Journal of medical microbiology
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Sepsis is a major cause of mortality in hospitalized patients worldwide, with lethality rates ranging from 30 to 70 %. Sepsis is caused by a variety of different pathogens, and rapid diagnosis is of outstanding importance, as early and adequate antimicrobial therapy correlates with positive clinical outcome. In recent years, matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) fingerprinting has become a powerful tool in microbiological diagnostics. ⋯ As differentiation of Staphylococcus aureus from coagulase-negative staphylococci is of clinical importance, a PCR was additionally established that was capable of identifying S. aureus directly from positive blood cultures, thus closing this diagnostic gap. Another benefit of the PCR approach is the possibility of directly detecting the genes responsible for meticillin resistance in staphylococci and for vancomycin resistance in enterococci, which is of high importance for early adequate treatment. Both of the described methods were finally integrated into a protocol for fast and effective identification of bacteria from positive blood cultures.
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The emergence of colistin or tigecycline resistance as well as imipenem resistance in Acinetobacter baumannii poses a great therapeutic challenge. The bactericidal and synergistic effects of several combinations of antimicrobial agents against imipenem-, colistin- or tigecycline-resistant A. baumannii isolates were investigated by in vitro time-kill experiments. Six imipenem-resistant A. baumannii blood isolates were examined in this study, including colistin- and tigecycline-susceptible, colistin-resistant but tigecycline-susceptible, and colistin-susceptible but tigecycline-resistant isolates. ⋯ Among the combinations of 0.5× MIC antimicrobial agents, the combination of colistin and tigecycline showed synergistic or bactericidal effects against four of the isolates. This in vitro time-kill analysis suggests that antimicrobial combinations are effective for killing imipenem-resistant A. baumannii isolates, even if they are simultaneously resistant to either colistin or tigecycline. However, the finding that the combinations of 0.5× MIC antimicrobial agents were effective on only some isolates may warrant further investigation of the doses of combination agents needed to kill resistant A. baumannii.