MALDI-TOF bacterial subtyping to detect antibiotic resistance.

The spread of bacterial resistance has been continuously increasing in the recent decade. Multi-drug resistant (MDR) bacteria now represent one of the most worrisome public health issues, as they seriously complicate the treatment of infections, often leaving few therapeutic options. Enterobacteria and Staphylococcus aureus are among the most common bacterial pathogens, while Bacteroides fragilis is the most frequent anaerobic pathogen. All of these species can cause severe and life-threatening infections, and represent the most frequent causes of antibiotic-resistant healthcare-associated infections worldwide, as they frequently exhibit resistance to various classes of antibiotics. Resistance to carbapenems, the last resort beta-lactam agent, is a particularly threatening problem. Achieved by different mechanisms, leads to total inefficacy of any beta-lactam agent. During the recent years, MALDI-TOF mass spectrometry has become established as the reference method for bacterial identification in routine practice. It has proven to be a reliable and robust method to detect specific peaks in bacterial mass spectra, corresponding to specific resistance markers, enabling the instant detection of resistant isolates in real time during the standard routine identification process. Here, we investigated the performance of the subtyping module of the MALDI Biotyper system (Bruker Daltonik, GmbH) for the instant identification of KPC-producing Klebsiella pneumoniae, methicillin-resistant Staphylococcus aureus, and carbapenemase-producing Bacteroides fragilis during the identification workflow. We evaluated accuracy and potential impact on turnaround time. Furthermore, we investigated the possibility to extend the subtyping for detection of the KPC-specific marker to bacterial species other than K. pneumoniae.