Growth and survival of Klebsiella pneumoniae in the presence of pyrithione.

Pyrithione (2-mercaptopyridine-N-oxide; Omadine) showed broad-spectrum antimicrobial activity with Gram-positive bacteria and yeasts being more sensitive than Gram-negative bacteria. This study examines the growth and survival profIles of Klebsiella pneumoniae in the presence of pyrithione . Studies of growth and survival of Bacillus licheniformis and Candida albicans are included for comparative purposes. In the presence of the drug , Kt. pneumoniae and B. licheniformis exhibited similar growth patterns, namely a drug concentration-dependent Jag phase followed by growth at a rate similar to that of untreated cells. In contrast, C. albicans exhibited a drug concentration-dependent rate of growth . Viable counts of Kl. pneumoniae and C. albicans in the presence of pyrithione , mirrored the growth patterns observed by turbidity measurements . Size analysis of ampicillin-treated ( divisioniess ) cells of Kl. pneumoniae in the presence and absence of pyrithione , suggested that all cells are inhibited from growth during the lag phase, and re-growth is due to recovery of all cells rather than the growth of a resistant population within the culture . Bacteria grown in the presence of sub-inhibitory concentrations of pyrithione were insensitive to further challenge with the same concentrations of the drug . The resistance of Kl. pneumoniae was maintained during 7 days of subculture in drug-free medium , but fell to a lower level after 4 days of subculture , and cross-resistance to chloramphenicol was observed, but not to 8-hydroxyquinoline . The fatty acid profIle of pyrithione-sensitive and pyrithione-resistant Kt. pneumoniae are essentially similar . Cells of B. licheniformis grown in the presence of pyrithione showed no crossresistance with any of the antimicrobial agents tested . Pyrithione also inhibited the incorporation of 14C-glycine , 14C-thyrnidine and 14C-urldine in both Kl. pneumoniae and B. licheniformis . Further investigation showed that in Kl. pneumoniae ,only the 14C-uridine uptake profIle resembled the