Abstract
Antimicrobial resistance, particularly in pathogens such as methicillin-resistant Staphylococcus aureus (MRSA), limits treatment options and increases healthcare costs. To understand patient risk factors, including household and animal contact, potentially associated with colonization with multidrug-resistant MRSA isolates, we performed a prospective study of case patients colonized with MRSA on admission to a rural tertiary care hospital. Patients were interviewed and antimicrobial resistance patterns were tested among isolates from admitted patients colonized with MRSA in 2009–10. Prevalence of resistance was compared by case-patient risk factors and length-of-stay outcome among 88 MRSA case patients. Results were compared to NHANES 2003–04. Overall prevalence of multidrug resistance (non-susceptibility to ≥four antimicrobial classes) in MRSA nasal isolates was high (73%) and was associated with a 1.5-day increase in subsequent length of stay (p = 0.008). History of hospitalization within the past six months, but not antimicrobial use in the same time period, was associated with resistance patterns. Within a subset of working-age case patients without recent history of hospitalization, animal contact was potentially associated with multidrug resistance. History of hospitalization, older age, and small household size were associated with multidrug resistance in NHANES data. In conclusion, recent hospitalization of case patients was predictive of antimicrobial resistance in MRSA isolates, but novel risk factors associated with the household may be emerging in CA-MRSA case patients. Understanding drivers of antimicrobial resistance in MRSA isolates is important to hospital infection control efforts, relevant to patient outcomes and to indicators of the economic burden of antimicrobial resistance.
Highlights
Methicillin-resistant Staphylococcus aureus (MRSA) is a pandemic antimicrobial-resistant pathogen [1]
Some authors have suggested that isolate antimicrobial susceptibility may continue to distinguish community-acquired (CA-)MRSA isolates from those acquired in the hospital, and that isolate resistance to certain antimicrobials may typify hospital-acquired (HA)MRSA isolates [9,10,11,12]
Among the 9004 National Health and Nutrition Examination Survey (NHANES) participants tested in 2003–04 for any nasal colonization with S. aureus (MRSA and MSSA combined), odds were 1.32 fold higher [95% CI: 1.10– 1.57] for colonization among participants who lived in larger households (p = 0.005). This association remained significant in survey-weighted, adjusted models controlling for gender, age, and hospitalization within the prior year. In this cohort of MRSA case-patients from primarily rural and suburban Pennsylvania, most isolates were susceptible to quinupristin-dalfopristin (Synercid); chloramphenicol; tetracycline; gentamicin; and trimethoprim/sufamethoxazole
Summary
Methicillin-resistant Staphylococcus aureus (MRSA) is a pandemic antimicrobial-resistant pathogen [1]. In 2004, an estimated 1.5% of the United States population, or approximately 4 million people, were nasally colonized with MRSA [2]. Antimicrobial-resistant pathogens, which include MRSA, have human costs in morbidity and mortality, and they have been estimated to have healthcare costs in excess of $4 billion annually in the U.S [4]. As a result, understanding the epidemiology of multidrug-resistant MRSA case-patients is both clinically and economically relevant to healthcare surveillance and control efforts. MRSA epidemiology in the United States is shifting rapidly, as strains historically considered community-associated enter hospitals, and hospital strains disseminate into the community [5,6,7,8]. Human households [13,14,15] and animals [16,17] recently have been described as potential community reservoirs for MRSA
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