MOLECULAR DIAGNOSIS OF CAR SCRATCH DISEASE - A 2-STEP APPROACH

Amplification of Bartonella henselae DNA has been proposed as a diagno stic test for cat scratch disease (CSD), The sensitivities of the foll owing three PCR assays were compared, PCR/rRNA with universal primers amplifies part of the 16S rRNA gene, followed by; hybridization, with a specific B, henselae probe; PCR/CS anti PCR/HSP amplify portions of the gltA and the htrA genes, respectively, each followed itp restricti on fragment length polymorphism analysis, The threshold of detection o f B. henselae DNA in pus was 10(-4), 10(-3), and 10(-2) ng for PCR/rRN A, PCR/CS, and PCR/HSP, respectively. np these three assays, B. hensel ae DNA was detected in 100, 94, and 69% of 32 pus and lymph node speci mens from GSD patients, respectively, The similar sensitivities of the PCR/rRNA and the PCR/CS assays for detecting B. henselae DNA in clini cal specimens are in contrast to the 10-fold difference in sensitiviti es in favor of PCR/rRNA demonstrated with purified B. henselae DNA in sterile pus, suggesting that in the majority of cases, the bacterial l oad in clinical specimens is large enough to be identified by Che PCR/ CS assay. A two-step approach is suggested to achieve maximal sensitiv ity for detecting B, henselae in clinical specimens: initial testing b y PCR/CS (which does not require hybridization), followed by; PCR/rRNA with PCR/CS-negative specimens when CSD is strongly suspected.