Direct identification of Staphylococcus aureus in blood culture fluid with a commercial latex agglutination test.

A commercial latex agglutination slide test (SeroSTAT Staph, Scott Laboratories, Inc., Fiskeville, R.I.) accurately identified Staphylococcus aureus when applied directly to blood culture fluid containing staphylococci. This latex agglutination test exhibited 100% accuracy when 30 seeded aerobic and anaerobic radiometric blood cultures (15 strains of S. aureus, 15 strains of other staphylococcal species) were tested blindly. In 36 actual clinical specimens yielding 16 isolates of S. aureus and 20 isolates of Staphylococcus epidermidis, 94.4% accuracy was achieved. The latex agglutination test provided positive test results before objective criteria of blood culture positivity such as radiometric growth indices and Gram stains became positive.     

Evaluation of three commercial agglutination tests for the identification of Staphylococcus aureus.

Three commercially available rapid slide agglutination tests for the identification of Staphylococcus aureus were evaluated with 354 recent clinical isolates (165 strains of S. aureus). The test results of two latex agglutination products, SeroSTAT Staph (Scott Laboratories, Inc.) and Staphylatex (American Micro Scan), and one hemagglutination product, Staphyloslide (BBL Microbiology Systems), were compared with the results of the tube coagulase test, which was read at 4 h (4-h tube coagulase test) and, if negative, again after overnight incubation at room temperature (24-h tube coagulase test). Discrepancies between agglutination and tube coagulase identifications were resolved by use of the thermonuclease, mannitol fermentation, and slide coagulase tests. All sensitivities, specificities, predictive values of a positive result, and predictive values of a negative result for the three agglutination tests were at least 98.8% and comparable with the 4-h tube coagulase test. Best results were obtained with the 24-h tube coagulase test, which yielded one false-negative and no false-positive tests. Agglutination identifications may be performed on organisms taken directly from a primary plate when sufficient growth is present. Kit agglutination procedures yield rapid and reliable identifications and are easy to perform. This study also demonstrates the usefulness of the 24-h tube coagulase test.     

Evaluation of the latex slide agglutination test for identification of Staphylococcus aureus.

This study evaluated the reliability of the latex slide agglutination test for identifying Staphylococcus aureus. A total of 806 clinical isolates of staphylococci were tested for latex agglutination, clumping factor, and free coagulase. Positive latex tests occurred in 98.3% of coagulase-positive strains, whereas 99.6% of coagulase-negative strains gave negative latex tests. It is concluded that in most instances, the latex slide agglutination test is a reliable method for identifying S. aureus in the clinical laboratory.     

Evaluation of a commercial latex agglutination test for identification of Staphylococcus aureus.

A new, commercially available latex agglutination test (SeroSTAT Staph; Scott Laboratories, Inc., Fiskeville, R.I.) was compared with the tube coagulase and slide coagulase tests as means for identifying Staphylococcus aureus. Of 160 clinical isolates of S. aureus, 159 (99.4%) yielded positive results with the latex agglutination test. Negative latex agglutination test results were obtained with 266 of 267 clinical isolates of Micrococcus spp. and staphylococcal species other than S. aureus (99.6%). The latex agglutination test was found to be a rapid, technically nondemanding method for identifying S. aureus. It was as accurate as the tube coagulase test and more accurate than the slide coagulase test.     

Evaluation of rapid coagulase methods for the identification of Staphylococcus aureus.

Four rapid latex agglutination assays, StaphAurex (Wellcome Diagnostics, Research Triangle Park, N.C.), Bacto Staph (Difco Laboratories, Detroit, Mich.), SeroSTAT (Scott Laboratories, Inc., Fiskeville, R.I.), Veri-Staph (Zeus Technologies, Raritan, N.J.), and two hemagglutination tests, Staphyloslide (BBL Microbiology Systems, Cockeysville, Md.) and Hemastaph (Remel, Lenexa, Kans.), were compared with the conventional slide coagulase, tube coagulase (TC), and thermonuclease (TNase) tests for the identification of Staphylococcus aureus. A total of 118 clinical isolates of S. aureus (52 methicillin resistant), 50 S. epidermidis, 5 S. capitis, 2 S. hominis, 3 S. simulans, 6 S. saprophyticus, and 2 S. warneri were tested. The slide coagulase, TC and TNase tests detected 115 (97.5%), 117 (99.2%), and 118 (100%) of the S. aureus isolates, respectively. All showed 100% specificity. The StaphAurex, Veri-Staph, Staphyloslide, Hemastaph, SeroSTAT, and Bacto Staph assays correctly identified 117 (99.2%), 117 (99.2%), 116 (98.3%), 110 (93.2%), 108 (91.5%), and 107 (90.7%) of the S. aureus isolates, respectively. For methicillin-resistant S. aureus isolates, StaphAurex, Veri-Staph, Staphyloslide, Hemastaph, SeroSTAT, and Bacto Staph showed 1 (2%), 1 (2%), 2 (4%), 7 (13.5%), 7 (13.5%), and 8 (15.4%) false-negative results, respectively. All the commercial agglutination assays demonstrated false-positive results with strains of S. capitis, S. saprophyticus and S. warneri. The overall accuracy of the commercial agglutination assays compared with TC and TNase ranged from 90.7 to 99.2%. We recommend that negative reactions with the rapid commercial test kits for methicillin-resistant Staphylococcus isolates be confirmed with the TC or TNase test.     

Comparison of identification and antimicrobial resistance pattern of Staphylococcus aureus isolated from Amassoma,Bayelsa state,Nigeria

Background

Staphylococcus aureus is often responsible for fatal infections and recent upsurge of resistant strains has resulted in therapeutic failure. The identification of this microorganism is a major challenge to medical microbiologists in developing countries.

Methods

One hundred and eighty five isolates which had been previously isolated from the nares of 185 healthy college students'' volunteers in Amassoma, Bayelsa State, South Nigeria were identified by MALDI TOF mass spectrometry, and PCR amplification of the spa gene. The identified isolates were compared with presumptive identities obtained by growth on MSA, tube coagulation and slide agglutination tests. Antimicrobial susceptibility testing of S. aureus isolates was performed by Kirby Bauer technique while MRSA was screened for by growth on chromlDTM MRSA plate and confirmed by PCR-amplification of mecA/mecC genes.

Results

From the 185 staphylococci that grew with yellow colonies on MSA, 24 were positive in the slide coagulase test, while 17 were positive in the tube coagulase test; MALDI TOF mass spectrometry and PCR amplification of the spa gene showed excellent concordance with the tube test, as all tube coagulase-positive strains were identified as S. aureus, while tube coagulase-test negative isolates in all cases were designated as other staphylococcal species by MALDI-TOF mass spectrometry and were spa PCR test negative. All S. aureus isolates were susceptible to clindamycin, vancomycin, fusidic acid, rifampicin and linezolid, while observed resistance to penicillin and trimethoprim were high. Only one MRSA strain was detected

Conclusion

The study confirms that the tube coagulase test is an accurate diagnostic method for identification of S. aureus, while growths on MSA and slide agglutination tests are inaccurate. We found a low prevalence of MRSA and a high rate of trimethroprim-resistance in the studied population.     

Comparison of four methods for rapid identification of Staphylococcus aureus directly from BACTEC 9240 blood culture system

Purpose: Differentiation of Staphylococcus aureus (S. aureus) from coagulase-negative staphylococci is very important in blood stream infections. Identification of S. aureus and coagulase-negative staphylococci (CoNS) from blood cultures takes generally 18–24 h after positive signaling on continuously monitored automated blood culture system. In this study, we evaluated the performance of tube coagulase test (TCT), slide agglutination test (Dry Spot Staphytect Plus), conventional polymerase chain reaction (PCR) and LightCycler Staphylococcus MGrade kit directly from blood culture bottles to achieve rapid identification of S. aureus by using the BACTEC 9240 blood culture system. Materials and Methods: A total of 129 BACTEC 9240 bottles growing gram-positive cocci suggesting Staphylococci were tested directly from blood culture broths (BCBs) with TCT, Dry Spot Staphytect Plus, conventional PCR and LightCycler Staphylococcus MGrade kit for rapid identification of S. aureus. Results: The sensitivities of the tests were 99, 68, 99 and 100%, respectively. Conclusion: Our results suggested that 2 h TCT was found to be simple and inexpensive method for the rapid identification of S. aureus directly from positive blood cultures.     

Evaluation of Hemofast MRSA for identification of Staphylococcus aureus and detection of methicillin-resistance staphylococci, directly in blood culture broths]

The newly developed Hemofast MRSA system for Staphylococcus aureus identification and methicillin-resistant staphylococci (MRS) detection in blood culture broths was evaluated in 106 Bactec broths containing grapelike clusters of Gram-positive cocci. All 26 S. aureus positive broths were correctly identified by Hemofast MRSA within two hours, and 81% were identified within one hour. Sensitivity and specificity were both 100%. Accuracy of MRS detection was 100%, i.e., no discrepancies versus the agar diffusion method were found. When the 28 broths containing coagulase negative staphylococci (CNS) were tested using an inoculum ten fold larger than for S. aureus testing, a number of discrepancy were recorded. For 49 other broths containing CNS, accuracy was 98.5% when the test was interpreted based on the growth rate of the strain, according to the manufacturer's instructions. One broth containing S. epidermidis strain susceptible yielded a false result with Hemofast MRSA, indicating that it probably contained a contaminant. The other discrepancies occurred with specimens containing mixed populations with CNS or a Micrococcus strain. Most (85%) results were available within 4 hrs 30 min, irrespective of the S. aureus or CNS strains. Avoiding the isolation step on agar, Hemofast MRSA saves 24 to 48 hours, thus allowing earlier antistaphylococcal treatment.     

A Shared noncapsular antigen is responsible for false-positive reactions by Staphylococcus epidermidis in commercial agglutination tests for Staphylococcus aureus

Many of the commercial slide agglutination tests for Staphylococcus aureus incorporate antibodies against cell surface antigens associated with methicillin resistance, including capsular polysaccharides and an uncharacterized antigen, serotype 18. These tests are more sensitive than the first-generation agglutination procedures that detected only bound coagulase and protein A, but they suffer from false-positive reactions with some coagulase-negative staphylococci. The aim of this study was to elucidate the mechanism for false-positive agglutination by S. epidermidis in these tests. A group of methicillin-resistant S. aureus (MRSA) isolates, including a serotype 18 strain, that were not detectable in the first-generation tests were found to be of capsular polysaccharide type 8. All of these isolates were deficient in bound coagulase and/or protein A, and they possessed a heat-stable, proteinaceous antigen that was absent from a prototype capsule type 8 strain. Enzyme-linked immunosorbent assay and agarose gel immunodiffusion experiments demonstrated that this proteinaceous antigen was also present on both methicillin-sensitive and methicillin-resistant S. epidermidis clinical isolates. S. epidermidis strains that gave false-positive agglutination test results had a considerably higher level of this antigen than strains that gave the correct negative result. These findings reveal the importance of the careful selection of MRSA strains for raising anti-capsular type 8 antibodies for use in agglutination tests. Strains devoid of the antigen shared with S. epidermidis should be used to eliminate potential cross-reactions with this coagulase-negative coccus.     

Performance of four slide agglutination methods for identification of Staphylococcus aureus when testing methicillin-resistant staphylococci.

Four commercially available slide agglutination systems for identifying Staphylococcus aureus were compared with the conventional slide (clumping factor) and tube coagulase tests. The systems evaluated included Bacto Staph Latex (Difco Laboratories, Detroit, Mich.), Staphyloslide (BBL Microbiology Systems, Cockeysville, Md.), Mini ID Accu-Staph (Carr-Scarborough Microbiologicals, Inc., Decatur, Ga.), and Staphaurex (Wellcome Diagnostics, Research Triangle Park, N.C.). A total of 338 clinical isolates, including methicillin-resistant S. aureus (n = 149), methicillin-susceptible S. aureus (n = 78), methicillin-resistant, coagulase-negative staphylococci (n = 45), and methicillin-susceptible, coagulase-negative staphylococci (n = 66), were tested by each method. The slide test for clumping factor, the 4-h tube coagulase test, Bacto Staph Latex, Staphyloslide, Mini ID Accu-Staph, and Staphaurex detected 212 (93.4%), 218 (96%), 223 (98.2%), 223 (98.2%), 221 (97.4%), and 224 (98.7%) of the S. aureus (44% methicillin-resistant) isolates, respectively. There were no false-positive results with any of the methods when the 111 strains of coagulase-negative staphylococci were tested. The results of this evaluation suggest that the four slide identification methods tested can provide rapid and accurate identification of methicillin-resistant S. aureus strains.     

Coagulase testing compared with commercial kits for routinely identifying Staphylococcus aureus.

Five commercial Staphylococcus aureus identification kits--Staphaurex (Wellcome), Staphylase (Oxoid), Staphyslide (bioMèrieux), Biostaph (Medlabs) and Bacto Latex (Difco)--were evaluated for the routine identification of S aureus from primary plates in the routine microbiology laboratory. Comparison was made with two methods of tube coagulase testing and five slide methods for detecting clumping factor (slide coagulase testing). Performances were assessed for two groups of organisms, staphylococcal species alone and a combined staphylococcal and non-staphylococcal species group. The effects of growth on selective media and storage of isolates at room temperature and 4 degrees C were investigated. Selective media cannot be recommended, nor can storage of isolates before testing. Ranked according to efficiency value with the combined staphylococcal and non-staphylococcal species group, the kits and coagulase methods performed as follows (the figures in parentheses are the efficiency values for the staphylococcal group alone): tube coagulase reference method 100% (100%), tube coagulase SJH method 99% (99%), Staphaurex 94% (97%), Staphylase 93% (96%), slide coagulase method No 4 93% (94%), slide coagulase method No 5 93% (93%), Bacto Latex 92% (95%), Staphyslide 92% (95%), and Biostaph 87% (91%). It is concluded that a commercial S aureus identification kit should not replace tube coagulase testing for the routine identification of the organism from primary plates and that, even the kits with the best performances, have little advantage over a good slide coagulase test method.     

Evaluation of various rapid agglutination methods for the identification of Staphylococcus aureus

A latex agglutination test (SeroSTAT Staph; Scott Laboratories, Fiskeville, R.I.) and two hemagglutination tests (Staphyloslide; BBL Microbiology Systems, Cockeysville, Md.; and Hemastaph; Remel, Lenexa, Kans.) were compared with the slide coagulase (SC) and tube coagulase (TC) tests at room temperature (22 to 25 degrees C) and at 37 degrees C for the rapid identification of Staphylococcus aureus. A total of 380 clinical strains of staphylococci were tested. The TC test performed at room temperature yielded the largest number of TC-positive results (n = 239), and based on this observation 239 organisms were classified as S. aureus and 141 were classified as non-S. aureus. The SC, TC (37 degrees C), SeroSTAT Staph, Staphyloslide, and Hemastaph tests correctly identified 210 (87.9%), 221 (92.5%), 238 (99.6%), 239 (100%), and 236 (98.7%) of the S. aureus isolates, respectively. Of the S. aureus isolates that were TC positive at room temperature 68% required 24 h of incubation before coagulase production was detected. There was one false-negative SeroSTAT Staph result and one false-negative Hemastaph result. The Staphyloslide test yielded two noninterpretable results (both organisms were later confirmed as non-S. aureus), whereas there were six noninterpretable results recorded with the Hemastaph test (four organisms were classified as non-S. aureus, and two were classified as S. aureus). The SeroSTAT Staph, Staphyloslide, and Hemastaph tests were all more sensitive than the conventional SC and TC (37 degrees C) tests and were considerably more rapid than the TC test at either temperature.     

Efficacies of rapid agglutination tests for identification of methicillin-resistant staphylococcal strains as Staphylococcus aureus.

Four commercially available rapid agglutination tests for the identification of Staphylococcus aureus were compared with the tube coagulase test for the identification of 300 methicillin-resistant isolates of staphylococci. Isolates tested included 207 methicillin-resistant S. aureus and 93 coagulase-negative staphylococci, collected from five medical centers. Strain variability was documented by phage typing and antimicrobial susceptibility patterns. Results of rapid identification tests ranged between 82 and 86% sensitivity, significantly poorer than the 98% sensitivity which the tube coagulase test provided.     

Comparison of two commercially available test methods with conventional coagulase tests for identification of Staphylococcus aureus

The API STAPHase (Analytab Products, Inc., Plainview, N.Y.) and SeroSTAT Staph (Scott Laboratories, Fiskville, R.I.) tests were compared to the conventional tube coagulase test and a slide coagulase test by using fresh isolates of members of the family Micrococcaceae. The 4-h, 24-h, and combined readings of the tube coagulase test detected 94.5, 99.5 and 100%, respectively, of 219 Staphylococcus aureus isolates. The API STAPHase, SeroSTAT Staph, and slide coagulase tests detected 95.9, 95.4 and 95.9% of the isolates of S. aureus, respectively. There were no false-positive results with any of the systems when tested with 103 strains of members of the family Micrococcaceae other than S. aureus. We concluded that the STAPHase and SeroSTAT Staph tests were equal in accuracy to the slide coagulase and 4-h tube coagulase tests and were suitable for use in the clinical microbiology laboratory. However, SeroSTAT Staph gave faster results than the API STAPHase, and the test was easier to perform. Also, the false-negative rate was high enough with the STAPHase, SeroSTAT Staph, and the slide coagulase tests that all negative reactions should be confirmed with a tube test.     

Identification of Staphylococcus aureus within 2 hours in blood culture broths

Staphylococcus aureus identification is one of the priorities of the microbiological diagnosis of the staphylococcal infections. Current identification methods are carried out after a first step of colony isolation on agar media. We describe a fluorogenic method for S. aureus identification, which is directly applied to blood culture broths. This method uses a gel tube which allows an optimized microculture of the bacteria. 129 clinical samples of blood cultures (HEC) containing gram positive cocci in grapelike clusters (35 Vital bottles, 94 Bactec bottles), and 77 inoculated blood culture (HE) with collection strains of S. aureus are included in the study. Bacteria are concentrated and separated from other components of sample in the gel tube. Staphylococci are revealed during a microculture in the gel phase, by using a colorimetric substrate of their dehydrogenases. Then, staphylococci are recovered in an adapted culture medium containing human prothrombin and a fluorogenic substrate, which is specific for the staphylocoagulase. After 1 to 2 h incubation at 37 degrees C, a blue fluorescence shows the presence of S. aureus. Among the 40 HEC containing S. aureus the test is positive for 37 samples. For 3 cases, the test is not interpretable, due to non lysis red blood cells in the gel phase of the tube. No false positive result is observed for the HEC containing coagulase-negative staphylococci. Moreover, our method is positive with the 77 HE. 94.7% of tested samples (HEC and HE) show a fluorescence after only one hour and half. Sensibility and specificity are both 100%. We propose a rapid method for S. aureus identification directly applied to blood culture broths. This method saves 24 h, avoiding the isolation step on agar. Therefore, the treatment of staphylococcal infections and possible isolation measures could earlier set up.     

The combined oxacillin resistance and coagulase (CORC) test for rapid identification and prediction of oxacillin resistance in Staphylococcus species directly from blood culture

The combined oxacillin resistance and coagulase (CORC) protocol for rapid identification and determination of oxacillin-susceptibility in Staphylococcus spp from blood culture is described. It incorporates a modified direct tube coagulase test (TCT) and a novel 4-hour multiplication-induction step, which increases the expression of staphylococcal PBP2a if present, facilitating detection by a commercial PBP2a latex agglutination kit. The protocol shows excellent sensitivity and specificity for determination of coagulase-positivity in staphylococci from patient blood cultures (96.8% (95% CI 81.5 to 99.8) and 100% (95% CI 75.9 to 100), respectively, n = 47), and for prediction of oxacillin resistance in S aureus directly from patient blood cultures (100% (95% CI 59.8 to 100) and 100% (95% CI 82.2 to 100), respectively (100% accuracy), n = 31) within 5 hours of blood culture positivity.     

Role of different classes of mammalian cell surface molecules in adherence of coagulase positive and coagulase negative staphylococci

In the present study the role of different mammalian cell receptors in adherence of the coagulase positive pathogen, Staphylococcus aureus and some coagulase negative staphylococci, namely Staphylococcus epidermidis and Staphylococcus saprophyticus was investigated. Upon testing the adherence to Vero and Hep-2 cells, S. aureus isolates showed an adherence to both cell lines while S. epidermidis and S. saprophyticus isolates adhered to Vero cells only. According to the obtained results, both O-linked and N-linked mammalian cell surface glycoproteins are involved in the adherence of S. aureus isolates to Vero and Hep-2 cells, whereas only the O-linked ones serve as receptors for adherence of S. epidermidis and S. saprophyticus isolates to Vero cells. Of the O-linked glycoproteins, GAG-like receptors are involved in adherence of all tested isolates to Vero cells. The coagulase positive staphylococci preferred to adhere to the highly sulphated GAGs (Heparin and chondroitin sulphate B) while the coagulase negative isolates showed higher affinity to the less sulphated ones (Chondroitin sulphate A and C). Mucin like receptors appeared to be important for the adherence of all tested staphylococci. The role exhibited by fibronectin- and fibrinogen-like receptors was detected with S. aureus and S. epidermidis but not with S. saprophyticus isolates. While, collagen and gelatin were found to contribute to the adherence of S. aureus isolates only. Neither carbohydrate moieties of the glycoconjugates nor lipid molecules on the mammalian cell surface played a role in the adherence of the tested staphylococcal isolates. Taken together, the results revealed that both coagulase negative and coagulase positive staphylococcal tested isolates adhere to the same classes of mammalian cell surface receptors such as mucin-like, fibrinogen-like, fibronectin-like and GAG-like receptors. However, the tested isolates exhibited different degrees of affinities to such receptors.     

Comparison of a yellow latex reagent with other agglutination methods for the identification of Staphylococcus aureus.

A new commercial yellow latex agglutination reagent (Bacto-Staph) was compared with the slide and tube coagulase tests and three other commercial reagents for the identification of 283 Staphylococcus aureus and 54 non-S. aureus staphylococcal strains. Test sensitivities for the identification of S. aureus were as follows: tube coagulase, 99.6%; slide coagulase, 98.6%; Bacto-Staph, 99.6%; Staphylatex, 98.6%; Sero STAT Staph, 98.2%; and Staphyloslide, 97.5%. No false-positive reactions were observed with any of the commercial reagents.     

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 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.