Hippurate hydrolysis and Christie, Atkins, Munch-Peterson tests as epidemiological diagnostic tools for Streptococcus agalactiae carriage in pregnancy.

OBJECTIVE To evaluate the Christie, Atkins, Munch-Peterson (CAMP) and hippurate hydrolysis reactions as diagnostic tools for Streptococcus agalactiae carriage in pregnancy. DESIGN Observational, analytical case-control study. SETTING Hospital-based study in a primary and a tertiary health care institution. PATIENTS One hundred and six pregnant and 56 non-pregnant (controls) women were included in the study. The participants were of different socio-economic status. A volunteer sample was used. About 800 subjects were contacted and 162 participated in the study. RESULTS The sensitivity of the screening test varied from 25% for the CAMP test to 77.78% for the hippurate hydrolysis reaction. The specificity was the same for both tests at (50%). A significant difference in positivity between the CAMP and hippurate hydrolysis reactions (95% confidence limit, P < 0.05) was observed. The predictive values of the positive test were 66.6% (CAMP) and 87.55% (hippurate hydrolysis) while the negative test were 14.29% (CAMP) and 33.30% (hippurate hydrolysis). Pregnant women had 0.33 chances of being GBS carriers with the CAMP compared to 3.5 with the hippurate hydrolysis. CONCLUSION The hippurate hydrolysis test is highly recommended since the reagents are easily available and the organism was easily isolated using this method. The presence of GBS in the anorectum and endocervix is likely to induce systemic and local immunity in the female genital tract. This can contribute to the development of a mucosal vaccine for GBS diseases.