Use of PCR-based Mycobacterium tuberculosis genotyping to prioritize tuberculosis outbreak control activities

Seattle Biomedical Research Institute, Seattle, Washington; Seattle-King County Tuberculosis Control Program, Seattle, Washington; University of Washington Dept. of Epidemiology, Seattle, Washington, University of Washington Dept of Pulmonary and Critical Care Medicine

^* To whom correspondence should be addressed. Email: jerry.cangelosi{at}sbri.org.

	Abstract

Genotypic analysis of Mycobacterium tuberculosis isolates is increasingly applied in direct support of tuberculosis outbreak control activities. This is facilitated by PCR-based strain typing methods that enable the genotypic characterization of samples containing small numbers of M. tuberculosis cells. Using DNA extracted directly from primary diagnostic cultures, PCR-based methods were applied to a tuberculosis outbreak investigation and to surveillance in King County, Washington. In the outbreak investigation, five epidemiologically linked M. tuberculosis isolates had a unique pattern at Mycobacterial Interspersed Repeating Unit (MIRU) loci 10 and 23 when compared to a local MIRU database. In order to quickly identify new cases involving this strain (termed SBRI10), targeted genotyping at these two loci was performed on cultures from epidemiologically associated tuberculosis cases. Isolates with the characteristic genotype at loci 10 and 23 were further analyzed by 12-locus MIRU panel and by repetitive-sequence-based PCR (rep-PCR). Between May 2004 and January 2005, 82 cases were screened, of which 14 were identified for further analysis and 13 were confirmed to be SBRI10. Between September 2005 and August 2006, surveillance universal genotyping was performed using 12-locus MIRU panel on DNA from primary diagnostic enrichment cultures. A total of 161 samples were submitted for analysis and 156 were successfully typed. Fifty-one cases formed 18 presumptive clusters by MIRU. Of these, 30 cases were confirmed as members of 11 clusters by rep-PCR. Presumptive genotypic data were available rapidly, sometimes within 2 weeks of diagnosis. In this fashion, PCR-based genotyping provided data to prioritize disease-control activities.