Antibiotic susceptibility pattern and identification of extended spectrum β-lactamases (ESBLs) in clinical isolates of Klebsiella pneumoniae from Shiraz, Iran

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Abstract

Background and Objectives:

Klebsiella pneumoniae, one of the important causes of nosocomial infections, is the most common extended spectrum β-lactamases (ESBLs) producing organism. ESBLs are defined as the enzymes capable of hydrolyzing oxyimino-cephalosporins, monobactams and carbapenems. The aims of this study were to identify ESBL-producing K. pneumoniae isolates and detect their antibiotic susceptibility pattern.

Materials and Methods:

This cross-sectional study was conducted from December 2012 to May 2013 in teaching hospitals in Shiraz. Clinical specimens from the urine, sputum, wound, blood, throat, and body fluids were isolated and identified as K. pneumoniae. Antibacterial susceptibility testing was performed for 14 antibiotics using disk diffusion method according to CLSI guidelines. Isolates showing resistant to at least one of the β-lactam antibiotics were then evaluated for production of β-lactamase enzymes using E-test ESBL and combined disk Method. Also, MICs for ceftazidime and imipenem were determined using E-test. The presence of the bla _SHV, bla _TEM, bla _PER and bla _CTX-M genes was assessed by PCR.

Results:

Of 144 K. pneumoniae isolates from different specimens, 38 (26.3 %) was identified as ESBL producer by phenotypic confirmatory test. All ESBL producing isolates were susceptible to imipenem and meropenem and resistant to aztreonam. The highest rate of resistance belonged to amoxicillin (100%), cefotaxime (50%) and gentamicin (42.3%) and the lowest rates were seen for meropenem (11.8%), imipenem and amikacin (both 15.9%). Sixty-two isolates had MICs≥ 4 μg/mL for ceftazidime, of which 38 were positive for ESBLs in phenotypic confirmatory tests (PCT). The prevalence of bla _SHV, bla _CTX-M, and bla _TEM genes among these isolates were 22.2%, 19% and 16%. bla _PER was not detected in the studied isolates.

Conclusions:

Due to the relatively high prevalence of ESBLs-producing K. pneumoniae isolates in the studied population, it seems that screening of infections caused by ESBL producers can lead to the most effective antibiotics therapies.

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Most cited references 16

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Extended-Spectrum β-Lactamases: a Clinical Update

David L. Paterson, Robert Bonomo (2005)

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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Resistance in gram-negative bacteria: enterobacteriaceae.

David L. Paterson (2006)

The emergence and spread of resistance in Enterobacteriaceae are complicating the treatment of serious nosocomial infections and threatening to create species resistant to all currently available agents. Approximately 20% of Klebsiella pneumoniae infections and 31% of Enterobacter spp infections in intensive care units in the United States now involve strains not susceptible to third-generation cephalosporins. Such resistance in K pneumoniae to third-generation cephalosporins is typically caused by the acquisition of plasmids containing genes that encode for extended-spectrum beta-lactamases (ESBLs), and these plasmids often carry other resistance genes as well. ESBL-producing K pneumoniae and Escherichia coli are now relatively common in healthcare settings and often exhibit multidrug resistance. ESBL-producing Enterobacteriaceae have now emerged in the community as well. Salmonella and other Enterobacteriaceae that cause gastroenteritis may also be ESBL producers, which is of relevance when children require treatment for invasive infections. Resistance of Enterobacter spp to third-generation cephalosporins is most typically caused by overproduction of AmpC beta-lactamases, and treatment with third-generation cephalosporins may select for AmpC-overproducing mutants. Some Enterobacter cloacae strains are now ESBL and AmpC producers, conferring resistance to both third- and fourth-generation cephalosporins. Quinolone resistance in Enterobacteriaceae is usually the result of chromosomal mutations leading to alterations in target enzymes or drug accumulation. More recently, however, plasmid-mediated quinolone resistance has been reported in K pneumoniae and E coli, associated with acquisition of the qnr gene. The vast majority of Enterobacteriaceae, including ESBL producers, remain susceptible to carbapenems, and these agents are considered preferred empiric therapy for serious Enterobacteriaceae infections. Carbapenem resistance, although rare, appears to be increasing. Particularly troublesome is the emergence of KPC-type carbapenemases in New York City. Better antibiotic stewardship and infection control are needed to prevent further spread of ESBLs and other forms of resistance in Enterobacteriaceae throughout the world.

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Contemporary assessment of antimicrobial susceptibility testing methods for polymyxin B and colistin: review of available interpretative criteria and quality control guidelines.

M Gales, Walton Jones, Celso Reis (2000)

The emergence of infections caused by multidrug-resistant Pseudomonas aeruginosa and Acinetobacter spp. has necessitated the search for alternative parenteral agents such as the polymyxins. The National Committee for Clinical Laboratory Standards (NCCLS) documents do not currently provide interpretative criteria for the testing of the polymyxins, colistin and polymyxin B. Therefore, an evaluation of the antimicrobial activity of colistin and polymyxin B was initiated using 200 bloodstream infection pathogens collected through the SENTRY Antimicrobial Surveillance Program. All susceptibility tests were performed according to the NCCLS recommendations. Polymyxin B and colistin displayed a nearly identical spectrum of activity, exhibiting excellent potency against P. aeruginosa (MIC(90), 2 microg/ml) and Acinetobacter sp. (MIC(90), 2 microg/ml). In contrast, they showed limited activity against some other nonfermentative bacilli such as Burkholderia cepacia (MIC(90), >/=128 microg/ml). Excellent correlation was achieved between broth microdilution and agar dilution tests (r = 0.96 to 0.98); 94.3% of the results were +/-1 log(2) dilution between the methods used for both compounds. At a resistance breakpoint of >/=4 microg/ml for both agents, unacceptable false-susceptible or very major errors were noted for colistin (5%) and polymyxin B (6%). Modified zone criteria for colistin ( /=14 mm) and polymyxin B ( /=14 mm) were suggested, but some degree of error persisted (>/=3.5%). It is recommended that all susceptible disk diffusion results be confirmed by MIC tests using the preferred reference NCCLS method. The quality control (QC) ranges listed in the product package insert require an adjusted range by approximately 3 mm for both NCCLS gram-negative quality control strains. This evaluation of in vitro susceptibility test methods for the polymyxin class drugs confirmed continued serious testing error with the disk diffusion method, the possible need for breakpoint adjustments, and the recalculation of disk diffusion QC ranges. Clinical laboratories should exclusively use MIC methods to assist the therapeutic application of colistin or polymyxin B until disk diffusion test modifications are sanctioned and published by the NCCLS.

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Author and article information

Journal

Journal ID (nlm-ta): Iran J Microbiol

Journal ID (iso-abbrev): Iran J Microbiol

Journal ID (publisher-id): IJM

Journal ID (pmc): IJM

Title: Iranian Journal of Microbiology

Publisher: Tehran University of Medical Sciences

ISSN (Print): 2008-3289

ISSN (Electronic): 2008-4447

Publication date (Print): February 2016

Volume: 8

Issue: 1

Pages: 55-61

Affiliations

[1 ]Department of Bacteriology and Virology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran

[2 ]Shiraz HIV/AIDS Research Center, Shiraz University of Medical Sciences, Shiraz, Iran

[3 ]Department of Pathology, School of Medicine, Shiraz University of Medical Sciences, Shiraz, Iran

[4 ]Antimicrobial Resistance Research Center, Avicenna Research Institute, Mashhad University of Medical Sciences, Mashhad, Iran

Author notes

[* ]Corresponding author: Mohammad Motamedifar PhD, Department of Bacteriology & Virology, School of Medicine, Shiraz University of Medical Sciences, Zand St, Imam Hossein Sq, Shiraz, Iran. Tel: +989173147718, Fax: +987132304356, E-mail: motamedm@ 123456sums.ac.ir

Article

Publisher ID: ijm-8-55

PMC ID: 4833741

PubMed ID: 27092225

SO-VID: 7123f3ba-4767-4fa1-9db1-e34f886be0a3

License:

This work is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported License which allows users to read, copy, distribute and make derivative works for non-commercial purposes from the material, as long as the author of the original work is cited properly.

Antibiotic susceptibility pattern and identification of extended spectrum β-lactamases (ESBLs) in clinical isolates of Klebsiella pneumoniae from Shiraz, Iran

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Abstract

Background and Objectives:

Materials and Methods:

Results:

Conclusions:

Related collections

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Most cited references 16

Extended-Spectrum β-Lactamases: a Clinical Update

Resistance in gram-negative bacteria: enterobacteriaceae.

Contemporary assessment of antimicrobial susceptibility testing methods for polymyxin B and colistin: review of available interpretative criteria and quality control guidelines.

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