Detection of $\beta$-lactamase was performed by the Masuda Test, the Double Disc Synergy Test (DDST), and a novel test developed during the course of this work for ESBL as follows: Serial dilutions of antibiotics against which enzyme activity is to be demonstrated are incorporated into Mueller-Hinton agar containing methylumbeliferyl-$\beta$-D-glucuronide (MUG) 70 $\mu$g/mL. Growth of Escherichia coli on this medium gives fluorescence but growth of K. pneumoniae does not. These plates are seeded with an E. coli lawn and K. pneumoniae strains are spot inoculated by Steers Replicator onto the lawn. At antibiotic concentrations above the MIC of E. coli, fluorescence on the lawn is inhibited. On the same plates, satellite growth of E. coli occurs around enzyme-producing K. pneumoniae isolates and this is manifested as a ring of fluorescence. The incorporation into the medium of clavulanic acid indicates if the enzyme is neutralized. In the Series I the K. pneumoniae isolates positive by DDST were also positive by the satellite fluorescence test. None of the isolates were positive by DDST and negative by fluorescence testing. Conclusions are (1) Routine susceptibility tests do not detect ESBL in K. pneumoniae isolates which may be clinically important. (2) The satellite fluorescence test is a more sensitive test than the DDST. (3) This fluorescence test is a convenient, flexible, and sensitive test for screening ESBL production in K. pneumoniae isolates. (4) A small number of K. pneumoniae isolates in Ottawa show a decreased susceptibility to third generation $\beta$-lactams with evidence of enzyme degradation but are susceptible by zone diameter measurements. (Abstract shortened by UMI.)
| Identifer | oai:union.ndltd.org:uottawa.ca/oai:ruor.uottawa.ca:10393/9978 |
| Date | January 1995 |
| Creators | Ferris, Wendy. |
| Contributors | Mackenzie, Andrew M. R., |
| Publisher | University of Ottawa (Canada) |
| Source Sets | Université d’Ottawa |
| Detected Language | English |
| Type | Thesis |
| Format | 149 p. |
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