There is now growing evidence that livestock may be involved in spread of community-associated Methicillin Resistant Staphylococcus aureus (CA-MRSA);recent studies from Europe and Canada report a new strain (ST 398) that maybe associated with pig farming. This study seeks to identify and characterize MRSA from pigs on farms and in feedlots in the United States and from their human handlers. Lt will determine if a strain of swine origin exists, and also explore the necessity and feasibility of implementing a nation-wide farm screening scheme as a surveillance tool not only for MRSA but for other emerging zoonoses, which would serve as a complement to existing surveillance systems. The study will test the following two null hypotheses: (1) there is no association between MRSA carriage in pigs and farmers, in terms of prevalence rate and strain;(2) genetic difference do not exist in MRSA strains found in pig farmers compared to the strains circulating in the US. These will be tested by the following specific aims:
Aim 1 a: characterize MRSA strains in pigs, compare these to strains isolated from humans living or working on pig farms and feedlots located in southern New England (CT, MA, Rl,), Maryland, Pennsylvania and eastern Wyoming/western Nebraska. These data will help determine the baseline prevalence of MRSA on pig farms and feedlots and identify emerging strains of swine origin. To achieve this, nasal swabs will be taken from both pigs and their human handlers, and specific laboratory analysis will be done to identify MRSA.
Aim 1 b: determine risk factors for MRSA infection in pig handlers. This will be achieved by administrating a questionnaire to the humans to identify possible risk factors associated with MRSA colonization. If such risk factors exist, this study will provide data to develop systems to test for and eventually prevent transmission of MRSA from pigs to humans, thereby reducing the spread of an emerging strain within the human population.
Aim 2 : compare the MRSA strains identified in Aim 1 to existing strains circulating in the US. Data on strains isolated from human MRSA cases obtained through Active Bacterial Core surveillance (ABCs) by CDC's'Emerging Infections Program will be compared to the strains obtained in this study. This will be able to address the burden and scope of the emerging strains if they exist.
As the epidemiology of MRSA changes, accurate information on its scope and magnitude of the burden is needed to enable public health professionals to set priorities for prevention and control especially with regards to occupational exposure. Also it will reveal the public health implications of MRSA in pigs since pig farmers or handlers maybe a source of infection for the rest of the community they reside in.
