Effect of hyperproduction of TEM-1 beta-lactamase on in vitro susceptibility of Escherichia coli to beta-lactam antibiotics.

Beta-lactamases are the most common cause of bacterial resistance to beta-lactam antibiotics. AmpC-type beta-lactamases hydrolyze cephalosporins, penicillins, and cephamycins. Therefore, the study aims was to determine antibiotic resistance and to investigate the presence of AmpC beta-lactamase gene in clinical strains of Escherichia coli isolated from hospitalized patients in Tabriz. In this cross-sectional descriptive study, 289 E. coli specimens were collected from clinical specimens. Disk diffusion method and combined disk method were used to determine the phenotype of extended spectrum β-Lactamase producing (ESBLs) strains. Then PCR was used to evaluate the presence of AmpC (FOX) beta-lactamase gene in the strains confirmed in phenotypic tests. Antibiotic resistance was also determined using disk diffusion by the Kibry-Bauer method. A total of 121 isolates were identified as generators of beta-lactamase genes. 72 (59.5 %) isolates producing ESBL and 49 (40.5 %) isolates were identified as AmpC generators. In the PCR test, 31 isolates contained the FOX gene. The highest resistance was related to the antibiotics amoxicillin (76.12%), ceftazidime (70.24%) and nalidixic acid (65.05%). The results indicate an increase in the prevalence of beta-lactamase genes and increased resistance to beta-lactam antibiotics, which can be the result of improper use of antibiotics and not using antibiotic susceptibility tests before starting treatment. Also, using phenotypic and molecular diagnostic methods such as PCR together can be very useful.

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Predictors of effect of ampicillin-sulbactam against TEM-1 beta-lactamase-producing Escherichia coli in an in vitro dynamic model: enzyme activity versus MIC.

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.40.3.734 ◽

1996 ◽

Vol 40 (3) ◽

pp. 734-738 ◽

Cited By ~ 28

Author(s):

A A Firsov ◽

D Saverino ◽

D Savarino ◽

M Ruble ◽

D Gilbert ◽

...

Keyword(s):

Escherichia Coli ◽

In Vitro Model ◽

Dynamic Models ◽

Beta Lactamase ◽

Beta Lactam ◽

Time Curve ◽

Peripheral Tissues ◽

Vitro Model

The clinical outcome in patients treated with ampicillin-sulbactam may not always be predictable by disc susceptibility testing or with the MIC as determined with a constant level (4 micrograms/ml) of the beta-lactamase inhibitor (MIC1). The enzyme activities (EA) and the MICs estimated at a constant ratio of ampicillin to sulbactam of 2:1 (MIC2) for 15 TEM-1 beta-lactamase-producing strains of Escherichia coli were examined as alternatives to MIC1 as predictors of the antibacterial effects of this combined drug as studied in an in vitro model which simulates ampicillin-sulbactam pharmacokinetic profiles observed in human peripheral tissues. Integral parameters describing the area under the bacterial count-time curve (AUBC), the area between the normal growth curve, and the killing curve of bacteria exposed to antibiotic (ABBC), and the second parameter expressed as a percentage of its maximal hypothetical value (ABBC/ABBCmax) were calculated. All three parameters correlated well with EA (AUBC, r = 0.93; ABBC, r = -0.88; ABBC/ABBCmax, r = -0.91) and with MIC2 (r = 0.94, -0.94, and -0.95, respectively) but not with MIC1. Both EA and MIC2 can be considered reliable predictors of the antibacterial effect of ampicillin-sulbactam in an in vitro model. These correlations suggest that in vitro kinetic-dynamic models might be useful to reexamine established susceptibility breakpoints obtained with data based on the MIC1 (MICs obtained with constant levels of beta-lactamase inhibitors). These data also suggest that quantitative determinations of bacterial beta-lactamase production and MICs based on the component concentration ratio observed in vivo might be useful predictors of the effect of ampicillin-sulbactam and other beta-lactam-inhibitor combinations.

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Antibiotic Resistance: Relationship to Persistence of Group A Streptococci in the Upper Respiratory Tract

PEDIATRICS ◽

10.1542/peds.97.6.971 ◽

1996 ◽

Vol 97 (6) ◽

pp. 971-975

Author(s):

Michael A. Gerber

Keyword(s):

Respiratory Tract ◽

Upper Respiratory Tract ◽

Beta Lactam ◽

Erythromycin Resistance ◽

In Vitro Susceptibility ◽

Beta Lactam Antibiotics ◽

Group A ◽

Resistant Strains ◽

Upper Respiratory

Despite the use of penicillin for more than 40 years in treating GABHS infections, there has been no significant change in the in vitro susceptibility of GABHS to penicillin. Reported failures to eradicate GABHS from the upper respiratory tracts of patients with pharyngitis and the apparent resurgence of serious Group A streptococcal infections and their sequelae probably are not related to the emergence of penicillin resistance. Although erythromycin resistance in GABHS had been a major problem in Japan and continues to be a major problem in Finland, it has not been a problem in this country. The susceptibility of GABHS to the newer macrolide antibiotics appears to be similar to that of erythromycin. Comprehensive, community-wide programs to continuously monitor for erythromycin resistance in GABHS would be difficult to justify. However, because little is known about how erythromycin resistance in GABHS is acquired or spread, it would be reasonable to periodically monitor isolates of GABHS for erythromycin resistance. A substantial proportion of GABHS are currently resistant to tetracyclines and these agents are inappropriate for treating GABHS infections. Although little recent information is available about the susceptibility of GABHS to sulfonamides, these agents have been shown to be ineffective in eradicating GABHS from the upper respiratory tract regardless of the in vitro sensitivities. GABHS have not been shown to be resistant to any of the commonly used oral cephalosporins; however, there is a great deal of variability among these agents in their activity against GABHS. Clindamycin resistance in GABHS has remained unusual. This agent is an alternative for treating GABHS infections due to macrolide-resistant strains in patients who cannot be treated with beta-lactam antibiotics. There is no reason, based on the in vitro susceptibilities of GABHS, to change the current recommendations for treating GABHS infections with penicillin and for using erythromycin for patients who are allergic to penicillin.

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In Vitro Susceptibilities of Capnocytophaga Isolates to beta -Lactam Antibiotics and beta -Lactamase Inhibitors

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.44.11.3186-3188.2000 ◽

2000 ◽

Vol 44 (11) ◽

pp. 3186-3188 ◽

Cited By ~ 18

Author(s):

A. Jolivet-Gougeon ◽

A. Buffet ◽

C. Dupuy ◽

J.-L. Sixou ◽

M. Bonnaure-Mallet ◽

...

Keyword(s):

Beta Lactamase ◽

Beta Lactam ◽

Beta Lactam Antibiotics

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ESBL and AmpC beta-lactamase-producing Enterobacteriaceae in poultry in the Czech Republic

Veterinární Medicína ◽

10.17221/165/2009-vetmed ◽

2010 ◽

Vol 55 (No. 3) ◽

pp. 119-124 ◽

Cited By ~ 17

Author(s):

M. Kolar ◽

J. Bardon ◽

M. Chroma ◽

K. Hricova ◽

T. Stosova ◽

...

Keyword(s):

Escherichia Coli ◽

Czech Republic ◽

Molecular Characteristics ◽

Beta Lactamase ◽

Beta Lactam ◽

The Czech Republic ◽

Beta Lactamases ◽

E Coli ◽

Beta Lactam Antibiotics ◽

Composite Samples

A major reason for resistance of Enterobacteriaceae to beta-lactam antibiotics is production of ESBLs and AmpC beta-lactamases. As their more detailed description in poultry is unavailable in the Czech Republic, the presented study aimed at assessing their occurrence and molecular characteristics. A total of 154 composite samples from broilers and 150 cloacal swabs from turkeys were examined. Production of ESBLs was detected in seven Escherichia coli isolates and AmpC enzymes in two E. coli isolates. The most frequent ESBL types were CTX-M-1 and SHV-12 and the most common AmpC enzymes were the CMY-2 types.

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