[In vivo and in vitro antibiotic sensitivity changes]

Spontaneous changes in staphylococcal sensitivity to 7 antibiotics were studied during a year. 9 hospital strains of Staph. aureus were used. The strains were subculture-in vitro. One of the cultures was subcultured in vivo in 17 dogs with experimental chronic osteomyelitis. It was found that sensitivity of the same culture increased in vivo to 4 antibiotics and in vitro to 1 antibiotic. The increased sensitivity to all 7 antibiotics in vitro was recorded with respect to 4 strains, to 6 antibiotics with respect to 1 culture and to 3 and 4 antibiotics with respect to 2 strains. 4 strains manifested a decrease in sensitivity to 1--6 antibiotics. The causes of the changes found require further investigation.