Multiclonal methicillin-resistant Staphylococcus aureus (MRSA) outbreak and its control after use of the Veterans Affairs (VA) MRSA bundle in a VA long-term care facility, 2004-2014.

A multiclonal methicillin-resistant Staphylococcus aureus (MRSA) outbreak with 91 infections occurred in our Veterans Affairs (VA) community living center over 46 months. Both similar and unique strains were shown by repetitive polymerase chain reaction to contribute to the outbreak, including 1 strain causing infections over a 33-month period. Most infections were soft tissue infections (67%). For 21 months after the initiation of the VA MRSA bundle, no infections were identified, and low rates of infection have been sustained an additional 4 years. The average annual rate of MRSA infection decreased by 62% (P < .001) from 0.6 per 1,000 resident days for 4 years prior to the bundle implementation to 0.09 per 1,000 resident days for 4 years after the bundle implementation.

Cost-benefit and effectiveness analysis of rapid testing for MRSA carriage in a hospital setting.

A cost-effectiveness analysis was conducted comparing the polymerase chain reaction assay and traditional microbiological culture as screening tools for the identification of methicillin-resistant Staphylococcus aureus (MRSA) in patients admitted to the pediatric and surgical intensive care units (PICU and SICU) at a 722 bed academic medical center. In addition, the cost benefits of identification of colonized MRSA patients were determined. The cost-effectiveness analysis employed actual hospital and laboratory costs, not patient costs. The actual cost of the PCR assay was higher than the microbiological culture identification of MRSA ($602.95 versus $364.30 per positive carrier identified). However, this did not include the decreased turn-around time of PCR assays compared to traditional culture techniques. Patient costs were determined indirectly in the cost-benefit analysis of clinical outcome. There was a reduction in MRSA hospital-acquired infection (3.5 MRSA HAI/month without screening versus 0.6/month with screening by PCR). A cost-benefit analysis based on differences in length of stay suggests an associated savings in hospitalization costs: MRSA HAI with 29.5 day median LOS at $63,810 versus MRSA identified on admission with 6 day median LOS at $14,561, a difference of $49,249 per hospitalization. Although this pilot study was small and it is not possible to directly relate the cost-effectiveness and cost-benefit analysis due to confounding factors such as patient underlying morbidity and mortality, a reduction of 2.9 MRSA HAI/month associated with PCR screening suggests potential savings in hospitalization costs of $142,822 per month.

Serum resistance and biofilm formation in clinical isolates of Acinetobacter baumannii.

Acinetobacter baumannii has few known virulence factors and yet causes a variety of opportunistic infections. Many gram-negative bacteria are directly killed by complement, but we hypothesized that A. baumannii would be resistant to serum killing. A serum bactericidal assay assessed the resistance of seven A. baumannii isolates to serum killing, and C2-deficient serum was used to examine its activation of the alternative pathway. Flow cytometry was utilized to determine whether complement regulator factor H (FH) was bound by A. baumannii, and to assay C3 deposition on cells. A microtiter biofilm assay compared biofilm production among isolates. Of seven isolates, four were serum sensitive and three were serum resistant. The C2-deficient serum demonstrated that A. baumannii can activate the alternative pathway. None of the isolates bound FH. Serum-resistant strains accumulated little C3 when exposed to human serum, while sensitive strains had a high amount of surface C3 deposition. Biofilm production varied extensively among strains. Most serum-resistant isolates formed a substantial amount of biofilm, while sensitive isolates produced negligible amounts of biofilm. Our data indicate that some strains of A. baumannii are resistant to serum killing and produce biofilms and by understanding the resistance mechanisms used by this bacterium, we can further elucidate its complex pathogenicity.