Maternal β-hemolytic streptococcal pharyngeal exposure and colonization in pregnancy

Abstract

Objectives: To report the pharyngeal colonization rate of β-hemolytic streptococci and changes in the value of antistreptolysin O (ASO) and anti-DNase B serology titers during pregnancy.

Methods: Healthy pregnant women were recruited and blood was drawn in each trimester. The upper limit of normal (ULN) values for ASO and anti-DNase B was calculated for each trimester. Throat swabs were collected for culture and positive cultures were further assessed for the identification of serogroup of the isolated β-hemolytic streptococcus.

Results: Out of a total of 126 pregnant women, 34.1% had positive throat cultures. Group C and group G strains were isolated in 18.2% of throat cultures while group F was detected in 13.5% of cases. The rate of colonization with GAS was 1.6%. There was an overall drop in ASO titer during pregnancy while anti-DNase B titers remained relatively unchanged. ULN values of 164(IU), 157(IU), and 156(IU) were calculated for ASO at the first, second, and third trimesters, respectively. Based on the ULN values, 28.6% of patients had recent streptococcal exposure.

Conclusions: These results show that pregnant women act as a reservoir for spreading potentially immunogenic (groups C and G) and disease producing (group F) virulent strains of streptococci.

Figure 1

Correlation between ASO and anti-DNase B titers in pregnancy trimesters. Scatter plots showing correlation between values of ASO and anti-DNase-B antibodies in different pregnancy trimesters. Values less than laboratory lower limit for anti-DNase B detection were converted to the lower limit value of the assay. Correlation coefficients and Pearson correlation P values are shown on the plots: (a) Trimester 1, (b) Trimester 2, and (c) Trimester 3.