Characterization of nalidixic acid and ciprofloxacin resistance mechanisms in isolates from Bangladesh.The 38 isolates from Bangladesh were categorized into the following 5 ciprofloxacin susceptibility groups: a susceptible group, with MICs of ≤0.03 μg/ml; a group with reduced susceptibility, with MICs of 0.12 to 0.5 μg/ml; and resistant groups, with MICs of 4 μg/ml, 8 μg/ml, and 16 μg/ml (Table 3). The isolates with reduced susceptibility to ciprofloxacin were resistant to nalidixic acid (MICs of 128 to 256 μg/ml), and the trait of resistance was associated with a mutation in gyrase subunit A (S83F, S83Y, or D87N) and enhanced activity of the efflux pump for nalidixic acid. The isolates with a ciprofloxacin MIC of 4 μg/ml were highly resistant to nalidixic acid (MICs of ≥256 μg/ml), and the resistance was associated with a mutation (S83Y) in gyrase A, the presence of qnrS, and enhanced activity of the efflux pumps for ciprofloxacin and nalidixic acid. The isolates with ciprofloxacin MICs of 8 and 16 μg/ml also displayed high nalidixic acid resistance (MICs of >256 μg/ml), carried two mutations (S83F and D87G) in gyrase A and one mutation (E92K) in topoisomerase IV, and showed enhanced efflux pump activity for nalidixic acid. The isolates with a ciprofloxacin MIC of 16 μg/ml also showed enhanced efflux pump activity for ciprofloxacin.

It accomplishes this by inhibiting protein synthesis and causes calcium ions to rush in [13]. After the virulence factors have done their duty, the bacteria can move to the liver or spleen, where they are able to replicate. After replication, they can migrate back to the intestines where they can be expelled and transmitted to new hosts.