Genomic characterization of pseudomonas aeruginosa clinical isolates by pulsed field gel electrophoresis method

Alipour Ghorbani, Nader
Pseudomonas aeruginosa is a common cause of nosocomial infections, particularly in intensive care units (ICUs), bronchoscopy, oncology, and urology. The aim of this study was to characterize P. aeruginosa clinical isolates clonally relatedness by pulsed-field gel electrophoresis (PFGE) typing and it’s cut off value determination. We did retrospective study and analyzed genotypically a collection of 58 clinical isolates recovered during the period 2006–2011 from MESA private hospital microbiology department’s bacterial archive, PFGE was carried out at the Rafık Saydam National Hygiene Center. We used isolates’ drug resistance pattern as a control phenotypic character and compared it with observed “A-Z” PFGE pulsed types and drawn dendograms. Most of the Pseudomonas aeruginosa isolates were resistant to chloramphenicol (60 %), gentamycine (55 %) and to a lesser extent to imipenem (11 %), meropenem (39 %), pipracilin (31 %), ciprofloxacilin (10 %), ceftazidim (23 %), cefepim (6 %), cefoxitin (16 %), tobramycin (25 %), and aztreonam (10 %), 33 % were multidrug resistant. Pulsed-field gel electrophoresis with SpeI-digested genomic DNA resulted in 53 different pulsed types “With upper 95 % dice similarity cut off”, while with decreasing cut off value to upper 80 % dice similarity strains accumulated in 25 clusters each one representing different wards of hospital and nine individuals. This cut off value fully described same patients’ different samples “Pseudomonas placement in a same cluster correctly, while former cut off value interpret them with contradiction in separate genotypes. PFGE cut- off value with SpeІ restriction enzyme is different from XbaІ. Tenover criteria, scales must be adjusted to such restriction enzymes due to halfing “restriction fragment bands” numbers and scales. A-Z pulsed types were observed; special pulsed types were merely observed in bronchoscopy patients isolates and was not observed in other wards of hospital, with correct sterilization of bronchoscope, incidence of above pulsed types was decreased. Special pulsed types were observed in intensive care units (ICU). Multi drug resistant strains showed to be genetically identical origin. PFGE demonstrated the existence of a common clone in a (ICU) critical care area and bronchoscope unites due to this, we defined it bronchoscope related infection. Despite not existing horizontal transferring from patient to patient due to high level of hygiene plans of this hospital, isolating similar strain (Pseudomonas aeruginosa) between year 2006-2010 maybe due to biofilm formation and non-correct sterilization of medical equipments e.g. bronchoscope, Oxygen mask, laryngoscope These means may be sources of infection in this hospital. Reinforcement of infection control measurement is needed to avoid iatrogenic and horizontal transmission and severe infections. Morphological typing method based on anti-biotic Resistance method fully overlapped with PFGE method and confirmed our results in higher level of sensitivity and reliance. Aztreonam, colistin appeared to be the most effective agent against multidrug-resistant Pseudomonas aeruginosa isolates.
Citation Formats
N. Alipour Ghorbani, “Genomic characterization of pseudomonas aeruginosa clinical isolates by pulsed field gel electrophoresis method,” Ph.D. - Doctoral Program, Middle East Technical University, 2014.