title: Physiological studies of chloramine resistance developed by Klebsiella pneumoniae under low-nutrient growth conditions.
abstract: This study investigated the physiological mechanisms of resistance to chloramines developed by Klebsiella pneumoniae grown in a nutrient-limited environment. Growth under these conditions resulted in cells that were smaller than cells grown under high-nutrient conditions and extensively aggregated. Cellular aggregates ranged from 10 to more than 10,000 cells per aggregate, with a mean population aggregate size of 90 cells. This aggregation may have been facilitated by the presence of extracellular polymer material. By using glucose as a reference of capsule content, it was determined that growth under low-nutrient conditions produced cells with 8 x 10(-14) to 41 x 10(-14) g of carbohydrate per cell, with a mean +/- standard deviation of 27 x 10(-14) +/- 16 x 10(-14) g of carbohydrate per cell. In comparison, growth under high-nutrient conditions resulted in 2.7 x 10(-14) to 5.9 x 10(-14) g of carbohydrate per cell, with a mean and standard deviation of 4.3 x 10(-14) +/- 1.2 x 10(-14) g of carbohydrate per cell. Cell wall and cell membrane lipids also varied with growth conditions. The ratio of saturated to unsaturated fatty acids in cells grown under low-nutrient conditions was approximately five times greater than that in cells grown under high-nutrient conditions, suggesting possible differences in membrane permeability. An analysis of sulfhydryl (-SH) groups revealed no quantitative difference with respect to growth conditions. However, upon exposure to chloramines, only 33% of the -SH groups of cells grown under low-nutrient conditions were oxidized, compared with 80% oxidization of -SH groups in cells grown under high-nutrient conditions. The reduced effectiveness of chloramine oxidization of -SH groups in cells grown under low-nutrient conditions may be due to restricted penetration of chloramines into the cells, conformational changes of enzymes, or a combination of both factors. The results of this study suggest that chloramine resistance developed under low-nutrient growth conditions may be a function of multiple physiological factors, including cellular aggregation and protection of sulfhydryl groups within the cell.
authors.affiliation: Metropolitan Water District of Southern California, La Verne 91750.
authors.forename: M H
authors.initials: MH
authors.lastname: Stewart
authors.forename: B H
authors.initials: BH
authors.lastname: Olson
mesh_terms: D001422:Bacterial Adhesion / Q000187:drug effects; D002700:Chloramines / Q000494:pharmacology*; D003470:Culture Media / Q000494:pharmacology; D004352:Drug Resistance, Microbial; D007711:Klebsiella pneumoniae / Q000187:drug effects* / Q000254:growth & development* / Q000502:physiology; D008055:Lipids / Q000032:analysis; D011108:Polymers / Q000032:analysis; D013438:Sulfhydryl Compounds / Q000032:analysis
chemical_list: D002700:Chloramines; D003470:Culture Media; D008055:Lipids; D011108:Polymers; D013438:Sulfhydryl Compounds; C030816:chloramine