Detection, Isolation, and Molecular Characterization of Escherichia albertii from Wild Birds in West Japan.

Escherichia albertii is an emerging zoonotic foodborne pathogen. Several outbreaks of E. albertii have occurred, particularly in Japan. Although birds have been considered as one of the most important reservoirs of this bacterium, information regarding its prevalence in birds is still scarce. We performed a survey of E. albertii in wild birds in Japan and examined the characteristics of these isolates. E. albertii-specific genes were detected in five cloacal swabs from 156 birds by PCR. Four E. albertii strains were isolated from a swallow with two different E. albertii strains and two pigeons in a flock using XRM-MacConkey agar. These isolates were assigned to biogroup 3, showed no resistance to any tested antimicrobials, and were classified into two EAO-genotypes (EAOg2 and EAOg33) and were untypable. Similar to clinical E. albertii strains, these isolates carried virulence genes, including eae (n = 4), paa (n = 4), Eccdt-I (n = 2), and stx2f (n = 1), as well as Eacdt. Furthermore, stx2f genes in a strain were located on an inducible bacteriophage, which can confer the ability to produce Stx2f in E. coli. In conclusion, Japanese wild birds carried E. albertii at levels similar to the reported prevalence in birds. These isolates may have the potential to cause gastroenteritis in humans.

Prevalence of Escherichia albertii in Raccoons (Procyon lotor), Japan.

Natural reservoirs of Escherichia albertii remain unclear. In this study, we detected E. albertii by PCR in 248 (57.7%) of 430 raccoons from Osaka, Japan, and isolated 143 E. albertii strains from the 62 PCR-positive samples. These data indicate that raccoons could be a natural reservoir of E. albertii in Japan.

Development of XRM-MacConkey agar selective medium for the isolation of Escherichia albertii.

Escherichia albertii has increasingly been recognized as an emerging pathogen. However, lack of selective medium for E. albertii is the bottleneck for clinical and epidemiological investigations. In this study, a selective medium for E. albertii named XRM-MacConkey agar, which is modified MacConkey agar supplemented with xylose (X), rhamnose (R), and melibiose (M) instead of lactose, was developed and evaluated. All 49 E. albertii and 6 different species out of 23 grew as colorless colonies, whereas 17 remaining species grew as red colonies. Detection limit of E. albertii by this medium was 105 CFU/g stool when examined with spiked healthy human stool. Furthermore, colorless colonies on XRM-MacConkey agar obtained from 7 E. albertii-positive diarrheal stools were consistently E. albertii. In contrast, 57%, 18%, and 36% colorless colonies on MacConkey, DHL, and mEA agars, respectively, were non-E. albertii. We concluded that XRM-MacConkey agar could specifically be used for isolation of E. albertii.