A 5-month-old male harbour seal was admitted for rehabilitation to the Sealcentre Pieterburen on November 16th, 2015. During the initial veterinary examination parasitic pneumonia and secondary bacterial pneumonia were suspected. Therefore, the seal received antiparasitic and antibiotic treatment and appeared to be recovering but died unexpectedly after several weeks. The main necropsy findings were a large amount of blood in the pericardial space and two perforating lesions: one in the aortic wall and the second in the tricuspid valve. Histopathological examination of the aorta revealed mural necrosis with haemorrhage, suppurative to mixed inflammation and presence of granular cystic structures. The latter structures were considered as microsporidia as the most likely micro-organisms by the pathologist but could not be confirmed by PCR. Bacterial culture resulted in the isolation of a methicillin resistant Staphylococcus aureus (MRSA) from the pericardial effusion. Subsequent culture of rectal swabs collected at arrival and during the seal rehabilitation process revealed that the animal was already colonized when admitted to the Sealcentre. MRSA has been isolated from marine mammals before, including from two harbour seals (Phoca vitulina), two pilot whales (Globicephala macrorhynchus) and five bottlenose dolphins (Tursiops truncatus).1-6 In addition, Staphylococcus aureus has been related to endocarditis in a harp seal.7 However, to our knowledge this is the first report of MRSA associated endocarditis in seals. Also, the isolation of an MRSA in rectal swabs of this seal strengthens the idea to use seals as bio-indicators for antimicrobial resistance prevalence in marine ecosystems.
The authors wish to thank Izore, UMCG and Sophie Maes for the support with the analysis of the samples. The authors wish to thank also the staff and volunteers of the Sealcentre Pieterburen that helped with the sample collection.
1. Mahony RO, Abbott Y, Leonard FC, Markey BK, Quinn PJ, Pollock PJ, Fanning S, Rossney A.S. 2005. Methicillin-resistant Staphylococcus aureus (MRSA) isolated from animals and veterinary personnel in Ireland. Vet Microb 109:285–96.
2. Fravel V, Bonn W Van, Rios C, Gulland F.2011. Meticillin-resistant Staphylococcus aureus in a harbour seal (Phoca vitulina) Vet Record. 169 (6):155.
3. Hower S, Phillips MC, Brodsky M, Dameron A, Tamargo M, Salazar NC, Jackson CR, Barrett JB, Davidson M, Davis J, Mukherjee S, Ewing RY, Gidley ML, Sinigalliano CD, Johns L, Johnson FE, Adebanjo O, Plano LRW. 2013. Clonally related methicillin-resistant Staphylococcus aureus isolated from short-finned pilot whales (Globicephala macrorhynchus), human volunteers, and a bayfront cetacean rehabilitation facility. Microb Ecol. 65(4):1024–38.
4. Schaefer AM, Goldstein JD, Reif JS, Fair PA, Bossart GD.2009. Antibiotic-resistant organisms cultured from Atlantic bottlenose dolphins (Tursiops truncatus) inhabiting estuarine waters of Charleston, SC and Indian River Lagoon, FL. Ecohealth. 6(1):33–41.
5. Faires MC, Tater KC, Weese JS.2009. An investigation of methicillin-resistant Staphylococcus aureus colonization in people and pets in the same household with an infected person or infected pet. J Am Vet Med Assoc. 235(5):540–3.
6. Morris PJ, Johnson WR, Pisani J, Bossart GD, Adams J, Reif JS, Fair P.2011. Isolation of culturable microorganisms from free-ranging bottlenose dolphins (Tursiops truncatus) from the southeastern United States. Vet Microbiol. 148(2–4):440–7.
7. Chinnadurai SK, Troan B V, Wolf KN, DeVoe RS, Huijsmans CJJ, Hermans MH, Wever PC.2009. Septicemia, endocarditis, and cerebral infarction due to Staphylococcus aureus in a harp seal (Phoca groenlandica). J Zoo Wildl Med. 40(2):393–7.