Comparative Study for Detection of Carbapenemase Producers among Non-fermenting Gram Negative Uropathogens with Special Reference to Risk Factors and Fosfomycin Susceptibility DC14-DC21
Dr. Asmaa M. Elbrolosy,
Introduction: Urinary Tract Infections (UTIs) are among the commonest type of bacterial infections. Non-Fermenting Gram-Negative Bacilli (NFGNB) are now emerging as important uropathogens. Accurate detection of carbapenemase-producing NFGNB is essential to prevent their dissemination within healthcare settings. Fosfomycin would be an alternative treatment option for multidrug-resistant (MDR) NFGNB.
Aim: To determine the incidence and variety of NFGNB associated with UTIs, to compare between different phenotypic methods for detection of carbapenemase-producing NFGNB as well as to address fosfomycin susceptibility against these isolates.
Materials and Methods: A total of 52 P.aeruginosa and 43 Acinetobacter isolates were recovered from 403 urine samples collected from hospitalised patients of Menoufia University Hospitals (MUHs) with UTIs. The isolates were subjected to antimicrobial susceptibility screening by disk diffusion test and those with reduced zone diameters to carbapenems were phenotypically tested for carbapenemase production by the modified Carbapenem Inactivation Method (mCIM), modified Carpa NP (CNPt-direct) and CarbAcineto NP tests. The sensitivity, specificity and accuracy of each test were estimated in relation to PCR results. Fosfomycin susceptibility was determined by disk diffusion test.
Results: 84.6% (44/52) of P.aeruginosa and 81.3% (35/43) of Acinetobacter isolates were carbapenem non-susceptible. The sensitivity and specificity of the mCIM were 90% and 91.7% with class B genes and 85.7% and 91.8% with class B+D genes for P.aeruginosa but the test performed poorly with Acinetobacter isolates. The CNPt-direct achieved excellent sensitivity (85.7%:100%) and specificity (88.2%:95.8%) for both P.aeruginosa and Acinetobacter isolates. For Acinetobacter spp., the CarbAcineto NP test was 100% sensitive. Fosfomycin retained good levels of in-vitro activity against the examined uropathogenic isolates.
Conclusion: Both mCIM and CarbAcineto NP tests are reliable and affordable techniques for identifying carbapenemases in P.aeruginosa and Acinetobacter spp. respectively. Fosfomycin has shown promising activity against MDR urinary pathogens; however, clinical data are lacking.