BACKGROUND: The dwindling antibiotic reserve owing to augmented drug-resistant bacteria is a major handicap for treating physicians. , a gram-negative encapsulated member of family, is one such pathogenic bacteria. Carbapenemase-producing globally recognized as one of the most critical bacterial threats to public health due to its extremely limited treatment options. Carbapenem-resistant (CRKP) infections pose therapeutic challenges due to simultaneous resistance to various other groups of antibiotics. In this study, we have evaluated the synergistic effect of fosfomycinagainst CRKP isolates when used in combination with colistin by applying the Checkerboard method.
METHODS: A laboratory-based prospective study was conducted in the Department of Microbiology, JSS Hospital, Mysuru, for a period of one year after obtaining ethical clearance. isolates obtained from clinical samples were screened for carbapenem resistance by the VITEK-2 compact system (bioM��rieux, Marcy-l'��toile, France). The minimum inhibitory concentration (MIC) of colistin and fosfomycin was individually ascertained by broth microdilution (BMD). Finally, the synergistic activity of the fosfomycin-colistin combination was determined by the BMD-based Checkerboard method.
RESULTS: Among the 50 CRKP isolates, 36 (72%) isolates showed synergism, eight (16%) isolates showed indifference and six (12%) isolates showed partial synergism, while none of them showed additivity and antagonism by the Checkerboard method. These results are found to be statistically significant (chi-square value of 116.204 and p-value of < 0.00001).
CONCLUSION: This study showed a promising in-vitro synergy between the drugs fosfomycin and colistin by Checkerboard BMD testing protocol. Colistin being a reserve antibiotic, monotherapy comes with the limitations of higher chances of resistance as well as toxicity, which can be overcome by combination therapy, thereby decreasing CRKP-associated mortality rates and delivering holistic patient benefit.
