Background . Elucidation of a pathogen’s antimicrobial susceptibility requires subculture after the organism is first isolated. This takes several days, requiring patients to be treated with broad-spectrum antibiotics. This approach contributes to the development of bacterial resistance. Methods . Microtiter wells were coated with a polyclonal antibody targeting the pathogen of interest. Bacterial suspensions were added in the presence/absence of selected antibiotics. After washing, captured bacteria were detected. Findings . Group B streptococcus (GBS), Enterococcus faecalis , and Neisseria gonorrhoeae were each detected at 10 5 bacteria/mL following a 20-minute incubation period. Susceptibility to select antibiotics was discernable following a 6-hour incubation period (GBS and Enterococcus ). Sensitivity was increased to 10 −2 bacteria/mL for GBS, 10 −1 bacteria/mL for E. faecalis , and 10 1 bacteria/mL for N. gonorrhoeae following 18–24-hour culture. Conclusion . This novel assay allows for the highly sensitive and specific identification of a pathogen and simultaneous determination of its antimicrobial susceptibility in a reduced time.

OBJECTIVE:To determine the validity of a novel Group B Streptococcus (GBS) diagnostic assay for the detection of GBS in antepartum patients.STUDY DESIGN:Women were screened for GBS colonization at 35 to 37 weeks of gestation. Three vaginal-rectal swabs were collected per patient; two were processed by traditional culture (commercial laboratory versus in-house culture), and the third was processed by an immunoblot-based test, in which a sample is placed over an antibody-coated nitrocellulose membrane, and after a six-hour culture, bound GBS is detected with a secondary antibody.RESULTS:356 patients were evaluated. Commercial processing revealed a GBS prevalence rate of 85/356 (23.6%). In-house culture provided a prevalence rate of 105/356 (29.5%). When the accelerated GBS test result was compared to the in-house GBS culture, it demonstrated a sensitivity of 97.1% and a specificity of 88.4%. Interobserver reliability for the novel GBS test was 88.2%.CONCLUSIONS:The accelerated GBS test provides a high level of validity for the detection of GBS colonization in antepartum patients within 6.5 hours and demonstrates a substantial agreement between observers.

To determine the validity of a novel Group B streptococcus (GBS) diagnostic assay for the detection of GBS in antepartum patients. Women were screened for GBS colonization at 35 to 37 weeks gestation. Three vaginal-rectal swabs were collected per patient; two were processed by traditional culture (commercial laboratory versus in-house culture), the third was processed by a novel diagnostic assay. 356 patients were evaluated. Commercial processing revealed a GBS prevalence rate of 85/356 (23.6%). In-house culture provided a prevalence rate of 105/356 (29.5%). When the rapid GBS result was compared to the in-house GBS culture, it demonstrated a sensitivity of 97.1% and a specificity of 88.4%. Inter-observer reliability for the novel GBS test was 88.2%. The rapid GBS test provides a high level of validity for the detection of GBS colonization in antepartum patients within 6.5 hours, and demonstrates substantial agreement between observers.

We determined if a new method of rapidly growing GBS in 6 hours could also determine antibiotic sensitivities in a shorter period compared to standard cultures. Women were screened between 35 to 37 weeks gestation. Vaginal-rectal swabs were collected in Stuarts transport medium. Swabs were then inoculated on a nitrocellulose membrane (NCM) that had been coated previously with polyclonal rabbit antibody against GBS in the presence or absence of clindamycin. At six hours, the NCM was removed from the sheep blood agar medium, and horseradish-peroxidase conjugate polyclonal antibody against GBS was added. An additional swab from each patient was cultured by traditional methods for 48-72 hours and those positive for GBS were then tested for resistance/sensitivity to clindamycin. A final control consisted of sending a separate swab from each patient to a commercial lab. 124 patient samples were screened, of which 33 were positive for GBS by the rapid test (97.0% concordance with traditional culture). Of these 33 positive samples, 10 were resistant to clindamycin, which agreed 100% with traditional culture. Results of the both the rapid and traditional culture showed 100% concordance with sensitivity or resistance to clindamycin when compared with commercial lab results. This new NCM assay offers a rapid and unique method for both detection and determination of antibiotic sensitivities for GBS; thus improving the targeting of antibiotic prophylaxis for GBS colonization.

We analyzed the performance of a new rapid diagnostic test for use in determining group B streptococcus colonization in pregnancy. Vaginal–rectal specimens were compared by the rapid test, a commercial laboratory culture result, and an in-house culture. Of 150 patient samples, 72 were positive by the rapid test, giving a prevalence of 48.0% versus 24.7% by traditional culture. Characterization of these results showed cross-reactivity with Enterococcus. The addition of bacitracin reduced this interference, and when reanalyzed, a colonization rate of 31.3% was found (P = 0.3961, chi-square), as well as a sensitivity of 100% (95% confidence interval [CI] 89.1–100) and a specificity of 93.6% (95% CI 86.9–97.2). The addition of bacitracin greatly improves the reliability of this diagnostic test and demonstrates a novel approach to reduce interference. An accurate determination of the test's sensitivity and specificity, however, awaits enrollment of the remaining subjects.

Neonatal infection with Streptococcus agalactiae (group B streptococcus [GBS]) causes significant morbidity and mortality. A truly rapid diagnostic test for identifying GBS would allow for more timely initiation of antibiotic prophylaxis and also reduce the administration of antibiotics for the prevention of early onset neonatal GBS infection. A stock culture was formed from a laboratory reference strain of GBS and was diluted from 10 (7) to 10 (1) bacteria/mL. Specific concentrations were used to inoculate nitrocellulose membranes (NCMs) that had been coated previously with polyclonal rabbit antibody against GBS. After specific times, the NCMs were removed from the sheep blood agar medium, and horseradish-peroxidase conjugate polyclonal antibody against GBS was added. Bound antibody was detected with diaminobenzidine. After 6 hours of incubation, GBS was detected at concentrations from 10 (7) through 10 (4) bacterial/mL. After 4 hours of incubation, GBS was detected at concentrations from 10 (7) through 10 (5) bacteria/mL. GBS was not detected at 2 hours of incubation. Rapid growth and detection of GBS can be performed, and the results can be reliably attained as early as 4 hours. This is in marked contrast to the 48 to 72 hours required by current methods.

Recent investigations have demonstrated decreased morbidity in the newborn following maternal administration of antibiotics to mothers with a diagnosis of chorioamnionitis. These benefits are based upon transplacental passage of antibiotics. Fifteen preterm and term women with the diagnosis of chorioamnionitis were given 3 or 4 g of mezlocillin intravenously every 4 to 6 h. Maternal serum and umbilical cord samples were collected at delivery and the concentrations of antibiotics were determined by high-pressure liquid chromatography. Peak serum levels of mezlocillin in the cord and mother occurred within 60 min, but were eliminated more rapidly in the mother. Umbilical cord levels, while initially lower with the 3 g dose, were present longer than 4 hr for both regimens. Placental transfer of antibiotics appeared to be affected by the aging placenta with decreased initial levels and slower fetal clearance at term.Key Words: AntibioticsFetalPenicillinsTransplacental