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.

Effect of Candida albicans infection and clotrimazole treatment on vaginal microflora in vitro.

OBJECTIVE: To determine the effect of Candida albicans infection and clotrimazole treatment on vaginal microflora. METHODS: Studies were conducted using a model simulating the healthy vaginal ecosystem. The model consisted of a mixed culture of Lactobacillus acidophilus, Staphylococcus epidermidis, Prevotella bivia, and group D Streptococcus sp grown in continuous culture in a chemically defined medium. The status of the model was assessed using a mathematical equation that determines the probability a microflora is normal or abnormal. RESULTS: Challenge of the model with C albicans was followed within 24 hours by the development of microbial populations representing an abnormal microflora. Treatment of the system with clotrimazole (100 micrograms/mL) resulted in a decrease in C albicans counts to 0 within 48 hours. However, treatment also altered other components of the vaginal microflora, which did not return to normal. Addition of clotrimazole (100 micrograms/mL) to the system in the absence of C albicans also resulted in an abnormal model by 24 hours. CONCLUSIONS: Candida albicans infection of the vaginal ecosystem, as represented by this in vitro model, has a deleterious effect on members of the normal microflora. Clotrimazole, although effective against C albicans infection, also has a deleterious effect on components of the normal vaginal microflora. One of the implications for women using clotrimazole for microbiologically undocumented vaginal yeast infections is an increased risk of infection or disease through the disruption of the protective microflora barrier.

Therapy for experimental intraabdominal sepsis: comparison of four cephalosporins with clindamycin plus gentamicin.

An experimental model of intraabdominal sepsis in rats was used for evaluation of treatment with four cephalosporins: cephalothin, cefazolin, cefoxitin, and cefamandole. Doses were 115 mg of each of the cephalosporins/kg and, in additional experiments, 350 mg of cephalothin or cefazolin/kg. Response to treatment was evaluated by mortality rate and the incidence of intraabdominal abscess. All four cephalosporins and gentamicin produced a similar reduction in mortality rates. There was a marked variation in incidence of abscess dependent upon the cephalosporin selected and the dosage tested. Regimens most effective in reducing abscesses were clindamycin, low-dose cefoxitin, or high-dose cephalothin.

Effects of time and growth media on short-chain fatty acid production by Bacteroides fragilis.

Gas-liquid chromatography was used to monitor the evolution of short chain fatty acids by Bacteroides fragilis in five media. Acetic and succinic acids, the prominent end products encountered, were readily detected within 24 h. Propionic, isobutyric, isovaleric, and lactic acids were usually recorded in more limited quantities. Maximum rates of bacterial multiplication, glucose catabolism, and end-production coincided with the first 24 h in carbohydrate-supplemented media. Extended incubation (672 h) favored substantial succinate increases in three of five media. These observations suggest that incubation time and composition of the medium are important determinants in short chain fatty acid production by B. fragilis.