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Distribution of Ambler class A, B and D β-lactamases among Pseudomonas aeruginosa isolates

Abdulkader F Tawfik1, Atef M Shibl, Mohamed A Aljohi

  • 1Department of Pharmaceutics and Microbiology, College of Pharmacy, King Saud University, Riyadh, Saudi Arabia.

Burns : Journal of the International Society for Burn Injuries
|February 22, 2012
PubMed
Abstract

Insights

Extended-spectrum cephalosporin-non-susceptible Pseudomonas aeruginosa in burned patients predominantly carry VEB-1 and OXA-10 beta-lactamase genes. The bla(VIM) gene was the most common among carbapenem-resistant isolates in Saudi Arabia.

Area of Science:

  • Microbiology
  • Molecular Biology
  • Clinical Infectious Diseases

Background:

  • Pseudomonas aeruginosa is a significant opportunistic pathogen, particularly in immunocompromised patients such as burn victims.
  • Extended-spectrum cephalosporins (ESCs) are crucial antibiotics, but resistance mediated by beta-lactamases is a growing global concern.
  • Understanding the prevalence and types of beta-lactamases in clinical isolates is vital for guiding antimicrobial therapy.

Purpose of the Study:

  • To determine the prevalence of Ambler classes A, B, and D beta-lactamases in extended-spectrum cephalosporin (ESC)-non-susceptible Pseudomonas aeruginosa clinical isolates from burned patients.
  • To identify specific beta-lactamase genes, including those for extended-spectrum beta-lactamases (ESBLs) and metallo-beta-lactamases (MBLs).

Main Methods:

  • Phenotypic susceptibility testing was performed on 156 P. aeruginosa isolates from burned patients.
  • Isolates resistant to ceftazidime underwent phenotypic screening for ESBLs and MBLs.
  • Polymerase chain reaction (PCR) was used to detect genes encoding ESBLs and MBLs in relevant isolates.

Main Results:

  • A ceftazidime resistance rate of 22.43% was observed. Among ESC-non-susceptible isolates, resistance to piperacillin, cefepime, and imipenem was high (100%, 88.57%, and 70.0%, respectively).
  • The prevalence of ESBL-producing isolates was 69.44%, and MBL-producing isolates was 42.85%.
  • Predominant ESBL genes were VEB-1 (68%) and OXA-10 (56%), while the bla(VIM) gene was detected in all MBL-producing isolates (100%). Co-occurrence of OXA-10 with other genes was noted.

Conclusions:

  • VEB-1 and OXA-10 are the most prevalent ESBL genes, and bla(VIM) is the dominant MBL gene in ESC-non-susceptible P. aeruginosa from burned patients in Saudi Arabia.
  • The findings indicate the emergence and spread of specific beta-lactamase genes in this clinical setting.
  • The presence of VEB, OXA-10, and GES ESBLs, and the bla(VIM) MBL gene, highlights the need for enhanced surveillance and infection control measures.

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