Bifidobacterium: An Emerging Clinically Significant Metronidazole-resistant Anaerobe of Mixed Pyogenic Infections

Bifidobacterium sp. are anaerobic, Gram-positive, short, irregular rods with rudimentary branching. These organisms are reported to be associated with health benefits and their significance as a pathogen is not much reported. We are reporting two cases of mixed pyogenic infections due to Bifidobacterium sp. In the first patient, the infection mimicked tubercular bone infection. The second patient was a case of hydronephrosis with double J (DJ) stent blockage. In both cases, Bifidobacterium sp. was isolated in combination with Escherichia coli from the evacuated pus samples. The factors which contributed significantly for detecting Bifidobacterium sp. were gram stain examination, use of rapid and automatic anaerobic cultivation system (Anoxomat, MART Microbiology B.V., The Netherlands), and quick identification by MALDI-TOF (Matrix-Assisted Laser Desorption-Time-of-Flight) Mass Spectrometry (Biomerieux, France). Both strains were found to be resistant to metronidazole and both patients showed a good clinical response to treatment with beta-lactam antibiotics. So, we highlight the importance of seeking Bifidobacterium species in all clinical pyogenic samples.