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United States Department of Agriculture

Agricultural Research Service

Research Project: MOLECULAR APPROACHES FOR THE IDENTIFICATION AND CHARACTERIZATION OF ANTIMICROBIAL RESISTANCE IN FOODBORNE PATHOGENS

Location: Bacterial Epidemiology and Antimicrobial Resistance

Title: Clonally related methicillin-resistant Staphylococcus aureus isolated from short-finned pilot whales (Globicephala macrorhynchus), human volunteers, and a bayfront cetacean rehabilitation facility

Authors
item Hower, Suzanne -
item Phillips, Matthew -
item Brodsky, Micah -
item Dameron, Adrienne -
item Tamargo, Manuel -
item Salazar, Norma -
item Jackson, Charlene
item Barrett, John
item Davidson, Maureen -
item Davis, Johnnie -
item Mukherjee, Sampa -
item Ewing, Ruth -
item Gidley, Maribeth -
item Sinigalliano, Christopher -
item Johns, Lisa -
item Johnson Iii, Frank -
item Adebanjo, Olufummilola -
item Plano, Lisa -

Submitted to: Microbial Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: March 1, 2013
Publication Date: May 1, 2013
Citation: Hower, S., Phillips, M.C., Brodsky, M., Dameron, A., Tamargo, M.A., Salazar, N.C., Jackson, C.R., Barrett, J.B., Davidson, M., Davis, J., Mukherjee, S., Ewing, R.Y., Gidley, M.L., Sinigalliano, C.D., Johns, L., Johnson Iii, F.E., Adebanjo, O., Plano, L.R. 2013. Clonally related methicillin-resistant Staphylococcus aureus isolated from short-finned pilot whales (Globicephala macrorhynchus), human volunteers, and a bayfront cetacean rehabilitation facility. Microbial Ecology. 65(4):1024-1038.

Interpretive Summary: Staphylococcus aureus is a Gram-positive bacterium that can be commonly found on the skin or in the nasal passages of most humans and animals. It has been implicated in a number of diseases in humans ranging from minor skin infections to more serious infections such as pneumonia. Studies have shown that humans shed S. aureus onto surfaces in their environment (including water) and that this is a source of spread to other individuals. Just as spread of S. aureus is a major concern in humans (especially Methicillin-Resistant S. aureus-MRSA), it has also become an increasing problem in animals including marine mammals. In 2011, a live mass stranding of 26 short-finned pilot whales occurred in the lower Florida Keys. Five surviving whales were transferred from the original stranding site to a nearby marine mammal rehabilitation facility where they were constantly attended to by a team of volunteers. Bacteria recovered from the whales during the routine clinical care and necropsy of a deceased whale included Methicillin-Sensitive S. aureus (MSSA) and MRSA. In order to investigate potential sources or reservoirs of MSSA and MRSA, samples were obtained from human volunteers, whales, seawater, and sand from multiple sites at the facility, nearby recreational beaches, and a canal. Molecular typing of the isolates revealed clonally related MRSA from multiple environmental locations as well as from humans and animals. Genetically similar MSSA and MRSA were also identified from distinct sources within this sample pool. PFGE indicated that the majority of MRSA isolates were clonally related to the prototype human strain USA300. These studies serve as an indication that S. aureus may be shed into an environment by humans or pilot whales and subsequently colonize or infect exposed new hosts. This information is especially useful for physicians, veterinarians, and scientists who establish prevention and control measures for MRSA.

Technical Abstract: In May of 2011 a live mass stranding of 26 short-finned pilot whales (Globicephala macrorhynchus) occurred in the lower Florida Keys. Five surviving whales were transferred from the original stranding site to a nearby marine mammal rehabilitation facility where they were constantly attended to by a team of volunteers. Bacteria cultured during the routine clinical care of the whales and necropsy of a deceased whale included methicillin-sensitive and methicillin-resistant Staphylococcus aureus (MSSA and MRSA). In order to investigate potential sources or reservoirs of MSSA and MRSA, samples were obtained from human volunteers, whales, seawater, and sand from multiple sites at the facility, nearby recreational beaches, and a canal. Samples were collected on three days. The second collection day was two weeks after the first, and the third collection day was two months after the last animal was removed from the facility. MRSA and MSSA were isolated on each day from the facility when animals and volunteers were present. MSSA was found at an adjacent beach on all three collection days. Isolates were characterized by utilizing a combination of qPCR to determine the presence of mecA and genes associated with virulence, spa typing, staphylococcal cassette chromosome mec (SCCmec) typing, multi-locus sequence typing (MLST), and pulsed field gel electrophoresis (PFGE). Using these methods, clonally related MRSA were isolated from multiple environmental locations as well as from humans and animals. Non-identical but genetically similar MSSA and MRSA were also identified from distinct sources within this sample pool. PFGE indicated that the majority of MRSA isolates were clonally related to the prototype human strain USA300. These studies support the notion that S. aureus may be shed into an environment by humans or pilot whales and subsequently colonize or infect exposed new hosts.

Last Modified: 7/28/2014
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