Abstract
Klebsiella pneumoniae is a gram-negative facultative anaerobic bacterium belonging to the family Enterobacteriaceae. Typically found on mammalian mucosal surfaces and in the environment, K. pneumoniae has been associated with a wide range of infections in humans and animals.1,2 Emergent hypermucoviscous K. pneumoniae (HMV) has been associated with increased invasiveness and pathogenicity in marine mammals;3,4 however, very little is known about the ecology of HMV and the water conditions that allow for its survival and infectious capacities outside the animal host. In this study, HMV and non-HMV isolates recovered from stranded marine mammals were used to investigate and compare their culturability in sea and fresh water microcosoms at 15 and 25°C; and their capacity to form biofilms. Results indicate that HMV and non-HMV isolates present similar survivability in both sea- and freshwater microcosms incubated at 15 and 25°C and are able to persist in these environment for over 2 weeks. Additionally, although HMV isolates were significantly more mucoviscous, non-HMV isolates displayed significantly greater capacity to form biofilms (p<0.05). This phenomenon could be associated to the greater growth observed in non-HMV isolates indicated in in vitro growth-curve assays (p<0.05). The final study aim was to identify the biocide efficacy of four frequently used disinfectants in aquaculture and health care facilities.5,6 Similar susceptibility to disinfectants were detected in HMV and non-HMV isolates when exposed for 24 h; however, the minimal biofilm eradication concentration of chloramine T, ethanol, hydrogen peroxide, and chlorine to HMV isolates was significantly higher than those for non-HMV when exposed to disinfectants for 0.5 h (p=0.0388; p<0.001; p<0.001 and p<0.001, respectively). In this regard, we demonstrate that a dose of at least 2.5 mg/L Chloramine T, 891 mg/L available chlorine, 25% ethanol or 0.19% hydrogen peroxide for 24 h would be efficient for disinfecting facilities and equipment contaminated with K. pneumoniae. However, significantly greater concentrations of disinfectants are needed to kill the biofilm formed by K. pneumoniae, particularly those formed by HMV isolates. In this regard, concentrations of 5 mg/L, 3565 mg/L, 50% and >3% of Chloramine T, available chlorine, ethanol and hydrogen peroxide are necessary to kill biofilm formed by HMV isolates when exposed for 0.5 h. This information should be taken into consideration when developing biosecurity protocols in facilities holding marine mammals in captivity.
Acknowledgements
The authors would like acknowledge support of The Marine Mammal Center, Sausalito and the UC Davis Veterinary Teaching Hospital.
* Presenting author
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