C Letourneau | PubMed Health

PubMed1996

Rapid antigen testing for group A Streptococcus by DNA probe.

The Gen-probe group A Streptococcus direct test (GASD), a nucleic acid probe assay for detecting GAS from throat swabs, has recently been developed. The test uses an acridium ester-labeled DNA probe which is complementary to the rRNA of Streptococcus pyogenes. In this study, 318 single culturette throat swabs were tested by this method using culture as a "gold standard." After plating onto trypticase soy agar plates with 5% sheep blood, swabs were stored at 4 degrees C for no more than 72 h before the probe assay was performed. Our patient population consisted of symptomatic outpatients seen in the Memorial Hospital Emergency Department and in the Family Care Center. After discrepancy testing, sensitivity, specificity, and positive and negative predictive values were 91.4%, 97%, 91.4%, and 97%. The GASD is a rapid, easy-to-perform method for batch screening for streptococcal pharyngitis.

Antigens, Bacterial↗

PubMed1995

Detection of group B Streptococcus by immunoassay following enrichment in LIM-selective broth medium.

Rapid immunoassays have been developed to decrease the time to detection of Group B Streptococcus (GBS) carriage in pregnant women. In this study, a total of 162 pregnant women, considered to be high-risk obstetric patients, were seen in the Family Care Center at Memorial Hospital of Rhode Island, a 300-bed teaching hospital associated with Brown University Medical School. Vaginal and rectal specimens were taken and tested for GBS by using two rapid enzyme immunoassays (EIAs) that were compared with culture. Quidel and Hybritech ICON Group B strep tests were run following 4 h incubation in the selective enrichment LIM Group B strep broth; cultures were done both directly and after enrichment. Results with both EIAs were identical, with overall sensitivity, specificity, and positive and negative predictive values of 38%, 98%, 88%, and 84% respectively. However, when women having positive cultures were separated into moderately to heavily colonized (> or = 3 +) and lightly colonized (< or = 2 +) populations, the sensitivities were 82% and 19%, respectively. Although GBS assays are useful in the rapid diagnosis of heavily colonized women, culture following enrichment remains the most sensitive method for a lightly colonized population.

Colony Count, Microbial↗