Isolation of ciprofloxacin resistant Elizabethkingia anopheles

Abstract

Elizabethkingia anophelis is an extensively antibiotic resistant emerging pathogen that causes mortality in the most vulnerable populations. Because of it's high antibiotic resistance, there are very effective treatments for infections. The fluouroquinolone ciprofloxacin is an example of such treatment, which makes finding the cause of fluoroquinolone resistance in these organism of the upmost importance. Previous work in Gram-negative organisms, including E. anophelis, has shown that mutations in gyrA confers ciprofloxacin resistance. I hypothesized that laboratory-selected ciprofloxacin resistance in E. anophelis will result from mutation(s) in gyrA as well. To test this hypothesis, I isolated and sequenced five ciprofloxacin-resistant mutants of E, anophelis. All five strains exhibited increased ciprofloxacin minimal inhibitory concentrations (MICs) (8-16 mg/L) when compared to the parent strain (0.25 mg/L). After a population analysis, I found that each of the mutant strains had subpopulations the survived well beyond the normal MIC. Through DNA sequencing, I found eight unique and three shared mutations in gyrA, and no mutations in gyrB, parC, or parE. This demonstrated that even after a single exposure to ciprofloxacin, E. anophelis gyrA mutants emerged that were resistant to this drug.