Impact of growth conditions on resistance of Klebsiella pneumoniae to chloramines

Abstract

The resistance of Klebsiella pneumoniae to inorganic monochloramine (1.5 mg/liter; 3:1 C12:N ratio, pH 8.0) was examined in relation to growth phase, temperature of growth, and growth under decreased nutrient conditions. Growth phase did not impact resistance to chloramines. Mid-exponential and stationary-phase cells, grown in a yeast extract-based medium, had CT99 values and standard deviations of 4.8 + 0.1 and 4.6-+-0.2 mg. min/liter, respectively. Growth temperature did not alter chloramine resistance at short contact times. CT99 values of cells grown at 15 and 23°C were 4.5 + 0.2 and 4.6 + 0.2 mg. min/liter, respectively. However, at longer contact times, CT99.99 values of cells grown at 15 and 23°C were 14 and 8 mg. min/liter, respectively, suggesting a small resistant subpopulation for cells grown at the lower temperature. Growth under decreased nutrient conditions resulted in a concomitant increase in resistance to chloramines. When K. pneumoniae was grown in undiluted Ristroph medium and Ristroph medium diluted by 1:100 and 1:1,000, the CT99 values were 4.6 0.2, 9.6 0.4, and 24 + 7.0 mg-min/liter, respectively. These results indicate that nutrient availability has a greater impact than growth phase or growth temperature in promoting the resistance of K. pneumoniae to inorganic monochloramine.

Transposon mutagenesis identifies genes which control antimicrobial drug tolerance in stationary-phaseEscherichia coli

“…During the process of the adaptation to stationary phase, E. coli becomes resistant to stress conditions, such as starvation, heat, low pH, high osmolarity and oxidative radicals [7][8][9]. In addition to stress adaptation, stationary-phase bacteria become tolerant to antibiotic treatment [5,26,2,3,27,4]. We set out to investigate which molecular mechanisms underpin kanamycin tolerance in E. coli.…”

“…Firstly, bacteria quickly become tolerant [2][3][4] to the agents. This is temporary, reversible, is associated with slowing of the rate of multiplication [5,2,6,4] and enables bacteria to survive a broad range of agents and other stress conditions such as starvation [7][8][9]. Secondly, bacteria can undergo genetic mutation which leads to permanent clonal resistance to antimicrobial agents.…”

Survival of allochthonous bacteria in still mineral water bottled in polyvinyl chloride (PVC) and glass

“…pneumoniae and Ent. cloacae are commonly found in tap water (Gavini et al 1985) and are capable of growth in drinking water systems (Camper et al 1991;Stewart and Olson 1992). The presence of the latter organisms in mineral water may not signify faecal contamination but clearly indicates that the aquifer and/or the bottling system are contaminated with non-mineral water sources.…”

A review of biofilms in domestic plumbing

“…Stewart and Olson (1992) showed that nutrient limitation influenced the ability of Klebsiella pneumoniae to resist inorganic monochloramine. When K. pneumoniae was grown in Ristroph medium diluted by 1:1, 1:100, and 1:1,000, the concentrations of disinfectant required to inactivate 99% of the cells were found to be 4.6 ± 0.2, 9.6 ± 0.4, and 24 ± 7.0 mg/L, respectively.…”