Novel coagglutination method for serotyping group B streptococci.

A group G streptococcal strain was coated with antibody against six different serotypes (Ia, Ib, II, III, IV, and V) of group B streptococci. The coagglutination patterns of 114 strains of group B streptococci were compared with the serotypes determined after immunoprecipitation. The specificity of the method was 100% and the sensitivity 97%. It was used for the typing of 89 invasive and 101 colonizing isolates. The new method is swift, specific, and highly sensitive. It consumes only minute amounts of antibody.     

Evaluation of slide agglutination methods for identifying group D streptococci.

Three commercial reagents for the rapid identification of group D streptococci by slide agglutination were evaluated. These included SeroSTAT (Scott Laboratories, Fiskeville, R.I.), Streptex (Wellcome Laboratories, Research Triangle Park, N.C.), and Phadebact (Pharmacia Diagnostics, Piscataway, N.J.). The methods included direct colony testing, enzyme extraction with pronase, and broth culture. A total of 72 strains of group D streptococci were tested. The SeroSTAT and Streptex reagents with pronase extraction each identified 65 (90%) of the strains. The SeroSTAT reagent was somewhat more specific since it did not cross-react with other streptococci of the viridans group. The Phadebact reagent was nonreactive. We conclude that the latex reagents can be very useful for the quick recognition of group D streptococci in the clinical laboratory.     

Rapid isolation and identification of group B streptococci from selective broth medium by slide co-agglutination test.

Direct identification of group B streptococci from a selective broth medium was performed with the Phadebact streptococcus test to determine the feasibility of this technique for early detection of streptococcal colonization. Of 124 clinical isolates, 122 (98.4%) were correctly identified in less than 24 h from the selective broth medium, whereas standard cultures from blood agar plates identified, after 48 h, only 66 (53.2%). The presence of group B streptococci in mixed cultures was always detected by the Phadebact test, and no false-positive co-agglutination tests were observed in 372 cultures from which organisms other than group B streptococci were isolated.     

Rapid coagglutination test for the direct detection of group A streptococci from throat swabs

A one-minute antigen detection test was compared with a conventional culture method for detecting group A -hemolytic streptococci. The test detects coagglutination between protein A and streptococcal antigen extracted directly from throat swabs. Of the 307 specimens tested, 66 (21.5%) were positive for group A streptococci by culture and 16 specimens (5.2%) were positive for other -hemolytic streptococci. The direct test agreed with the culture in 274 of 307 specimens (accuracy 89.3 %). The sensitivity of the test was 86.4 % (57/66), the specificity 90 % (217/241), the positive predictive value 70.4 % and the negative predictive value 96 %. If only throat cultures with more than 100 colonies of group A streptococci per plate, were considered, the sensitivity of the direct test rose to 96 %. If only a strong agglutination was considered positive, the specificity of the direct test rose to 98 %. Further studies are needed to determine whether this test could be used alone or in addition to culture.     

Rapid slide agglutination test for Lancefield grouping of streptococci.

A rapid slide agglutination test (the Phadebact [PB] Streptococcus test) was compared with the standard autoclave extraction method of Lancefield and presumptive clinical laboratory tests for grouping of streptococci (bacitracin disk sensitivity for group A and sodium hippurate hydrolysis for group B). Identification of group A streptococci by the PB kit was statistically as accurate as by the Lancefield method, whereas bacitracin grouping was significantly less accurate than the Lancefield method (P = less than .02). With regard to group B, there was no statistically significant difference between the PB test and the sodium hippurate test. The PB test correctly identified all group C and G streptococci. The PB kit provides a rapid and reliable method for Lancefield grouping of streptococci.     

New phenotypic typing scheme for group B streptococci.

AIMS: To develop a new typing system for group B streptococci based on 35S-methionine-labelled protein profiles of bacterial proteins. METHODS: 377 clinical isolates of group B streptococci were examined by incorporation of 35S-methionine into bacterial proteins under strict anaerobic conditions. After sodium dodecylsulphate-polyacrylamide gel electrophoresis, autoradiography was performed. The patterns produced were visually analysed and categorised into clusters of organisms based on the pattern of band production between 32-46 kilodaltons. RESULTS: 294 of the typed strains classified into seven different groups designated a-g. 32 strains failed to incorporate 35S-methionine sufficiently to be grouped and 11 strains did not fall into one of the seven identified groups. Typability, reproducibility, and discrimination of the system was evident. CONCLUSIONS: This typing system may help to distinguish between colonising and invasive strains of the organism.     

Multicentre evaluation of a direct coagglutination test for group A streptococci

A coagglutination test for detection of group A streptococci in throat samples was evaluated in a multicentre study and found to be about 95 % sensitive when applied to swabs taken from symptomatic patients which yielded more than 100 colonies per plate on culture. The sensitivity of the test dropped significantly when it was applied to swabs giving fewer than 100 colonies on culture. The specificity of the test was high regardless of colony count on conventional media.     

Serological grouping of streptococci by a slide coagglutination method.

A new method for the serological grouping of streptococci by coagglutination with specific antibodies absorbed to protein A-containing staphylococci has been assessed. A total of 242 strains of streptococci, including beta-haemolytic streptococci of groups A, B, C, F, and G, Streptococcus pneumoniae and Strep. faecalis were studied. All streptococci of groups A, B, C, and G, groupable by standard methods, were correctly grouped by coagglutination, although 7-3% showed varying degrees of cross-agglutination. Two beta-haemolytic strains of Strep. faecalis produced coagglutination with group C streptococcal reagent. The method appears to be quick, accurate, reproducible, and simple to perform.     

Lim group B Strep Broth and coagglutination for rapid identification of group B streptococci in preterm pregnant women.

A total of 147 preterm pregnant women at Orlando Regional Medical Center were screened for group B streptococci by using Lim Group B Strep Broth (GIBCO Laboratories, Madison, Wis.) and the Phadebact Strep B Test (Pharmacia Diagnostics, Piscataway, N.J.). Test results were available within 20 h of culture and, in the case of heavily colonized women, within 5 h. This procedure is useful in rapid diagnosis of preterm pregnant women for group B streptococcal colonization.     

Rapid coagglutination test for the detection and typing of foot and mouth disease virus

Protein A containing Staphylococcus aureus was used to develop a coagglutination (COA) test for the detection and typing of foot and mouth disease virus (FMDV) O, A and C serotypes in infected cells and tissues. Different batches and amounts of guinea pig anti-FMDV sera were assessed to optimize the preparation of COA conjugates. The sensitivity and specificity of the COA Test for the detection of FMDV O, A and C serotypes and heterologous viruses was also characterized. Comparison between the COA Test and complement fixation test for the detection and typing of FMDV obtained from extracts of tongue epithelial tissues from infected cattle revealed high agreement in the results and indicated a potential application of the COA Test for the direct diagnosis of viruses.     

Evaluation of rapid methods of identifying group B streptococci.

Rapid methods of identifying Lancefield group B streptococci were compared to the standard Fuller's extraction method. Such tests as sodium hippurate hydrolysis, bile tolerance, aesculin hydrolysis, pyruvate fermentation, Camp factor, pigmentation, and bacitracin haemolysis were tested on both routine clinical specimens and National Collection of Type Culture strains. The results show that pigmentation on Islams's medium was the most definitive test available rapidly to identify group B streptococci.     

Improved methods for typing nontypeable isolates of group B streptococci

Group B streptococci (GBS) are classified by capsular polysaccharide (CPS) type and by cell surface-expressed proteins (c and R). Isolates lacking detectable CPS are considered nontypeable (NT) although they frequently express surface proteins. Immunological and genetic methods were used to study 91 NT GBS isolates collected during surveillance studies for invasive disease or colonization in pregnant or non-pregnant women and neonates less than seven days of age. CPS production was upregulated by the addition of glucose and sodium phosphate to Todd-Hewitt broth (THB) and cells were extracted using hot HCl or mutanolysin. Extracts were tested with antisera for specific CPS types Ia, Ib, and II - VIII by double immunodiffusion (DD) in agarose. By mutanolysin extraction, 12 (13.2%) of the 91 isolates were typeable. In contrast, only four of these 12 newly typeable isolates tested positive for CPS with the HCl extracts of cells grown in modified THB. DNA was analyzed by pulsed-field gel electrophoresis (PFGE) using SmaI restriction with NT isolates grouped by protein profile to facilitate analysis. PFGE results of the NT isolates were compared to DNA profiles of typeable isolates and were correlated with the DD results. The DNA profiles of the newly typeable isolates were similar to profiles of isolates with corresponding defined CPS type. Of the remaining 78 NT isolates digested by SmaI, 63 (80.8%) had DNA profiles that resembled those of specific types of GBS. These approaches will be useful for classification of NT isolates in continued epidemiological surveillance associated with GBS vaccine trials.     

CAMP-disk test for presumptive identification of group B streptococci.

Standaridizing test results for rheumatoid factor by comparing results obtained for an unknown with results obtained for a serum reference preparation decreased variance between laboratories, as measured in the Center for Disease Control proficiency testing program, by 77%. The amount of improvement was also estimated by the type of test and by the manufacturer's product. Standardization resulted in an increase in the number of reported results that were within a twofold dilution of the median value. The percentage increased from 50.3 to 93.7% for the slide tests and from 78.1 to 91.2% fro the tube tests. Decrease in variance by manufacturer's product ranged from 94 to 27%. The study demonstrated that adopting a reference serum standard could substantially improve the comparability of rheumatoid factor test results and that proficiency testing programs can be used to estimate improvement which could be expected as a result of standardization.     

Rapid identification of group B streptococci by counterimmunoelectrophoresis.

Beta-hemolytic streptococcal isolates have been examined by counterimmunoelectrophoresis (CIE) with group B antiserum to determine whether this techinque is of value in the rapid identification of group B strains. Ninety stock cultures and 100 clinical isolates of beta-hemolytic streptococci including representatives of groups A, D, C, G, and B were inoculated into Todd-Hewitt broth; after incubation at 37 C for 1, 2, 3, and 4 h, aliquots of the whole broth cultures were removed and tested by CIE. Antigen was not regularly detected in the 1-, 2-, and 3-h samples, but after 4 h all 126 group B streptococcal strains identified by the capillary precipitin reaction gave CIE precipitin bands with group B antiserum. None of the 58 non-group B strains gave precipitin reactions with this antiserum. Cerebrospinal fluid from an infant with group B streptococcal meningitis and peritoneal fluid from a patient with group B streptococcal peritonitis had free group B antigen detected by the CIE technique. CIE of broth cultures and direct body fluids appears to be a rapid and sensitive method for the identification of group B streptococcal strains.     

Comparison of slide coagglutination test and countercurrent immunoelectrophoresis for detection of group B streptococcal antigen in cerebrospinal fluid from infants with meningitis.

The usefulness of Phadebact streptococcus reagents for the detection of group B streptococcal antigen in cerebrospinal fluid was evaluated in 54 infants with meningitis and in 22 normal infants. Antigens was detected by slide coagglutination in 19 (82.6%) and by countercurrent immunoelectrophoresis in 20 (87.0%) of 23 cerebrospinal fluid specimens from infants with group B streptococcal meningitis at admission. After initiation of antimicrobial therapy, antigen could be detected in 11 of 19 (by slide coagglutination) and 7 of 18 (by countercurrent immunoelectrophoresis) cerebrospinal fluids. False-positive reactions were noted by slide coagglutination in one infant with S. bovis meningitis and one with group B streptococcal bacteremia without meningitis; none occurred with countercurrent immunoelectrophoresis. The commercial availiability, simplicity, sensitivity (82.6%), and specificity (96.4%) of the Phadebact slide coaggluatination test for detecting group B streptococcal antigen in cerebrospinal fluid suggest that it may be useful for the early and rapid diagnosis of group B streptococcal meningitis.     

Multiplex PCR assay for rapid and accurate capsular typing of group B streptococci

We developed a simple, specific, and sensitive two-multiplex-PCR assay that enabled the detection of all known group B streptococcal (GBS) capsular polysaccharides. This test is well adapted for GBS capsular polysaccharide typing in large-scale epidemiological studies.     

Evaluation of spot CAMP test for identification of group B streptococci.

The CAMP (Christie-Atkins-Munch-Petersen) test is commonly used for the presumptive identification of Streptococcus agalactiae (Lancefield group B). Using 350 clinical isolates of beta-hemolytic streptococci, we compared a 30-min spot CAMP test with the standard overnight CAMP test and the Lancefield precipitin test. We found 99% agreement among all three tests for all streptococci tested. The spot CAMP test is a rapid, inexpensive, and accurate method for identifying group B streptococci.     

Rapid detection of group B streptococci directly from vaginal swabs.

Duplicate vaginal swabs were obtained from patients who attended obstetric or gynecologic clinics affiliated with the Magee Womens Hospital in Pittsburgh. One swab was cultured semiquantitatively on 5% sheep blood agar to detect group B streptococci (GBS). The other swab was subjected to a rapid method (25 min) for antigen detection and micronitrous acid exposure to extract the GBS antigen, followed by latex particle agglutination. A total of 464 swabs were evaluated by direct plating. Fifty-two swabs (11.2%) were found to contain GBS. Overall, the rapid method detected 21 of 52, or 40.4%, positive specimens. The sensitivity of the rapid method for identifying the most heavily colonized samples was 85.7%. This method can be used to identify maternity patients who are heavily colonized with GBS and are at high risk of delivering septic infants.     

Rapid recognition of group B streptococci by pigment production and counterimmunoelectrophoresis.

Streptococci from clinical isolates were studied for their ability to produce pigment in stab cultures in Columbia agar. Serological grouping of these organisms was done by counterimmunoelectrophoresis using Burroughs-Wellcome antisera. In this group of isolates, 66 of the 68 organisms grouped as B by serological testing produced pigment in the Columbia agar stab cultures. Pigment was not produced by any of the other 36 streptococci studied (11 group A, 9 group C, 4 group D, and 12 nongroupable). The use of the Columbia agar stab culture is recommended as a rapid and simple test for recognition of group B streptococci. The counterimmunoelectrophoresis test is also suggested as a convenient, rapid, and sensitive method for grouping the streptococci.     

Rapid method for identification of group B streptococci in neonatal blood cultures.

A rapid technique used for the identification of Streptococcus agalactiae, Lancefield group B, from the blood cultures of two neonatal infants is reported. The method utilized the Phadebact Streptococcus Test System (Pharmacia Diagnostics, Piscataway, N.J.) and the supernatant from 13- and 14-h blood cultures. Additional studies with simulated neonatal blood cultures revealed that this method was reproducible. Additional studies also revealed that some non-specific agglutination did occur, which could not be eliminated with dithiothreitol, but was visibly reduced by treatment with soluble staphylococcal protein A.