Changes in bacterial profile during amebiasis: demonstration of anaerobic bacteria in ALA pus samples.

Little is known about the changes in gut resident flora during amebic colitis and amebic liver abscess (ALA) caused by Entamoeba histolytica infection. Fecal samples from ALA patients, from healthy E. histolytica negative and positive (asymptomatic) individuals, and from pre- and post-metronidazole-treated healthy volunteers and pus samples from ALA patients were tested for the presence of various bacterial genera using 16S rRNA-based primers. Statistically significant reduction in Lactobacillus due to E. histolytica infection was observed in asymptomatic individuals and ALA patients. On the other hand, reduction in Bacteroides, Bifidobacterium, and Clostridium in the same samples was due to metronidazole treatment. Two anaerobic genera, viz. Bacteroides and Peptostreptococcus, were detected in ALA pus samples, and this observation is unprecedented. In addition, PCR revealed metronidazole resistance genes in fecal and pus samples of metronidazole-treated individuals. Re-examination of the ameba-bacterium relationship in amebiasis is suggested.