Efficacy of an Anaerobic Swab Transport System to Maintain Aerobic and Anaerobic Microorganism Viability after Storage at −80°C

Abstract

An Amies agar gel swab transport system was evaluated for its ability to maintain bacterial viability and relative quantity after freezing at −80°C. Nine American Type Culture Collection (ATCC) bacterial strains were used: 3 anaerobic strains ( Propionibacterium acnes, Peptostreptococcus anaerobius, and Clostridium sporogenes) and 6 facultative or strict aerobic bacterial strains ( Stenotrophomonas maltophilia, Escherichia coli ([ATCC 25922 and ATCC 11775], Salmonella enterica subsp. enterica serovar Typhimurium, Staphylococcus saprophyticus, and Lactobacillus casei). The bacterial species were chosen because they corresponded to bacteria identified in psittacine feces and cloacal samples. There were no significant differences between growth scores at baseline and after storage at −80°C for 40 days for any of the bacteria examined after 48 and 72 hr of incubation, with the exception of P. anaerobius. For P. anaerobius, there was a significant reduction ( P < 0.001) in the growth score after storage at −80°C for 40 days from that of the baseline; however, the bacteria were still viable. The tested swab transport system may be useful when lengthy storage and transport times necessitate freezing samples prior to culture.