MALDI-TOF - Oh no another alpha haemolytic streptococcus

If, like me, you perform regular bench rounds of the diagnostic bacteriology laboratory, you will often see an alpha-haemolytic organism on the plate that Gram stains as a streptococcus. Now comes a dilemma, do you attempt to put this through the MALDI-TOF (ours is a Bruker, by the way) or go straight for ViTEK?

Currently, we would go for the latter, but after seeing this paper, I wonder if this should be reconsidered.  Angeletti et al, using a Bruker loaded with the BioTyper software version 3, seem to imply that not only can viridans group streptococci be identified, but that the Bruker was able to discriminate between S. mitis and S. oralis. This would be much leaner in the laboratory and represent a significant cost saving, especially as no extraction was performed in this study.


MALDI-TOF MS - what does the future hold?

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) is now a routine finding in most diagnostic microbiology laboratories. The technology is by no means perfect (I sometimes miss APIs!) but it can be backed up by conventional ViTEK identification and with 16S rRNA PCR remaining the final arbiter. What is exciting now is that the technology has been used to identify organisms from positive blood culture broths (local publication on this coming soon) as well the identifcation of organisms directly from the sample as well as a larger repertoire of organisms (fungi, mycobacteria etc).

Penicillin allergy and carbapenems

This subject has again resurfaced after a post last year on this subject. In this systematic review published in Clinical Infectious Diseases, the authors looked at 10 studies and 12 case reports (n=838). The incidence of any type of suspected hypersentivity was 4.3%, with the rates of proven, suspected or possible reactions totalling 2.4%. 295/838 had a positive penicillin skin test, with 1/838 having a hypersensitivity reaction to a carbapenem.


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