2c). A higher magnification in these areas revealed biofilm clusters consisting of live and dead cocci surrounded by EPS containing eDNA (Fig. 2d). Although it has long been recognized that monofilament sutures may generally harbor fewer microorganisms than multifilament sutures (e.g. Osterberg & Blomstedt, 1979), these

striking images show that the knotted area itself, unavoidable with any suture configuration, can provide an adequate microenvironment in which biofilm may accumulate. In light of the above findings, the patient’s clinical history is thrown into sharper relief and is consistent with the biofilm paradigm, fulfilling all of Parsek and

Singh’s suggested criteria for the clinical diagnosis of a biofilm infectious process (Parsek & Singh, 2003). These include: ‘(a) The infecting bacteria were adherent to some substratum RAD001 chemical structure or are surface associated’– clearly, in this case, bacteria were adherent to the xenograft and to the sutures, as demonstrated by CM. ‘(b) Direct examination of infected tissue shows bacteria living in cell clusters, or microcolonies, encased in an extracellular matrix’– again, our confocal results show just this. ‘(c) The infection is generally confined to a particular location. RNA Synthesis inhibitor Although dissemination may occur, it is a secondary phenomenon’– the present case is a particularly good example of this. On the patient’s left side, despite months of pain (now understood to be the result of an infectious process), no systemic spread occurred; nor was the infection visible externally. We suspect the patient likely had a similar biofilm-elicited process on the right side that did progress to development of a frank draining sinus, but even this remained a localized process, with no cellulitic or systemic spread over months. ‘(d) The infection is difficult or impossible to eradicate with antibiotics

despite the fact that the responsible organisms are susceptible to killing in the planktonic state’– this characteristic was never tested in this patient. Because we suspected a biofilm the etiology to the patient’s infections, we relied on surgical exploration rather than antibiosis as the mainstay of intervention. Antibiotics were only administered adjuvantly, after the substrata hosting the biofilms were surgically removed. This case also conforms to other typical features of biofilm infections. Despite numerous bacteria present and visible on explanted xenograft tissues, laboratory culture was positive in only one instance, consistent with the difficulty in recovering biofilm organisms using standard microbiological cultural techniques.