QUINOLONE AND GLYCOPEPTIDE THERAPY FOR INFECTION IN MOUSE FOLLOWING EXPOSURE TO MIXED-FIELD NEUTRON-GAMMA-PHOTON RADIATION

The effects of increased doses of mixed-field neutron-gamma-photon irr adiation on bacterial translocation and subsequent sepsis, and the inf luence of antimicrobial therapy on these events, were studied in the C 3H/HeN mouse. Animals were given 4.25, 4.50, 4.75, 5.00 and 5.25 Gy of mixed-field [n/(n+gamma) = 0.7] radiation. The mortality rate of mice and recovery of bacteria were directly related to the radiation dose. Enterobacteriaceae were mostly isolated from the livers of mice expos ed to 5.00 and 5.25 Gy, and aerobic Gram-positive cocci were recovered from those exposed to 4.50 and 4.75 Gy. Oral therapy with L-ofloxacin reduced mortality of all groups of animals except those given 4.25 an d 4.50 Gy. This reduction was associated with a decrease in the number of the recovered Enterobacteriaceae. However, the number of Gram-posi tive cocci was unaffected. Addition of i.m. glycopeptide therapy faile d to prevent Gram-positive coccal infection, due to the development of glycopeptide-resistant Enterococcus faecalis. These data demonstrate a relationship between the doses of mixed-field radiation and the rate s of infection due to Enterobacteriaceae. While L-ofloxacin therapy re duces the infection rate, prolongs survival and prevents mortality, th e addition of a glycopeptide can enhance systemic infection by resista nt bacteria in the irradiated host.