Rapid detection of extended-spectrum beta-lactamase-producing Gram-negative bacilli in blood cultures.
OBJECTIVE
Conventional detection of extended-spectrum beta-lactamase (ESBL) producers in blood cultures usually requires overnight incubation. This could delay the prescribing of appropriate therapy. We evaluated whether the chromogenic cephalosporin HMRZ-86, which is hydrolysed by ESBLs, could be used for the rapid detection of ESBL producers directly in blood culture broths.


METHODS
The HMRZ-86 test was first applied to broth cultures of isolates producing known beta-lactamases. A colour change indicating hydrolysis, which was inhibited by clavulanic acid, was taken as an indication of ESBL production. A similar method was used for testing blood culture supernatants and broth subcultures of blood cultures.


RESULTS
The HMRZ-86 test detected all the ESBL producers among 83 clinical isolates and control strains. Only one false positive was seen. The usefulness of HMRZ-86 for the direct testing of blood culture broths was limited by the presence of lysed blood. However, by using a 2 h broth subculture of the blood culture broths, the HMRZ-86 test was able to detect all those blood cultures containing an ESBL producer. No false positive or negative tests occurred according to the results of our standard phenotypic tests.


CONCLUSIONS
The HMRZ-86 test is a simple and rapid method that can be used for detecting ESBL producers in blood cultures.
Jain
Sarjana
S
Department of Microbiology, City Hospital, Dudley Road, Birmingham B18 7QH, UK.
Andrews
Jenny
J
Fraise
Adam
A
Brenwald
Nigel
N
D000900:Anti-Bacterial Agents / Q000378:metabolism*; D001769:Blood / Q000382:microbiology*; D002511:Cephalosporins; D019818:Clavulanic Acid / Q000494:pharmacology; D003116:Color; D003470:Culture Media; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005189:False Positive Reactions; D006090:Gram-Negative Bacteria / Q000187:drug effects / Q000201:enzymology*; D016905:Gram-Negative Bacterial Infections / Q000382:microbiology; D006801:Humans; D006868:Hydrolysis; D065093:beta-Lactamase Inhibitors; D001618:beta-Lactamases / Q000032:analysis* / Q000096:biosynthesis
D000900:Anti-Bacterial Agents; D002511:Cephalosporins; D003470:Culture Media; D004791:Enzyme Inhibitors; C487639:HMRZ 86; D065093:beta-Lactamase Inhibitors; D019818:Clavulanic Acid; D001618:beta-Lactamases