Resistance of Commensal Intestinal Escherichia Coli and Other Enterics to Co-trimoxazole and Commonly Used Antibiotics in HIV/AIDS Patients

Trimethoprim-sulfamethoxazole (CTX) has been recommended by the World Health Organization as a prophylactic drug for HIV/AIDS-patients against opportunistic infections. However, daily use of CTX may reduce its efficacy to enteric Escherichia coli, thus increasing the burden of CTX-resistant pathogens. Resistance of enteric pathogens to CTX may affect empiric treatment approaches especially in HIV/AIDS patients. We prospectively investigated incidences of fecal E. coli resistance to CTX in 188 HIV-infected patients of 15-72 years of age, and determined changes in susceptibility patterns. The study was conducted in Dar es Salaam, Tanzania involving collection of stool specimens from HIV-patients prior and after initiation of CTX prophylaxis. Specimens were collected on 1st, 4th, and 24th weeks upon commencing CTX prophylaxis. Susceptibility profiling of E. coli and other enteric bacteria to CTX and other widely used antibiotics were done using Kirby-Bauer disk diffusion method. On the first visit, 143(76.1%) enteric bacteria were isolated. Of those, 123(86%) were E. coli. About 98.6% were resistant to CTX. On the second visit, 103(54.2%) bacteria were isolated; of those, 100(98.4%) of them exhibited resistance to CTX. On the third visit, 64(34%) out of 188 patients had significant enteric bacteria, and of those 63 (98.4%) were resistant to CTX. About 53.2% of bacterial isolates were resistant to ciprofloxacin and ampicillin. Majority (95.2%) of the patients had initiated CTX prophylaxis prior to testing at the care and treatment clinics. About 32% of the patients reported to have skipped some doses of CTX prophylaxis. Non-adherence to CTX prophylaxis and self-medication among patients may have attributed to the observed high prevalence rate of E. coli resistance to CTX and other commonly used antibiotics. For better understanding of the observed pattern of bacterial resistance to CTX, phenotypic and/or genotypic characterization of the isolated bacteria needs to be conducted.