Abstract
Klebsiella pneumoniae is a gram-negative, aerobic, and non-motile bacillus frequently observed as a common commensal in captive marine mammals. However, a hypermucoviscous (HMV) phenotype has been reported in California sea lions (CSL) with pleuritis and bronchopneumonia and has been considered a minor yet persistent cause of strandings.1 Here, we describe an increase in the number of confirmed cases of K. pneumoniae in CSL along the California coast from 2017 to 2022 and applied whole-genome sequencing (WGS) to eight isolates obtained from stranded CSL in 2022. Since 2017, 2,146 CSL strandings have been observed by The Marine Mammal Center in Sausalito, California, of which 99% were alive. From 2017 to 2022, 47 CSL tested positive for K. pneumoniae, with a steep rise in annual incidence from 0.92% (3/331) in 2017 to 8.5% (14/165) and 7.2% (23/320) in 2021 and 2022, respectively. These strandings occurred across a broad geographic range from Bodega Bay, Sonoma, to Avila Beach, San Luis Obispo, along the central California coast. At the center of this range, a similar pattern was observed in dead stranded CSL identified by the Long Marine Lab Stranding Network in Santa Cruz, California. While K. pneumoniae was virtually absent in CSLs in this range before 2021, 8 CSLs tested positive for K. pneumoniae with an annual incidence rate of 1.9% (1/54) and 11.3% (7/62) in 2021 and 2022, respectively. The WGS analysis revealed a high nucleotide similarity (>99.9% average nucleotide identity) between any pair of the isolates. The multilocus sequence typing showed that all eight isolates belonged to sequence type 65, a well-documented sequence type of hypervirulent K. pneumoniae. Furthermore, the isolates contained the K2 polysaccharide capsule and siderophore aerobactin, also characteristic of hypervirulent K. pneumoniae. We will discuss several possible causes of the rise in cases and the need for future research focused on the ecology of K. pneumoniae in CSL in Central California.
*Presenting author
+Student presenter
Literature Cited
1. Jang S, Wheeler L, Carey RB, Jensen B, Crandall CM, Schrader KN, Jessup D, Colegrove K, Gulland FM. Pleuritis and suppurative pneumonia associated with a hypermucoviscosity phenotype of Klebsiella pneumoniae in California sea lions (Zalophus californianus). Vet Microbiol. 2010;141(1–2):174–177.
2. Chang EK, Miller M, Shahin K, Batac F, Field CL, Duignan P, Struve C, Byrne BA, Murray MJ, Greenwald K, Smith WA, Ziccardi M, Soto E. Genetics and pathology associated with Klebsiella pneumoniae and Klebsiella spp. isolates from North American Pacific coastal marine mammals. Vet Microbiol. 2021;265:109307.