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Detection of AmpC-β-lactamases producing isolates among carbapenem resistant P. aeruginosa isolated from burn patient.

Mirsalehian A, Kalantar-Neyestanaki D, Nourijelyani K, Asadollahi K, Taherikalani M, Emaneini M, Jabalameli F - Iran J Microbiol (2014)

Bottom Line: Fifty two isolates showed a twofold or threefold dilution difference between the minimum inhibitory concentration of imipenem or ceftazidime and the minimum inhibitory concentration of imipenem or ceftazidime plus cloxacillin.Six isolates were AmpC producer as shown by the MICs of both imipenem and ceftazidime.According to the results of this study, AmpC- β-lactamase looks to be the main mechanism of resistance of Pseudomonas aeruginosa to cephalosporins and carbapenems in the study hospital.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, School of Medicine, Tehran University of Medical Sciences. Tehran, Iran.

ABSTRACT

Background and objectives: Pseudomonas aeruginosa is responsible for devastating nosocomial infections among severely burn patients. Class C of cephalosporinase (AmpC-β-lactamases) is important cause of multiple β-lactam resistance in P. aeruginosa. The aim of this study was to detect the AmpC-β-lactamases producing isolates among carbapenem resistant P. aeruginosa isolated from burn patient.

Material and methods: a total of 100 isolates of carbapenem resistant P. aeruginosa isolates from different burn patients were investigated. Three phenotypic methods were selected for identification of the AmpC-β-lactamases producing isolates.

Results: Fifty four isolates were AmpC producer as detected by AmpC disk test. Seventeen isolates were identified as AmpC producer using combined disk method. Fifty two isolates showed a twofold or threefold dilution difference between the minimum inhibitory concentration of imipenem or ceftazidime and the minimum inhibitory concentration of imipenem or ceftazidime plus cloxacillin. One isolate was identified as AmpC producer using three methods. Three isolates produced AmpC as detected by both AmpC disk test and combined disk methods and 19 isolates were found as AmpC producer using both AmpC disk test and minimum inhibitory concentration methods. Six isolates were AmpC producer as shown by the MICs of both imipenem and ceftazidime.

Conclusion: According to the results of this study, AmpC- β-lactamase looks to be the main mechanism of resistance of Pseudomonas aeruginosa to cephalosporins and carbapenems in the study hospital.

No MeSH data available.


Related in: MedlinePlus

AmpC Disk Test.A; Positive test,B; Negative test,C; Negative control (P. aeruginosa ATCC 27853),D, Lawn culture (E. coli ATCC 25922).
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Figure 1: AmpC Disk Test.A; Positive test,B; Negative test,C; Negative control (P. aeruginosa ATCC 27853),D, Lawn culture (E. coli ATCC 25922).

Mentions: The AmpC disk test was performed as described by Black et al. (13). In brief, the surface of a Mueller-Hinton agar plate was inoculated with a lawn of the cefoxitin (FOX) susceptible (E. coli ATCC 25922) according to the standard disk diffusion method. A FOX (30μg) disk was placed on the bacterial lawn on the surface of the Mueller-Hinton agar and flanked by two blank disks, each containing 20 μl of a 1:1 mixture of saline and 100X Tris-EDTA solution. Colonies of the test strain and control strains were applied to blank disks (Fig.1). Flattening or indentation of the growth inhibition zone of the FOX disk at the side of blank disks containing the test strain indicated the release of AmpC-β-lactamase.


Detection of AmpC-β-lactamases producing isolates among carbapenem resistant P. aeruginosa isolated from burn patient.

Mirsalehian A, Kalantar-Neyestanaki D, Nourijelyani K, Asadollahi K, Taherikalani M, Emaneini M, Jabalameli F - Iran J Microbiol (2014)

AmpC Disk Test.A; Positive test,B; Negative test,C; Negative control (P. aeruginosa ATCC 27853),D, Lawn culture (E. coli ATCC 25922).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC4385569&req=5

Figure 1: AmpC Disk Test.A; Positive test,B; Negative test,C; Negative control (P. aeruginosa ATCC 27853),D, Lawn culture (E. coli ATCC 25922).
Mentions: The AmpC disk test was performed as described by Black et al. (13). In brief, the surface of a Mueller-Hinton agar plate was inoculated with a lawn of the cefoxitin (FOX) susceptible (E. coli ATCC 25922) according to the standard disk diffusion method. A FOX (30μg) disk was placed on the bacterial lawn on the surface of the Mueller-Hinton agar and flanked by two blank disks, each containing 20 μl of a 1:1 mixture of saline and 100X Tris-EDTA solution. Colonies of the test strain and control strains were applied to blank disks (Fig.1). Flattening or indentation of the growth inhibition zone of the FOX disk at the side of blank disks containing the test strain indicated the release of AmpC-β-lactamase.

Bottom Line: Fifty two isolates showed a twofold or threefold dilution difference between the minimum inhibitory concentration of imipenem or ceftazidime and the minimum inhibitory concentration of imipenem or ceftazidime plus cloxacillin.Six isolates were AmpC producer as shown by the MICs of both imipenem and ceftazidime.According to the results of this study, AmpC- β-lactamase looks to be the main mechanism of resistance of Pseudomonas aeruginosa to cephalosporins and carbapenems in the study hospital.

View Article: PubMed Central - PubMed

Affiliation: Department of Microbiology, School of Medicine, Tehran University of Medical Sciences. Tehran, Iran.

ABSTRACT

Background and objectives: Pseudomonas aeruginosa is responsible for devastating nosocomial infections among severely burn patients. Class C of cephalosporinase (AmpC-β-lactamases) is important cause of multiple β-lactam resistance in P. aeruginosa. The aim of this study was to detect the AmpC-β-lactamases producing isolates among carbapenem resistant P. aeruginosa isolated from burn patient.

Material and methods: a total of 100 isolates of carbapenem resistant P. aeruginosa isolates from different burn patients were investigated. Three phenotypic methods were selected for identification of the AmpC-β-lactamases producing isolates.

Results: Fifty four isolates were AmpC producer as detected by AmpC disk test. Seventeen isolates were identified as AmpC producer using combined disk method. Fifty two isolates showed a twofold or threefold dilution difference between the minimum inhibitory concentration of imipenem or ceftazidime and the minimum inhibitory concentration of imipenem or ceftazidime plus cloxacillin. One isolate was identified as AmpC producer using three methods. Three isolates produced AmpC as detected by both AmpC disk test and combined disk methods and 19 isolates were found as AmpC producer using both AmpC disk test and minimum inhibitory concentration methods. Six isolates were AmpC producer as shown by the MICs of both imipenem and ceftazidime.

Conclusion: According to the results of this study, AmpC- β-lactamase looks to be the main mechanism of resistance of Pseudomonas aeruginosa to cephalosporins and carbapenems in the study hospital.

No MeSH data available.


Related in: MedlinePlus