Multidrug Resistant Bacteria in the Community: Trends and Lessons Learned

Abstract

Multidrug resistant (MDR) bacteria are one of the most important current threats to public health. Typically, MDR bacteria are associated with nosocomial infections. However, some MDR bacteria have become quite prevalent causes of community-acquired infections. The spread of MDR bacteria into the community is a crucial development, and is associated with increased morbidity, mortality, healthcare costs and antibiotic use. Factors associated with community dissemination of MDR bacteria overlap but are distinct from those associated with nosocomial spread. Community-associated (CA) MDR bacteria have an antibiotic resistance phenotype that is stable in the absence of antibiotic pressure of the type normally observed in hospitals or nursing homes. An exception to this rule may be those CA-MDR bacteria, of which the prevalence is driven by the presence of antibiotics in the food chain. Additionally, the colonization of otherwise healthy hosts is a common characteristic of CA-MDR bacteria. However, subtle immune deficiencies may still be present in the subjects colonized with specific CA-MDR bacteria. Methicillin-resistant S. aureus (MRSA) is the most prevalent of CA-MDR bacteria. CA-MRSA also has the greatest impact on morbidity and mortality. The main threat on the horizon is represented by Enterobacteriaceae. The production of extended spectrum β-lactamases in Enterobacteriaceae encountered in the community is becoming increasingly prevalent. Of great concern is the potential for the acquisition of carbapenemase genes in CA-Enterobacteriaceae. Prevention of further community spread of MDR bacteria is of the utmost importance, and will require a multi-disciplinary approach involving all stakeholders.