AZT--does it prevent occurrence of salmonelloses in AIDS patients?

In vitro activity of zidovudine alone and in combination with ciprofloxacin against Salmonella and Escherichia coli

The in vitro antibacterial activity of zidovudine alone and in combination with ciprofloxacin was investigated. Zidovudine showed a good activity against Escherichia coli and Salmonella (MIC range 0.5-8 micrograms/ml and 1.5-62 micrograms/ml respectively) isolated from biological samples of HIV-infected patients. These strains proved to be extremely susceptible to ciprofloxacin alone. The interaction between zidovudine and ciprofloxacin ranged from additive activity to indifference. No antagonism was observed: the FIC index for every combination resulted < or = 1.5. The addition of AZT 1 mg/l (clinically achievable plasma concentration after therapeutic doses of 1200 mg/day) did not affect the bactericidal activity of ciprofloxacin; on the contrary, in some cases we observed an increase of bactericidal effect of the quinolone. These data have to be considered in patients with AIDS who can be treated concomitantly with zidovudine and ciprofloxacin.

In vitro activities of nucleoside analog antiviral agents against salmonellae

Zidovudine (ZDV) has antibacterial activity against many members of the family Enterobacteriaceae, including Salmonella species, and may be responsible for a decrease in the frequency of salmonellosis in persons infected with human immunodeficiency virus (HIV). Other nucleoside analogs, such as didanosine (2',3'-dideoxyinosine [ddI]) and zalcitabine (2',3'-dideoxycytidine [ddC]), which have undefined anti-salmonella activity, increasingly are being used in the treatment of HIV infection. To evaluate the anti-Salmonella activity of the antiviral agents ZDV, ddI, ddC, and acyclovir (ACV), we determined MICs for 39 nontyphoidal Salmonella blood isolates. ZDV (MIC for 50% of strains tested [MIC50], 0.5 microgram/ml; MIC range, 0.125 to 4 micrograms/ml) and ddI (MIC50, 8 micrograms/ml; MIC range, 2 to 125 micrograms/ml) had concentration-dependent activity. Anti-Salmonella activity was not observed for ddC or ACV. Nine Escherichia coli blood isolates were inhibited by ZDV (MIC50, 0.125 microgram/ml; MIC range, 0.031 to 1 microgram/ml) to a greater degree than they were by ddI (MIC50, 62.5 micrograms/ml; MIC range, 31 to > 62.5 micrograms/ml). Inoculum size affected susceptibility to ZDV and ddI for Salmonella and E. coli isolates. Resistance to ZDV or to ddI could be induced in vitro in Salmonella isolates, but cross-resistance was not observed. These results indicate that at concentrations achieved during the treatment of HIV infection, ZDV has activity against nontyphoidal salmonellae, although resistance can develop. ddI, ddC, and ACV at currently used dosages would not be expected to be effective in the prevention or treatment of Salmonella infections.