Normally corynebacteria do not cause much excitement when isolated from wound swabs or pus from abscesses. In fact most of the time we virtually ignore such isolates.
We only usually pay much attention to corynebacteria when prosthetic material is involved, as these bacteria usually only cause clinical problems when there is something “foreign” to cling to.
However this is not the case for breast abscesses and mastitis. Corynebacteria, including both lipophilic ( Corynebacterium kroppenstedtii, C. tuberculostearicum, C. accolens ) as well as non-lipophilic strains (C. striatum, C. minutissimum )are now well established as causative agents in breast abscesses.
Even more interesting, the lipophilic corynebacteria seem to cause a specific type of histological pattern called granulomatous lobar mastitis, with granulomas, neutrophil inflammation, and cystic spaces visualised.
This is all very well, but from a practical point of view, what implications does all the above have for the clinical microbiology laboratory?
Here are my thoughts…
- All specimens from breast abscesses should be put up on media encouraging the growth of lipophilic bacteria, such as polysorbate (Tween).
- All recurrent breast abscesses or recalcitrant cases of mastitis should have tissue excised and histology performed. Along the same lines the finding of granulomas on histology should prompt the clinician to consider not just mycobacteria, but also corynebacterium infection.
- Given the aetiological importance of corynebacteria, all pus from breast abscesses should probably be incubated for 5 days as routine. (We don’t do this currently at my laboratory, but we probably should….)
Here are a couple of articles on this topic to have a read through: (5 min each)
Now that Maldi-TOF is well established in most clinical microbiology laboratory networks, corynebacteria can now generally be diagnosed more quickly and easily, and this I am sure will further improve our understanding of breast infections in the future.