Abstract
Klebsiella pneumoniae (Kp) is a gram-negative, facultative anaerobic bacterium belonging to the family Enterobacteriaceae. In both human and veterinary medicine, this bacterium is regarded as an emergent and common nosocomial pathogen.1-9 A novel, invasive and hypervirulent form of Kp associated with the hypermucoviscosity (HMV) phenotype has emerged over the last two decades.4,6,8,9 The HMV phenotype is mainly associated with K1, K2, and K5 capsular serotypes, and with several virulence genes including the rmpA, magA and wacG genes.3,8,9 While fatal multisystemic abscesses caused by HMV Kp have been reported in multiple marine mammal species found throughout the North-Pacific coast of the US3, very little is known about the pathogenesis and ecology of HMV Kp infection in these free-ranging hosts.1-3,8 Knowledge of virulence genes associated with pathogenic bacteria improves pathogen characterization and can provide researchers with specific genetic markers for use in molecular epidemiological studies.7,9 Kp isolates with the HMV phenotype, that were PCR positive for the rmpA and the K2 serotype associated gene wyz have been reported as the etiologic agent of suppurative pneumonia, pleuritis and abscesses in California sea lions (CSL) (Zalophus californianus).3 Since 1996 Kp has been isolated in over 200 diagnosed cases of klebsiellosis at the Marine Mammal Center, Sausalito, CA. CSL (n = 128) and Pacific harbor seals (PHS) (Phoca vitulina) (n = 54) accounted for ~ 90% of the cases. In > 90% of the cases, bacterial septicemia, meningitis, pneumonia, pleuritis, pyothorax or renal failure was suspected as the cause of death, highlighting the likely role Kp played as the etiologic agent of these conditions. Some of these isolates have been saved in the UC Davis Veterinary Teaching Hospital Microbiology collection3, however, they are un-characterized and heterogeneity is unknown. The main objective of this study was to characterize HMV Kp isolates recovered during 2015 in free-ranging and in stranded populations of CSL. The genotype, serotype and antimicrobial susceptibility of over 30 Kp isolates obtained from both clinically ill and apparently healthy hosts from 2000 to 2015 was investigated using molecular methods and the broth microdilution method. This line of work improves our understanding of potential Kp reservoirs, as well as the source and circulation of antimicrobial-resistant strains of Kp and their genetic determinants of resistance. The majority of HMV Kp isolates recovered from CSL was found to be positive for the rmpA and K2 associated gene (wyz); however, several of the recovered isolates were also found to be PCR positive for the rmpA and K1 serotype associated gene (magA), demonstrating that more than one type of HMV Kp is associated with marine mammals in CA.
* Presenting author
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