Molecular laboratory tools for rapid diagnostics of systemic infections, and in clinical epidemiological practice

*István Barcs¹, Anita Becker¹, Barbara Sauer¹, Gyula Domján²

Summary
The aims of a clinical microbiology laboratory are rapid demonstration of pathogens from clinical samples and providing a dependable base for managing infections. Three cases are discussed with aspects of rapid clinical diagnosis and application of molecular tools. Microscopic examination of positive blood cultures of septic patients demonstrated elongated bacterial forms which were identified as Escherichia coli within 4 hours by fluorescent in situ hybridization (FISH). Irregular shape was attributed to previous administration of cefuroxime. In the second case, blood and urine cultures of a cancer patient yielded identical strains of E. coli and Enterococcus faecalis, as well. Strains from blood were demonstrated and identified by the FISH method. Pulsed field gel electrophoresis (PFGE) demonstrated identity of isolates of different origin. We diagnosed sepsis provoked by pyelonephritis. In the third case, using a real time polymerase chain reaction (PCR) method, methicillin-resistant Staphylococcus aureus (MRSA) was detected from the wound infection of a patient who was infected by an MRSA during his former hospitalization. PFGE documented that these repeated isolates were different from all strains isolated in the same period from patients at the same ward, that is he was not re-infected after his second admission.

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