Enterotoxin and toxic shock syndrome toxin-1 production by staphylococci isolated from goat's milk

Staphylococcus haemolyticus: An updated review on nosocomial infections, antimicrobial resistance, virulence, genetic traits, and strategies for combating this emerging opportunistic pathogen

Staphylococcus haemolyticus, a key species of the Staphylococcus genus, holds significant importance in healthcare-associated infections, due to its notable resistance to antimicrobials, like methicillin, and proficient biofilms-forming capabilities. This coagulase-negative bacterium poses a substantial challenge in the battle against nosocomial infections. Recent research has shed light on Staph. haemolyticus genomic plasticity, unveiling genetic elements responsible for antibiotic resistance and their widespread dissemination within the genus. This review presents an updated and comprehensive overview of the clinical significance and prevalence of Staph. haemolyticus, underscores its zoonotic potential and relevance in the one health framework, explores crucial virulence factors, and examines genetics features contributing to its success in causing emergent and challenging infections. Additionally, we scrutinize ongoing studies aimed at controlling spread and alternative approaches for combating it.

Enterotoxigenic and Antimicrobic Susceptibility Profile of Staphylococcus aureus Isolates from Fresh Cheese in Croatia

Certain Staphylococcus aureus strains harbour staphylococcal enterotoxin genes and hence can produce enterotoxin during their growth in food. Therefore, food can be a source of staphylococcal food poisoning, one of the most common food-borne diseases worldwide. Epidemiological data show that S. aureus is often present in raw milk cheeses, and consequently, cheeses are often the source of staphylococcal food poisoning outbreaks. The aim of this study was to determine the phenotypic characteristics of S. aureus isolates from fresh cheese, including antibiotic susceptibility; the presence of classical sea-see enterotoxin genes through molecular methods; and the isolate's ability to produce SEA-SEE enterotoxins in vitro through reversed passive latex agglutination. A total of 180 coagulase-positive staphylococci were isolated from 18 out of 30 cheese samples, and 175 were confirmed as S. aureus through latex agglutination and API STAPH tests. All isolates possessed phenotypic characteristics typical for S. aureus, with certain variations in the egg yolk reaction (18.3% of the isolates showed a weak reaction and 28% no reaction at all) and haemolysis pattern (36.6% of the isolates produced double-haemolysis and 4.6% were non-haemolytic). Antibiotic resistance was observed in 1.1% of the isolates and to mupirocin only. Real-time PCR detected the sec gene in 34 (19.4%) isolates, but most isolates (80.6%) were not enterotoxigenic. For all 34 (19.4%) strains that carried the sec gene, the RPLA method detected the production of the SEC enterotoxin in vitro. For those enterotoxigenic strains, the possibility of enterotoxin production in fresh cheese could not be ruled out.

Association Between the Methicillin Resistance of Staphylococcus aureus Isolated from Slaughter Poultry, Their Toxin Gene Profiles and Prophage Patterns

In this work, 85 strains of Staphylococcus aureus were isolated from samples taken from slaughter poultry in Poland. Attempts were made to determine the prophage profile of the strains and to investigate the presence in their genome of genes responsible for the production of five classical enterotoxins (A–E), toxic shock syndrome toxin (TSST-1), exfoliative toxins (ETA and ETB) and staphylokinase (SAK). For this purpose, multiplex PCR was performed using primer-specific pairs for targeted genes. The presence of the mecA gene was found in 26 strains (30.6%). The genomes of one of the methicillin-resistant S. aureus (MRSA) strains and two methicillin-sensitive S. aureus (MSSA) strains contained the gene responsible for the production of enterotoxin A. Only one MRSA strain and two MSSA strains showed the presence of the toxic shock syndrome toxin (tst) gene. Only one of the MSSA strains had the gene (eta) responsible for the production of exfoliative toxins A. The presence of the staphylokinase gene (sak) was confirmed in 13 MRSA strains and in 5 MSSA strains. The study results indicated a high prevalence of prophages among the test isolates of Staphylococcus aureus. In all, 15 prophage patterns were observed among the isolates. The presence of 77-like prophages incorporated into bacterial genome was especially often demonstrated. Various authors emphasize the special role of these prophages in the spread of virulence factors (staphylokinase, enterotoxin A) not only within strains of the same species but also between species and even types of bacteria.

Staphylococcus aureus and staphylococcal food-borne disease: an ongoing challenge in public health

Staphylococcal food-borne disease (SFD) is one of the most common food-borne diseases worldwide resulting from the contamination of food by preformed S. aureus enterotoxins. It is one of the most common causes of reported food-borne diseases in the United States. Although several Staphylococcal enterotoxins (SEs) have been identified, SEA, a highly heat-stable SE, is the most common cause of SFD worldwide. Outbreak investigations have found that improper food handling practices in the retail industry account for the majority of SFD outbreaks. However, several studies have documented prevalence of S. aureus in many food products including raw retail meat indicating that consumers are at potential risk of S. aureus colonization and subsequent infection. Presence of pathogens in food products imposes potential hazard for consumers and causes grave economic loss and loss in human productivity via food-borne disease. Symptoms of SFD include nausea, vomiting, and abdominal cramps with or without diarrhea. Preventive measures include safe food handling and processing practice, maintaining cold chain, adequate cleaning and disinfection of equipment, prevention of cross-contamination in home and kitchen, and prevention of contamination from farm to fork. This paper provides a brief overview of SFD, contributing factors, risk that it imposes to the consumers, current research gaps, and preventive measures.

Enterotoxigenic potential of coagulase-negative staphylococci

Staphylococci are a worldwide cause of human and animal infections including life-threatening cases of bacteraemia, wound infections, pyogenic lesions, and mastitis. Enterotoxins produced by some staphylococcal species were recognized as causative agents of staphylococcal food poisoning (SFP), being also able to interrupt human and animal immune responses. Only enterotoxins produced by Staphylococcus aureus were as yet well characterized. Much less is known about enterotoxigenic potential of coagulase-negative species of genus Staphylococcus (CNS). The pathogenic role of CNS and their enterotoxigenicity in developing SFP has not been well established. Although it has been reported that enterotoxigenic CNS strains have been associated with human and animal infections and food poisoning, most of research lacked a deeper insight into structure of elements encoding CNS enterotoxins. Recent studies provided us with strong evidence for the presence and localization of enterotoxin-coding elements in CNS genomes and production of enterotoxins. Thus, the importance of pathogenic potential of CNS as a source of staphylococcal enterotoxins has been highlighted in human and animal infections as well as in food poisoning.

Staphylococcus aureus and its food poisoning toxins: characterization and outbreak investigation

Staphylococcal food poisoning (SFP) is one of the most common food-borne diseases and results from the ingestion of staphylococcal enterotoxins (SEs) preformed in food by enterotoxigenic strains of Staphylococcus aureus. To date, more than 20 SEs have been described: SEA to SElV. All of them have superantigenic activity whereas half of them have been proved to be emetic, representing a potential hazard for consumers. This review, divided into four parts, will focus on the following: (1) the worldwide story of SFP outbreaks, (2) the characteristics and behaviour of S. aureus in food environment, (3) the toxinogenic conditions and characteristics of SEs, and (4) SFP outbreaks including symptomatology, occurrence in the European Union and currently available methods used to characterize staphylococcal outbreaks.

Characterization of Staphylococcus aureus strains associated with food poisoning outbreaks in France

Enterotoxins produced by Staphylococcus aureus are responsible for staphylococcal food-poisoning outbreaks (SFPO). In France, SFPO are the second cause of food-borne diseases after Salmonella. However, very little is known about the strains involved. The objective of this study was to characterize the staphylococcal strains related to these SFPO through phenotypic and genotypic analyses. A total of 178 coagulase-positive staphylococcal isolates recovered from 31 SFPO (1981-2002) were screened through biotyping. Thirty-three strains representative of the different biotypes in each SFPO were further examined for SmaI macrorestriction-type, phage-type, resistance to various antimicrobial drugs, presence of staphylococcal enterotoxin (se) genes sea to sei, and production of enterotoxins SEA to SED. All these 33 strains were identified as S. aureus species: 27 were of human biotypes and six ovine or non-host-specific biotypes. Most (74.1%) strains reacted with group III phages. Eleven strains were resistant to at least two classes of antibiotics and among them, two were resistant to methicillin. Twenty-nine strains carried one or several of the eight se genes tested; the gene sea was most common (n=23), and often linked to sed (n=12) or seh (n=5). The novel se genes seg-i were in all cases associated with se genes sea to sed except for one strain which carried only seg and sei. Pulsed-Field Gel Electrophoresis (PFGE) of SmaI macrorestriction digests of the 33 strains discriminated 32 PFGE patterns grouped into nine biotype-specific clusters. All five strains carrying sea and seh were grouped together into the same sub-cluster. Three of the four se-gene-negative strains were in one PFGE cluster: all four should be tested for se genes not included in this study and, if negative, be further investigated for the presence of unidentified SEs.

Occurrence, characterization and antimicrobial resistance of enterotoxigenic Staphylococcus aureus isolated from meat and dairy products

Staphylococcus aureus is considered to be one of the leading causes of food-borne illnesses. Milk, dairy products and meats are often contaminated with enterotoxigenic strains of this bacterium. Foodstuff contamination may occur directly from infected food-producing animals or may result from poor hygiene during production processes, or the retail and storage of foods, since humans may carry the microorganism. The number of S. aureus strains that exhibits antimicrobial-resistance properties has increased, together with the potential risk of transmitting the same properties to the human microflora via foods or inducing infections hard to be treated. This paper reports the results of a 3-year survey (2003-2005) on the occurrence of S. aureus in meat and dairy products. Of 1634 samples examined, 209 (12.8%) were contaminated with S. aureus. A total of 125 enterotoxigenic S. aureus strains were biotyped and their antimicrobial resistance pattern tested. Most of the isolated strains produced SED (33.6%), followed by SEA (18.4%), SEC (15.2%), SEB (6.4%) and belonged mainly to the Human ecovar (50.4%), followed by Ovine (23.2%), Non-Host-Specific (17.6%), Bovine (7.2%) and Poultry-like (1.6%) ecovars. Finally, the 68.8% analysed strains showed antimicrobial resistance properties at least at one of antibiotics tested. Human biotype showed antimicrobial resistance at more than one antibiotic than the other biotypes (p<0.05). The results provided evidence that the presence of enterotoxigenic and antimicrobial resistant strains of S. aureus has become remarkably widespread in foods. This calls for better control of sources of food contamination and of the spread of antimicrobial-resistance organisms.

Enterotoxigenic Staphylococcus aureus in bulk milk in Norway

AIMS

To investigate the presence of enterotoxigenic Staphylococcus aureus in bulk milk and in a selection of raw milk products.

METHODS AND RESULTS

Samples of bovine (n = 220) and caprine (n = 213) bulk milk, and raw milk products (n = 82) were analysed for S. aureus. Isolates were tested for staphylococcal enterotoxin (SE) production (SEA-SED) by reversed passive latex agglutination and for SE genes (sea-see, seg-sej) by multiplex PCR. Staphylococcus aureus was detected in 165 (75%) bovine and 205 (96.2%) caprine bulk milk samples and in 31 (37.8%) raw milk product samples. Enterotoxin production was observed in 22.1% and 57.3% of S. aureus isolates from bovine and caprine bulk milk, respectively, while SE genes were detected in 52.5% of the bovine and 55.8% of the caprine bulk milk isolates. SEC and sec were most commonly detected. A greater diversity of SE genes were observed in bovine vs caprine isolates.

CONCLUSIONS

Staphylococcus aureus seems highly prevalent in Norwegian bulk milk and isolates frequently produce SEs and contain SE genes. Enterotoxigenic S. aureus were also found in raw milk products.

SIGNIFICANCE AND IMPACT OF THE STUDY

Staphylococcus aureus in Norwegian bovine and caprine bulk milk may constitute a risk with respect to staphylococcal food poisoning from raw milk products.

Discrimination of Staphylococcus aureus biotypes by pulsed-field gel electrophoresis of DNA macro-restriction fragments

AIMS

To examine whether pulsed-field gel electrophoresis (PFGE) of DNA macro-restriction fragments could provide better discrimination among the different biotypes previously described within the species Staphylococcus aureus than the traditional biochemical approach.

METHODS AND RESULTS

Seventy three Staph. aureus strains from various sources (human, animal or food origin) and belonging to eight biotypes, including the poultry-like biotype, tentatively designated as an 'abattoir' biotype, were genotyped by PFGE after SmaI digestion of DNA. The PFGE patterns were compared using the average linkage matching method (UPGMA) with the Dice coefficient. A total of 61 PFGE patterns were observed, showing between 31 and 100% similarity. In most cases, strains with the same biotype were grouped specifically into one, two or three separate sub-clusters. Strains from the 'abattoir' biotype were clustered in one separate sub-cluster.

CONCLUSIONS

The PFGE typing is useful to distinguish the traditional biotypes of Staph. aureus and has a more discriminatory power than the biochemical typing.

SIGNIFICANCE AND IMPACT OF THE STUDY

The PFGE typing confirms the 'abattoir' biotype as a separate group on a genetic level and is well suited to investigate modes of staphylococcal contamination of food.

Enterotoxin production by staphylococci isolated from foods in France

Two hundred and thirteen Staphylococcus aureus and 51 other staphylococcal strains were isolated from 121 foodstuffs of current consumption and two cutaneous samples. Their ability to produce staphylococcal enterotoxins was tested and S. aureus strains were biotyped. The S. aureus strains (30.5%) produced at least one of the five known staphylococcal enterotoxins whereas coagulase negative staphylococci did not produce any of them. The raw milk cheeses analysed were primarily contaminated by strains belonging to animal or unspecified biovars. Only 15.9% of the S. aureus strains isolated from these products produced enterotoxins whereas 43% were found to be enterotoxigenic amongst the S. aureus strains isolated from the other foodstuffs. The scheme of biotyping used seems to be reliable, allowing the classification of 73.7% of the strains. S. aureus strains of human biovar origin were most often enterotoxigenic and enterotoxin C was the predominant type identified. It was produced by 66% of the enterotoxigenic strains, singly or in combination with other enterotoxins. Approximately 77% of the human strains also produced enterotoxin C, which is an amazing epidemiological distinctive feature of the strains studied. Moreover ELISA tests used in this work exhibit problems of specificity.

Enterotoxin production by coagulase-negative staphylococci isolated from goats' milk and cheese

An antigen related to the Enterotoxin E from Staphylococcus aureus was produced by ten of 187 coagulase-negative staphylococci (CNS) isolated from goats' milk, whey and cheese in quantities ranging from 10 to 90 ng/ml supernatant. The enterotoxin-producing strains were identified at the species level as S. simulans, S. xylosus, S. equorum, S. lentus and S. capitis. Detection of the enterotoxins was done by the VIDAS SET test (bioMérieux) and by an indirect double-sandwich ELISA technique using anti-enterotoxin monoclonal antibodies. The results obtained were further confirmed by Southern blotting, using two radioactive oligonucleotide probes that hybridized specifically with the gene of S. aureus coding for the enterotoxin E.

Identification of micrococcaceae isolated from goat's milk and cheese in the Poitou-Charentes region

One hundred and ninety strains of coagulase-negative staphylococci were isolated from goat's milk, whey and cheese at various stages of manufacture. Sixteen different coagulase negative Staphylococci (CNS) species were recovered, 3 of which were predominant: Staphylococcus simulans, Staphylococcus epidermidis and Staphylococcus xylosus. The prevalent species were recovered at least at two different stages of cheese manufacturing, suggesting a better adaptation to the environment. After 15 days of ripening, the cheeses showed lower counts of Micrococcaceae.

Toxic shock syndrome toxin-1 (TSST-1) production and phage susceptibility of Staphylococcus aureus strains from human vaginas and anterior nares in Trinidad

The carriage rates of Staphylococcus aureus in the anterior nares of children and women as well as in the vagina of women were determined. The ability of strains of S. aureus to produce toxic shock syndrome toxin-1 (TSST-1) and their susceptibility to phages of the international phage set (IPS) for human strains were also investigated. Of 200 women studied, the carriage rate of S. aureus in high vaginal swabs and anterior nares swabs was 57 (28.5%) and 73 (36.5%), respectively. Eight (4.0%) and 16 (8.0%) patients were carriers of TSST-1-producing strains in their vaginas and anterior nares, respectively. Amongst the 220 children sampled, 100 (45.5%) were carriers of S. aureus in their anterior nares, with 51 (23.2%) children being positive for TSST-1 producing strains. Overall, of the 233 strains of S. aureus isolated from all sources 176 (75.5%) were typable and 75 (32.2%) were positive for TSST-1 production. For strains from anterior nares, isolates from children were more susceptible (81.2%) to IPS phages than those from women (67.1%) but the difference was not significant (P > or = 0.05; chi 2). Forty-five (76.3%) of 59 strains of vaginal origin were typable. The frequency of production of TSST-1 amongst strains isolated from children, i.e. (50.5% (51 of 101), was significantly higher (P > or = 0.001; chi 2) than that found for isolates from women's anterior nares (21.9%) and vagina (13.6%). S. aureus was recovered from both the anterior nares and vaginal swabs of 11 patients sampled. The phage patterns of 5 of the 6 typable pairs of isolates established their relatedness suggesting that the same strains colonized the anterior nares and vagina of each of these patients. It was concluded that the carriage of TSST-1-producing strains of S. aureus in the anterior nares and vagina of women was much lower than that detected in children's anterior nares and that the risk of vaginal toxic shock syndrome (TSS) in Trinidadian women was relatively low. Susceptibility of strains was high to IPS phages. Epidemiological significance was attributed to the finding that the same strains of S. aureus colonized the anterior nares and vaginas of some women.

Detection of enterotoxins and TSST-1 secreted by Staphylococcus aureus isolated from ruminant mastitis. Comparison of ELISA and immunoblot

The production of staphylococcal enterotoxins (SE) and toxic shock syndrome toxin-1 (TSST-1) was studied in 81 strains of Staphylococcus aureus isolated from cases of mastitis in cattle, goats and sheep. SE and TSST-1 were detected by two techniques: ELISA double antibody sandwich, and an immunoblot technique combined with a semiautomated electrophoresis system. More Staph. aureus strains isolated from sheep produced enterotoxins than those from goats and cattle. SEC was the predominant type in all isolates from these animal species. The highest proportion of strains producing TSST-1 were obtained from sheep, twice as many as those from goats or cows. The two techniques gave similar results, as all the strains positive by immunoblot were also positive by ELISA, and only three were positive by ELISA but negative by immunoblot.

Characteristics of bovine Staphylococcus aureus with special regard to clumping factor activity

The occurrence of the following groups of bovine Staphylococcus aureus with characteristic patterns of biochemical reactions and sensitivities to phages was confirmed by the present investigation of 662 isolates from the udders of cows in 53 dairy herds: (1) host-specific variety (v) bovis, (2) not alloted strains with the basic marker, crystal violet type A (group na CV A), (3) group na CV C. The latter was split into three subgroups clearly differing in phage susceptibility patterns: I/119, I without 119 and III, respectively. Lack of clumping factor activity occurred in 323 out of 346 (93%) phage pattern I/119 strains examined while most or all isolates of the other groups of bovine strains proved to be clumping-positive.

Enterotoxin production in different Staphylococcus aureus biotypes isolated from food and meat plants

Strains of Staphylococcus aureus isolated in Belgium and Zaïre from food and from various sources in the meat industry were biotyped, phage typed and tested for staphylococcal enterotoxin (SE) production. Thirty of the 185 strains examined produced one or more SE, and 23 of these belonged to the human biotype. Most SE-positive strains belonged to phage groups III and Mixed, or were not typable. None of the poultry-like biotype strains, which were frequent in nasal carriers among workers in meat plants as well as in minced meat, produced enterotoxins. Avian biotype strains similarly were negative.

Screening of staphylococci for the toxic shock syndrome toxin-1 (TSST-1) gene

Dot blot hybridization was used to screen 820 staphylococci for the presence of the gene coding for TSST-1. The DNA of 33 strains among 70 Staph. aureus strains isolated from suspected toxic shock syndrome (TSS) cases hybridized with the probe. These results agreed perfectly with those obtained with a phenotypic method (immunodiffusion). Among 608 Staph. aureus strains isolated over a period of one month from hospitalized patients, 66 (11%) hybridized with the probe; of these strains, 64 (97%) were found to produce TSST-1 in vitro. None of 145 coagulase-negative staphylococcal strains harboured DNA hybridizing with the probe. The data indicate that this genotypic assay is suitable for epidemiological studies.

Toxic shock syndrome toxin 1 (TSST-1) production by staphylococci isolated from goats and presence of specific antibodies to TSST-1 in serum and milk

The ability of staphylococcal strains isolated from different anatomical sites in 133 healthy goats to produce toxic shock syndrome toxin 1 (TSST-1) and the presence of antibodies to this toxin in serum and milk were studied. The enzyme-linked immunosorbent assay method was used to detect both the toxin and the presence of antibodies. Of a total of 342 staphylococcal strains studied, 86 (25.2%) were found to produce TSST-1. Specific antibodies to TSST-1 were found in the serum of 57 (42.9%) of the animals studied and the milk of 63 (47.4%) of the animals. These results suggest that goats are frequently in contact with staphylococci that produce TSST-1, a toxin usually associated with Staphylococcus aureus strains isolated from cases of toxic shock syndrome in humans.

Staphylococci isolated from healthy goats

A study was made of the staphylococcal population on the skin and on the nasal mucosa and in the milk of 133 healthy goats. Of a total of 346 strains isolated and characterised as belonging to the genus Staphylococcus, 74 (21.4%) were coagulase-positive (68 S. aureus and 6 S. hyicus), and 272 (78.6%) coagulase-negative. The novobiocin-sensitive species S. haemolyticus (23.5%), S. warneri (16.5%), S. epidermidis (11.8%), S. chromogenes (8.5%), S. caprae (6.6%) and S. hyicus (2.6%), and the novobiocin-resistant species S. xylosus (8.5%), S. sciuri (7.4%), S. saprophyticus (4.8%), S. cohnii (2.2%), S. lentus (1.1%), S. equorum (1.1%) and S. kloosii (1.1%) were identified. Twelve (4.4%) of coagulase-negative strains remained unidentified. Strains isolated in the skin of the udder and teats of the 133 goats were mainly novobiocin-sensitive coagulase-negative staphylococci, the most prevalent species being S. haemolyticus, S. warneri and S. epidermidis. Staphylococci indicative of subclinical infection were determined in the milk of 47 (35.3%) of the 133 goats sampled.

Enterotoxin production by staphylococci isolated from healthy goats

The ability of 342 staphylococcal isolates from different anatomical sites in healthy goats to produce staphylococcal enterotoxins (SE) was investigated. SE were produced by 74.3% of the 70 coagulase-positive strains and by 22% of the coagulase-negative strains studied. Most enterotoxigenic strains were isolated from the skin of udders and teats and from milk. SEC was the SE type most frequently produced, either alone (67.9%) or in combination with others. Five coagulase-negative species not previously reported as SE producers were identified (Staphylococcus chromogenes, S. warneri, S. sciuri, S. saprophyticus, and S. lentus). SEA, SEB, and SEC were detected in the milk of 17 of the 133 healthy goats studied. These results suggest that the goat is an important reservoir of enterotoxigenic staphylococci, most of which produce SEC.

Bacteriological quality of on-farm manufactured goat cheese

The bacteriological quality of 198 ripened soft or semi-soft goat cheeses obtained from dairy farms and the retail trade was investigated. The cheeses were examined for total counts of aerobic bacteria, coliform bacteria (37 and 44 degrees C respectively), enterococci, coagulase positive staphylococci, Bacillus cereus and Clostridium perfringens. Cheeses obtained from dairy-farms were also determined for pH value. In terms of all tests performed, cheeses made of heat-treated milk with starter culture had the best prospects for fulfilling the criteria for 'fit for consumption'. Cheeses made of raw milk without starter culture made up the most unsatisfactory group from a food-hygiene point of view. Bacteriological guidelines for on-farm manufactured goat cheese are suggested.

Production of a toxic shock syndrome toxin variant by Staphylococcus aureus strains associated with sheep, goats, and cows

A toxic shock syndrome toxin (TSST) variant with an isoelectric point (pI) of 8.6 produced by an ovine-associated Staphylococcus aureus strain was described previously. Analysis of additional strains associated with sheep, goats, cows, and humans by isoelectric focusing with immunoblotting using monoclonal antibodies revealed that all 18 strains associated with sheep and all 12 strains associated with goats produced the TSST variant. Only 1 of 10 bovine-associated strains and no human-associated strains produced the variant, whereas the others produced TSST-1 (pI between 7.0 and 7.2). Sodium dodecyl sulfate-polyacrylamide gel electrophoresis with immunoblotting indicated that both TSST-1 and the TSST variant had a molecular size of 24 kilodaltons.

Enterotoxigenicity of Staphylococcus intermedius of canine origin

Seventy-three staphylococcal strains isolated from pyrodermatitis in dogs were classified as Staphylococcus intermedius (52 strains) or Staphylococcus aureus (21 strains) on the basis of acetoin formation, anaerobic mannitol fermentation, aerobic maltose fermentation, pigmentation, coagulation of human plasma, and reaction on crystal violet agar. Enterotoxin was produced by 13 of the 52 S. intermedius strains and 6 of the S. aureus strains. The highest percentage of enterotoxigenic strains produced enterotoxins C (6 strains), D (7 strains), and E (6 strains). Four strains produced the toxic shock syndrome toxin-1. There was little difference in the antibiotic susceptibility between the enterotoxigenic and non-enterotoxigenic strains.