Prevalence and characterization of Salmonella spp. among marine animals in the Channel Islands, California

Abstract

Salmonella enterica is a zoonotic pathogen that has been isolated from free-ranging marine mammals throughout the world, with animals in the Channel Islands of California (USA) showing the highest prevalence. The goal of this study was to determine prevalence, antimicrobial sensitivity and genetic similarity using pulsed-field gel electrophoresis (PFGE) of Salmonella in several non-domestic animal species on San Miguel and San Nicolas Islands. Fecal samples were collected from 90 California sea lion Zalophus californianus pups, 30 northern elephant seal Mirounga angustirostris pups and 87 western gulls Larus occidentalis in the Channel Islands and 59 adult male sea lions in Puget Sound, WA (USA). Salmonella were isolated, identified and serotyped, followed by antimicrobial susceptibility testing and PFGE. Of the California sea lion pups that were sampled on the islands, 21% (n = 19) were positive for Salmonella, whereas no adults males in Puget Sound were positive. Of the northern elephant seal pups sampled, 87% (n = 26) were harboring Salmonella. Only 9% (n = 8) of western gulls were shedding Salmonella, with one of these gulls harboring the only antimicrobial resistant isolate. The serotypes found in these animals were Enteritidis, Montevideo, Newport, Reading, and Saint Paul. The only serotype that showed variation on PFGE was Newport. The pinnipeds of the Channel Islands harbor Salmonella at a higher prevalence than pinnipeds from other geographic areas observed in previous studies. Researchers and veterinarians should exercise increased caution when working with these animals due to the zoonotic potential of Salmonella.

Occurrence and Persistence of Bacterial Pathogens and Indicator Organisms in Beach Sand along the California Coast

“…The correlation observed between Salmonella and cEC in beach sands may suggest that these microorganisms originated from similar sources (26,53). Moreover, the lack of association between the HF marker, Salmonella, and Campylobacter in sand was suggestive of nonhuman sources of these pathogens in beach sand, such as marine birds and mammals (44,64). The microcosm studies demonstrated that the HF marker was long lived in beach sand ( Fig.…”

M. J. Moore, R. J. Gast, A. L. Bogomolni

“…Antibiotic resistance in the isolates was very rare, in dramatic contrast to the situation reported in another paper in this issue for isolates of diverse other bacteria from free-ranging marine mammals on the US NE coast (Bogomolni et al 2008). Stoddard et al (2008) caution people handling such animals to be aware of the zoonotic risk, especially in California, where the prevalence seems unusually high, and they discuss the potential sources of these Salmonella infections in terms of island land-mammal populations.…”

“…The Stoddard et al (2008) study documents a high prevalence of a variety of Salmonella serovars with zoonotic potential in sea lions and elephant seals in the Channel Islands, California, USA, but a much lower prevalence of serovars in Puget Sound, Washington, USA. Antibiotic resistance in the isolates was very rare, in dramatic contrast to the situation reported in another paper in this issue for isolates of diverse other bacteria from free-ranging marine mammals on the US NE coast (Bogomolni et al 2008).…”

Isolation and Antimicrobial Susceptibility of Salmonella Typhimurium and Salmonella Enteritidis in Fecal Samples from Animals

“…It is also important to mention that many of the serovars isolated from seagulls showed an intermediate sensitivity according to the Kirby-Bauer qualitative method of susceptibility, but susceptibility to them will depend on which species will be infected by these serovars. It was reported that 9% of seagulls (Larus occidentalis) studied, in 2008, in California were carriers of Salmonella but only from one of those seagulls an antibiotic resistant Salmonella was isolated [32]. Subsequently, was reported a 24% (n = 216) isolation of Salmonella from young blackheaded gulls (Larus ridibundus) being S. Enteritidis (PT 8 and 4) the most prevalent showing a 28% of resistance to antibiotics [33].…”