Microbial interactions in the vaginal ecosystem, with emphasis on the pathogenesis of bacterial vaginosis.

During bacterial vaginosis (BV), populations of lactobacilli which are generally dominant in the vagina of overtly healthy women are replaced by other facultative and anaerobic microorganisms. Some Lactobacillus strains produce hydrogen peroxide and all produce lactic acid; however, the antagonistic role of these metabolites in vivo remains controversial. Positive interactions among BV-associated organisms may contribute to the pathogenesis of BV and its sequelae.

A commensal symbiosis between Prevotella bivia and Peptostreptococcus anaerobius involves amino acids: potential significance to the pathogenesis of bacterial vaginosis.

In both batch and continuous culture, Peptostreptococcus anaerobius was able to grow in vaginal defined medium with Prevotella bivia, but not in pure culture. Growth of P. anaerobius was increased by 238% (P < 0.001) in peptone-supplemented vaginal defined medium conditioned by prior growth of P. bivia. Analysis of P. bivia culture supernatants showed a net accumulation of amino acids and subsequent growth of P. anaerobius in the conditioned supernatants resulted generally in amino acid utilization. Supplementation of peptone-supplemented vaginal defined medium with amino acids in concentrations similar to those available after prior growth with P. bivia were growth-stimulatory (246%, P=0.006) for P. anaerobius. Increased availability of amino acids by P. bivia is proposed as a mechanism to support the observed in vitro commensal symbiosis between P. bivia and P. anaerobius.

Evidence for a commensal, symbiotic relationship between Gardnerella vaginalis and Prevotella bivia involving ammonia: potential significance for bacterial vaginosis.

Six strains of Prevotella bivia and 4 of Gardnerella vaginalis were examined for nutrient substrate utilization as part of ongoing studies on the pathogenesis of bacterial vaginosis. Addition of single amino acids to vaginal defined medium (VDM) was stimulatory to the growth of P. bivia but not to G. vaginalis. However, peptides significantly promoted the growth of both organisms. Growth of P. bivia in VDM and VDM supplemented with either amino acids or peptone was accompanied by net ammonia production, while growth of G. vaginalis under the same conditions resulted in net ammonia utilization. Ammonia-enriched supernatants from the growth of P. bivia in peptone-supplemented VDM were stimulatory to G. vaginalis growth. However, ammonia-reduced supernatants from G. vaginalis growth in peptone-supplemented VDM had a neutral effect on P. bivia growth. A commensal relationship between P. bivia to G. vaginalis is proposed, with ammonia flow as a mechanism to support this hypothesis.

Regulatory influences on the production of gamma-aminobutyric Acid by a marine pseudomonad.

A pseudomonad capable of producing gamma-aminobutyric acid (GABA) was isolated from seawater via an enrichment in which glutamate was the sole carbon and nitrogen source. The organism grew optimally at pH 7.3 and at 25 degrees C. Putrescine, alanine, and glucose-nitrate also served as effective growth substrates. The isolate grew poorly on GABA. Cell suspensions of the organism in 0.02 M phosphate buffer (pH 7.6) containing NaCl (19.4 g liter) and MgCl(2). 6H(2)O(3 g liter) produced GABA from succinic semialdehyde in combination with glutamate or alanine but not from any substrate alone. Little or no GABA was produced with putrescine or glucose-nitrate as substrates. GABA production in the amino acid cosubstrate systems was transitory with optimum levels occurring in the suspension fluid after 3 h of incubation (0.3 and 0.03 mM for glutamate and alanine cosubstrates, respectively). However, yields of GABA in the cell suspension fluid were low, and quantities near that predicted from stoichiometry could be obtained only by extracting cell suspensions with methanol. GABA release in the suspension fluid was increased with higher pH or by decreasing NaCl. Substitution of the salt by the equivalent Tris-HCl or KCl likewise resulted in increased GABA release. When nigericin (10 mug ml) was added to cell suspensions in which NaCl was not decreased, GABA release increased in a way similar to that observed in suspensions with decreased NaCl. The ionophore also decreased GABA uptake by cell suspensions of GABA-grown cells, and the effect was duplicated by lowering NaCl in cell suspensions. The results indicate a role for an Na-dependent transport system in GABA release.

Application of inhibitor typing in a study of the transmission and retention in the human mouth of the bacterium Streptococcus salivarius.

Inhibitor production (P)-typing was used as a strain marker in epidemiological studies of Streptococcus salivarius. 43 per cent of 180 adult subjects had inhibitory Strep. salivarius strains as components of their oral microbiota. Strains of 13 different P-type patterns were detected and strains of different P-types often co-existed in the same subject. Adults from whom inhibitor-producing Strep. salivarius strains had been isolated retained their characteristic bacteriocinogenic strains over a 3-yr period. A specific Strep. salivarius-inhibitor screening method was used to study oral acquisition of Strep. salivarius by 14 newborn babies. Initially the babies were colonized by a wide variety of strains, many of which were not detected in the mothers' mouths. By the fifth day of life, strains with P-types identical with those in the mother had often become established as quantitatively prominent members of the babies' Strep. salivarius population.