Answer by Tirumalai Kamala:

I think “ bacterial immunities” is a mistake in the question. I assume the OP meant bacterial communities, i.e. how does cirpofloxacin (cipro) influence microbiota composition.

In a 2008 study of 3 healthy volunteers, Dethlefsen et al did 16S rRNA sequencing of stool samples to assess microbiota composition before and after 5 days of cipro monotherapy (Page on plosbiology.org). One-third of gut microbiota were affected by this treatment though the volunteers did not report feeling any obvious symptoms.  Most microbiota community members returned to pre-treatment levels within 4 weeks of stopping cipro though some compositional changes took 6 months to fully recover. The authors inferred that these individuals demonstrated microbiota community resilience. Another study also reported similar effects (Development of antimicrobial resistance in the normal anaerobic mic…). What happens with repeat cipro? In a follow-up study published in 2011 (Incomplete recovery and individualized responses of the human distal gut microbiota to repeated antibiotic perturbation), Dethlefsen et al found that a 2nd cipro treatment 6 months after the first one caused similar acute effects but that the biggest difference was in the recovery, as in incomplete recovery. In other words, the gut microbial composition reverted back to being stable once the 2nd antibiotic course was over but it didn’t revert back to the base line composition that had existed originally before any cipro.

From Page on bu.edu

Thus, cipro in specific or antibiotic in general alter several aspects of gut microbiota composition: reduce bacterial diversity, select for bacterial resistance and encourage gut colonization by pathogens, e.g. Clostridium difficile.

Now, did the OP really mean immunities and not communities as in how would elimination of microbes by cipro affect immunity to bacteria in general? Not directly but possible indirectly. How? Same way. By clearing out normal gut microbes, by promoting antibiotic resistance and by creating niche openings that encourage colonization by pathogens such as Clostridium difficile, cipro could influence anti-bacterial immunity indirectly.

Does taking CIPRO eliminate bacterial immunities that might have been acquired over years of traveling?