Evaluation Of Organism Recovery After Twelve Months Using the Roll Plate Method Described Document M40 Quality Control Of Microbiological Transport Devices

ABSTRACT (REVISED)
Objective: This study was designed to compare two commercial Amies transport systems without charcoal for their ability to support bacterial growth at different temperatures after the swabs were stored at room temperature for 12 months. The swabs compared were the M40 Transystem (Copan Diagnostics Inc.) and the Starswab II (Starplex Scientific Inc.). The roll plate method described in CLSI M40 was used.
Methods: CLSI M40 document recommended ATCC strains of Pseudomonas aeruginosa BAA-427,  Streptococcus pneumoniae 6305, Streptococcus pneumoniae 49619, Streptococcus pyogenes 19615, Haemophilus influenzae 10211, Neisseria gonorrhoeae 43069 (GC), Propionibacterium acnes 6919, Prevotella melaninogenica 25845, Bacteroides fragilis 25285, Fusobacterium nucleatum 25586 and Peptostreptococcus anaerobius 27337 were inoculated to Amies without charcoal. Swabs were held at room temperature and 4º C for 0, 24 (GC only) or 48 hours. Bacteria were plated and counted following appropriate incubation conditions. Baseline colony counts were achieved by plating out the zero hour swabs immediately and incubating appropriately.
Results: Acceptable recovery was considered as >5 colonies following the specified holding time from the specific dilution that yielded baseline counts closest to 300 colonies. At 12 months, P. aeruginosa, S. pyogenes, S. pneumoniae 6305, S. pneumoniae 49619, H. influenzae, N. gonorrhoeae, B. fragilis and P. acnes were recovered from both systems at both holding temperatures. P. anaerobius and P. melaninogenica were recovered by the M40 swab at both holding temperatures, but at 4º C only from the Starplex swab. F. nucleatum was not recovered from either system.
Conclusions: Storage temperature was a critical factor for recovery of organisms from both systems. The Starswab II transport system performed well for most organisms at 4º C, but the M40 Transystem swab allowed greater stability of all species at both 4º C and room temperature.

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