RESUMEN
Background and aim of the work: in healthy adult women, the normal vaginal pH is < 4.5 which is mainly maintained by lactobacilli. Some species of lactobacilli are hydrogen peroxide [H2O2] producers. Lactobacilli, principally the strains that are hydrogen peroxide producing, may have a protective effect against vaginal colonization by pathogenic species such as those that cause bacterial vaginosis. The aim of this study was to investigate the lactobacillary flora in normal pregnant women and pregnant women with preterm labor, to compare vaginal flora by smear and score by Nugent criteria on Gram stain and to assess the distribution of lactobacilli generating hydrogen peroxide in both groups and its correlation to preterm labor
Methods: vaginal specimens were obtained from 60 normal pregnant women and 40 pregnant women with preterm labor with intact membranes. Leukocytic counts, pH detection and Gram stain for scoring by Nugent criteria were done. Isolation and semiquantification of vaginal lactobacilli on Man-Rogosa-Sharp media [MRS] and identification of lactobacilli by detection of 1,350 bp fragment of 16S rRNA gene by polymerase chain reaction [PCR] was done. Lactobacilli were then tested for their production of hydrogen peroxide on MRS media containing 0.25 mg/ml tetramethyl-benzidine and 0.1 mg/ml of horseradish peroxidase
Results: nugent score was significantly higher in women with preterm labor with intact membranes than normal pregnant women [P<0.001]. There was significant high isolation of lactobacilli in normal pregnant women as it was isolated from 47[78.3%] normal pregnant women and from 15[37.5%] pregnant women with preterm labor with intact membranes [P<0.001]. As regards hydrogen peroxide production from the isolated strains there was highly significant difference between both groups as after 30 min hydrogen peroxide producing lactobacilli were isolated from 59.6% of normal pregnant women isolates and 20% of preterm labor women isolates [P<0.001]. After 1h, the percentage of isolation had increased to 72.5% and 30% in both groups respectively. The number of hydrogen peroxide producing lactobacilli colonies in women with preterm labor with intact membrane after 30 min and 1h was significantly lower than the normal pregnant for the strong positive, weak positive and negative groups .With regard to the pregnancy outcomes in relation to strong positive and negative hydrogen peroxide producing groups there was significant difference for the gestational age at delivery as it was 37.34 w for the strong positive group and 32.31 w for the negative group [P<0.001]]. Also, the incidence of preterm delivery was significantly reduced in the strong positive group as it was 2 women [11%], while it was 8 women [40%] for the negative group
Conclusion: hydrogen peroxide production by vaginal lactobacilli may be used as a simple test for detection of women at high risk of preterm labor