Comparison of the QuadFERM+ 2-hr identification system with conventional carbohydrate degradation tests for confirmatory identification of Neisseria gonorrhoeae.

The QuadFERM+ (Analytab Products, Plainview, NY) rapid identification system was evaluated for its ability to identify correctly Neisseria gonorhoeae isolates from specimens obtained at a sexually transmitted disease clinic. One hundred eighty-five isolates (115 N. gonorrhoeae, 45 Neisseria meningitidis, 16 Neisseria species, and nine Branhamella catarrhalis; fresh isolates, frozen stock cultures, and cultures referred from local health agencies) were tested with the QuadFERM+ system and conventional biochemical tests. The two discrepant results were obtained with QuadFERM+, for a lactose-positive isolate of Neisseria sicca and a maltose-positive N. meningitidis. Both were negative by conventional sugar degradation tests. The N. sicca was negative when repeated in the QuadFERM+, and the N. meningitidis reverted from maltose-positive to maltose-negative after 3 hr. Twelve beta-lactamase positive organisms (six N. gonorrhoeae plus six B. catarrhalis) and 173 beta-lactamase-negative organisms showed 100% agreement between the acidometric QuadFERM+ beta-lactamase test and the conventional starch-iodine method. Thus the QuadFERM+ is a rapid and acceptable alternative for the identification of N. gonorrhoeae in a sexually transmitted disease clinic.