Comparative epidemiological study of Pseudomonas aeruginosa isolates during two time periods in a tertiary care hospital

Pseudomonas aeruginosa is a nosocomial pathogen of clinical importance carrying virulence and antibiotic resistance determinants. In the present study, phenotypic and genotypic characteristics of P. aeruginosa isolates collected at the University General Hospital of Patras (UGHP) in two time periods were investigated. Two groups of P. aeruginosa clinical isolates were compared collected with one year interval, in the UGHP. Group A consisted of 120 isolates recovered during one year (2004), whereas, group B included 240 recovered during a two year period (2006-2007). P. aeruginosa isolates were identified at the species level by standard methods (Oxiferm, BD, BBL). Antibiotic susceptibility testing was performed for the group A by the Etest for piperacillin, aztreonam, imipenem, tobramycin and ciprofloxacin, whereas, in group B by the agar disk diffusion method for piperacillin, carbenicillin, azlocillin, ticarcillin-clavulanic acid, ceftazidime, aztreonam, imipenemamikacin, tobramycin, netilmicin and ciprofloxacin, while MIC determination of colistin by the Etest (bioMerieux, Marcy l' Etoile, France), (CLSI 2008). The production of metallo-beta-lactamases (MBL) was investigated by the double strip Etest-MBL (bioMerieux). Serotyping was performed by 16 monovalent antisera. In group B, blaVIM , exoY, exoT, exoS and exoU genes were investigated by PCR and blaVIM genes were identified by sequencing analysis. PFGE (SpeI) was performed in all isolates of bothgroups. The main PFGE types of group B were characterized by MLST. Phenotypic and genotypic characteristics of P. aeruginosa were compared between groups. According to our results, phenotypic and genotypic analysis of isolates demonstrated the prevalence of multidrug-resistant P. aeruginosa (MDRPA) mainly serotype O11 clones, especially in the Internal Medicine during 2004 (group A) and in the ICU during 2006 and 2007 (group B). Fifty nine patients from group A (59/120), mainly hospitalized in the Internal Medicine, and 152 from group B (152/240), mainly in the ICU, were colonized or infected with MDRPA. High rate of MBL-positive isolates was observed in group A compared to group B (45% vs 33%), mainly in the Internal Medicine. All MBL-positive isolates of group B carried blaVIM- 2 and blaVIM-1 genes. Among isolates of group B, exoU gene was detected mainly in isolates from the ICU, whereas, exoS in isolates from other wards. In group A strains, four dominant PFGE types were characterized: A, B, C and D. In group B five PFGE types, a, d, b, c and s, different from the aforementioned pulsotypes, which were associated with ST235, ST111, ST253, ST309 and ST639. Significant polyclonality was observed in group A as compared to group B. In conclusion, this study describes two independent clonal outbreaks of MDRPA in the UGHP which occurred primarily in the Internal Medicine Ward (group A) and after one year interval in the ICU (group B)

Spread of Multidrug-Resistant Pseudomonas aeruginosa Clones in a University Hospital

An outbreak of multidrug-resistant Pseudomonas aeruginosa (MDRPA) infections in a university hospital is described. Phenotypic and genotypic analysis of 240 isolates revealed that 152 patients, mainly in the intensive care unit (ICU), were colonized or infected with MDRPA, the majority with O11. All metallo-beta-lactamase (MBL)-positive isolates carried the bla(VIM-2) or bla(VIM-1) gene. One or more type III secretion system toxin genes were detected in most isolates. Five dominant pulsed-field gel electrophoresis (PFGE) types were characterized, associated with ST235, ST111, ST253, ST309, and ST639

Carbapenemase-producing Pseudomonas aeruginosa from central Greece: molecular epidemiology and genetic analysis of class I integrons

Background: Multidrug-resistant Pseudomonas aeruginosa is a serious challenge for antimicrobial therapy of nosocomial infections, as it possesses several mechanisms of antimicrobial resistance. In Central Greece, a sudden increase of infections caused by carbapenem-resistant P. aeruginosa was observed during 2011, indicating the need for further analysis. Methods: Five-hundred and sixty-eight P. aeruginosa isolates were collected consecutively during an 8-month period in 2011 from inpatients treated in three hospitals in the Thessaly region (1,000,000 habitants) of Greece. Carbapenem resistant P. aeruginosa (n = 284) were characterized by antimicrobial susceptibility testing and beta-lactamase content, and the genetic relatedness of carbapenemase-producing isolates was assessed by BOX-PCR, multilocus sequence typing, and eBURST analysis. Mapping of the class I integrons of Verona integron-encoded metallo-beta-lactamase (VIM)-carrying isolates was also performed, and clinical data of the VIM producers were reviewed. Results: Eighty (14.1%) out of the 568 P. aeruginosa isolates recovered from clinical specimens were VIM producers. Multilocus sequence typing revealed high prevalence of the international clones ST111 and ST235 among blaVIM-2- and blaVIM-4-positive isolates, respectively. blaVIM-17 was identified in an isolate of a novel sequence type (ST1457). bla(VIM) gene cassettes were carried by five distinct class I integrons, including two novel ones. Conclusions: Since the first report of VIM-producing P. aeruginosa in 2000, this microorganism still remains among the most prevalent multidrug resistant pathogens in Greece. The spread of VIM-producers belonging to the most common international clones (ST111 and ST235), the spread of integrons of divergent structures, and the emergence of novel integrons underscore their ongoing evolution

Multidrug resistant Pseudomonas aeruginosa survey in a stream receiving effluents from ineffective wastewater hospital plants

BACKGROUND: Multi-drug resistant forms of Pseudomonas aeruginosa (MDRPA) are a major source of nosocomial infections and when discharged into streams and rivers from hospital wastewater treatment plants (HWWTP) they are known to be able to persist for extended periods. In the city of Manaus (Western Brazilian Amazon), the effluent of three HWWTPs feed into the urban Mindu stream which crosses the city from its rainforest source before draining into the Rio Negro. The stream is routinely used by Manaus residents for bathing and cleaning (of clothes as well as domestic utensils) and, during periods of flooding, can contaminate wells used for drinking water. RESULTS: 16S rRNA metagenomic sequence analysis of 293 cloned PCR fragments, detected an abundance of Pseudomonas aeruginosa (P. aeruginosa) at the stream’s Rio Negro drainage site, but failed to detect it at the stream’s source. An array of antimicrobial resistance profiles and resistance to all 14 tested antimicrobials was detected among P. aeruginosa cultures prepared from wastewater samples taken from water entering and being discharged from a Manaus HWWTP. Just one P. aeruginosa antimicrobial resistance profile, however, was detected from cultures made from Mindu stream isolates. Comparisons made between P. aeruginosa isolates’ genomic DNA restriction enzyme digest fingerprints, failed to determine if any of the P. aeruginosa found in the Mindu stream were of HWWTP origin, but suggested that Mindu stream P. aeruginosa are from diverse origins. Culturing experiments also showed that P. aeruginosa biofilm formation and the extent of biofilm formation produced were both significantly higher in multi drug resistant forms of P. aeruginosa. CONCLUSIONS: Our results show that a diverse range of MDRPA are being discharged in an urban stream from a HWWTP in Manaus and that P. aeruginosa strains with ampicillin and amikacin can persist well within it