Molecular typing of Stenotrophomonas(Xanthomonas) maltophilia by Pulse-field Gel Electrophoresis(PFGE) and Arbitrarily-Primed PCR(AP-PCR).

J. Yao*, J.Conly, and M. Krajden.

Optimal methods fro typing S. maltophilia(Sm) isolates in epidemiologic investigations of nosocomial outbreaks due to this organism have not yet been defined. We compared PFGE with AP-PCR for molecular typing of 109 multi-resistant strains of Sm from multiple outbreaks at our institution over a 10-month period (Jan. to Oct 1993). Anatomic sources of these nonduplicate isolates included sputum, 33(30%); endotracheal aspirate 24(22%); bronchoalveolar lavage, 13 (12%); wound, 11(10%); urine, 8(7%); blood, 5(5%); and other sites, 15(14%). PFGE using Dral restriction digest revealed 61 unique DNA restriction profiles among the 109 strains, with 19, 12, 7 and 4 concordant profiles in each of 4 types and unique profiles for the remaining 57 strains. Further analysis by ap-pcr showed the same number of distinct strain types as that of PFGE but more subtype diversity within each clonal type.
We conclude that PFGE and AP-PCR are sufficiently discriminatory and useful in typing Sm strains for epidemiologic investigations of nosocomial outbreaks. However AP-PCR is a more rapid and less laborious method for molecular typing.

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