Degree Name

PhD (Doctor of Philosophy)

Program

Biomedical Sciences

Date of Award

May 1995

Abstract

Moraxella (Branhamella) catarrhalis is the third-most-frequently isolated microorganism associated with acute exacerbations of chronic bronchitis in patients during their stay at the Mountain Home VA Medical Center (MHVAMC). In order to develop a practical, epidemiologically-meaningful typing method for M. (B.) catarrhalis, we tested two methods based on analysis of chromosomal DNA for typeability, reproducibility, and ability to differentiate between unrelated strains (discriminatory power, D). M. (B.) catarrhalis isolants from MHVAMC from 7/1/87-6/30/88 were grown overnight in broth and embedded in agarose. DNA was isolated by standard methods. The DNA was subjected to: (1) restriction endonuclease digestion (with either Bgl II or Pme I) followed by pulsed-field gel electrophoresis (PFGE) and (2) restriction endonuclease digestion (with Hae III), followed by horizontal gel electrophoresis, Southern transfer and hybridization with a M. (B.) catarrhalis-specific DNA probe (M46). Reliable and reproducible patterns were produced from 144 of 159 isolants (91%) using Hae III, 155 of 159 (97%) using Pme I, and all isolants using Bgl II. Three clusters of isolants, Groups A (n = 18), B (n = 18), and C (n = 12) were detected. Within each group, isolants were identical by all typing methods tested. Chart review revealed no apparent epidemiologic link for Group A, while in Group B, 16 of 18 patients were housed on two wards, and in Group C, all cases occurred within two months, suggesting epidemiologic links within Groups B and C. Comparisons of results from isolants from various wards and isolants from outpatients were used to determine D of each method. Digestion with Pme I followed by PFGE was the most discriminating technique (D = 0.978) followed by Bgl II with PFGE (D = 0.962), then M46 probe hybridization (D = 0.929). The restriction endonucleases Pme I and Bgl II were highly discriminating and useful in the epidemiologic typing of M. (B.) catarrhalis. While useful, the M46 probe following Hae III digestion was not as discriminating.

Document Type

Dissertation - unrestricted

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