Nalidixic Acid Resistant Salmonella with Decreased Ciprofloxacin Susceptibility

Abstract

A total of 534 patients suspected of enteric fever were studied in Kathmandu ModelHospital from May 2006 to August 2006. Among them 19.28percentpatientswereculture positive. Theprevalence of culture positive was highest among the age groupof 0-10 years (31.42%) and the result was statistically significant (p > 0.05). Among103 culture positive cases, the incidence rate was more in female (23.15) than male(17.15%) and it was statistically insignificant (p<0.05). The culture positive rate wasfound maximum from out patients (19.76%) than inpatients (12.12%). Among 103 isolates, 67(65.04%) were Salmonella typhi and 36(34.95%) wereSalmonella paratyphi A. The most sensitive drugs for Salmonella typhi were found to be Amoxycillin,Ceftriaxone, Chloramphenicol and CotrimoxazoleandleastsensitivebeingOfloxacin.The same pattern ofsusceptibility was shown bySalmonella paratyphi A. Among 73 Nalidixic acid resistant isolates 45(61.64%) wereSalmonella typhiand28(38.35%) were Salmonella paratyphi A. In contrast, among 30 Nalidixic andsusceptible isolates 22(73.33%) were Salmonella typhi and 8(26.66%) wereSalmonella paratyphi A. In thisstudy, none of the nalidixic acid resistance isolates were found Ciprofloxacinresistance, but all Nalidixic acid susceptible isolates were also susceptible toCiprofloxacin. Among 72 bacterial isolates with increased susceptibility to Ciprofloxacin (0.125g/ml), 67 isolates showed Nalidixic acid resistance in disc diffusion method. Andamong 31 isolates with MIC value < 0.125g/ml (Ciprofloxacin) 25 isolates were Nalidixic acid susceptible in disc diffusion method.The sensitivity and specificity of Nalidixic acid resistance test by disc diffusion method to screen for isolates having MICs of Ciprofloxacin0.125g/ml were91.98% and 83.33% respectively.