In vitro activities of various beta-lactam antimicrobial agents against clinical isolates of Escherichia coli and Klebsiella spp. resistant to oxyimino cephalosporins

Jett, Bradley D.; Ritchie, David J.; Reichley, Richard M.; Bailey, Thomas C.; Sahm, Daniel F.

doi:10.1128/aac.39.5.1187

Cited by 52 publications

(36 citation statements)

References 37 publications

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“…Maximum isolates of K.pneumoniae (75.6%) were resistance to ampicillin as comparable with other studies [24]. Cephalosporins, particularly second and third generation have been used to treat Klebsiella pneumoniae infections [25]. Low resistance to second and third generation cephalosporins (63.4%) is seen in our studies compared to (84%) other reports [26].…”

Section: Discussionsupporting

confidence: 69%

Antibiotic Susceptibility Pattern of ESβL Producing Klebsiella pneumoniae Isolated from Urine Samples of Pregnant Women in Karnataka

Nagshetty

Gaddad

et al. 2014

JCDR

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Background: Klebsiella pneumoniae possess a new problem to health care professionals worldwide, which complicates and limits therapeutic options. It is one of the leading nosocomial bacterial pathogens, and the present study aims to determine the prevalence of ESβL producing K. pneumoniae isolates with their antibiotic susceptibility pattern in urine samples of the pregnant women with UTI. Materials and Methods:Using standard isolation and identification procedures a total of 41 isolates were obtained from 417 midstream urine samples of pregnant women with suspected UTI in Karnataka. The antibiotic resistance profile of each isolate was performed by Kirby-Bauer disc diffusion method and ESβL production by standard phenotypic method.Results: Isolation rate of K. pneumoniae in pregnant women was 19.9% and overall incidence rate was 9.8%. Among the 41 K.

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Section: Discussionsupporting

confidence: 69%

Antibiotic Susceptibility Pattern of ESβL Producing Klebsiella pneumoniae Isolated from Urine Samples of Pregnant Women in Karnataka

Nagshetty

Gaddad

et al. 2014

JCDR

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“…However, inoculum effects in ESBL-producing Klebsiella spp. have been reported for cefepime both in vitro and in vivo (12,29), and they could be due, at least in part, to the hydrolysis of this drug by ESBLs.…”

Section: Discussionmentioning

confidence: 99%

“…It has been observed that an increase in inoculum size can be correlated with an increase in ␤-lactam MICs and a decrease in efficacy in vivo (11,12,29,30). Factors that could contribute to these effects are the number, type, and amount of ␤-lactamases; outer membrane permeability; efflux; number and susceptibility of penicillin-binding protein targets; and phase of growth.…”

Section: Discussionmentioning

confidence: 99%

Effects of Inoculum and β-Lactamase Activity in AmpC- and Extended-Spectrum β-Lactamase (ESBL)-Producing Escherichia coli and Klebsiella pneumoniae Clinical Isolates Tested by Using NCCLS ESBL Methodology

et al. 2004

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Escherichia coli and Klebsiella pneumoniae isolates with extended-spectrum ␤-lactamases (ESBLs) or AmpC cephalosporinases generally respond as predicted to NCCLS tests for ESBL production. However, inoculum size may affect MICs. The effect of inoculum level in clinical isolates expressing ␤-lactamases were studied at inocula within 0.5 log unit of the standard inoculum, using broth microdilution methodology with ceftazidime, cefotaxime, cefepime, cefpodoxime, and aztreonam. Strains with TEM-1 or no ␤-lactamases gave consistent MIC results with inocula of 10 5 and 10 6 CFU/ml. When the bacteria were screened for ESBL production and the lower inoculum was used, several strains with ESBLs, including CTX-M-10, TEM-3, TEM-10, TEM-12, TEM-6, SHV-18, and K1, gave false-negative results for one or more antimicrobial agents (MICs below the NCCLS screening concentration for detecting suspected ESBLs). When the higher inoculum was used, MICs of at least one antimicrobial agent increased at least fourfold in strains producing TEM-3, TEM-10, TEM-28, TEM-43, SHV-5, SHV-18, and K1. All antimicrobial agents showed an inoculum effect with at least one ESBL producer. Confirmatory clavulanate effects were seen for both inocula for all ESBL-producing strains with all antimicrobial agents tested, except for the CTX-M-10-producing E. coli with ceftazidime and the SHV-18-producing K. pneumoniae with cefotaxime. In kinetic studies, cefpodoxime and cefepime were hydrolyzed by ESBLs in a manner similar to that of cefotaxime. When total ␤-lactamase activity and hydrolysis parameters were evaluated, however, no single factor was predictive of inoculum effects. These results indicate that the NCCLS screening and confirmation tests are generally predictive of ESBL production, but false-negative results can arise when a lower inoculum is used in testing.Extended-spectrum ␤-lactamases (ESBLs) are considered one of the most important resistance mechanisms for penicillins and cephalosporins when these enzymes are produced in Escherichia coli and Klebsiella spp. (7). The genes encoding these enzymes are most often carried by multidrug-resistant plasmids and are capable of being readily transferred among different species of the family Enterobacteriaceae (2). Infections caused by ESBL-producing pathogens may not be responsive to treatment by most penicillins and cephalosporins (32). Hence, their appearance in a hospital setting creates a situation in which ESBL-producing organisms should be identified quickly so that appropriate antibiotic usage and containment measures can be implemented (21).Clinical microbiologists have devised a number of testing strategies based on phenotypic testing to identify putative ESBL-producing organisms. One testing strategy is the recently adopted set of NCCLS guidelines for E. coli, Klebsiella pneumoniae, and Klebsiella oxytoca isolates with elevated cephalosporin MICs (16). In the protocol for MIC testing, strains with cefotaxime, ceftazidime, ceftriaxone, or aztreonam MICs of Ն2 g/ml or cefpodoxime MICs of Ն8 g/m...

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“…Another viewpoint is that the inoculum effect is important for ESBL-producing organisms and that the MIC alone may give erroneous information. In vitro, the MICs of cephalosporins rise as the inoculum of ESBL-producing organisms increases (184,244,344,391). For example, for a Klebsiella pneumoniae strain producing TEM-26, at an inoculum of 10 5 CFU/ml the cefotaxime MIC was 0.25 g/ml, rising to 64 g/ml when the inoculum rose to 10 7 CFU/ml (391).…”

Section: Need For Clinical Microbiology Laboratories To Detect Esbl Pmentioning

confidence: 99%

Extended-Spectrum β-Lactamases: a Clinical Update

2005

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SUMMARY Extended-spectrum β-lactamases (ESBLs) are a rapidly evolving group of β-lactamases which share the ability to hydrolyze third-generation cephalosporins and aztreonam yet are inhibited by clavulanic acid. Typically, they derive from genes for TEM-1, TEM-2, or SHV-1 by mutations that alter the amino acid configuration around the active site of these β-lactamases. This extends the spectrum of β-lactam antibiotics susceptible to hydrolysis by these enzymes. An increasing number of ESBLs not of TEM or SHV lineage have recently been described. The presence of ESBLs carries tremendous clinical significance. The ESBLs are frequently plasmid encoded. Plasmids responsible for ESBL production frequently carry genes encoding resistance to other drug classes (for example, aminoglycosides). Therefore, antibiotic options in the treatment of ESBL-producing organisms are extremely limited. Carbapenems are the treatment of choice for serious infections due to ESBL-producing organisms, yet carbapenem-resistant isolates have recently been reported. ESBL-producing organisms may appear susceptible to some extended-spectrum cephalosporins. However, treatment with such antibiotics has been associated with high failure rates. There is substantial debate as to the optimal method to prevent this occurrence. It has been proposed that cephalosporin breakpoints for the Enterobacteriaceae should be altered so that the need for ESBL detection would be obviated. At present, however, organizations such as the Clinical and Laboratory Standards Institute (formerly the National Committee for Clinical Laboratory Standards) provide guidelines for the detection of ESBLs in klebsiellae and Escherichia coli. In common to all ESBL detection methods is the general principle that the activity of extended-spectrum cephalosporins against ESBL-producing organisms will be enhanced by the presence of clavulanic acid. ESBLs represent an impressive example of the ability of gram-negative bacteria to develop new antibiotic resistance mechanisms in the face of the introduction of new antimicrobial agents.

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In vitro activities of various beta-lactam antimicrobial agents against clinical isolates of Escherichia coli and Klebsiella spp. resistant to oxyimino cephalosporins

Cited by 52 publications

References 37 publications

Antibiotic Susceptibility Pattern of ESβL Producing Klebsiella pneumoniae Isolated from Urine Samples of Pregnant Women in Karnataka

Antibiotic Susceptibility Pattern of ESβL Producing Klebsiella pneumoniae Isolated from Urine Samples of Pregnant Women in Karnataka

Effects of Inoculum and β-Lactamase Activity in AmpC- and Extended-Spectrum β-Lactamase (ESBL)-Producing Escherichia coli and Klebsiella pneumoniae Clinical Isolates Tested by Using NCCLS ESBL Methodology

Extended-Spectrum β-Lactamases: a Clinical Update

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