Abstract
Salmonella and Campylobacter spp. are zoonotic, pathogenic bacteria that can cause gastrointestinal disease. Salmonella has previously been reported in multiple marine mammal species, although not in northern elephant seals (Mirounga angustirostris). Campylobacter has not previously been reported in marine mammals. The Centers for Disease Control is finding increasing antibiotic resistance in both of these bacterial species.1 Increasing antibiotic resistance in both of these bacterial genera is a concern for human and veterinary medicine because it causes an increase in mortality, morbidity, and cost-of-treatment. There are also increasing reports of antibiotic resistance in marine wildlife.2-3 The source of the resistance in marine wildlife is not known; however, they may be exposed to bacteria and/or antibiotics when near high-population coastal areas, which may be contaminating the marine environment. Once these marine animals are exposed, they can continue to shed antibiotic resistant bacteria in the environment. The prevalence and antibiotic sensitivity of Salmonella and Campylobacter have not been previously established in northern elephant seals.
In this study, Campylobacter and Salmonella species were isolated from juvenile wild northern elephant seals at two different colonies in California (Point Reyes and Año Nuevo) and from seals presenting for rehabilitation at The Marine Mammal Center (TMMC) in the months of February through June in 2003. Rectal swabs were performed on the seals, selective culture techniques were used, and isolates were then identified as Campylobacter and Salmonella through standard identification techniques. Antibiotic sensitivities were obtained by either broth microdilution or agar dilution methods.
In the Point Reyes colony, Campylobacter was detected in only one animal (n=32) with no evidence of Salmonella infections. In the Año Nuevo colony, Salmonella prevalence was 8.8% and Campylobacter prevalence was 32.4% (n=34). The difference in Campylobacter prevalence between the two colonies was found to be statistically significant. In elephant seals stranded and admitted to rehabilitation, the prevalence of Salmonella spp. was 37.3% (n=102), Campylobacter jejuni was 33.7% (n=101), Campylobacter lari was 6.9% (n=101), and a novel Campylobacter sp. was 11.9% (n=101). Salmonella serotypes were Typhimurium, Newport, Saint-Paul, Montevideo, or Reading. Seals which were stranded and being admitted to TMMC showed a higher prevalence of both Salmonella and Campylobacter when compared to wild seals, which was statistically significant. Salmonella and Campylobacter jejuni isolates were sensitive to all antibiotics tested for, with a few exceptions in stranded seals. This study demonstrates that Campylobacter and Salmonella are common in seals that are in relatively close association with humans, and that prevalence of antibiotic resistance exists but is low in these seals.
Literature Cited
1. Centers for Disease Control. 2002. NARMS 2001 Annual Report. www.cdc.gov/narms/annual/2001/01sum.htm. (VIN editor: link was not accessible as of February 2, 2021.)
2. Wong S. Ocean Sentinels: Marine Mammals and Antimicrobial Resistance. www.asmusa.org/pcsrc/42icaac/2640.htm. (VIN editor: link was not accessible as of February 2, 2021.) 2002.
3. O’Rourke, K. Antimicrobial resistance in wildlife: it’s making a bigger splash than you think. JAVMA. 223(6):756–757.