TYPING OF LISTERIA-MONOCYTOGENES BY MONOCIN AND PHAGE RECEPTORS

One hundred strains of Listeria monocytogenes from both sporadic and e pidemic cases were typed by monocin production combined with phage rec eptor and reverse phage receptor methods. The monocin-phage combinatio n gave 72 types with 100% typability and 97% reproducibility. The resu lts were compared to those of serotyping, phage typing, ribotyping, mu ltilocus enzyme electrophoresis, restriction enzyme analysis and RAPD (random amplification of polymorphic DNA). The monocin/phage types wer e comparable in terms of discrimination with other methods for epidemi ological investigations. The index of discrimination of using the mono cin typing and phage receptor/reverse phage receptor method combinatio n (0.99) for both the 87 epidemiologically unrelated strains and the e pidemiologically important serogroup 4 strains was the highest of the seven different methods analysed. This combination of methods was simp le, highly discriminatory and reproducible and can be carried out in a non-specialized laboratory. However, like most of the other Listeria typing methods, both the method and the indicator test strains need to be standardized.