Dataset Information

An Improved Extended-Spectrum-?-Lactamase Detection Test Utilizing Aztreonam plus Clavulanate.

ABSTRACT: Clinical laboratories test for extended-spectrum ?-lactamases (ESBLs) for epidemiological and infection control purposes and also for the potential of cephalosporins to cause therapeutic failures. Testing can be problematic, because the CLSI does not recommend the testing of all producers of ESBLs and also falsely negative results may occur with isolates that coproduce AmpC. Boronic acid-supplemented tests can enhance ESBL detection in AmpC producers. Because aztreonam inhibits AmpCs, a study was designed to compare ESBL detection by the CLSI disk test (CLSI), a boronic acid-supplemented CLSI disk test (CLSI plus BA), and an aztreonam plus clavulanate disk test (ATM plus CA). The study tested 100 well-characterized Enterobacteriaceae, Acinetobacter baumannii, and Pseudomonas aeruginosa isolates. Seventy produced TEM, SHV, or CTX-M ESBLs, with 15 coproducing an AmpC and 11 coproducing a metallo-?-lactamase. Thirty ESBL-negative isolates were also tested. Tests were inoculated by CLSI methodology and interpreted as positive if an inhibitor caused a zone diameter increase of ?5 mm. The percentages of ESBL producers detected were as follows: ATM plus CA, 95.7%; CLSI plus BA, 88.6%; and CLSI, 78.6%. When AmpC was coproduced, the sensitivities of the tests were as follows: ATM plus CA, 100%; CLSI plus BA, 93.3%; and CLSI, 60%. ATM plus CA also detected an ESBL in 90.1% of isolates that coproduced a metallo-?-lactamase. Falsely positive tests occurred only with the CLSI and CLSI plus BA tests. Overall, the ATM plus CA test detected ESBLs more accurately than the CLSI and CLSI plus BA tests, especially with isolates coproducing an AmpC or metallo-?-lactamase.

SUBMITTER: Thomson GK

PROVIDER: S-EPMC5744226 | biostudies-literature | 2018 Jan

REPOSITORIES: biostudies-literature

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An Improved Extended-Spectrum-β-Lactamase Detection Test Utilizing Aztreonam plus Clavulanate.

Thomson Gina K GK Ayaz Maaz M Lutes Kelli K Thomson Kenneth S KS

Journal of clinical microbiology 20171226 1

Clinical laboratories test for extended-spectrum β-lactamases (ESBLs) for epidemiological and infection control purposes and also for the potential of cephalosporins to cause therapeutic failures. Testing can be problematic, because the CLSI does not recommend the testing of all producers of ESBLs and also falsely negative results may occur with isolates that coproduce AmpC. Boronic acid-supplemented tests can enhance ESBL detection in AmpC producers. Because aztreonam inhibits AmpCs, a study wa ...[more]

PMID: 29046407

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Project description:Metallo-β-lactamase (MBL)-producing Gram-negative bacteria are often extremely resistant, leading to a real therapeutic dead end. Here, we evaluated the in vitro and in vivo efficacy of aztreonam in combination with ceftazidime-avibactam, ceftolozane-tazobactam, or amoxicillin-clavulanate for the treatment of infections caused by MBL-producing Enterobacteriaceae, MBL-producing Pseudomonas aeruginosa, and extremely drug-resistant Stenotrophomonas maltophilia First, we report two clinical cases, namely, a urinary tract infection caused by an NDM-5-producing Escherichia coli isolate and a pulmonary infection caused by a S. maltophilia isolate efficiently treated with the association of aztreonam-ceftazidime-avibactam and aztreonam-amoxicillin-clavulanate, respectively. Then, a total of 50 MBL-producing Enterobacteriaceae isolates, 3 MBL-producing P. aeruginosa isolates, and 5 extremely drug-resistant S. maltophilia isolates were used to test aztreonam susceptibility in combination with ceftolozane-tazobactam, ceftazidime-avibactam, or amoxicillin-clavulanate. The Etest strip superposition method was used to determine the MICs of the aztreonam/inhibitor combinations. According to CLSI breakpoints, aztreonam susceptibility was fully restored for 86%, 20%, and 50% of the MBL-producing Enterobacteriaceae isolates when combined with ceftazidime-avibactam, ceftolozane-tazobactam, and amoxicillin-clavulanate, respectively. In P. aeruginosa, the aztreonam-ceftazidime-avibactam combination was the most potent, even though the reduction in MICs was at most 2-fold. With the 5 S. maltophilia isolates, aztreonam-ceftazidime-avibactam and aztreonam-amoxicillin-clavulanate were found to be equal (100% susceptibility). Overall, aztreonam-ceftazidime-avibactam was the most potent combination to treat infections caused by MBL producers compared with aztreonam-amoxicillin-clavulanate and aztreonam-ceftolozane-tazobactam. However, in many cases aztreonam-amoxicillin-clavulanate was found to be as efficient as aztreonam-ceftazidime-avibactam, offering the main advantage to be markedly cheaper. We also confirmed the validity of Etest superpositions as a very simple method to determine MICs of aztreonam combinations.

Dataset Information

An Improved Extended-Spectrum-?-Lactamase Detection Test Utilizing Aztreonam plus Clavulanate.

Publications

An Improved Extended-Spectrum-β-Lactamase Detection Test Utilizing Aztreonam plus Clavulanate.

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