Problematic clinical isolates of Pseudomonas aeruginosa from the university hospitals in Sofia, Bulgaria: Current status of antimicrobial resistance and prevailing resistance mechanisms

Department of Microbiology, Medical University of Sofia, 2 Zdrave Street, 1431 Sofia, Bulgaria.
Journal of Medical Microbiology (Impact Factor: 2.25). 08/2007; 56(Pt 7):956-63. DOI: 10.1099/jmm.0.46986-0
Source: PubMed


A total of 203 clinical isolates of Pseudomonas aeruginosa was collected during 2001-2006 from five university hospitals in Sofia, Bulgaria, to assess the current levels of antimicrobial susceptibility and to evaluate resistance mechanisms to antipseudomonal antimicrobial agents. The antibiotic resistance rates against the following antimicrobials were: carbenicillin 93.1 %, azlocillin 91.6 %, piperacillin 86.2 %, piperacillin/tazobactam 56.8 %, ceftazidime 45.8 %, cefepime 48.9 %, cefpirome 58.2 %, aztreonam 49.8 %, imipenem 42.3 %, meropenem 45.5 %, amikacin 59.1 %, gentamicin 79.7 %, tobramycin 89.6 %, netilmicin 69.6 % and ciprofloxacin 80.3 %. A total of 101 of the studied P. aeruginosa isolates (49.8 %) were multidrug resistant. Structural genes encoding class A and class D beta-lactamases showed the following frequencies: bla(VEB-1) 33.1 %, bla(PSE-1) 22.5 %, bla(PER-1) 0 %, bla(OXA-groupI) 41.3 % and bla(OXA-groupII) 8.8 %. IMP- and VIM-type carbapenemases were not detected. In conclusion, the studied clinical strains of P. aeruginosa were problematic nosocomial pathogens. VEB-1 extended-spectrum beta-lactamases appear to have a significant presence among clinical P. aeruginosa isolates from Sofia. Carbapenem resistance was related to non-enzymic mechanisms such as a deficiency of OprD proteins and active efflux.

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    • "The emergence of multidrug-resistant bacteria is a world health problem [1,2]. Staphylococcus aureus is one of the most important human pathogens associated with hospital and community-acquired infections. "
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    ABSTRACT: Background The emergence of multidrug-resistant bacteria is a world health problem. Staphylococcus aureus, including methicillin-resistant S. aureus (MRSA) strains, is one of the most important human pathogens associated with hospital and community-acquired infections. The aim of this work was to evaluate the antibacterial activity of a Pseudomonas aeruginosa-derived compound against MRSA strains. Methods Thirty clinical MRSA strains were isolated, and three standard MRSA strains were evaluated. The extracellular compounds were purified by vacuum liquid chromatography. Evaluation of antibacterial activity was performed by agar diffusion technique, determination of the minimal inhibitory concentration, curve of growth and viability and scanning electron microscopy. Interaction of an extracellular compound with silver nanoparticle was studied to evaluate antibacterial effect. Results The F3 (ethyl acetate) and F3d (dichloromethane- ethyl acetate) fractions demonstrated antibacterial activity against the MRSA strains. Phenazine-1-carboxamide was identified and purified from the F3d fraction and demonstrated slight antibacterial activity against MRSA, and synergic effect when combined with silver nanoparticles produced by Fusarium oxysporum. Organohalogen compound was purified from this fraction showing high antibacterial effect. Using scanning electron microscopy, we show that the F3d fraction caused morphological changes to the cell wall of the MRSA strains. Conclusions These results suggest that P. aeruginosa-produced compounds such as phenazines have inhibitory effects against MRSA and may be a good alternative treatment to control infections caused by MRSA.
    Annals of Clinical Microbiology and Antimicrobials 06/2013; 12(1):12. DOI:10.1186/1476-0711-12-12 · 2.19 Impact Factor
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    • ". aeruginosa isolates Primer Sequence Amplicon size (bp) Reference VEB-F 5'-CGACTTCCATTTCCCGATGC-3' 643 Strateva et al., 2007 VEB-B 5'-GGACTCTGCAACAAATACGC-3' PER-F 5'-AATTTGGGCTTAGGGCAGAA-3' 925 Strateva et al., 2007 PER-B 5'-ATGAATGTCATTATAAAAGC-3' PSE-F 5'-AATGGCAATCAGCGCTTC-3' 699 Strateva et al., 2007 PSE-B 5'-GCGCGACTGTGATGTATA-3' OXA-10-F 5'-TCTTTCGAGTACGGCATTAGC-3' 759 Strateva et al., 2007 OXA-10-B 5'-CCAATGATGCCCTCACTTTCC-3' OXA-2-F 5'-GCCAAAGGCACGATAGTTGT-3' 701 Strateva et al., 2007 OXA-2-B 5'-GCGTCCGAGTTGACTGCCGG-3' IMP-F 5'-GAAGGYGTTTATGTTCATAC 587 Strateva et al., 2007 IMP-B 5'-GTAMGTTTCAAGAGTGATGC VIM-F 5'-ATGGTGTTTGGTCGCATATC 510 Strateva et al., 2007 VIM-B 5'-TGGGCCATTCAGCCAGATC SPM-F 5'-CCTACAATCTAACGGCGACC-3' 649 Gales et al., 2003 SPM-R 5'-TCGCCGTGTCCAGGTATAAC-3' GES-F 5'-GTTTTGCAATGTGCTCAACG-3' 371 Weldhagen, 2004 GES-R 5'-TGCCATAGCAATAGGCGTAG-3' TEM-F 5'-ATAAAATTCTTGAAGAC-3' 1075 Jiang et al., 2006 TEM-R 5'-TTACCAATGCTTAATCA-3' SHV-F 5'-TGGTTATGCGTTATATTCGCC-3' 867 Jiang et al., 2006 SHV-R 5'-GCTTAGCGTTGCCAGTGCT -3' ampR-F 5'-AGGATTGGCGTCCTTTGTC-3' 1058 Tam et al., 2007 ampR-R 5'-CTTGAATCGCCTGCATAACC-3' ampE-F 5'-GCCTGGACCCGAACGAAC-3' 1231 Juan et al., 2005 ampE-R 5'-TCAGAGGAACAGCGCGCAG-3' ampD-F 5'-GTACGCCTGCTGGACGATG-3' 916 Juan et al., 2005 ampD-R 5'-GAGGGCAGATCCTCGACCAG-3' ampC-F* 5'-CAGAAGGACCAGGCACAG-3' 113 this study ampC-R* 5'-GCGAGATAGCCGAACAGG-3' oprM-F* 5'-CAACGCTCGCTGTTCACC-3' 115 this study oprM-R* 5'-TCACGGTCTGCTGGTTCC-3' rpoD-F* 5'-GGGCGAAGAAGGAAATGGTC-3' 178 Savli et al., 2003 rpoD-R* 5'-CAGGTGGCGTAGGTGGAGAA-3' *RT-qPCR Original Paper Veterinarni Medicina, 55, 2010 (4): 172–182 176 "
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    ABSTRACT: Sixty-six clinical P. aeruginosa isolates, 17 obtained from canine otitis specimens and 49 received from human patients with bloodstream infections, were collected between February 2007 and January 2008. The minimal inhibitory concentrations (MICs) of the antimicrobial agents of these isolates were determined. Multidrug resistance was common, with 23 (34.8%) isolates found to be ceftazidime resistant. To explore the mechanisms of ceftazidime resistance, PCR analyses were performed to detect drug-resistance genes. The prevalence rate of Ambler class A, B, and D β-lactamase genes were obtained, with bla TEM-1 100%, bla PSE-1 100%, bla OXA-2 96.2%, bla SHV-18 91.3%, bla OXA-17 78.3%, bla VIM-3 26.1%, bla OXA-10 21.7% and bla SHV-1 8.7%. An efflux inhibition assay with the PAβN compound was conducted. The ceftazidime resistance isolates were also tested by RT-qPCR to deter-mine the mRNA expression levels of the oprM and ampC genes. Five (21.7%) of the ceftazidime resistance iso-lates appeared to overactivate the OprM efflux system. The ampD, ampE, and ampR genes and the ampC-ampR intergenic region were subsequently amplified and sequenced. Five (21.7%) of the ceftazidime resistance isolates from humans and canines had a point mutation in AmpR (Asp135-Asn, n = 3; Als194-Ser, n = 2), which induces AmpC overproduction from 10-to 80-fold. This study first reported ceftazidime resistance in P. aeruginosa from canine otitis specimens, which are closely related to ESBLs (50%), including the overproduction of AmpC (25%) and the OprM efflux system (25%). The ESBLs (100%) played an important role in all ceftazidime resistance iso-lates from humans, and either AmpC (21.1%) or OprM (21.1%) might be overexpressed within the same isolate. A human patient isolate (H307B) showed simultaneous expression of ESBLs, the OprM efflux system, and AmpC overproduction. Pseudomonas aeruginosa causes septicemia and nosocomial infections in humans (El Amary et al., 2001; Berthelot et al., 2005) and otitis externa, pyo-derma, wound infections and abscesses in canines (Griffin, 1993; Cole et al., 1998; Scott et al., 2001; Peterson et al., 2002). Ceftazidime is an important and effective antimicrobial agent for the therapy of serious infections due to multidrug resistance in P. aeruginosa. A surge in ceftazidime resistance in human clinical isolates of P. aeruginosa results from the production of acquired β-lactamase, the constitutive overproduction of AmpC, or an acti-vation of the MexAB-OprM or MexXY-OprM ef-flux systems (Lindberg et al., 1987; Li et al., 1994; Stapleton et al., 1995; Nordmann and Guibert, 1998; Aires et al., 1999; Kuga et al., 2000; Masuda et al., 2000; Livermore, 2002). The molecular mechanism of canine ceftazidime resistance in P. aeruginosa isolates still requires further clarification. In this study, we attempt to elucidate the different ceftazi-dime resistance mechanisms between canine and human isolates of P. aeruginosa.
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    ABSTRACT: ZET Yatan hastalardan 01.08.2007 ile 31.07.2008 tarihleri arasında gönderilen çeşitli klinik örneklerinden izole edilen toplam 94 Pseudomonas aeruginosa suşunun antibiyotiklere duyarlılıkları retrospektif olarak araştırılmıştır. Suşların identi-fikasyonu ve antibiyotik duyarlılıkları Phoenix (Becton Dickinson) sistemi kullanılarak üretici firma önerilerine göre belirlen-miştir. P.aeruginosa suşlarında en düşük direnç amikasine (% 1), en yüksek direnç siprofloksasine (% 16) karşı belirlenmiştir. Test edilen diğer antibiyotiklerden imipeneme % 3, gentamisine % 4, piperasiline % 5, seftazidime % 11, sefepime % 13, aztreonama % 14 oranında direnç belirlenmiştir. Hastanemizde P.aeruginosa infeksiyonlarında ampirik tedavi düzenlenirken bu direnç oranlarının göz önünde bulundurulması ve tedavinin antibiyotik duyarlılık sonucuna göre düzenlenmesi uygun olacaktır.
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