Comparison of different methods for bacteriocin typing of Klebsiella strains

Epidemiological analysis of Klebsiella strains from nosocomial infections needs a simple, stable and reproducible technique of typing. We have evaluated three bacteriocin typing methods for Klebsiella spp. by means of 15 bacteriocin-producing strains, with special reference to stability and reproducibility. With the three methods indicator strains and clinical strains were retyped on different days under constant test procedures. Stability of bacteriocins was tested by titration immediately after preparation and after 4 weeks of storage at -70 degrees C. Thereafter, reproducibility of typing was tested by means of these freshly prepared bacteriocin lysates and of portions of the same lysates stored at -70 degrees C. A moderate reproducibility was obtained with one method after two typing experiments: 79.2% and 61.3% for indicator strains and clinical strains respectively. The other two methods gave a much lower reproducibility of 38.5% and 32.5% for indicator strains and of 11.1% and 25.5% for clinical strains after two experiments. The reproducibility decreased after retyping three, four or five times. These methods are simple to perform but their usefulness for epidemiological studies is doubtful. Possible causes of the lack of reproducibility of the methods are discussed.