Abstract
Gram-positive anaerobic cocci (GPAC) are a commensal part of human flora but are also opportunistic pathogens. This is possibly the first study to report a case of Peptoniphilus harei bacteremia in an abdominal aortic aneurysm (AAA) patient. Matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF MS) failed to identify the isolate and molecular analysis confirmed it as P. harei. A comprehensive literature review revealed that P. harei is an emergent pathogen. This study serves as a reminder for practicing clinicians to include anaerobic blood cultures as part of their blood culture procedures; this is particularly important situations with a high level of suspicion of infection factors in some noninfectious diseases, as mentioned in this publication. Clinical microbiologists should be aware that the pathogenic potential of GPAC can be greatly underestimated leading to incorrect diagnosis on using only one method for pathogen identification. Upgradation and correction of the MALDI-TOF MS databases is recommended to provide reliable and rapid identification of GPAC at species level in medical diagnostic microbiology laboratories.
Highlights
Gram-positive anaerobic cocci (GPAC), a large group of anaerobic bacteria, comprise several bacterial genera
We report a patient who presented with abdominal aortic aneurysm (AAA) and was found to have anaerobic bacteremia that was initially missed because anaerobic blood cultures had been eliminated from the standard blood culture protocol of the institution where he was first assessed
The results of mass spectrometry are dependent on the quantity and accuracy of the database; we reidentified the isolate by Vitek MS as P. asaccharolyticus based on a confidence level of 99.9%
Summary
Gram-positive anaerobic cocci (GPAC), a large group of anaerobic bacteria, comprise several bacterial genera. They are members of the normal microbiota, they are known to be important pathogens causing human diseases, accounting for approximately 25%-30% of all isolated anaerobic bacteria from clinical specimens (Murphy and Frick, 2013). The early identification of anaerobes is important for the initiation of appropriate treatment in patients with bacteremia, and the correct identification up to the species level of GPAC often helps to distinguish between clinically relevant microorganisms and culture. Two MALDI-TOF MS systems are commercially available for routine use: Bruker Biotyper and VITEK MS. The methodology of the two systems is similar, but they contain differences in the composition of databases and the application of software packages for data analysis, as well as Bruker Biotyper provides results in a log(score), while VITEK MS provides results in percentage of similarity (Lee et al, 2017)
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