Identification of Plasmid-Mediated AmpC β-Lactamases in Escherichia coli , Klebsiella spp., and Proteus Species Can Potentially Improve Reporting of Cephalosporin Susceptibility Testing Results

Abstract

The goal of this study was to determine if the interpretations of extended-spectrum and advanced-spectrum cephalosporins (ESCs and ASCs, respectively) for isolates of Enterobacteriaceae would be impacted by the results of aminophenylboronic acid (APBA) testing. Fifty-three isolates of Escherichia coli, 21 Klebsiella species, and 6 Proteus species that were resistant to at least one ESC were tested by disk diffusion with ceftazidime and cefotetan disks with and without APBA. Ceftazidime disks with and without clavulanic acid (CLAV) were also tested to confirm extended-spectrum ␤-lactamase (ESBL) carriage. Twenty-nine (36.3%) isolates were only APBA test positive, 27 were only CLAV test positive, 2 were positive with both substrates, and 22 were negative with both substrates. Thirteen (41.9%) of the 31 APBA-test-positive isolates (all E. coli) tested susceptible to cefotaxime, ceftriaxone, or ceftazidime. Since clinical data suggest that AmpC-producing isolates should be reported as resistant to all ESCs, APBA testing can be helpful in identifying such organisms. Screening for AmpC-producing organisms using nonsusceptibility to cefoxitin and amoxicillin-clavulanate was less specific than APBA testing; it identified ESBL as well as AmpC-producing organisms. Only 18 of 31 APBA-positive isolates were positive by PCR for an AmpC ␤-lactamase gene. Thus, testing with APBA could improve the accuracy of reporting ESCs, especially for E. coli. However, results of APBA and CLAV testing did not correlate well for isolates containing both AmpC ␤-lactamases and ESBLs. Thus, additional data are needed before formal recommendations can be made on changing the reporting of ASC test results.

Phenotypic and molecular characterization of CTX-M-14 extended-spectrum β-lactamase and plasmid-mediated ACT-like AmpC β-lactamase produced by Klebsiella pneumoniae isolates from chickens in Henan Province, China

“…Recently, genotypes and subtypes of ESBL-producing and AmpC β-lactamase-producing have been reported from several different countries: TEM-1-and SHV-11 β-lactamase-producing K. pneumoniae strains were isolated from Switzerland (Lartigue et al, 2007); CTX-M-14 ESBL-producing K. pneumoniae and Enterobacter cloacae strains were isolated from Egypt (Khalaf et al, 2009); CTX-M-15 ESBL-, TEM-1-, and SHV-11 β-lactamase-producing K. pneumoniae strains were reported in Iran (Feizabadi et al, 2010); ACT-1 AmpC-producing K. pneumoniae strains were first reported in America (Bradford et al, 1997); ACT-1 and FOX-5 AmpC-producing K. pneumoniae strains were isolated from America (Coudron et al, 2003), and ACT-3 AmpC-producing K. pneumoniae strains were isolated from China (Chen et al, 2009). SHV-type ESBL-producing K. pneumoniae strains and ACT-1-type AmpC-producing K. pneumoniae strains were isolated from New Jersey (Queenan et al, 2004); TEM-and SHV-type ESBL-producing K. pneumoniae strains and ACT-1-type AmpC-producing K. pneumoniae strains were isolated from the United States (Tenover et al, 2009). Pathogens producing ESBLs and transferable AmpC β-lactamases are an increasing cause of concern in veterinary medicine.…”

Prevalence of co-existence genes and clonal spread of ESBL-producing isolates causing hospital and community-acquired infections in Zenica-Doboj Canton, Bosnia and Herzegovina

“…strains resistant to expanded-spectrum cephalosporins, cefoxitin, and beta-lactam combinations with inhibitors were screened for the production of AmpC beta-lactamase. Production of AmpC beta-lactamase was tested by combined disk test using 3-amino phenylboronic acid (PBA) (15).…”

“…Multiplex PCR with primers specific for MOX, CMY, DHA, ACT, MIR, and FOX βlactamases was used to detect plasmid-mediated Amp β-lactamases in strains resistant to cefoxitin and β-lactam/inhibitor combinations (15).…”

Epidemiology of Extended-Spectrum ^|^beta;-Lactamase, AmpC, and Carbapenemase Production in Proteus mirabilis

“…The various types of P. mirabilis infections are difficult to treat because of simultaneous production of enzymes, such as extended-spectrum b-lactamases (ESBLs), AmpC, and carbapenemases (1)(2)(3).…”