THE CLINICAL-SIGNIFICANCE OF ESCHERICHIA-COLI ALKALESCENS-DISPAR IN TASMANIA

An investigation in 1989 of human fecal specimens revealed that of 111 diarrheal samples examined Escherichia coli Alkalescens-Dispar (A-D) were found in 9 (8.1%), but none were isolated from normal stool sampl es. Further studies have shown that although these isolates may be pot ential pathogens, they seem to remain unrecognized by routine laborato ries due to their biochemical similarity to shigellae, a problem furth er exacerbated by their extensive sharing of O antigens. All the isola tes were screened with an invasive DNA probe and all but three isolate s were found to have a common plasmid. They were also confirmed to be invasive in HEp-2 monolayers. No isolates were shown to produce heat-l abile or heat-stable toxin but electronmicroscopy revealed the presenc e of pili. The A-D isolates were biotyped using the two-tier schema of Crichton and Old and were categorized into biotypes 11, 12 and 16. Th ese data confirm the importance of introducing an awareness of this in termediate strain into routine laboratories.