Serotyping of clinical isolates of Acinetobacter: serovars of genospecies 3.

A total of 156 clinical isolates of genospecies 3, the second most commonly encountered member of the genus Acinetobacter at our institution, were identified with carbon source utilization tests among 400 Acinetobacter isolates. Checkerboard tube agglutination tests and reciprocal cross-absorption studies with polyclonal rabbit immune sera against heated (100 degrees C, 1 h) cells of serovar candidate strains of genospecies 3 permitted identification of 13 serovars. Minor one-way crossreactions were noted between serovars 10 and 8 and between serovars 2 and 12, respectively. Isolates of serovar 13 cross-reacted extensively one-way with serovar 2 and less so with serovars 4 and 12. Genospecies 3 serovars 3, 7, 8, and 9 cross-reacted with Acinetobacter baumannii serovars 19, 21, 6, and 15, respectively.