Anaerobiosis beyond anaerobic bacteria: its role in the recovery of aerobic microorganisms from purulent samples

Abstract

The main objective of incubation in anaerobiosis is the recovery of obligate anaerobic bacteria, not excluding other microorganisms. In 2003, we conducted a comparative and prospective study from consecutive clinical samples on the recovery of aerobic microorganisms from primary cultures both in anaerobiosis and aerobiosis of the same sample. The aims were to evaluate the methodology used in anaerobiosis in the recovery of aerobic microorganisms not diagnosed in primary aerobic cultures, and to establish a relationship between them and the origin of the sample. From 2003 to 2004, 2776 bacteriological samples were analyzed and 1884 aerobic microorganisms were cultured altogether. The result was that 69.4% of the samples showed growth both in aerobic and anaerobic incubation from primary cultures of the sample, whereas 30.6% only in one of the mentioned incubation atmosphere: 49.2% in aerobiosis and 50.8% in anaerobiosis. According to these results, the methodology used in anaerobiosis (anaerobic incubation, culture media, stereoscopic microscope or hand lens to examine the primary plates), allowed an extra yield of aerobic organisms, especially gram positive facultative and microaerophilic cocci, which was particularly evident in polimicrobial cultures, and especially when gram negative accompanying flora was present, independently of the type of sample.