Chromosomal Restriction Endonuclease Analysis Research Articles

Chromosomal restriction endonuclease analysis and ribotyping of Bacteroides fragilis

We have analysed the restriction fragment length patterns of chromosomal DNA and of ribosomal RNA (rRNA) genes in order to investigate the clonal distribution within Bacteroides fragilis isolates. Eighteen blood culture isolates from 18 patients and 4 faecal isolates from 4 subjects were examined. Chromosomal restriction endonuclease analysis (REA) was performed by separating BamHI-generated DNA fragments using polyacrylamide gel electrophoresis (PAGE). Ribotyping was accomplished by hybridizing EcoRI-treated genomic DNA subjected to conventional REA on agarose to a radiolabelled probe obtained from 16+23S rRNA of E. coli. All 22 isolates could be differentiated by their REA patterns with a varying percentage of similar fragments. Analysis of the rRNA gene patterns displayed heterogeneity, and revealed 14 ribotypes among the 18 blood culture isolates and 3 among the 4 faecal isolates. The predominant ribotype among the clinical isolates was also shared by one faecal isolate. The results suggest that no particular clones are predominantly responsible for systemic infection.

Epidemiologic typing of Enterobacter sakazakii in two neonatal nosocomial outbreaks

Two unrelated hospital outbreaks of Enterobacter sakazakii, involving meningitis, bacteremia, and colonization of neonates, were investigated. In each of these outbreaks, E. sakazakii was isolated from both patients and dried infant formula. In previous outbreaks, the source and mode of transmission of E. sakazakii in neonatal infections was not determined. In this study, we used a combination of typing methods (plasmid analysis, antibiograms, chromosomal restriction endonuclease analysis, ribotyping, and multilocus enzyme electrophoresis) to evaluate the isolates from each outbreak as to their relatedness. The typing results differed among outbreaks, but in each one, patient and formula isolates shared the same typing pattern. The only exceptions were disk antibiograms, which often varied among colonies selected from each of the isolates. Plasmid analysis, chromosomal restriction endonuclease analysis, ribotyping, and multilocus enzyme electrophoresis all were effective as epidemiological typing methods for E. sakazakii, especially when used in combination. By using this typing scheme, we have confirmed that E. sakazakii from intrinsically contaminated dried infant formula was the source of neonatal infection.

Nosocomial Clostridium difficile colonisation and disease

To assess the risk of acquiring Clostridium difficile diarrhoea or colitis in patients colonised with C difficile, rectal swabs taken weekly for 9 weeks from patients with long-term (at least 7 days) hospital stays on three wards were cultured for C difficile. 60 (21%) of 282 patients were culture-positive for C difficile during their hospital stay, of whom 51 were symptom-free faecal excretors. C difficile diarrhoea developed in the other 9 patients; 2 were culture-positive for C difficile and had diarrhoea at the time of first culture, and 7 had diarrhoea or pseudomembranous colitis after 1-6 previously negative weekly rectal cultures. All patients with diarrhoea were on one ward, but symptom-free, excretors were found on all wards. HindIII chromosomal restriction endonuclease analysis (REA) of the C difficile isolates revealed 18 distinct types. All isolates from the patients with diarrhoea were one of two nearly identical REA types, B or B2. 26 of the 29 total B/B2 isolates were from patients on the same ward, which points to a nosocomial outbreak. The symptom-free excretors were not at increased risk of subsequent clinical illness.

Antibiotic and toxicant susceptibility profiles of clinical and environmental Klebsiella pneumoniae isolates

AbstractKlebsiella pneumoniae strains isolated from different clinical and environmental sources were examined for resistance to antibiotics, pentachlorophenol, and heavy metals using intracellular ATP measurements. Resistance to kanamycin, neomycin, gentamicin, and tobramycin was noted for the hospital strain but not for the environmentally derived isolates. On the other hand, strains isolated from pulp and paper mill effluents and receiving waters exhibited a higher degree of pentachlorophenol and heavy metal resistance. Chromosomal restriction endonuclease analysis (REA) digests of three environmental strains produced patterns that were different and readily distinguishable. Plasmids were detectable in these same environmental isolates; two of the three carried a 70 × 106 Da plasmid that is thought to mediate both antibiotic and heavy metal resistance.

Evaluation of restriction endonuclease analysis as an epidemiologic typing system for Branhamella catarrhalis

Restriction endonuclease analysis (REA) was evaluated as an epidemiologic typing tool to distinguish Branhamella catarrhalis strains. Fourteen beta-lactamase-producing strains were collected over a 16-month period at a hospital where a nosocomial outbreak of this organism was previously documented by REA. REA produced 12 distinct patterns which correlated with epidemiologic data. Chromosomal REA appears to be a useful technique for distinguishing B. catarrhalis strains.

Investigation of a Campylobacter jejuni outbreak by serotyping and chromosomal restriction endonuclease analysis.

Fifty Campylobacter jejuni isolates, including 29 from humans associated with an outbreak of enteritis, 20 from cattle, and 1 from a milk source, were serotyped on the basis of extractable thermostable antigens and examined by bacterial chromosomal restriction endonuclease digest analysis. Serotyping showed specific differences between the human isolates and the milk isolates, but each of these generally, although not consistently, reacted with 4 of the 42 C. jejuni typing antisera. Restriction patterns of all of the human isolates and some of the cattle isolates were indistinguishable, confirming the suspected link between the cattle and the human outbreak. The single milk isolate had a restriction pattern unlike those of the human isolates, and therefore its involvement in the transmission of infection from the cattle to the humans could not be confirmed.