Identification of Staphylococcus species of bovine origin with the API Staph-Ident system

Nasal carriage of Methicillin-Resistant Staphylococcus aureus among sympatric free-ranging domestic pigs and wild Chlorocebus pygerythrus in a rural African setting

BACKGROUND

Methicillin Resistant Staphylococcus aureus (MRSA) nasal carriage in domestic pigs and vervet monkeys is a risk factor for subsequent severe infections in domestic pigs and for dissemination to the human population. This study assessed nasal carriage of MRSA in domestic pigs and sympatric vervet monkeys in a rural African village during an outbreak of a virus hemorrhagic fever suspected to be contracted from wild primates. This study was conducted during the 2012 Ebola outbreak to determine nasal carriage of MRSA in free-ranging domestic pigs and sympatric freely roaming vervet monkeys using conventional methods. Staphylococcus aureus (S. aureus) isolated from the anterior nares were tested for susceptibility to commonly used antibiotics and conventional PCR was used to confirm methicillin resistance. The MRSA strains were then genotyped using SCCmec typing.

RESULTS

Overall, there was a high level of resistance to tetracycline [90% (63/70) in pigs and 67% (10/15) in vervet monkeys], trimethoprim/sulphamethoxazole [90% (63/70) in pigs and 67% (10/15) in vervet monkeys], and penicillin [83% (58/70) in pigs and 67% (10/15) in vervet monkeys]. Most of the MRSA strains (91.6%, 11/12) were of the SCCmec type I [1B] genotype.

CONCLUSION

The nasal carriage of drug resistant S. aureus in freely roaming domestic and wild animals presents a risk for widespread environmental spread of antimicrobial resistance thus presenting a risk for treatment failure in domestic animals, wild animals, and humans.

Development of a PCR test to differentiate between Staphylococcus aureus and Staphylococcus intermedius

The presence of Staphylococcus intermedius in food remains unclear because routine laboratory analysis does not discriminate between S. intermedius and Staphylococcus aureus, a major cause of food poisoning. Both species share many phenotypic characteristics, including coagulase and thermonuclease production. In both species, some strains can produce enterotoxin and therefore can be the cause of food poisoning outbreaks. Although the ID32 Staph System (bioMérieux, SA, Marcy l'Etoile, France), based on a miniaturized phenotypic characterization, gives satisfactory results for discriminating between these two species, some rapid molecular PCR-based methods have been developed to identify S. aureus specifically, but they do not identify S. intermedius. Here, we developed a rapid, accurate, and discriminative multiplex PCR method that targets species-specific sequences in the nuc gene, which encodes thermonuclease in the two species. The test includes an internal positive control that targets a highly conserved region of 16S ribosomal RNA gene (rDNA). A total of 116 strains were used to validate our test. The test gave no signal on the following Staphylococcus species: S. epidermidis, S. chromogenes, S. hyicus, S. warneri, S. xylosus, S. lentus, and S. sciuri. It allowed a 100% successful discrimination between S. aureus (44 strains tested) and S. intermedius (57 strains) isolated from different origins.

A survey on the microbiological changes during the manufacture of dry-cured lacón, a Spanish traditional meat product

This article describes a microbiological study carried out on lacón, a dry-cured meat product made in the north-west of Spain from the fore extremity of pig. Using classical methods, aerobic mesophilic flora, salt-tolerant flora, lactic acid bacteria, Enterobacteriaceae, enterococci, moulds and yeasts were enumerated, some physicochemical parameters (pH, aw and moisture and NaCl contents) were determined and a representative number of isolates of the salt-tolerant flora (the main microbial group) were identified during the manufacture of five batches. All the microbial groups, with the exception of Enterobacteriaceae and enterococci, reached maximum counts both on the surface and in the interior of the pieces at the end of the post-salting stage and afterwards progressively dropped during the drying-ripening stage. Staphylococcus xylosus, Staph. saprophyticus, Staph. simulans, Staph. sciuri and Micrococcus luteus were the main species isolated throughout manufacturing. This study will significantly increase knowledge of the microbiology of cured meat products made from entire pieces.

Evaluation of two commercial systems and a new identification scheme based on solid substrates for identifying coagulase-negative staphylococci from bovine mastitis

Coagulase-negative staphylococci (CNS), mainly isolated from bovine mastitis (n = 89, representing 11 different species), were used to evaluate two commercial identification systems: ID 32 Staph and Staph-Zym. The level of agreement between the ID 32 Staph and Staph-Zym systems and conventional methods was 77 and 94%, respectively. An alternative method, based on solid biochemical substrates, is also presented. This can be used for identifying novobiocin-sensitive CNS strains from bovine mastitis.

Use of enzyme tests in characterization and identification of aerobic and facultatively anaerobic gram-positive cocci

The contribution of enzyme tests to the accurate and rapid routine identification of gram-positive cocci is introduced. The current taxonomy of the genera of aerobic and facultatively anaerobic cocci based on genotypic and phenotypic characterization is reviewed. The clinical and economic importance of members of these taxa is briefly summarized. Tables summarizing test schemes and kits available for the identification of staphylococci, enterococci, and streptococci on the basis of general requirements, number of tests, number of taxa, test classes, and completion times are discussed. Enzyme tests included in each scheme are compared on the basis of their synthetic moiety. The current understanding of the activity of enzymes important for classification and identification of the major groups, methods of testing, and relevance to the ease and speed of identification are reviewed. Publications describing the use of different identification kits are listed, and overall identification successes and problems are discussed. The relationships between the results of conventional biochemical and rapid enzyme tests are described and considered. The use of synthetic substrates for the detection of glycosidases and peptidases is reviewed, and the advantages of fluorogenic synthetic moieties are discussed. The relevance of enzyme tests to accurate and meaningful rapid routine identification is discussed.

Identification of Streptococcus species by randomly amplified polymorphic deoxyribonucleic acid fingerprinting

Identification of Streptococcus species isolated from bovine milk by randomly amplified polymorphic DNA fingerprinting was evaluated. Bacterial DNA templates were prepared using a standardized method for randomly amplified polymorphic DNA amplification and previously evaluated arbitrary primers. Amplified DNA fragments were visualized by agarose gel electrophoresis and were analyzed by densitometry. Unidentified streptococci (n = 163) that were isolated from mammary secretions of dairy cows were evaluated. The DNA fingerprint patterns of unidentified bacteria were compared using a computerized database that contained DNA fingerprint patterns of test strains. Comparison with the API 20 Strep identification system (bioMérieux Vitek, Inc., Hazelwood, MO) and conventional biochemical tests showed that about 91% of isolates (148 of 163) were identified correctly by DNA fingerprinting. The sensitivity of the DNA fingerprinting technique was 90%, and the specificity was 92%. However, the DNA fingerprinting technique only identified 4 of the 11 species included in the study. Three of the 4 species, Streptococcus uberis, Streptococcus agalactiae, and Streptococcus dysgalactiae, represent the streptococci isolated most frequently from cows with mastitis. The other Streptococcus and Enterococcus species that were not identified by the DNA fingerprinting system are less frequently isolated as causative agents of mastitis. Expanding the DNA fingerprint database would likely increase the sensitivity and specificity of this technique.

Staphylococcal and other bacterial species associated with intramammary infections in Danish dairy herds

Four thousand six hundred forty-five quarter milk samples from 1179 cows from 20 commercial dairy herds were examined in order to determine the prevalence of bacterial species. A total of 859 isolates from 839 (18.1%) culture positive samples could be assigned to 34 different species and subspecies. Diagnostics of staphylococcal species was based on conventional procedures able to differentiate between all 36 species and subspecies presently acknowledged. Staphylococcus aureus was found in 10.2% of the samples and was the most common species isolated. Streptococcus dysgalactiae (1.6%) and Streptococcus uberis (1.4%) were the second and third most common species isolated. Seventeen different coagulase negative staphylococcal species (CNS) were found in 4.1% of the samples. The most frequently isolated CNS were S. epidermidis (1.3%), S. chromogenes (1.0%) and S. simulans (0.7%). Isolates of S. aureus were phage typed, and isolates of S. epidermidis were investigated by phage typing, antibiogram typing, and biotyping. A total of 378 (79.9%) isolates of S. aureus could be typed by phages, assigning them to 18 different phage types. However, 6 phage types accounted for 92.1% of the typable isolates. One to 2 phage types predominated within each herd. Eleven (18%) isolates of S. epidermidis could be typed by phages, assigning the isolates to 3 different types. Biotyping of S. epidermidis produced a total of 8 different types, the most common accounting for 29.5% of the isolates. A total of 6 different antibiogram types were observed among all isolates of S. epidermidis. Resistance towards penicillin (36.1%), tetracycline (9.8%) and streptomycin (9.8%), were recorded in the isolates of S. epidermidis. However, 35 (57.4%) of the isolates were susceptible to all 12 antibiotics tested.

Evaluation of Staph ID 32 system and Staph-Zym system for identification of coagulase-negative staphylococci

The purpose of the investigation was to evaluate two commercially available identification systems: a new modification of the Staph-Zym system (Rosco, Tåstrup, Denmark) and the Staph ID 32 API system (API System, BioMérieux, Paris, France). A local standard method to be used in routine laboratories was also evaluated. A total of 200 staphylococcal isolates, including strains from both the American Type Culture Collection and the Czechoslovak Collection of Microorganisms as well as 89 clinical isolates, were used in tests of all three identification systems. The Staph ID 32 API system identified from 50 to 100% of the reference strains and 82.1% of the clinical isolates correctly. The Staph-Zym system identified from 90 to 100% of the reference strains and 82.1% of the clinical isolates correctly. Most misidentifications were of minor importance, but in both systems major failures appeared (Staphylococcus aureus was identified as a coagulase-negative staphylococcus). Both systems needed backup from a reference laboratory to determine if two isolates were of the same strain.

Staphylococcal and other bacterial species associated with intramammary infections in Danish dairy herds

Four thousand six hundred forty-five quarter milk samples from 1179 cows from 20 commercial dairy herds were examined in order to determine the prevalence of bacterial species. A total of 859 isolates from 839 (18.1%) culture positive samples could be assigned to 34 different species and subspecies. Diagnostics of staphylococcal species was based on conventional procedures able to differentiate between all 36 species and subspecies presently acknowledged. Staphylococcus aureus was found in 10.2% of the samples and was the most common species isolated. Streptococcus dysgalactiae (1.6%) and Streptococcus uberis (1.4%) were the second and third most common species isolated. Seventeen different coagulase negative staphylococcal species (CNS) were found in 4.1% of the samples. The most frequently isolated CNS were S. epidermidis (1.3%), S. chromogenes (1.0%) and S. simulans (0.7%). Isolates of S. aureus were phage typed, and isolates of S. epidermidis were investigated by phage typing, antibiogram typing, and biotyping. A total of 378 (79.9%) isolates of S. aureus could be typed by phages, assigning them to 18 different phage types. However, 6 phage types accounted for 92.1% of the typable isolates. One to 2 phage types predominated within each herd. Eleven (18%) isolates of S. epidermidis could be typed by phages, assigning the isolates to 3 different types. Biotyping of S. epidermidis produced a total of 8 different types, the most common accounting for 29.5% of the isolates. A total of 6 different antibiogram types were observed among all isolates of S. epidermidis. Resistance towards penicillin (36.1%), tetracycline (9.8%) and streptomycin (9.8%), were recorded in the isolates of S. epidermidis. However, 35 (57.4%) of the isolates were susceptible to all 12 antibiotics tested.

A simple identification scheme for coagulase negative staphylococci from bovine mastitis

Coagulase-negative staphylococci from cases of bovine mastitis were identified to species level by using an identification scheme based on a three-plate test system which tested for DNase on DNA agar, for protease on calcium caseinate agar, and for the organism's sensitivity to novobiocin, desferrioxaminine (deferoxamine) and fosfomycin by agar diffusion tests. Testing for the inhibition of Staphylococcus delta haemolysin (Skalka 1991) can replace the protease tests.

Identification of veterinary pathogens by use of commercial identification systems and new trends in antimicrobial susceptibility testing of veterinary pathogens

Veterinary diagnostic microbiology is a unique specialty within microbiology. Although isolation and identification techniques are similar to those used for human pathogens, many veterinary pathogens require unique cultivation or identification procedures. Commercial identification systems provide rapid, accurate identification of human pathogens. However, the accuracy of these systems with veterinary pathogens varies widely depending on the bacterial species and the host animal from which it was isolated. Increased numbers of veterinary strains or species in the data bases of the various systems would improve their accuracy. Current procedures and interpretive criteria used for antimicrobial susceptibility testing of veterinary pathogens are based on guidelines used for human pathogens. The validity of these guidelines for use with veterinary pathogens has not been established. As with fastidious human pathogens, standardized methodologies and quality control isolates are needed for tests of organisms such as Actinobacillus pleuropneumoniae and Haemophilus somnus. Furthermore, interpretive criteria for veterinary antimicrobial agents based on the MIC for veterinary pathogens, the pharmacokinetics of the antimicrobial agent in the host animal, and in vivo efficacy of the antimicrobial agent are needed. This article reviews both the commercial identification systems evaluated with veterinary pathogens and current methods for performing and interpreting antimicrobial susceptibility tests with veterinary pathogens. Recommendations for future improvements in both areas are discussed.

Some properties of coagulase-negative staphylococci isolated from cases of ovine mastitis

Of 41 coagulase-negative staphylococcal isolates from cases of ovine mastitis, 80% were speciated by the 'API-Staph SYSTEM' and 90% by a combination of biochemical tests. Staphylococcus simulans and Staph. xylosus were the two most prevalent species.

Evaluation of methods for differentiation of coagulase-positive staphylococci

The purpose of this study was to determine the minimum number of tests that could be used to differentiate between the coagulase-positive strains of staphylococcus: Staphylococcus aureus, Staphylococcus hyicus, and Staphylococcus intermedius. Eighty coagulase-positive strains of each of the three species were examined. The five tests conducted were growth on modified Baird-Parker agar, growth on P agar supplemented with acriflavin, production of acetoin, anaerobic fermentation of mannitol, and presence of beta-galactosidase. Positive test percentages for S. aureus were 100% for growth on modified Baird-Parker agar, 100% for growth on P agar supplemented with acriflavin, 94% for production of acetoin, 99% for anaerobic fermentation of mannitol, and 0% for presence of beta-galactosidase. Positive test percentages for S. intermedius were 0% for growth on modified Baird-Parker agar, 0% for growth on P agar supplemented with acriflavin, 1% for production of acetoin, 0% for anaerobic fermentation of mannitol, and 100% for presence of beta-galactosidase. S. hyicus isolates were negative in all five tests. Results from the 240 coagulase-positive staphylococcus strains tested would suggest correct identification of coagulase-positive staphylococci with P agar supplemented with acriflavin and the beta-galactosidase test. These two tests are simple to conduct and result in quick and easy differentiation of the three coagulase-positive staphylococcal species.

A convenient method for differentiation of coagulase-negative staphylococci isolated from bovine mammary glands

The utility of trehalose-mannitol broth and arabinose-cellobiose broth for identification of Staphylococcus epidermidis and novobiocin-resistant staphylococci was determined using 236 coagulase-negative staphylococci isolated from bovine mammary glands. None of the 49 S. epidermidis strains was positive in trehalose-mannitol broth; whereas, all strains of Staphylococcus hyicus, Staphylococcus chromogenes, Staphylococcus haemolyticus, Staphylococcus hominis, Staphylococcus warneri, and Staphylococcus simulans were positive. Of the novobiocin-resistant staphylococcal species, only Staphylococcus saprophyticus was negative in arabinose-cellobiose broth. Except for one strain of Staphylococcus sciuri and one strain of Staphylococcus kloosii, all remaining strains of novobiocin-resistant staphylococcal species were positive in arabinose-cellobiose broth. Results indicate that trehalose-mannitol broth is an acceptable method for identification of S. epidermidis isolated from bovine mammary glands. Furthermore, arabinose-cellobiose broth is a useful method of screening for novobiocin-resistant staphylococci.

Evaluation of the Staph-Zym system with staphylococci isolated from bovine intramammary infections

A total of 148 staphylococci isolated from bovine intramammary infections were used to evaluate the Staph-Zym system (ROSCO, Taastrup, Denmark). The overall accuracy of the system was 91.9%. The system correctly identified all strains of Staphylococcus aureus, Staphylococcus simulans, and Staphylococcus xylosus and 95% of Staphylococcus intermedius strains. Of 33 Staphylococcus hyicus strains, 31 (93.9%) were classified correctly by the Staph-Zym system, as well as 8 (80%) of 10 Staphylococcus chromogenes strains. All 11 Staphylococcus epidermidis strains and the 1 Staphylococcus haemolyticus strain included in the study were identified, but the Staph-Zym system had difficulty distinguishing strains of Staphylococcus warneri and Staphylococcus hominis from other species in the S. epidermidis group. The Staph-Zym system correctly identified all six S. xylosus strains and two of three Staphyloccus sciuri strains. The Staph-Zym system was considered an acceptable alternative to conventional methods for identification of bovine mammary gland isolates.

Fluorogenic assay for differentiating Staphylococcus warneri and Staphylococcus hominis strains of bovine origin

A fluorogenic assay for the detection of beta-glucosidase was developed as part of a simplified conventional method to distinguish Staphylococcus warneri and Staphylococcus hominis isolated from bovine body sites. The assay is based on the fact that strains of S. warneri produce beta-glucosidase, while strains of S. hominis do not.

Antibodies to staphylococcal DNases in sera from different animal species, including humans

An agar diffusion method using microtiter plates was used to detect antibodies to the DNases produced by Staphylococcus aureus, S. intermedius, and S. hyicus. Antibodies to DNase from S. aureus were demonstrated in most of the sera from the species investigated, except dogs, only 11% of whose sera were positive. Positive titers to S. intermedius DNase were found in 84% of deg sera, 61% of Icelandic pony sera, 41% of pig sera, 21% of human sera, and 20% of cow sera but in only 2 and 4% of goat and sheep sera, respectively. Although antibodies to DNase from S. hyicus were not found in sera from humans, dogs, goats, or sheep, 84% of sera from pigs and cows and 29% of sera from Icelandic ponies were positive in this respect. The good accordance between the findings from bacteriological investigations performed elsewhere and the results of serologic tests performed in this study indicates that the results obtained with the serological method in this study properly reflect the actual antigenic exposure to and distribution of the three Staphylococcus spp. in animals and humans.

Etiological agents of bovine mastitis

A total of 137 microbial species, subspecies and serovars have been isolated from the bovine mammary gland. Nucleic acid hybridization studies have restructured the classification of many mastitis pathogens. Availability of defined species descriptions has permitted greater insight into the distribution and pathogenicity of many previously unrecognized microorganisms associated with bovine mastitis. Precise epidemiological studies are needed to better delineate the role of some microorganisms in bovine mastitis and to aid development of improved control methods.

Multiple infusions of cloxacillin for treatment of mastitis during the dry period

Efficacy of multiple and single intramammary infusions of benzathine cloxacillin (500 mg/quarter) were compared for treatment of mastitis during the dry period. Treatments were three infusions, one each at 0, 7, and 14 d into the dry period; one infusion at drying off; and no infusions. Cows were grouped (30/treatment) based on previous mastitis history, mean monthly SCC, mature equivalent milk production, and pathogen detected pretreatment. Infected quarters/cow at parturition, posttreatment were 1.26, 1.6, and 2.35 for multiple, single, and no infusion groups, respectively. Milk production and somatic cell count posttreatment were not affected by treatment. Across all genera of microorganism, 75.5, 73.6, and 52.8% of infections were eliminated in the multiple, single, and no infusion groups, respectively. Primary effect of multiple infusions with cloxacillin in the dry period was to prevent new streptococcal infections. Sensitivity tests on staphylococcal isolates indicated that cloxacillin was still an effective dry cow treatment after 7 yr of use in the herd. Resistance to cloxacillin in approximately half the posttreatment staphylococcal isolates appeared to be nonenzyme (penicillinase) dependent. Multiple dry cow treatments with cloxacillin do not offer any advantage over a single treatment.

Effects of teat dipping on intramammary infections by staphylococci other than Staphylococcus aureus

Effects of intramammary infections in herds 1) either not teat dipping or postmilking teat dipping with either 2) linear dodecyl benzene sulfonic acid, 3) chlorhexidine, or 4) iodophor containing products were determined. Duplicate quarter foremilk samples were collected once from all lactating cows in 16 herds, four for each practice. Mean percentage of quarters infected with Staphylococcus species other than Staph. aureus was 11.0 in herds not teat dipping and 7.2 in herds teat dipping. Prevalence of Staphylococcus species intramammary infections in herds teat dipping with linear dodecyl benzene sulfonic acid was comparable to herds not teat dipping and greater than in herds using chlorhexidine and iodophor. The predominant Staphylococcus species in herds not teat dipping was Staph. epidermidis (37.1%). Staphylococcus hyicus constituted 48.5% of total Staphylococcus species intramammary infections in herds teat dipping and 12.4% in herds not teat dipping. Differences were not observed among SCC for quarters infected with different Staphylococcus species. Application of germicidal teat dips appeared to have selectively altered both prevalence and distribution of Staphylococcus species intramammary infections.

Slime production by bovine milk Staphylococcus aureus and identification of coagulase-negative staphylococcal isolates

Staphylococcus aureus isolates from bovine milk were assessed for capsule or slime production. When pure S. aureus cultures in milk were inoculated directly into serum-soft agar constituted with a modified staphylococcus 110 medium, 100% of the isolates grew with diffuse colony morphology. Diffuse colony morphology was rapidly lost on subculture and was more rapidly lost in brain heart infusion-serum-soft agar. No evidence was seen for encapsulation in India ink preparations or by the clumping factor test. It was concluded that freshly isolated S. aureus strains produce slime, not true capsules. During examination of the 84 milk samples that grew staphylococci in addition to S. aureus (27.4%), a significant number of coagulase-negative staphylococcal species were encountered and identified by conventional tests as S. simulans (41.7%), S. xylosus (11.9%), S. epidermidis (3.6%), S. saprophyticus (3.6%), S. hyicus (2.9%), S. cohnii (1.2%), S. haemolyticus (1.2%), and S. warneri (1.2%). Five isolates (6.0%) were not identified. Attempts were also made to identify the isolates by the API Staph-Ident system, which gave an overall accuracy of 45.2%. The susceptibilities of the isolates to a variety of antibiotics were determined, and they appeared to be less resistant than human clinical isolates.

Evaluation of the Minitek gram-positive set for identification of staphylococci isolated from the bovine mammary gland

The Minitek Gram-Positive Set was evaluated as a means of identifying staphylococci isolated from bovine mammary glands. Initial accuracy was 79.2%. Misidentification of isolates due to data base deficiencies resulted with the animal-associated species Staphylococcus intermedius and S. hyicus. Minor modification to account for data base deficiencies permitted recognition of 87.7% of the isolates. Incorporation of additional veterinary isolates into the data base would improve the accuracy of the Minitek system and enhance acceptance by veterinary microbiologists.

Observations on intramammary infections in first calf heifers in early lactation

Intramammary infections and mastitis were monitored on four occasions at three-week intervals in 61 first calf heifers in five dairy herds during the first ten weeks of lactation. Of 940 quarter milk samples examined 65% were classed as negative, 10.4% as positive for mastitis (mainly subclinical), 1.8% as group 3 (infection present but no elevation in somatic cell count) and 22.8% as group 4 (elevated somatic cell count). Seventy-seven percent of the infections detected and identified were those due to coagulase-negative staphylococci, the main species being S. hyicus, S. epidermidis, S. simulans and S. hominis. Other infections detected with Corynebacterium pyogenes (three samples), Escherichia coli (one sample), Micrococcus spp. (one sample), S. aureus (two samples) and Streptococci (non-agalactiae) (seven samples).The geometric mean somatic cell count for 23 quarters infected with coagulase-negative staphylococci was 311 x 10(3) cells / mL compared to 134 x 10(3) cells / mL in noninfected adjacent contralateral quarters. The respective figures for% cell volume in Channel 8 (mainly neutrophils) were 10.6% and 3.5%. There was a highly significant association between herd and the proportion of quarter milk samples in the four mastitis categories.

Comparison of the API Staph-Ident and DMS Staph Trac micromethods for the identification of coagulase-negative staphylococci

Two rapid identification micromethods, the API Staph-Ident and the DMS Staph Trac, were compared for the identification of coagulase-negative staphylococci. Seventy-five isolates, mainly of bovine origin, were used as the test organisms. Species identification and profile numbers assigned to isolates by each system were compared. However, no clear correlation patterns emerged, indicating the two methods were not comparable.

Relationships among the results of coagulase, staphylococcal toxin, and thermonuclease tests on staphylococci from cow milk

Production of staphylococcal alpha- or alpha-beta-toxins correlated well with production of coagulase or thermonuclease (or both) in 203 Staphylococcus aureus isolates from milk and should be reliable indicators of S. aureus in the absence of Staphylococcus intermedius. Failures to produce toxin, tube coagulase, or thermonuclease occurred in only 1 to 2% of S. aureus. Evidence of beta- or alpha-beta-toxins was not found among 321 other staphylococci isolated from milk. A few coagulase- or thermonuclease-positive isolates not producing beta- or alpha-beta-toxins were found among the Staphylococcus hyicus isolates.

Evaluation of the Staph-Ident and STAPHase systems for identification of staphylococci from bovine intramammary infections

The Staph-Ident and STAPHase systems (Analytab Products, Plainview, N.Y.) were compared with conventional methods for identification of staphylococci isolated from bovine intramammary infections. Adjunct testing by colony morphology, pigmentation, and biochemical tests was conducted to resolve discrepant identifications. The initial accuracies of the conventional scheme and Staph-Ident were 92.1 and 89.2%, respectively. Staphylococcus hyicus subsp. chromogenes could not be identified by means of the Staph-Ident test, but the addition of pigment production as a key character permitted identification of most strains. The final accuracy of the Staph-Ident was 94.3%. The STAPHase system was as accurate as the conventional tube coagulase method. The Staph-Ident and STAPHase systems are acceptable alternatives to conventional methods for identification of staphylococcal species isolated from bovine intramammary infections.

Identification of Staphylococcus species of bovine origin with the DMS Staph-Trac system

The DMS Staph-Trac system was evaluated as a means for identifying the species of bovine strains of staphylococci routinely isolated from quarter-milk samples. The species identity of 83 of 91 (91.2%) isolates of staphylococci was correctly determined by this method. One isolate could not be identified by this system. The Staph-Trac system was able to distinguish between Staphylococcus hyicus and Staphylococcus epidermidis. We obtained a higher percentage of correct identifications with the DMS Staph-Trac system (91.2%) than we did in a previous study with the API Staph-Ident system (45.1%), using the same isolates (Langlois et al., J. Clin. Microbiol. 18:1212-1219, 1983).