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Susceptibility of extended-spectrum-beta-lactamase-producing Enterobacteriaceae according to the new CLSI breakpoints.

ABSTRACT: In 2010 the Clinical and Laboratory Standards Institute (CLSI) lowered the susceptibility breakpoints of some cephalosporins and aztreonam for Enterobacteriaceae and eliminated the need to perform screening for extended-spectrum ?-lactamases (ESBLs) and confirmatory tests. The aim of this study was to determine how many ESBL-producing strains of three common species of Enterobacteriaceae test susceptible using the new breakpoints. As determined with the CLSI screening and confirmatory tests, 382 consecutive ESBL-producing strains were collected at Huashan Hospital between 2007 and 2008, including 158 strains of Escherichia coli, 164 of Klebsiella pneumoniae, and 60 of Proteus mirabilis. Susceptibility was determined by the CLSI agar dilution method. CTX-M-, TEM-, and SHV-specific genes were determined by PCR amplification and sequencing. bla(CTX-M) genes alone or in combination with bla(SHV) were present in 92.7% (354/382) of these ESBL-producing strains. Forty-two (25.6%) strains of K. pneumoniae harbored SHV-type ESBLs alone or in combination. No TEM ESBLs were found. Utilizing the new breakpoints, all 382 strains were resistant to cefazolin, cefotaxime, and ceftriaxone, while 85.0 to 96.7% of P. mirabilis strains tested susceptible to ceftazidime, cefepime, and aztreonam, 41.8 to 45.6% of E. coli strains appeared to be susceptible to ceftazidime and cefepime, and 20.1% of K. pneumoniae were susceptible to cefepime. In conclusion, all ESBL-producing strains of Enterobacteriaceae would be reported to be resistant to cefazolin, cefotaxime, and ceftriaxone by using the new CLSI breakpoints, but a substantial number of ESBL-containing P. mirabilis and E. coli strains would be reported to be susceptible to ceftazidime, cefepime, and aztreonam, which is likely due to the high prevalence of CTX-M type ESBLs.

SUBMITTER: Wang P

PROVIDER: S-EPMC3165602 | biostudies-literature | 2011 Sep

REPOSITORIES: biostudies-literature

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Susceptibility of extended-spectrum-beta-lactamase-producing Enterobacteriaceae according to the new CLSI breakpoints.

Wang Peng P Hu Fupin F Xiong Zizhong Z Ye Xinyu X Zhu Demei D Wang Yun F YF Wang Minggui M

Journal of clinical microbiology 20110713 9

In 2010 the Clinical and Laboratory Standards Institute (CLSI) lowered the susceptibility breakpoints of some cephalosporins and aztreonam for Enterobacteriaceae and eliminated the need to perform screening for extended-spectrum β-lactamases (ESBLs) and confirmatory tests. The aim of this study was to determine how many ESBL-producing strains of three common species of Enterobacteriaceae test susceptible using the new breakpoints. As determined with the CLSI screening and confirmatory tests, 382 ...[more]

PMID: 21752977

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Project description:Plasmid-mediated AmpC beta-lactamase-producing (pAmpC) Enterobacteriaceae are increasing worldwide, difficult to identify and often confounded with extended-spectrum beta-lactamase (ESBL) producers. The low prevalence precludes routine universal admission screening. Therefore, we evaluated potential risk factors for carriage of pAmpC-producing Enterobacteriaceae that would allow targeted screening to improve yield and reduce cost.We performed a case control study at a tertiary care center from 1/2006 to 12/2010. Cases were adult patients in whom pAmpC-producing Enterobacteriaceae were isolated; controls were chosen among carriers of ESBL-producing Enterobacteriaceae. Both infected and colonized patients were included.Over five years, we identified 40 pAmpC producers in 39 patients among 16,247 screened consecutive isolates of Enterobacteriaceae. The pAmpC prevalence was low (0.25%), but more than 30% of pAmpC carriers received incorrect empirical antibiotic treatment. When compared with 39 ESBL controls, pAmpC carriage was associated with clinically confirmed infections in 74% (versus 51%) (p=0.035), mainly of the urinary tract, previous antibiotic exposure in 63% (versus 36%) (p=0.035) and carriage of a nasogastric tube in 23% (versus 0%) (p=0.002). In the multivariate regression analysis only clinically confirmed infections remained significantly associated with pAmpC carriage (OR 1.44 (95%CI 1.15-2.57)). No other clinical and blood test-associated risk factor allowed discrimination of pAmpC-carrying patients from ESBL controls. The type of acquisition - nosocomial versus community-acquired - was also non-informative for resistance type, as 46% of pAmpC- and 44% of ESBL-producing Enterobacteriaceae were community-acquired.This study could not identify a clinical profile that would allow targeted screening for pAmpC-producing Enterobacteriaceae when compared to ESBL carriers. Because empiric antimicrobial therapy was inappropriate in more than 30%, rapid identification of pAmpC carriers is needed. New microbiological methods are therefore required to simplify rapid and reliable detection of pAmpC carriers.

Dataset Information

Susceptibility of extended-spectrum-beta-lactamase-producing Enterobacteriaceae according to the new CLSI breakpoints.

Publications

Susceptibility of extended-spectrum-beta-lactamase-producing Enterobacteriaceae according to the new CLSI breakpoints.

Similar Datasets

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