Further analysis of the long duration clusters revealed potential transmission of non- spa type 2 MRSA strains.
For many of the long duration clusters, several non- spa type 2/t002 MRSA strains were identified in the patient population.
For 10 long duration clusters, seven (Cluster ID 1, 4, 7, 8, 12, 13, 26) were further characterized with molecular data.
Lastly, with the identification of a predominant spa type circulating in the patient population, the application of spa typing provided very little benefit for elucidating transmission events or recognizing potential outbreaks, especially for long duration clusters.
The identification of identical spa types and antibiograms in two long duration clusters, suggests that transmission events among patients, hospital staff, or possibly even the contaminated environment, may have occurred.
Although the exact biological relevance of these long duration clusters is not known, plausible scenarios include extended outbreaks, temporal trends, and the representation of systematic changes at the hospital level during the surveillance period.
Results from the statistical analyses indicated that a significant increase in the CDI incidence rate occurred during 2007 as compared to 2008 and 2009, which was concordant with the temporal scan statistic as all four long duration clusters spanned 2007.
For the long duration clusters (Cluster ID 1, 8, 11, 12), a significant increase in the rate of CDI cases were noted in the hospital overall, which was attributed to increases in the rate of CDI cases in two services (e.g., internal medicine and psychiatry) and one ward that was located in the internal medicine department.
Existing methods require a long duration on cluster head voting.
For the long duration, hospital wide cluster (Cluster ID 2), further examination of the six ribotype 027 cases revealed that three of the cases were located in the same ward and were identified with CDI over a 20 day period.
