RESUMO
Background: Pseudomonas aeruginosa is an opportunistic pathogen causing nosocomial infections in many hospitals. The aim of this study was to compare the different epidemiological typing techniques and their effectiveness in typing and discrimination of nosocomial Pseudomonas aeroginosa isolates
Methods: Seventy eight confirmed nosocomial Pseudomonus aeroginosa out of 1520 different sample [nosocomial infections and environmental samples] were collected during a period of one year. Six typing methods were evaluated, utilizing the confirmed 78 Pseudomonas strains, to assess their usefulness as tools to study the bacterial diversity. The methods used were antibiogram, pyocin typing, serotyping, extracellular enzyme typing, automated ribotyping and pulsed field gel electrophoresis [PFGE
Results: The distinctive capacity of four phenotyping methods was determined and compared to PFGE. Resistance to the antibiotics tested was in the 37.2% to 98.7% range; Imipenem was the most effective, whereas augmentin, carbenicillin and ceftazidime were the least effective antibiotics. Antibiogram for 78 isolates discriminate 13 different patterns
Pulsed field gel electrophoresis yielded 56 distinct types of P.aeruginosa with 100% distinction capacity [78/78] as all the strains were typable. Compared to PFGE, the distinctive capacities were 88.5% [69/78] for serotyping, 91% [71/78] for Pyocin typing and 100% [78/78] for automated ribotyping analysis. The results obtained in PFGE, were the easiest to read and interpret and most discriminating [0.99], followed by the pyocin typing [0.96], whereas ribotyping had [0.90] discriminatory power
Conclusion: Our results indicated that P.aeruginosa infections in Suez Canal University Hospital, mainly affect the hospitalized patients in orthopedic wards, surgical wards and burn units and played a great role in hospital associated infections. Imipenem was the best antibiotic as far as bacterial resistance is considered. Although, the lack of major PFGE type confirmed that no P.aeruginosa outbreak, typing results showed that PFGE was the best used typing method regarding high typability, sensitivity and discriminatory power. The used typing methods showed that cross transmission and treatment failure were the two main problems for spread of nosocomial infections inside surgical wards and should be considered to prevent this bacterial infection in medical units
RESUMO
Stenotrophomonus maltophilia is a multidrug resistant nosocomial pathogen for which optimal typing methods are needed to estimate epidemiologic relatedness especially among Intensive Care Unit [ICU]. Ventilator associated pneumonia [VAP] is a common complication in mechanically ventilated patients and it is accompanied by increased mortality. Pulsed field gel electrophoresis [PFGE] was applied to 12 nosocomial strains isolated from patients had VAP and six environmental specimens in ICU in Bahrain Hospital over 15 months period in 2004-2005. Antibiogram as a phenotypic marker failed to discriminate between these isolates. Five antibiogram patterns were identified among 18 isolates with predominance of pattern [I] that resisted five chemotherapeutic agents in 5 isolates [27.8%]. All the strains were sensitive to trimethoprim-sulfamethoxazole but only 72.2%, 55.6%, 44.4%, 22.2% and 11.1% were sensitive to minocycline, levofloxacin, ticarcillin-clavulanic acid, ceftazidime and chloramphenicol respectively. All the strains were typable by the genotypic marker PFGE. It revealed 14 patterns among 18 clinical and innate environmental isolates with a small two clusters included 3 strains that were epidemiologically related. Ten genotypic patterns were detected among twelve clinical isolates meanwhile six patterns were detected among the six environmental isolates. There were similar isolated PFGE patterns between environmental and clinical isolates suggestive of the source of infection to those patients and evidence of patient to patient transmission. These different genotypic patterns indicated different sources and genetic diversity of this opportunistic pathogen. This study proved high typability, sensitivity and discriminatory power of PFGE method for typing of nosocomial Stenotrophomonus maltophilia. It is recommended to add another genotypic marker in further studies like random amplified polymorphic DNA analysis [RAPD] to increase and augment the sensitivity and discriminatory power for typing of this important pathogen and trace the different sources of nosocomial infection