MSACL 2017 EU Abstract

Beyond “Bacterial Identification Revolution” – Detection of Resistance Markers by MALDI-TOF MS

Markus Kostrzewa (Presenter)
Bruker Daltonik GmbH

Bio: - Study of biology at the Justus-Liebig-University, Giessen, Germany. Diploma (1990) and Ph.D. thesis (1993) about molecular evolution of plastids. - 1993-1997 Postdoc at the Institute of Human Genetics, JLU Giessen (AG Prof. U. Müller). Diagnostic of hereditary human diseases, Research in the framework of the Human Genome Project Joined Bruker in 1998 Head of the new R&D group “Bioanalytical Development“. - Establishment of molecular biology development. - Development of DNA analysis by MALDI-TOF MS, “Clinical Proteomics”. - Development of microorganism identification by MALDI-TOF MS (“MALDI Biotyper” system). 2005 Director Molecular Biology, R&D 2012 Vice President Clinical Mass Spectrometry R&D 2017 Vice President Microbiology & Diagnostics R&D Heading the the microbiology and clinical R&D. More than 100 peer reviewed publication. Member of ESCMID, ASM, DGHM, DGNG.

Authorship: Cordovana M.(1), Pranada A.B.(2), Bienia M.(2), Landini M.P.(1), Kostrzewa M.(3)
(1)University Hospital S.Orsola-Malpighi, Bologna – Unit of Microbiology (2) MVZ Dr. Eberhard & Partner Dortmund, Department of Medical Microbiology, Dortmund, Germany (3) Bruker Daltonik GmbH, Bremen, Germany

Short Abstract

The globally increasing spread of bacterial antibiotic resistances demands for rapid detection methods. Novel applications of MALDI-TOF MS could fit this purpose; in particular, the possibility to detect specific peaks “in real time” in the bacterial identification mass spectrum, corresponding to antibiotic resistance markers, allows an innovative and extremely fast approach. Here, we investigate the use of MALDI-TOF MS (MALDI Biotyper – Bruker Daltonik, Germany) to subtype methicillin-resistant Staphylococcus aureus (testing n=1304 clinical isolates), and KPC-producing Klebsiella pneumoniae (testing n=4821 strains), and evaluate the possibility of a commercial software, to achieve an “instant resistance detection” directly during routine identification process.

Long Abstract


MALDI-TOF MS has become the reference method for bacterial identification in medical microbiology routine. The globally increasing spread of antibiotic resistances in bacteria involved in serious nosocomial infections demands for an accurate and rapid method to detect them. Novel applications of MALDI-TOF MS could fit this purpose. In particular, the presence of specific peaks in the bacterial mass spectrum corresponding to antibiotic resistance surrogate markers, allows a completely innovative and extremely fast approach to this problem of growing concern. Moreover, the possibility to detect such peaks “in real-time”, directly in the spectra recorded for bacterial identification, opened the way to the concept of “instant detection of antibiotic resistance”.

Aim of this study was to investigate the use of MALDI-TOF MS (MALDI Biotyper – Bruker Daltonik) to subtype methicillin-resistant Staphylococcus aureus (MRSA) by detection of a peak related to PSM-mec peptide (m/z 2413), and KPC-producing Klebsiella pneumoniae by detection of a peak related to the blaKPC-harbouring plasmid (m/z 11.109).


S. aureus and PSM-mec related peak. MALDI-TOF mass spectra of n=1304 S. aureus isolates from the years 2011-2014 were analyzed retrospectively. Among these, n=211 (16.8 %) resulted methicillin-resistant in routine antimicrobial susceptibility testing (VITEK 2, bioMérieux, France). Methicillin-resistant and methicillin-susceptible strains were screened for the specific peak with an automated algorithm we have developed.

K. pneumoniae and blaKPC-bearing plasmid related peak. MALDI-TOF mass spectra of n=4821 clinical and surveillance isolates of K. pneumoniae from Italy (n=1350) and Germany (n=3471), collected between 2009 and 2016, were analyzed with an automated algorithm we have developed.

For the strains that showed a reduced susceptibility to carbapenems with routine methods (VITEK2, bioMérieux, France) (n=1601), the carbapenemase-production was verified by PCR (n=266) or disk diffusion synergy test (Rosco, Denmark) (n=1335).


S. aureus and PSM-mec related peak. Among the 211 MRSA strains, 49 (23.2%) presented the PSM-mec related peak, and therefore could be directly identified as MRSA positive by peak analysis. None of the 1093 methicillin-susceptible S. aureus strains showed the described peak (specificity 100%).

K. pneumoniae and blaKPC-bearing plasmid related peak. The blaKPC related peak in was detected in 1050/1329 KPC-producing strains (79.0%), and in neither of n=114 PCR-negative strains nor n=3282 strains susceptible to carbapenems (specificity 100%).

A permanently increasing trend was observed, with 60.2% of strains showing the peak in 2010-2011 and 92.6% in 2016, suggesting an increasing spread of this specific plasmid among all blaKPC-harbouring clones.

Conclusions & Discussion

MALDI-TOF MS subtyping proved to be able to detect one of the mechanisms of methicillin-resistance in S. aureus, with sensitivity of 23.2%, and specificity of 100%.

It also proved to be able to detect the most common blaKPC-bearing plasmid, showing a high specificity (100%) and an overall good sensitivity (79.0 %); interestingly, the increase of sensitivity from 60.2% in 2010/11 to 92.6% in 2016 proves that it is likely related to the prevalence of the specific plasmid-harbouring clones among all of the KPC-producing circulating K. pneumoniae strains.

Both these automated algorithms have been optimized and implemented into commercial software of the Bruker MALDI Biotyper, and thereby could enable the instant detection of methicillin-resistant S. Aureus and KPC-producing K. pneumoniae during routine identification process. In future, this might allow early adaptation of the proper therapy and the measures of infection control.

Our results show that MALDI-TOF mass spectrometry offers innovative answers to the demand for fast and reliable approaches to detect strains bearing specific antibiotic resistances.

References & Acknowledgements:

Financial Disclosure

SalaryyesI am an employee of Bruker Daltonik
Board Memberno
Stockyes Bruker Corp.

IP Royalty: no

Planning to mention or discuss specific products or technology of the company(ies) listed above: