or regulatory gene expression of SEs production) or negative (i.e., manifests as the reduction in both aforementioned features) or none.

Staphylococcus pseudintermedius: an undocumented, emerging pathogen in humans

The first infections of methicillin-resistant Staphylococcus pseudintermedius in humans were recorded in 2006, and is now becoming a concern because of its close similarities to human pathogens in the Staphylococcusintermedius group (SIG). These bacteria have all the properties which a multidrug-resistant Staphylococcus aureus possesses.

The literature was searched using the term “Staphylococcus pseudintermedius” in PubMed and other reference databases. The virulence factor and the pathogenicity are under investigation, but reports have suggested that this commensal of animals is transmitted easily via close contact to animals by owners, veterinarians and staff.

Resistance to beta-lactams (including methicillin) is a primary concern. Drug resistance to methicillin is a considerable problem in developing countries, as antibiotic use is not regulated. Studies from Europe have reported multidrug resistant isolates from clinical specimens. Although data on drug resistance and pathogenesis of S. pseudintermedius are not sufficient, it is extremely important to identify the pathogen correctly. Only then can its pathogenesis be studied during the course of disease and appropriate measures developed to prevent it becoming a global problem.

In Vitro Efficacy of Essential Oils from Melaleuca Alternifolia and Rosmarinus Officinalis, Manuka Honey-based Gel, and Propolis as Antibacterial Agents Against Canine Staphylococcus Pseudintermedius Strains

Essential oils (EOs) and honeybee products (e.g., honey and propolis) are natural mixtures of different volatile compounds that are frequently used in traditional medicine and for pathogen eradication. The aim of this study was to evaluate the antibacterial properties of tea tree (Melaleuca alternifolia) EO (TTEO), Rosmarinus officinalis EO (ROEO), manuka-based gel, and propolis against 23 strains of Staphylococcus pseudintermedius (SP) isolated from canine pyoderma. Antimicrobial resistance screening was assessed using a panel of nine antimicrobial agents coupled with a PCR approach. An aromatogram was done for both EOs, using the disk diffusion method. The minimum inhibitory concentration (MIC) was determined for all the compounds. Among the 23 SP strains, 14 (60.9%) were multidrug-resistant (MDR), 11 strains (47.8%) were methicillin-resistant (MRSP), and 9 (39.1%) were non-MDR. The mean diameter of the inhibition zone for Melaleuca and Rosmarinus were 24.5 ± 8.8 mm and 15.2 ± 8.9 mm, respectively, resulting as statistically different (p = 0.0006). MIC values of TTEO and ROEO were similar (7.6 ± 3.2% and 8.9 ± 2.1%, respectively) and no statistical significances were found. Honeybee products showed lower MIC compared to those of EOs, 0.22 ± 0.1% for Manuka and 0.8 ± 0.5% for propolis. These findings reveal a significant antibacterial effect for all the tested products.

Molecular and phenotypic characterization of methicillin-resistant Staphylococcus pseudintermedius from ocular surfaces of dogs and cats suffering from ophthalmological diseases

Methicillin-resistant Staphylococcus pseudintermedius (MRSP) have recently emerged as a major therapeutic challenge in small animal medicine because of their antimicrobial multidrug resistance and their role as nosocomial pathogens. This study focused on the prevalence, molecular characteristics and antimicrobial resistance pheno- and genotypes of MRSP isolated from conjunctival swabs of dogs and cats. Conjunctival swabs were collected from 72 dogs and 24 cats suffering from conjunctivitis/blepharitis, keratitis or uveitis and screened for the presence of MRSP. S. pseudintermedius was isolated from 38 (39.6 %) of all samples. Three (7.9 %) S. pseudintermedius isolates were confirmed as MRSP. They harboured the mecA gene and originated from dogs. One MRSP isolate was from a case of uveitis while the other two MRSP isolates originated from cases of conjunctivitis/blepharitis. All MRSP isolates were subjected to broth microdilution and whole genome sequencing (WGS). Resistance and virulence genes, multilocus sequence (MLS), spa, dru and SCCmec types were deduced from WGS data. Two of the three MRSP isolates, IMT360/16 and IMT515/16, shared the same MLS type (ST71), spa type (t02), dru type (dt9a), SCCmec type (II-III), and indistinguishable multidrug resistance pheno- and genotypes, including resistance to β-lactams (blaZ, mecA), erythromycin and clindamycin (erm(B)), streptomycin (aphA3), gentamicin (aacA-aphD), enrofloxacin (mutations in grlA and gyrA), tetracycline (tet(K)), and trimethoprim (dfrG)/sulfamethoxazole. The third isolate, IMT1670/16, differed in all those characteristics (MLST (ST1403), dru type (dt10h), SCCmec type (IVg), except the spa type (t02). In addition, isolate IMT1670/16 carried a different tetracycline resistance gene (tet(M)) and was susceptible to erythromycin and clindamycin.

Enterotoxin gene profile of methicillin-resistant Staphylococcus pseudintermedius isolates from dogs, humans and the environment

PURPOSE

This study aimed to detect and identify staphylococcal enterotoxin (SE) genes in methicillin-resistant Staphylococcus pseudintermedius (MRSP) strains from different sources, and to investigate the relationship between their sequence types (STs) and SE gene patterns.

METHODOLOGY

The profiles of 17 SE genes in 93 MRSP strains isolated from dogs (n=43), humans (n=18) and the environment (n=32) were detected by PCR. Multilocus sequence typing (MLST), SCCmec typing and pulsed-field gel electrophoresis (PFGE) were used to analyse the clonal relatedness between the molecular type and SE gene profiles.Results/Key findings. The human MRSP strains harboured the greatest number of SE genes (12/17; sea, sec, seg, sei, sek, sel, sem, sen, seo, sep, seq and tst-1) compared to those from dogs (5/17; sec, sel, sem, seq and tst-1) and environmental sources (3/17; sec, seq and tst-1). Using MLST and PFGE, different SE gene profiles were found within the same clonal type.

CONCLUSION

We show that isolates of MRSP vary in their virulence gene profiles, depending on the source from which they have been isolated. This insight should encourage the development of appropriate monitoring and mitigation strategies to reduce the transmission of MRSP in veterinary hospitals and households.

Characterization of Staphylococcus pseudintermedius isolated from diseased dogs in Lithuania

The aim of this study was to characterize Staphylococcus pseudintermedius for its antimicrobial resistance and virulence factors with a special focus on methicillin-resistant (MRSP) strains isolated from sick dogs in Lithuania. Clinically sick adult dogs suffering from infections (n=214) and bitches with reproductive disorders (n=36) from kennels were selected for the study. Samples (n=192) from the 250 tested (76.8%) dogs were positive for Staphylococcus spp. Molecular profiling using the species-specific nuc gene identified 51 isolates as S. pseudintermedius (26.6% from a total number of isolated staphylococci) of which 15 isolates were identified as MRSP. Ten MRSP isolates were isolated from bitches with reproductive disorders from two large breeding kennels. Data on susceptibility of S. pseudintermedius to different antimicrobials revealed that all isolates were susceptible to vancomycin, daptomycin and linezolid. Two isolates (3.9%) were resistant to rifampicin. A high resistance was seen towards penicillin G (94.1%), tetracycline (64.7%) and macrolides (68.7%). Resistance to fluoroquinolones ranged from 25.5% (gatifloxacin) to 31.4% (ciprofloxacin). The most prevalent genes encoding resistance included blaZ, aac(6')-Ie-aph(2'')-Ia, mecA, and tet(M). The Luk-I gene encoding a leukotoxin was detected in 29% of the isolates, whereas the siet gene encoding exfoliative toxin was detected in 69% of the S. pseudintermedius isolates. This report of MRSP in companion animals represents a major challenge for veterinarians in terms of antibiotic therapy and is a concern for both animal and public health.

Characterisation of nasal Staphylococcus delphini and Staphylococcus pseudintermedius isolates from healthy donkeys in Tunisia

REASONS FOR PERFORMING STUDY

Staphylococcus intermedius group (SIG) bacteria can colonise the nares of some animals but are also emerging pathogens in humans and animals.

OBJECTIVES

To analyse SIG nasal carriage in healthy donkeys destined for food consumption in Tunisia and to characterise recovered isolates.

METHODS

Nasal swabs from 100 healthy donkeys were tested for SIG recovery, and isolates were identified by biochemical and molecular methods. Antimicrobial susceptibility of isolates was tested and detection of antimicrobial resistance and virulence genes was performed. Isolates were typed at the clonal level by multilocus sequence typing and SmaI pulsed-field gel electrophoresis.

RESULTS

Staphylococcus delphini and Staphylococcus pseudintermedius (included in SIG) were obtained in 19% and 2% of the tested samples, respectively, and one isolate per sample was characterised. All isolates were meticillin susceptible and mecA negative. Most S. delphini and S. pseudintermedius isolates showed susceptibility to all antimicrobials tested, with the exception of 2 isolates resistant to tetracycline (tet(M) gene) or fusidic acid. The following toxin genes were identified (percentage of isolates): lukS-I (100%), lukF-I (9.5%), siet (100%), se-int (90%), seccanine (19%) and expA (9.5%). Thirteen different pulsed-field gel electrophoresis profiles were identified among the 21 SIG isolates. Additionally, the following 9 different sequence types (STs) were detected by multilocus sequence typing, 6 of them new: ST219 (6 isolates), ST12 (5 isolates), ST220 (3 isolates), ST13, ST50, ST193, ST196, ST218 and ST221 (one isolate each).

CONCLUSIONS

Staphylococcus delphini and S. pseudintermedius are common nasal colonisers of donkeys, generally susceptible to the antimicrobials tested; nevertheless, these SIG isolates contain virulence genes, including the recently described exfoliative gene (expA) and several enterotoxin genes, with potential implications for public health. This is the first description of S. delphini in Tunisia. The Summary is available in Chinese - see Supporting information.

Antimicrobial resistance, virulence genes, and genetic lineages of Staphylococcus pseudintermedius in healthy dogs in tunisia

Nasal swabs of 100 healthy dogs were obtained in 2011 in Tunisia and tested for Staphylococcus pseudintermedius recovery. Antimicrobial resistance profile and virulence gene content were determined. Multilocus-sequence-typing (MLST) and SmaI-pulsed-field gel electrophoresis (PFGE) were investigated. S. pseudintermedius was recovered in 55 of the 100 tested samples (55 %), and one isolate per sample was further studied. All 55 S. pseudintermedius isolates were susceptible to methicillin (MSSP) but showed resistance to the following antimicrobials (% resistant isolates/resistance gene): penicillin (56.4/blaZ), tetracycline (40/tetM), trimethoprim-sulfamethoxazole (23.7), fusidic acid (9), kanamycin (3.7/aph(3´)-Ia), erythromycin-clindamycin (1.8/erm(B)), streptomycin (1.8/ant(6)-Ia), chloramphenicol (1.8) and ciprofloxacin (1.8). The following toxin genes were identified (% of isolates): lukS/F-I (98.2), expA (5.5), se-int (98.2), sec canine (1.8), siet (100), sea (5.5), seb (3.6), sec (10.9), sed (54.5), sei (5.5), sej (29.1), sek (3.6), ser (9.1), and hlg v (38.2). Ten different sequence-types were detected among 11 representative MSSP isolates: ST20, ST44, ST69, ST70, ST78, ST100, ST108, ST160, ST161, and ST162, the last three ones revealing novel alleles or allele combinations. Eleven different PFGE-patterns were identified in these isolates. The nares of healthy dogs could be a reservoir of antimicrobial resistant and virulent MSSP, highlighting the presence of the recently described exfoliating gene expA and several enterotoxin genes.

Staphylococcus pseudintermedius in the dog: taxonomy, diagnostics, ecology, epidemiology and pathogenicity

The dog is the natural host of Staphylococcus pseudintermedius. Many research efforts are currently being undertaken to expand our knowledge and understanding of this important canine commensal and opportunistic pathogen. The objective of this review is to summarize the current knowledge of the species, including the latest research outcomes, with emphasis on taxonomy, diagnostics, ecology, epidemiology and pathogenicity. Despite the important taxonomic changes that have occurred over the past few years, the risk of misidentification in canine specimens is low and does not have serious consequences for clinical practice. Staphylococcus pseudintermedius carriage in the dog is more frequent and genetically heterogeneous compared with that of Staphylococcus aureus in man. It appears that these staphylococcal species have evolved separately through adaptation to their respective natural hosts and differ with regard to various aspects concerning ecology, population structure and evolution of antibiotic resistance. Further understanding of the ecology and epidemiology of S. pseudintermedius is hampered by the lack of a standard method for rapid and discriminatory typing and by the limited data available on longitudinal carriage and population structure of meticillin-susceptible strains. With regard to pathogenicity, it is only now that we are starting to explore the virulence potential of S. pseudintermedius based on genomic and proteomic approaches, and more research is needed to assess the importance of individual virulence factors and the possible existence of hypervirulent strains.

Comparative genomics of the Staphylococcus intermedius group of animal pathogens

The Staphylococcus intermedius group consists of three closely related coagulase-positive bacterial species including S. intermedius, Staphylococcus pseudintermedius, and Staphylococcus delphini. S. pseudintermedius is a major skin pathogen of dogs, which occasionally causes severe zoonotic infections of humans. S. delphini has been isolated from an array of different animals including horses, mink, and pigeons, whereas S. intermedius has been isolated only from pigeons to date. Here we provide a detailed analysis of the S. pseudintermedius whole genome sequence in comparison to high quality draft S. intermedius and S. delphini genomes, and to other sequenced staphylococcal species. The core genome of the SIG was highly conserved with average nucleotide identity (ANI) between the three species of 93.61%, which is very close to the threshold of species delineation (95% ANI), highlighting the close-relatedness of the SIG species. However, considerable variation was identified in the content of mobile genetic elements, cell wall-associated proteins, and iron and sugar transporters, reflecting the distinct ecological niches inhabited. Of note, S. pseudintermedius ED99 contained a clustered regularly interspaced short palindromic repeat locus of the Nmeni subtype and S. intermedius contained both Nmeni and Mtube subtypes. In contrast to S. intermedius and S. delphini and most other staphylococci examined to date, S. pseudintermedius contained at least nine predicted reverse transcriptase Group II introns. Furthermore, S. pseudintermedius ED99 encoded several transposons which were largely responsible for its multi-resistant phenotype. Overall, the study highlights extensive differences in accessory genome content between closely related staphylococcal species inhabiting distinct host niches, providing new avenues for research into pathogenesis and bacterial host-adaptation.

Review on methicillin-resistant Staphylococcus pseudintermedius

Staphylococcus pseudintermedius is an important opportunistic pathogen of companion animals, especially dogs. Since 2006 there has been a significant emergence of methicillin-resistant S. pseudintermedius (MRSP) mainly due to clonal spread. This article reviews research on MRSP with a focus on occurrence, methods used for identification, risk factors for colonization and infection, zoonotic potential and control options. Potential areas for future research are also discussed.

Antibiotic resistance of canine Staphylococcus intermedius group (SIG)--practical implications

A total of 221 SIG strains were isolated from clinical samples of canine origin submitted to the Diagnostic Laboratory of the Division of Bacteriology and Molecular Biology at the Warsaw University of Life Sciences in Warsaw during the period 2006-2010. The aim of the study was to investigate the frequency of prevalence of methicillin-resistant SIG strains and to determine the MIC values of cephalotin, amoxicillin/clavulanic acid, ciprofloxacin, clindamycin, gentamicin, chloramphenicol, mupirocin for a collection of randomly selected 79 strains belonging to Staphylococcus intermedius group (SIG), including 23 mecA-positive and 56 mecA-negative strains. All isolates were identified as belonging to SIG based on their phenotypic properties and PCR amplification of S. intermedius-specific fragment of the 16S rRNA gene. The mecA gene was detected in 26 (12%) of 221 SIG strains. All tested mecA-negative SIG strains were susceptible to amoxicillin/clavulanic acid and cephalotin. One of the 56 mecA-negative SIG strains was resistant to ciprofloxacin, six (11%) to gentamicin. It was found that sixteen (29%) of 56 mecA-negative SIG strains were resistant to clindamycin. Most of the mecA-positive SIG strains were resistant to ciprofloxacin (96%), clindamycin (96%), and gentamicin (96%). Only one MRSIG strain was resistant to chloramphenicol. All examined mecA-positive SIG strains were found to be susceptible to mupirocin. Our results imply that staphylococcal multidrug resistance has become more prevalent, which could lead to difficulties in effective treatment. With some resistant strains the only therapeutic possibility are antimicrobial agents important in human medicine. New regulations for veterinary medicine concerning appropriate therapy of infections caused by multidrug-resistat staphylococci are needed.

Complete genome sequence of the canine pathogen Staphylococcus pseudintermedius

We report the first whole-genome sequence for a clinical isolate of Staphylococcus pseudintermedius (ED99), the major pathogen responsible for canine bacterial pyoderma. S. pseudintermedius contains numerous mobile genetic elements and encodes an array of putative virulence factors, including superantigenic, cytolytic, and exfoliative toxins and cell wall-associated surface proteins.

Identification of first exfoliative toxin in Staphylococcus pseudintermedius

Staphylococcus aureus, Staphylococcus hyicus, and Staphylococcus chromogenes are known to cause skin infections in human or animals by producing exfoliative toxins (ETs). Staphylococcus pseudintermedius can also cause canine pyoderma, but no exfoliative toxins or similar toxins have been reported. PCR with degenerate primers targeted to the conserved regions in ETA, ETB, and ETD from S. aureus and SHETB from S. hyicus, and subsequent chromosome walking identified a novel gene, designated as exi (exfoliative toxin of pseudintermedius) in S. pseudintermedius. EXI had significant homologies with the exfoliative toxins (43-68% identity), particularly with ETB (67.1%), ETD (67.9%), and SHETB (65.1%). Phylogenetic analysis showed close relation between EXI and ETB with a bootstrap value of 80%. Neonatal mice injected with the crude proteins from the culture supernatant or recombinant EXI showed gross blisters and/or characteristic skin exfoliation. The prevalence of exi assessed by dot-blot hybridization was 23.3% (10/43) in S. pseudintermedius isolates from canine pyoderma. The EXI reported herein is the first exfoliative toxin identified in S. pseudintermedius.

High occurrence of multi-antimicrobial resistance in Staphylococcus intermedius isolates from healthy and diseased dogs and domesticated pigeons

Staphylococcus intermedius isolates (n=106), including 44 dog isolates and 62 pigeon isolates, were examined for their susceptibility to ampicillin, cephalexin, erythromycin, gentamicin, kanamycin, lincomycin, norfloxacin, oxacillin, tetracycline, and vancomycin by standard disk-diffusion test. The frequencies of resistance to ampicillin, kanamycin, and tetracycline were significantly higher in dog isolates than pigeon isolates (95.5% vs. 0%, 31.8% vs. 0%, and 45.5% vs. 9.7%, respectively; P<0.01). Antimicrobial resistance patterns of dog isolates and pigeon isolates were categorized respectively into nine and five distinct profiles. Significantly higher occurrence of resistance to two or more antimicrobials was observed in dog isolates than pigeon isolates (54.5% vs. 12.9%; P<0.01) and also in domesticated pigeon isolates than non-domesticated pigeon isolates (53.3% vs. 0%; P<0.01).

Reclassification of phenotypically identified staphylococcus intermedius strains

To reclassify phenotypically identified Staphylococcus intermedius strains, which might include true S. intermedius strains and novel species such as Staphylococcus pseudintermedius and Staphylococcus delphini, we analyzed molecular phylogenies and phenotypic characteristics of 117 S. intermedius group (SIG) strains tentatively identified as being S. intermedius by the Rapid ID32 Staph assay. From phylogenetic analyses of sodA and hsp60 sequences, the SIG strains were divided into three clusters, which belonged to S. pseudintermedius LMG 22219(T), S. intermedius ATCC 29663(T), and S. delphini LMG 22190(T). All the SIG strains from dogs, cats, and humans were identified as being S. pseudintermedius. The wild pigeon strains, except one, were identified as being S. intermedius, and strains from all domestic pigeons, one wild pigeon, horses, and a mink were identified as being S. delphini. In addition, a phylogenetic analysis of nuc genes revealed that S. delphini strains were divided into two clusters: one was the cluster (S. delphini group A) that belonged to S. delphini LMG 22190(T), and the other was the cluster (S. delphini group B) that was more related to S. pseudintermedius LMG 22219(T) than S. delphini LMG 22190(T). The DNA-DNA hybridization results showed that S. delphini group B strains were distinguished from S. delphini group A, S. intermedius, and S. pseudintermedius strains. S. intermedius is distinguishable from S. pseudintermedius or S. delphini by positive arginine dihydrolase and acid production from beta-gentiobiose and d-mannitol. However, phenotypical characteristics to differentiate S. delphini group A, S. delphini group B, and S. pseudintermedius were not found. In conclusion, SIG strains were reclassified into four clusters with three established and one probably novel species.

Methicillin-resistant Staphylococcus pseudintermedius in a veterinary teaching hospital

We surveyed methicillin-resistant coagulase-positive staphylococcus (MRCPS) strains from 57 (26 inpatient and 31 outpatient) dogs and 20 veterinary staff in a veterinary teaching hospital. From the staff, three MRCPS strains were isolated, and two were methicillin-resistant Staphylococcus aureus (MRSA). In contrast, 18 MRCPS strains were detected in both inpatient (12 of 26 [46.2%]) and outpatient (6 of 31 [19.4%]) dogs. Among them, only one strain was MRSA. Using direct sequencing of sodA and hsp60 genes, the 18 MRCPS strains other than MRSA from a staff and 17 dogs, were finally identified as Staphylococcus pseudintermedius, a novel species of Staphylococcus from a cat. All of the methicillin-resistant S. pseudintermedius (MRSP) strains were multidrug resistant to erythromycin, clindamycin, trimethoprim-sulfamethoxazole, and levofloxacin. Most of the MRSP strains showed high-level resistance to oxacillin (>/=128 mug/ml, 15 of 18 [83.3%]), and 10 of 15 (66.7%) high-level oxacillin-resistant MRSP strains carried type III SCCmec. DNA fingerprinting of MRSP strains by pulsed-field gel electrophoresis yielded eight clusters: clone A with four subtypes, clone B with four subtypes, clone C with three subtypes, and five other different single clones. MRSP strains from the staff and some inpatient and outpatient dogs shared three major clones (clones A, B, and C), but the strains of the other five different clusters were distributed independently among inpatient or outpatient dogs. This genetic diversity suggested that the MRSP strains were not only acquired in this veterinary teaching hospital but also acquired in primary veterinary clinics in the community. To our knowledge, this is the first report of MRSP in dogs and humans in a veterinary institution.

Prevalence of virulence factors in Staphylococcus intermedius isolates from dogs and pigeons

Background

Staphylococcus intermedius has been isolated from healthy dogs and pigeons as well as diseased dogs. Similar to Staphylococcus aureus, S. intermedius is known to carry many virulence factors but most of these factors remain to be studied. In this study, we examined 106 S. intermedius isolates (44 dog isolates and 62 pigeon isolates) for their hemolytic activity, biofilm formation, protease activity, and clumping factor and protein A production.

Results

Forty-three dog isolates (97.7%) and all pigeon isolates were hemolytic on sheep RBCs with a mean hemolytic titer of 336.7 and 47.32, respectively, whereas 43 dog isolates (97.7%) and 11 pigeon isolates (17.7%) exhibited a significant difference in their hemolytic activity on rabbit RBCs with a mean hemolytic titer of 11.04 and 3.76, respectively (p < 0.0005). The mean biofilm formation activity for dog isolates was 0.49, which was significantly higher than that (0.33) for pigeon isolates (p < 0.0005). Twenty-four dog isolates (54.5%) and 11 pigeon isolates (17.7%) were protease positive. Twenty-four dog isolates (54.5%) were clumping factor- and protein A- positive.

Conclusion

S. intermedius strains carrying the virulence factors examined in this study were more prevalent in dogs than pigeons.

Prevalence and characterization of leukotoxin-producing Staphylococcus intermedius in Isolates from dogs and pigeons

Staphylococcus intermedius isolates from dogs (n = 44) and pigeons (n = 62) were categorized into 12 types by intergenic ribosomal DNA spacer polymorphism analysis. All isolates from pigeons were lukS positive and all isolates from dogs were lukS and lukF positive by dot blot analysis. The mean leukotoxicity titer for dog isolates was at least 129-fold higher than that for pigeon isolates.

Characteristics of Staphylococcus intermedius Isolates from Diseased and Healthy Dogs

Staphylococcus intermedius isolates from diseased and healthy dogs were examined for production of extracellular enzymes and toxins, and phage patterns. There were no significant differences between the two groups of isolates in the production rates of DNase, protease, lipase, gelatinase, hyaluronidase, hemolysins, protein A, and TSST-1, or in phage patterns. But the production rate of enterotoxins in isolates from diseased dogs was significantly higher than that in isolates from healthy dogs. PFGE analysis was performed with isolates from different body sites in individual dogs. In 3 of 6 healthy dogs, identical PFGE patterns were seen in isolates from the nares, external auditory meatus or skin. The remaining 3 dogs yielded isolates of different patterns. In 4 of 6 diseased dogs, identical patterns were seen in isolates from lesions as well as from the other normal sites.