Increased culture recovery of zygomycetes under physiologic temperature conditions

Poor recovery of Zygomycetes hyphae from tissue specimens may result from failure of current culture methods to mimic physiologic conditions found in hyphae-laden infected tissue. We describe the use of an in vitro model simulating Zygomycetes growth under necrotic or hypoxic tissue conditions. We preconditioned hyphae of clinical Zygomycetes isolates in flasks under anaerobic conditions using Ana-Packs (Becton Dickinson Microbiology Systems, Sparks, MD) at 37°C for 48 hours, thus simulating in vivo growth in an infracted hypoxic lesion, and compared the recovery of paired inocula at 37°C and 25°C. Incubation of stock culture isolates at 37°C resulted in significantly better culture recovery (about 10-fold) when compared with incubation at 25°C (P < .0001). In addition, we similarly evaluated 25,291 consecutive clinical specimens. Among 41 specimens, the yield of Zygomycetes cultures incubated at 37°C (23/41 [56%]) was significantly higher than that incubated at 25°C (9/41 [22%]; P = .0001). Overall, we found that culture recovery was significantly (254%) enhanced at 37°C.