Background: Community-acquired methicillin-resistant Staphylococcus
aureus (CA-MRSA), a novel strain of MRSA, has recently emerged and rapidly
spread in the community. Invasion into the hospital setting with replacement of the
hospital-acquired MRSA (HA-MRSA) has also been documented. Co-colonization with both
CA-MRSA and HA-MRSA would have important clinical implications given differences in
antimicrobial susceptibility profiles and the potential for exchange of genetic
information.
Methods: A deterministic mathematical model was developed to characterize
the transmission dynamics of HA-MRSA and CA-MRSA in the hospital setting and to quantify
the emergence of co-colonization with both strains
Results: The model analysis shows that the state of co-colonization becomes
endemic over time and that typically there is no competitive exclusion of either strain.
Increasing the length of stay or rate of hospital entry among patients colonized with
CA-MRSA leads to a rapid increase in the co-colonized state. Compared to MRSA
decolonization strategy, improving hand hygiene compliance has the greatest impact on
decreasing the prevalence of HA-MRSA, CA-MRSA and the co-colonized state.
Conclusions: The model predicts that with the expanding community reservoir
of CA-MRSA, the majority of hospitalized patients will become colonized with both CA-MRSA
and HA-MRSA.