In Vitro Ability of the Group B Streptococci to Inhibit Gram‐Positive and Gram‐Variable Constituents of theBacterial Flora of the Female Genital Tract

Abstract

Objective: The purpose of this study was to analyze the ability of septicemic and nonsepticemic isolates of group B streptococci (GBS) to inhibit in vitro the principal bacterial groups found in the normal bacterial flora of the female genital tract.Methods: The target groups were composed of 1) 10 strains each of the following: viridans streptococci, nonhemolytic streptococci (not group B or D), group A streptococci, GBS, peptostreptococci, coagulase-negative staphylococci, Staphylococcus aureus, and Gardnerella vaginalis; 2) 9 strains of enterococci; 3)9 strains of group C or G streptococci; 4) 7 strains of lactobacilli; and 5) 7 strains of diphtheroids. All target groups were tested for inhibition by a test panel of either a group of 10 or 41 GBS isolates. If the GBS isolates failed to inhibit a target group, that group was tested for its ability to inhibit the GBS test panel.Results: The GBS test panel did not inhibit the growth of coagulase-negative staphylococci or S. aureus but uniformly inhibited groups A, B, C, and G streptococci, lactobacilli, and G. vaginalis. One of the 7 strains of diphtheroids was inhibited by 37 of the 41 GBS isolates; the other 6 strains of diphtheroids were uniformly inhibited. Variable inhibition by GBS was observed with viridans streptococci, nonhemolytic (not group B or D) streptococci, peptostreptococci, and enterococci; however, inhibition or noninhibition was uniform for a given target strain against the entire GBS test panel. The 23 GBS isolates obtained from septicemic neonates or adults did not differ from the 18 nonsepticemic isolates in their ability to inhibit other species of streptococci or other gram-positive or gram-variable constituents of the bacterial flora of the female genital tract. When converse testing was done, all 10 GBS isolates were uniformly inhibited by coagulase-negative staphylococci and by the majority of enterococci, but were not inhibited by S. aureus.Conclusions: These studies suggest that GBS may be significant regulators of other [3-hemolytic streptococci, diphtheroids, lactobacilli, and G. vaginalis within the bacterial flora of the female genital tract. Moreover, the absence of GBS in the vaginal flora may be the result of mediation by coagulase-negative staphylococci and selected strains of enterococci. (C)

Influence of the Vaginal Microbiota on Toxic Shock Syndrome Toxin 1 Production by Staphylococcus aureus

“…Multiple studies have found that S. agalactiae inhibits Lactobacillus spp. and G. vaginalis without inhibiting S. aureus (34)(35)(36) and that S. aureus colonization is significantly associated with colonization by S. agalactiae in a population of pregnant women (37). Our findings thus illustrate another way in which GBS could promote the virulence of S. aureus.…”

Definition of a type of abnormal vaginal flora that is distinct from bacterial vaginosis: aerobic vaginitis

“…The more severe the microscopic findings, the more likely these organisms will be cultured. Case studies have recently drawn attention to the possibility of vaginitis due to group B streptococci 4 , and Monif et al provide in vitro evidence that group B streptococci inhibits growth of lactobacilli and G. vaginalis, but not S. aureus 22,23 . There is increasing evidence that some pregnant women develop mid-trimester chorioamnionitis caused by invasive group B streptococci 24,25 .…”

Semiquantitative bacterial observations with group B streptococcal vulvovaginitis

“…3 The GBS strains tested did not inhibit the growth of coagulase-negative staphylococci, S. aureus, or any gram-negative organisms. 3 Isolates of GBS were uniformly inhibited by coagulase-negative staphylococci, but were not inhibited by S. aureus. 4 When quantitative studies were performed analyzing the interrelationships within the bacterial flora of the female genital tract, GBS was found not to be an infrequent isolate with either G. vaginalis, lactobacillus, or the coagulasenegative staphylococci.…”

“…3 In vitro, GBS was shown to inhibit other beta hemolytic streptococci, diphtheroides, lactobacillus, and Gardnerella vaginalis. Variable inhibition by GBS was observed with viridans, streptococci, nonhemolytic (not group B or D) streptococci, peptostreptococci, and enterococci.…”

“…In reviewing records from a number of clinical vaginitis studies in which more comprehensive microbiologic study was performed, four women were identified who had clinical symptoms, findings, and microbiologic prerequisites that warranted the diagnosis of GBS vulvovaginitis. The purpose of this paper is to characterize their semiquantitative microbiologic data as it relates to qualitative microbiologic observations dealing with GBS 3 and to in vitro inhibition data dealing with GBS. 4 …”