No abstract

No abstract

Twelve hundred enterobacterial Escherichia coli isolates of porcine origin were screened phenotypically for antibiotic resistance. The bacteria were isolated from 10 herds of swine with different histories of exposure to antimicrobial agents for therapeutic purposes. The bacterial isolates were part of the normal bacterial flora of the intestines of the animals because they were isolated from healthy individuals. The strains were tested for phenotypic antibiotic resistance against sulfonamides, trimethoprim, streptomycin, ampicillin, neomycin, chloramphenicol, and tetracycline. Resistance against streptomycin was found to be most common, followed by resistance against sulfonamides and tetracycline. The highest number of resistant bacteria was found in herds where the use of antimicrobial agents was considered to be high. A selection of multiresistant bacterial isolates were further genetically characterized by hybridization with probes specific for the antibiotic resistance genes; sulI, sulII, dfrI, dfrIIb, dfrIX, and the class A, B, C, and D tetracycline resistance determinants. A PCR was developed and used for detection of the strA-strB gene pair encoding streptomycin resistance in gram-negative bacteria. The strA-strB gene pair was the most frequent resistance determinant in the isolates examined. This study indicates that nonpathogenic E. coli from swine may represent a considerable reservoir of antibiotic resistance genes that might be transferable to pathogens.

No abstract

This investigation was initiated as a consequence of several cases of diarrhea in a nursery ward for preterm babies in Nairobi, Kenya. Ten lactose-positive colonies were isolated from the stools of each of 30 neonates, regardless of whether they had diarrhea; 229 strains were identified as Escherichia coli and 65 strains were identified as Klebsiella pneumoniae. Six strains were lost during laboratory handling. No other bacterial, viral, or parasitic enteropathogens were identified. Using synthetic alkaline phosphatase-labeled probes, the bacterial isolates were found to be negative for the presence of genes coding for heat-stable and heat-labile enterotoxins. Seventy-eight E. coli strains isolated from a total of 13 neonates possessed the E. coli enteropathogenic adhesion factor (EAF) gene, as demonstrated by the use of a cloned radiolabeled DNA fragment probe. These strains possessed similar plasmid profiles constituting a core plasmid profile, and while all adhered to HeLa cells, none produced Vero cell cytotoxins. The EAF gene was located on a 65-megadalton plasmid. Serotyping showed the strains to be of serogroup 0111 and serotype H nontypable, a well known enteropathogenic type. Five neonates died during the outbreak, and the fatality rate was 30.7% (4 of 13) for neonates infected with EAF-positive E. coli strains compared with 7.7% (1 of 13) for neonates from whom only EAF-negative E. coli strains were isolated. K. pneumoniae only was isolated from five neonates.