A New Method for Arcobacter butzleri, Arcobacter cryaerophilus, and Arcobacter skirrowii Detection using a Novel Chromogenic Agar

Arcobacter species are Gram-negative rods that have been implicated in food- and waterborne illness. Although various cultural isolation methods have been proposed, the current procedures are unable to fully suppress growth of background microbiota present in food samples which inhibits Arcobacter isolation. The purpose of this study was to develop a selective enrichment broth and chromogenic plating medium to detect three Arcobacter species that have been recognized as emerging foodborne pathogens: Arcobacter butzleri , Arcobacter cryaerophilus and Arcobacter skirrowii . The developed Nguyen-Restaino-Juárez Arcobacter detection system consists of a selective enrichment broth (NRJ-B) and a selective/differential plating media (NRJ-M). The protocol of the detection method was determined by evaluating growth of A. butzleri , A. cryaerophilus and A. skirrowii under various temperature (30, 35 and 42ᴼC) and incubation (aerobic, microaerophilic and anaerobic) conditions. Additionally, 47 Arcobacter strains and 39 non- Arcobacter strains were tested in the inclusivity and exclusivity evaluations of NRJ-B and NRJ-M. Overall, the study determined the optimal growth conditions of Arcobacter species using the NRJ- Arcobacter detection system was aerobic incubation at 30ᴼC. NRJ-B supported good growth of A. butzleri , A. cryaerophilus , and A. skirrowii while effectively suppressing growth of non- Arcobacter strains after 48 h. Furthermore, NRJ-M yielded 97.8% inclusivity and 100.0% exclusivity using the tested strains and resulted in salmon-pigmented Arcobacter colonies (1.0 to 1.5 mm in diameter) after 72 h. The novel protocol is the first to develop a chromogenic plating media for the isolation of Arcobacter species. This simple and reliable test method would greatly contribute to understanding the distribution of pathogenic Arcobacter species in food samples.

Detection of Burkholderia pseudomallei in Sputum using Selective Enrichment Broth and Ashdown’s Medium at Kampong Cham Provincial Hospital, Cambodia

Melioidosis, infection caused by Burkholderia pseudomallei, is increasingly reported in Cambodia. We hypothesized that implementation of an enhanced sputum testing protocol in a provincial hospital diagnostic microbiology laboratory would increase detection of B. pseudomallei. We tested 241 sputum specimens that were deemed acceptable for culture, comparing culture in selective enrichment broth followed by sub-culture on Ashdown’s medium to standard culture methods. Two specimens (0.8%) were positive for B. pseudomallei using the enhanced protocol whereas one specimen (0.4%) was positive using standard methods. Given the low numbers of positive specimens, we could not conclusively determine the utility of the enhanced sputum testing protocol. However, the ramifications of identification of B. pseudomallei are substantial, and the benefit of the enhanced testing protocol may be more apparent in patients selected based on risk factors and clinical presentation. Promoting clinician awareness of the infection and encouraging utilization of diagnostic microbiology services are also likely to be important factors in facilitating identification of melioidosis.

Detection of Burkholderia pseudomallei in Sputum using Selective Enrichment Broth and Ashdown’s Medium at Kampong Cham Provincial Hospital, Cambodia

Melioidosis infection, caused by Burkholderia pseudomallei, is increasingly reported in Cambodia. We hypothesized that implementation of an enhanced sputum testing protocol in a provincial hospital diagnostic microbiology laboratory would increase detection of B. pseudomallei. We tested 241 sputum specimens that were deemed acceptable for culture, comparing culture in selective enrichment broth followed by sub-culture on Ashdown’s medium to standard culture methods. Two specimens (0.8%) were positive for B. pseudomallei using the enhanced protocol whereas one specimen (0.4%) was positive using standard methods. These findings demonstrate that B. pseudomallei is rarely detected in sputum at this hospital. The low frequency of B. pseudomallei in sputum specimens precludes drawing any conclusions about the relative benefits of an enhanced sputum testing protocol at this site. Promoting clinician awareness of the infection and encouraging utilization of diagnostic microbiology services are likely to be important factors in facilitating identification of melioidosis.