Abstract
Klebsiella pneumoniae, a Gram negative, facultative anaerobe belonging to the family Enterobacteriaceae is considered an emergent pathogen in both human and veterinary medicine.1-3 A novel, invasive strain associated with hypermucoviscosity (HMV) has been recognized in the past 2 decades,4 and has been reported in multiple marine mammal species5,6. However, little is known about its epidemiology and pathogenesis in marine mammals.7,5 In this study, we swabbed mucosal sites and affected tissues and attempted isolation of HMV K. pneumoniae from 270 wild-caught California sea lions (CSL, Zalophus californianus) from 3 sampling sites from coastal North America, as well as 336 stranded marine mammals including CSL, pacific harbor seals (PHS, Phoca vitulina), northern fur seals (NFS, Callorhinus ursinus), and northern elephant seals (ES, Mirounga angustirostris). The only isolates recovered were from CSL and we detected a prevalence of 1.5% in stranded CSL and 1.1% in wild caught CSL. To establish baseline data and develop adequate diagnostic methods, we assessed the phenotype and genotype of all HMV K. pneumoniae isolates recovered from our sampled animals (n=11), as well as archival isolates from stranded marine mammals (n=19) including HMV and non-HMV isolates. All but 2 of the HMV isolates were capsular type K2 serotype and were positive for the wyz gene, while all non-HMV isolates were negative for this serotype and gene. Of the analyzed HMV isolates 24/25 were positive for HMV associated gene p-rmpA and 23/25 were positive for p-rmpA2. One non-HMV isolate tested positive for these genes. All Klebsiella spp. isolates recovered from aquatic animals were identified by rpoB and gyrB sequence as K. pneumoniae, and genetic fingerprinting by repetitive extragenic palindromic PCR showed four discrete clusters demonstrating genotypic variability that loosely correlated with phenotype. Antimicrobial susceptibility testing revealed all our stranded CSL isolates were susceptible to ceftiofur, indicating this antimicrobial is an adequate first choice for treatment of suspected HMV K. pneumoniae infections in stranded CSL. To assess the limit of detection of our culture assay, we used swab inoculums from 10 mg/ml suspended fecal solutions and could reliably detect HMV K. pneumoniae from concentrations as low as 102 CFU/mg of feces. This study shows HMV K. pneumoniae infections occur in wild-caught and stranded CSL. Further studies are needed to assess the epidemiologic dynamics of this pathogen in marine mammals and to understand its potential impact on marine mammal populations.
Acknowledgements
The authors wish to thank the members of the UC Davis Aquatic Animal Health Laboratory, the UC Davis School of Veterinary Medicine Department of Medicine and Epidemiology, the Marine Mammal Center, and funding from the National Science Foundation (OCE-1335657). The authors also thank Drs. Irina Udaltsova, Ashley Hill, and Janet Foley of the UC Davis School of Veterinary Medicine, and classmates Drs. Maris Brenn-White, Ketki Raje, and Yehonatan Berkowic for their support.
* Presenting author
+ Student presenter
Literature Cited
1. Podschun R, Ullmann U. 1998. Klebsiella spp. as nosocomial pathogens: epidemiology, taxonomy, typing methods, and pathogenicity factors. Clin Microbiol Rev. 11(4):589–603.
2. Kikuchi N, Iguchi I, Hiramune T. 1987. Capsule types of Klebsiella pneumoniae isolated from the genital tract of mares with metritis, extra-genital sites of healthy mares and the genital tract of stallions. Vet Microbiol. 15(3):219–228.
3. Ling GV, Norris CR, Franti CE, et al. 2001. Interrelations of organism prevalence, specimen collection method, and host age, sex, and breed among 8,354 canine urinary tract infections (1969–1995). J Vet Intern Med. 15(4):341–347.
4. Kawai T. 2006. Hypermucoviscosity: an extremely sticky phenotype of Klebsiella pneumoniae associated with emerging destructive tissue abscess syndrome. Clin Infect Dis. 42(10):1359–1361.
5. Castinel A, Grinberg A, Pattison R, et al. 2007. Characterization of Klebsiella pneumoniae isolates from New Zealand sea lion (Phocarctos hookeri) pups during and after the epidemics on Enderby Island, Auckland Islands. Vet Microbiol. 122(1–2):178–184.
6. Jang S, Wheeler L, Carey RB, et al. 2010. Pleuritis and suppurative pneumonia associated with a hypermucoviscosity phenotype of Klebsiella pneumoniae in California sea lions (Zalophus californianus). Vet Microbiol. 141(1–2):174–177.
7. Roe WD, Rogers L, Pinpimai K, Dittmer K, Marshall J, Chilvers BL. 2015. Septicaemia and meningitis caused by infection of New Zealand sea lion pups with a hypermucoviscous strain of Klebsiella pneumoniae. Vet Microbiol. 176(3–4):301–308.