Evaluation of RapiDEC Staph for identification of Staphylococcus aureus, Staphylococcus epidermidis, and Staphylococcus saprophyticus.

RapiDEC Staph is a test for presumptive identification of the principal human staphylococcal species, Staphylococcus aureus, S. epidermidis, and S. saprophyticus. The test includes control and test cupules for fluorogenic detection of coagulase and chromogenic substrates for alkaline phosphatase and beta-galactosidase. These tests identify S. aureus, S. epidermidis, and S. saprophyticus, respectively. Positive results with both chromogenic substrates provide a presumptive identification of S. xylosus or S. intermedius (S. xylosus-S. intermedius). Test cupules are inoculated with an organism suspension, and reactions are read after a 2-h incubation. RapiDEC-Staph was evaluated with 303 clinical and stock staphylococcal strains. Identifications were compared with those obtained by the tube coagulase test, a latex slide coagulase test (StaphAUREX), another commercial identification system (Staph-TRAC), and additional conventional tests. RapiDEC-Staph correctly identified 100% of 130 S. aureus strains, 70.3% of 74 S. epidermidis strains, and 81.3% of 32 S. saprophyticus strains. Four of five S. xylosus isolates were called S. xylosus-S. intermedius. Unidentified S. epidermidis and S. saprophyticus strains were called "Staphylococcus spp." Among the 62 other coagulase-negative staphylococci, 4 were misidentified as S. epidermidis and 7 were misidentified as S. saprophyticus. While the sensitivity and specificity of the fluorogenic coagulase test for S. aureus were 100%, failure to detect alkaline phosphatase activity in several S. epidermidis isolates resulted in fewer correct identifications by the RapiDEC-Staph test for this species.     

Comparative performances of six agglutination kits assessed by using typical and atypical strains of Staphylococcus aureus.

Six commercial agglutination tests designed for the identification of Staphylococcus aureus were compared by using a strain collection which included 512 staphylococci representing 33 species (318 isolates of Staphylococcus aureus [including 144 oxacillin resistant], 46 S. epidermidis isolates, 15 S. haemolyticus isolates, 12 S. saprophyticus isolates, 29 S. schleiferi isolates, 30 S. lugdunensis isolates, and 62 other coagulase-negative staphylococci). This group also included a proportion of strains with unusual phenotypes (e.g., 19 coagulase-negative S. aureus isolates, 26 clumping factor-negative S. aureus isolates, and 4 S. aureus isolates each with a double deficiency). The overall sensitivity for identification of typical and atypical S. aureus was high with the Staphaurex Plus test (Murex Biotech) (99.7%), the Pastorex Staph Plus test (Sanofi Diagnostics Pasteur) (99.7%), and the Slidex Staph Plus test (bioMérieux) (100%). The overall rate of specificity was affected by the unusual inclusion in this study of a high proportion of non-S. aureus species, such as S. lugdunensis and S. schleiferi, which express a clumping factor and therefore produce a positive result with the agglutination tests.     

Evaluation of different disk diffusion/media combinations for detection of methicillin resistance in Staphylococcus aureus and coagulase-negative staphylococci

In order to find a disk diffusion method with both high sensitivity and specificity for determination of methicillin resistance primarily for S. aureus but also for coagulase-negative staphylococci we screened several methodological variants using a material of 66 S. aureus comprising of 11 methicillin-susceptible, 18 borderline-resistant, and 37 methicillin-resistant strains. Only four of the combinations studied performed with both high sensitivity and specificity. Two of these, the Columbia agar +4.5% NaCl and Mueller Hinton agar +2% NaCl combined with a 5 microg oxacillin disk, confluent inoculum and 24 h incubation at 35 degrees C were further evaluated using 105 MRSA and 91 mecA-negative S. aureus and 193 clinical isolates of coagulase-negative staphylococci. The Columbia agar +4.5% NaCl performed excellently for both S. aureus and coagulase-negative staphylococci. For Columbia agar +4.5% NaCl using a 5 microg oxacillin disk we suggest an interpretive zone diameter of R < or =15 mm and S > or =16 mm for S. aureus and R < or =24 mm and S >or =26 mm for coagulase-negative staphylococci. The Mueller Hinton agar +2% NaCl performed well for coagulase-negative staphylococci but for S. aureus at least three (3%) very major errors were found, making this method less attractive.     

Recognition of Staphylococcus saprophyticus in urine cultures by screening colonies for production of phosphatase.

Phenolphthalein diphosphate was incorporated into a primary blood agar medium for use in performing quantitative urine cultures. Phosphatase-negative staphylococci, such as Staphylococcus saprophyticus, were differentiated from phosphatase-positive species, such as Staphylococcus epidermidis, by spot testing colonies on filter paper saturated with 1 N NaOH. Phosphatase-positive colonies turned pink within seconds, and phosphatase-negative colonies showed no color. None of 55 S. saprophyticus isolates showed production of phosphatase on this medium. Of 193 consecutive coagulase-negative staphylococci isolated from the urine of 190 adolescent female patients, 84% were phosphatase positive, non-S. saprophyticus species; 16% were phosphatase-negative and indicated S. saprophyticus (22), Staphylococcus haemolyticus (4), Staphylococcus simulans (2), Staphylococcus warneri (1), and Staphylococcus hominis (1). Phosphatase activity was variable in the other flora encountered in the urine cultures. Mixtures of phosphatase-positive and -negative organisms did not cause false-positive reactions.     

Comparison of rapid identification assays for Staphylococcus aureus.

A total of 137 strains of Staphylococcus species were blindly tested by four rapid serological assays, and the results were compared with those of the tube coagulase assay. For the S. aureus isolates, the Sero-STAT Staph assay gave six false-negative results, four of which were for methicillin-resistant strains. The Accu -Staph, Staphylatex , and Staphyloslide assays identified all the coagulase-positive strains as Staphylococcus aureus. Among the coagulase-negative staphylococci, false-positive results were seen with strains of S. capitis. S. saprophyticus, and S. cohnii. The overall accuracy of the kits compared with the tube coagulase test ranged from 95.1 to 100%.     

Characterization of coagulase-negative staphylococci from urinary tract specimens.

Species of coagulase-negative staphylococci isolated from urine specimens submitted from both inpatients and outpatients to the clinical microbiology laboratory of a teaching hospital were identified with a biotyping system, with species then correlated by clinical features and antimicrobial susceptibility. Of 145 isolates, 102 (70%) were Staphylococcus epidermidis, 24 (17%) were Staphylococcus saprophyticus, 7 (4.7%) were Staphylococcus haemolyticus, 4 (2.8%) were Staphylococcus hominis, 3 (2.1%) were Staphylococcus simulans, and 5 (3.4%) were other species. Features characterizing persons with bacteriuria with S. saprophyticus compared with bacteriuria with any other species included female sex (95% versus 52%), young age (median age, 22 years versus 61 years), ambulatory status (hospital outpatients, 86% versus 23%), and absence of indwelling catheters (4.5% versus 49%). All other coagulase-negative staphylococci were isolated in a setting suggesting nosocomial acquisition, were more frequently resistant to common antimicrobial agents (42% multiply resistant versus 4.2% of S. saprophyticus), and were not distinguished by clinical features. Novobiocin susceptibility, with a sensitivity of 100% and specificity of 96%, provided a simple and reliable test for differentiation of S. saprophyticus from other coagulase-negative staphylococci and should be routinely used for urinary tract specimens in the clinical laboratory.     

Identification of coagulase-negative staphylococci with the API staph system.

A kit for the identification of staphylococci based on the biochemical criteria proposed by Kloos and Schleifer (W.E. Kloos and K.H. Schleifer, J. Clin. Microbiol., 1:82-88, 1975) is now available commercially. The system was used to identify 100 strains of coagulase-negative staphylococci isolated from various body sites as the primary etiological agent of clinical infection. The increasing importance of staphylococci and their resistance to antibiotics provided the rationale for such an investigation. Over 90% of the Staphylococcus isolates were easily identified as to their species on the basis of their reaction profile to 19 biochemical tests included in the kit. The remainder, which showed minor variations, could also be assigned to the various species. Identification of the isolates was as follows: S. epidermidis, 54; S. haemolyticus, 5; S. simulans, 2; S. hominis, 1; S. capitis, 4; S. cohnii, 2; S. warneri, 2; S. xylosus, 8; and S. saprophyticus, 22. Antibiotic sensitivity patterns were determined for each of the isolates. Novobiocin resistance was detected in strains of S. saprophyticus and S. xylosus, a property hitherto recognized in Micrococcus sp. type 3 causing bacteriuria in young women. Resistance to penicillin was widespread among strains of several species, whereas resistance to tetracycline was mainly confined to strains of S. epidermidis. General resistance to sulfamethoxazole and nalidixic acid was found among all strains, with almost uniform sensitivity to the other drugs tested.     

Problems with rapid agglutination methods for identification of Staphylococcus aureus when Staphylococcus saprophyticus is being tested.

Six rapid agglutination tests for identification of Staphylococcus aureus were evaluated by using 62 strains of S. aureus, 63 strains of S. saprophyticus, and 67 strains of other coagulase-negative staphylococci. S. saprophyticus was responsible for 19 of 26 false-positive results and 20 uninterpretable reactions. Thus, urinary staphylococcal isolates that are positive by rapid agglutination tests may require other confirmatory tests for the identification of possible S. saprophyticus.     

Presumptive identification of Staphylococcus saprophyticus from urine specimens by colony appearance and coagulase testing: an evaluation

Two hundred one urine specimens with pure or nearly pure cultures (greater than 5 X 10(4) CFU/mL) of coagulase-negative staphylococcus were identified in reviewing all significant urine isolates over a ten-month period. The majority of these were from young female adult outpatients with Staphylococcus saprophyticus constituting 88.9% of isolates determined with the API Staph-Ident System. For urine specimens, particularly for outpatients, coagulase-negative, nonhemolytic staphylococcal colonies with yellow pigmentation could be identified presumptively as S. saprophyticus with a sensitivity of 97.8% and a specificity of 98.3%, compared with novobiocin susceptibility testing with a sensitivity of 100% and a specificity of 96.9%.     

Species identification of coagulase-negative staphylococci from urinary tract isolates.

A new scheme for identification of coagulase-negative staphylococci was applied to 138 consecutive urinary isolates of coagulase-negative staphylococci. The most common species were Staphylococcus epidermidis (53%), S. hominis (12%), and S. haemolyticus (10%). S. saprophyticus comprised only 5%. The disk method for antibiotic susceptibility for all species grouped together disclosed resistance most commonly to penicillin (35%), tetracycline (33%), methicillin (27%), and sulfonamide (24%). This pattern was also seen specifically with S. epidermidis. Further studies are needed to determine the incidence of species-specific antibiotic resistance and species-specific infection by site. This may be of particular interest in those patients with nosocomial infections due to coagulase-negative staphylococci.     

Isolation of methicillin-resistant coagulase-negative staphylococci from chickens.

Methicillin-resistant coagulase-negative staphylococci were isolated from the nares and skin of 1- to 8-week-old healthy chickens in three flocks from a farm. Isolation of methicillin-resistant coagulase-negative staphylococci was positive for 72 (25.7%) of the 280 chickens tested, with the frequency varying from 2.2 to 100% according to flock. A total of 45 appropriate isolates were selected and subjected to identification. Of the 45 methicillin-resistant coagulase-negative staphylococcal isolates selected, 37 were identified as Staphylococcus sciuri, 5 were identified as Staphylococcus epidermidis, and 3 were identified as Staphylococcus saprophyticus. The distribution of the species was different among the flocks. Comparative analysis of the SmaI-digested chromosomal DNA by pulsed-field gel electrophoresis revealed that the isolates could have originated from a single clone of each of S. sciuri and S. saprophyticus and three clones of S. epidermidis. By two methods based on the PCR technique, the mecA gene was detected in all five representative isolates of each methicillin-resistant coagulase-negative staphylococcal clone. The nucleotide sequence of a PCR fragment obtained from an isolate of S. sciuri was completely identical to the corresponding region of mecA genes reported in human methicillin-resistant Staphylococcus aureus isolates and Staphylococcus epidermidis isolates. The representative methicillin-resistant coagulase-negative staphylococcal isolates were resistant to many beta-lactam antibiotics, and some isolates were also resistant to macrolide and aminoglycoside antibiotics. This is the first evidence of the existence of methicillin-resistant coagulase-negative staphylococci from animals possessing the mecA gene.     

Practical disk diffusion method for detection of inducible clindamycin resistance in Staphylococcus aureus and coagulase-negative staphylococci

Resistance to macrolides in staphylococci may be due to active efflux (encoded by msrA) or ribosomal target modification (macrolide-lincosamide-streptogramin B [MLSB] resistance; usually encoded by ermA or ermC). MLSB resistance is either constitutive or inducible following exposure to a macrolide. Induction tests utilize closely approximated erythromycin and clindamycin disks; the flattening of the clindamycin zone adjacent to the erythromycin disk indicates inducible MLSB resistance. The present study reassessed the reliability of placing erythromycin and clindamycin disks in adjacent positions (26 to 28 mm apart) in a standard disk dispenser, compared to distances of 15 or 20 mm. A group of 130 clinical isolates of Staphylococcus aureus and 100 isolates of erythromycin-resistant coagulase-negative staphylococci (CNS) were examined by disk approximation; all CNS isolates and a subset of S. aureus isolates were examined by PCR for ermA, ermC, and msrA. Of 114 erythromycin-resistant S. aureus isolates, 39 demonstrated constitutive resistance to clindamycin, while 33 showed inducible resistance by disk approximation at all three distances. Only one isolate failed to clearly demonstrate induction at 26 mm. Of 82 erythromycin-resistant CNS isolates that contained ermA or ermC, 57 demonstrated constitutive clindamycin resistance, and 25 demonstrated inducible resistance, at 20 and 26 mm. None of the 42 S. aureus isolates or 18 CNS isolates containing only msrA and none of the erythromycin-susceptible isolates yielded positive disk approximation tests. Simple placement of erythromycin and clindamycin disks at a distance achieved with a standard disk dispenser allowed detection of 97% of S. aureus strains and 100% of CNS strains with inducible MLSB resistance in this study.     

Identification of methicillin-resistant strains of staphylococci by polymerase chain reaction.

A simple and reliable method using a polymerase chain reaction (PCR) was devised to identify methicillin-resistant staphylococci. By using lysates of the strain to be tested as templates and 22-mer oligonucleotides as primers, a 533-bp region of mecA, the structural gene of a low-affinity penicillin-binding protein (PBP 2'), was amplified by PCR and detected by agarose gel electrophoresis. Results obtained by this method were compared with those obtained by broth microdilution MIC determination for 210 and 100 clinical isolates of Staphylococcus aureus and coagulase-negative staphylococci, respectively. Of 99 mecA-negative S. aureus isolates, 100% of the strains were methicillin susceptible and 98% of the strains were oxacillin susceptible. Three strains (3%) of 111 mecA-positive S. aureus isolates exhibited almost the same susceptibility to beta-lactams as the mecA-negative ones and did not produce detectable amounts of PBP 2' despite the presence of the mecA gene. One of them yielded typically methicillin-resistant variants at a low frequency with concomitant recovery of PBP 2' production. The mecA gene was also found in coagulase-negative Staphylococcus epidermidis, Staphylococcus haemolyticus, Staphylococcus sciuri, Staphylococcus saprophyticus, and Staphylococcus caprae and conferred resistance on most of the bacteria.     

New quadriplex PCR assay for detection of methicillin and mupirocin resistance and simultaneous discrimination of Staphylococcus aureus from coagulase-negative staphylococci

Major challenges in diagnostic molecular microbiology are to develop a simple assay to distinguish Staphylococcus aureus from the less virulent but clinically important coagulase-negative staphylococci (CoNS) and to simultaneously determine their antibiotic resistance profiles. Multiplex PCR assays have been developed for the detection of methicillin- and mupirocin-resistant S. aureus and CoNS but not for the simultaneous discrimination of S. aureus from CoNS. We designed a new set of Staphylococcus genus-specific primers and developed a novel quadriplex PCR assay targeting the 16S rRNA (Staphylococcus genus specific), nuc (S. aureus species specific), mecA (a determinant of methicillin resistance), and mupA (a determinant of mupirocin resistance) genes to identify most staphylococci, to discriminate S. aureus from CoNS and other bacteria, and to simultaneously detect methicillin and mupirocin resistance. Validation of the assay with 96 ATCC control strains and 323 previously characterized clinical isolates, including methicillin- and mupirocin-sensitive and -resistant S. aureus and CoNS isolates and other bacteria, demonstrated 100% sensitivity, specificity, and accuracy. This assay represents a simple, rapid, accurate, and reliable approach for the detection of methicillin- and mupirocin-resistant staphylococci and offers the hope of preventing their widespread dissemination through early and reliable detection.     

Rapid Detection of Methicillin Resistance in Staphylococcus aureus Isolates by the MRSA-Screen Latex Agglutination Test

The slide agglutination test MRSA-Screen (Denka Seiken Co., Niigata, Japan) was compared with the mecA PCR ("gold standard") for the detection of methicillin resistance in Staphylococcus aureus. The MRSA-Screen test detected the penicillin-binding protein 2a (PBP2a) antigen in 87 of 90 genetically diverse methicillin-resistant S. aureus (MRSA) stock culture strains, leading to a sensitivity of 97%. The three discrepant MRSA strains displayed positive results only after induction of the mecA gene by exposure to methicillin. Both mecA PCR and MRSA-Screen displayed negative results among the methicillin-susceptible S. aureus strains (n = 106), as well as for Micrococcus spp. (n = 10), members of the family Enterobacteriaceae (n = 10), Streptococcus pneumoniae (n = 10), and Enterococcus spp. (n = 10) (specificity = 100%). Producing the same PBP2a antigen, all 10 methicillin-resistant Staphylococcus epidermidis strains score positived in both the latex test and the mecA PCR. Consequently, the MRSA-Screen test should be applied only after identification of the MRSA strain to the species level to rule out coagulase-negative staphylococci. In conclusion, due to excellent specificity and sensitivity the MRSA-Screen latex test has the potential to be successfully used for routine applications in the microbiology laboratory.     

Problems with the laboratory identification and evaluation of coagulase-negative staphylococci

During a 105 day period in mid 1984, 796 isolates of coagulase-negative staphylococci were recovered from routine specimens handled in the Microbiology Laboratory, Dunedin Hospital. Of these isolates 504 (63.3%) were from wounds, 170 (21.4%) from urines, 58 (7.3%) from intravascular catheter tips, 44 (5.5%) from blood cultures and 20 (2.5%) from sputa. Presumptive identification of 315 consecutive isolates revealed 175 (55.6% of total) strains of Staphylococcus epidermidis, 44 (14.0%) S. capitis, 36 (11.4%) S. haemolyticus/hominis, 29 (9.2%) S. warneri, 19 (6.0%) S. simulans and 12 (3.8%) members of the S. saprophyticus group. Using laboratory generated criteria, 44.8%, 25.9% and 4.5% of coagulase-negative isolates from catheter tips, urines and blood cultures respectively, were deemed pathologically potentially significant. Although more common, S. epidermidis did not appear to be significantly more virulent than other members of the epidermidis species group or S. simulans; 67% of the S. saprophyticus group isolates from urine were considered pathologically significant. Antibiograms on the 796 coagulase-negative isolates revealed 63.2% resistant to penicillin, 22.6% to methicillin, 34.8% to cephradine, 27.5% to gentamicin, and 14.4% to erythromycin; multiple resistance was common. Methicillin resistance was a feature of S. saprophyticus group strains. With isolates from catheter tips and blood cultures, a significantly higher percentage of those regarded as significant were gentamicin resistant. Apart from penicillin, antibiotic resistance was not so marked in strains of coagulase-positive staphylococci recovered over the same period.     

Rapid identification of fibronectin, vitronectin, laminin, and collagen cell surface binding proteins on coagulase-negative staphylococci by particle agglutination assays.

Seventeen strains of ten different species of coagulase-negative staphylococci were shown to interact with collagen, laminin, fibronectin, and vitronectin immobilized on latex beads. Different species of coagulase-negative staphylococci have different capacities to agglutinate proteins. Cells of 18 strains of Staphylococcus haemolyticus reacted more strongly than did cells of 18 Staphylococcus epidermidis strains with proteincoated latex beads, although no significant difference in cell surface hydrophobicity or charge could be shown. The cell surface receptors of S. haemolyticus were more heat and protease resistant than were Staphylococcus aureus receptors. Strains of Staphylococcus saprophyticus isolated from urinary tract infections showed a high capacity to adhere to laminin. The ability to agglutinate fibronectin and collagen was common among coagulase-negative staphylococci isolated from other infections; 55% (31 of 56) and 63% (35 of 56) agglutinated fibronectin and/or collagen. S. haemolyticus and S. epidermidis bound to both N-terminal (29-kDa) and C-terminal (120-kDa) fragments of fibronectin.     

Characteristics of coagulase-negative staphylococci that help differentiate these species and other members of the family Micrococcaceae.

One hundred reference strains and 1,240 clinical isolates representing 26 species of the family Micrococcaceae were used to evaluate the potential of tests for synergistic hemolysis, adherence to glass, pyroglutamyl-beta-naphthylamide hydrolysis, and susceptibility to a set of five antimicrobial agents for differentiating these species and strains within the species. Sixty-eight percent of the clinical isolates exhibited synergistic hemolysis; 69% of the clinical staphylococci but none of the micrococci or stomatococci were adherence positive, and 92% of the strong positive adherence reactions were produced by strains of Staphylococcus epidermidis. Strains from 15 of the species were pyroglutamyl-beta-naphthylamide positive, but this test separated Staphylococcus xylosus from other novobiocin-resistant staphylococci and Staphylococcus intermedius from other coagulase-positive species. A polymyxin B disk helped differentiate S. epidermidis from most other coagulase-negative staphylococci, and a bacitracin disk (10 U) helped differentiate Staphylococcus haemolyticus from most other novobiocin-susceptible staphylococci. All strains that were susceptible to furazolidone and resistant to Taxo A disks (bacitracin, 0.04 U; BBL Microbiology Systems, Cockeysville, Md.) were staphylococci. We observed a 91% correlation between species identification obtained with the Staph-Ident system (Analytab Products, Plainview, N.Y.) and conventional methods; but the micrococci and stomatococci were incorrectly identified as staphylococci with Staph-Ident, and several isolates of S. epidermidis were misidentified as Staphylococcus hominis because they were alkaline phosphatase negative. Both these problems can be prevented by adding the simple tests we describe to those already recommended when the Staph-Ident system is used to identify isolates of gram-positive, catalase-positive cocci.     

Hemolysins and other characteristics that help differentiate and biotype Staphylococcus lugdunensis and Staphylococcus schleiferi.

Reference strains and clinical isolates representing the newly defined species Staphylococcus lugdunensis and Staphylococcus schleiferi were examined with the battery of tests previously recommended (G.A. Hébert, C.G. Crowder, G.A. Hancock, W.R. Jarvis, and C. Thornsberry, J. Clin. Microbiol. 26:1939-1949, 1988) for other species of coagulase-negative staphylococci (CNS). The Staph-Ident system (Analytab Products, Plainview, N.Y.) supplemented with tests for synergistic hemolysis, adherence to glass, pyroglutamyl-beta-naphthylamide hydrolysis, and susceptibility to a set of five antimicrobial disks differentiated each of these species from other species of CNS and separated strains within each species into several biotypes. Most strains (95%) of S. lugdunensis produced a delta hemolysin like that seen with nine other species of CNS. Most strains (91%) of S. schleiferi produced a beta hemolysin, which is a unique characteristic among CNS. Most (95%) of the S. schleiferi but very few (12%) of the S. lugdunensis were adherence positive. Both hemolysins and adherins are potential virulence factors among CNS. Some (29%) of the S. lugdunensis were beta-lactamase positive. The S. lugdunensis were resistant to polymyxin B and bacitracin (10 U), but the S. schleiferi were susceptible to both disks. Clinical isolates of S. lugdunensis were aligned in 18 biotypes because of eight biochemical profiles and eight physiologic subtypes; isolates of S. schleiferi were in 8 biotypes because of three biochemical profiles and subtypes. These tools for correctly identifying and then biotyping two more clinical species of CNS should enhance both epidemiologic and ecologic investigations.     

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.