Growth and gaseous emissions of pure and mixed small intestinal bacterial cultures: Effects of bile and vancomycin

Abstract

Simultaneous cultivations in anaerobiosis, aerobiosis and with microaerobic gas mixture were used to clarify the bile (oxgall) effects on the pure and mixed cultures of enterobacterial strains in simulations in Portable Microbe Enrichment Unit (PMEU) linked with ChemPro100i ® gas detector. The effects of vancomycin were evaluated in aerobic cultures. Growth and metabolic activity of cultures were also followed by measuring sugar consumption, pH alterations, and colony counts on BD CHROMagar™ Orientation plates. Results showed that the two fermentatively different strains of facultative anaerobes, Escherichia coli E 17 and Klebsiella mobilis ATCC 13048 grew in balance regardless of oxygen level, bile acid concentration or other components of the mixed cultures, Bacillus cereus or Staphylococcus aureus. When the evaporations of the mixed cultures of E. coli, K. mobilis and S. aureus were compared with the emissions of the corresponding pure cultures by ChemPro100i ® gas sensing detector, the pure cultures of bile resistant E. coli and K. mobilis produced more gaseous components than the mixed culture indicating that these organisms cooperate and use the substrate more effectively together than separately. A survey of the aseptic bacterial isolations from the bile tract in a big University Hospital, (Salzburg, Austria) during 3 years, showed that these bacterial groups dominated. Only 13.24% of the 287 patient samples were sterile, and around 180 strains of both E. coli and Klebsiella/ Enterobacter groups were found amongst 973 isolates from 249 patients (together 35.57%). Enterococcus sp. accounted for 246 isolates being the largest group of strains (24.25% of all the isolates). In anaerobiosis it was shown that Klebsiella neutralized the acids produced in the mixed acid fermentation of the E. coli. The ethanol produced from both groups evaporated in the gas stream of the PMEU culturing step and its formation also removes excess acidity from the cultures. The synergistic behaviour and symbiotic function between E. coli and Klebsiella/ Enterobacter strains is suggested.