Hospital-acquired pneumonia (HAP), particularly ventilator-associated pneumonia (VAP), causes considerable morbidity and mortality despite antimicrobial therapy and advances in supportive care Pseudomonas(P) aeruginosa is a leading cause of nosocomial infections all over the world, especially of HAP and VAP, The extended spectrum β-lactamase P. aeruginosa producers (ESBLs) have recently emerged as one of the most worrisome resistance that have been rapidly spreading through many countries The aim of this study was to evaluate the mortality of the subset of patients with HAP due to P. aeruginosa in a setting of beta-lactamases such as ESBL (Extended spectrum beta-lactamase production . New media were used in their isolation to be tested for pseudomonas selectivity and enhancement of different pigment that are produced by Pseudomonas aeruginosa.
Methods:In this study, 76 samples were collected from nasocomial pneumonia cases. P. aeruginosa isolates were recovered. Conventional microbiology methods were used for P. aeruginosa identification,isolation, antibiotic susceptibility testing(using disk-diffusion methods) and β-lactamase production testing.P.aeruginosa isolates were recovered and grown on different types of media[basic,enriched and selective media e.g P. aeruginosa selective agar(PASA),Kings A and B]; to demarcate its colonies,isolate pigments producers and to isolate the extended spectrum P. aeruginosa β-lactamase(ESBL) producers.ESBL testing was done using disc diffusion testing susceptibility and Epsilon(E) test. A prospective observational study was performed and it was constructed to identify risk factors for 30-day mortality.
Results: All P. aeruginosa isolates in this study were grown (100%) on all media used. Gram positive isolates were inhibited (100%) on PASA, Kings A and Kings B. While Gram negative isolates were inhibited (100%) on PASA only and were not inhibited on other used media. The demarcation of P. aeruginosa colonies were detected in 100% on PASA, 22.58%on Kings A, 37.50% on Kings B, while nutrient and blood agar media could not demarcate colonies at all.
In this study, Kings B agar was the best medium for isolation of pigmented producers (68% fluorescein and 31.50% rubrin), pigments detected on other media with variable range: 67.50%) on PASA (only fluorescein), 40.70 % on nutrient and 32.80% on Kings A agar (only pyocyanin).
The isolated P. aeruginosa gave 100% positivity for production of β-lactamase by the colorimetric method in detection of β-lactamase by nitrocefin method.
In this study, the tested isolates for ESBL revealed that the results were (28%) positive, (54%) negative and(18%) not detected. 76 patients with P. aeruginosa HAP were evaluated. The 30-day mortality was 36.80% (28 of 76 ): 57.10% (12 of 21) for patients with HAP by ESBL-producing P. aeruginosa and 29.60% (16 of 55) for non-ESBL-producing P. aeruginosa, indicating higher
mortality in ESBL producers than non producers especially in ventilated [8/11(72.70%)] patients despite appropriate treatment.
Conclusions: ESBL-producing P. aeruginosa HAP resulted in higher mortality rates, particularly in patients with ventilator-associated pneumonia, most probably related to the less frequent institution of appropriate antimicrobial therapy. Therapeutic approaches should be reviewed at institutions with a high prevalence of ESBL.This reflects the serious problem of impending resistance to all known sensitive drugs. In this study Kings B agar was the best medium for isolation of pigmented producers
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