Beta-lactams resistance and presence of class 1 integron in Pseudomonas spp. isolated from untreated hospital effluents in Brazil

Antonie Van Leeuwenhoek. 2012 Jun;102(1):73-81. doi: 10.1007/s10482-012-9714-2. Epub 2012 Mar 1.


The aim of the present study was to investigate the resistance profile, to detect the presence of beta-lactam resistance genes, phenotypic expression of efflux pump systems and class 1 integrons in Pseudomonas spp. strains obtained from untreated hospital effluents. Effluent samples were collected from four hospitals in Porto Alegre, RS, Brazil. Pseudomonas were isolated on MacConkey agar plates and the identification was confirmed by 16S rRNA PCR and biochemical tests. Susceptibility testing was determined by disk-diffusion method using 11 different beta-lactams and MIC assays were performed on isolates resistant to imipenem and ceftazidime. The beta-lactamase genes bla (IMP), bla (VIM), bla (SPM-1), bla (OXA-23-like), bla (OXA-24-like), bla (OXA-51-like) and the intl1 gene from class 1 integron were analysed by PCR. One hundred and twenty-four isolates were recovered and the most common species was Pseudomonas pseudoalcaligenes. The resistance found among the isolates was considered high, 62 (50%) isolates were multiresistant. No isolate carrying the beta-lactamase genes tested was found among the strains. Seven isolates showed reduction of MIC for imipenem and ceftazidime in the presence of cyanide m-chlorophenylhydrazone, indicating the hyper expression of efflux pumps. From the 124 isolates, 52 (41.9%) were identified as carrying the class 1 integron gene, intI1. Untreated hospital effluents could be a source of environmental contamination due to discharge of antimicrobial resistant bacteria which can carry integron class 1 and act as a reservoir of resistance genes and have efflux pump systems.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anti-Bacterial Agents / pharmacology
  • Brazil
  • DNA, Bacterial / chemistry
  • DNA, Bacterial / genetics
  • DNA, Ribosomal / chemistry
  • DNA, Ribosomal / genetics
  • Hospitals
  • Humans
  • Integrons*
  • Microbial Sensitivity Tests
  • Pseudomonas / classification
  • Pseudomonas / enzymology*
  • Pseudomonas / genetics
  • Pseudomonas / isolation & purification*
  • RNA, Ribosomal, 16S / genetics
  • Sequence Analysis, DNA
  • Sewage / microbiology*
  • beta-Lactam Resistance*
  • beta-Lactamases / genetics*


  • Anti-Bacterial Agents
  • DNA, Bacterial
  • DNA, Ribosomal
  • RNA, Ribosomal, 16S
  • Sewage
  • beta-Lactamases