Zagazig University

Background: Non-carbapenemase mediated mechanisms of carbapenem resistance in Pseudomonas aeruginosa (P. aeruginosa) are increasingly recognized. Ceftolozane/tazobactam (C/T) has emerged as a promising treatment option however resistance driven by structural alterations in Pseudomonas derived cephalosporinase (PDC) raises concern. Objective: to investigate the non-carbapenemase mediated mechanisms of carbapenem resistance and role of PDC alterations in C/T resistance. Methodology: One hundred and forty-two P. aeruginosa clinical isolates were tested for carbapenem resistance. The carbapenemase activity and the underlying carbapenemase genes were assessed in the carbapenem resistant (CR) isolates. Expression levels of outer membrane porin D, PDC and Efflux pumps genes were assessed by real time polymerase chain reaction in non-carbapenemase producing isolates. Susceptibility to C/T was tested by MIC test strips and blaPDC gene was sequenced in C/T resistant isolates to study alterations in PDC amino acid structure. Results: Thirty-eight (36.2%) of 105 CR P. aeruginosa isolates were non-carbapenemase producers. These isolates showed overexpression of PDC, by both phenotypic (16/38, 42.1%) and genotypic (23/38, 60.5%) methods, and of efflux pumps; mexB (29/38, 76.3%), mexD (14/38, 36.8%) and mexY (9/38, 23.7%), in addition to reduced expression of oprD (34/38, 89.5%). Twenty isolates (52.6%) showed non-susceptibility to C/T. PDC amino acid sequences from C/T resistant isolates showed G1D, T79A, V179L, D123E, L150R and G360A substitutions in different combinations, all located outside the substrate binding site of PDC. Conclusion: Porin deficiency, mexAB-oprM and PDC overexpression are the frequent drivers of carbapenem resistance in non-carbapenemase producing CR P. aeruginosa isolates. PDC amino acid alterations are likely not the cause of C/T resistance detected in these isolates.

Background: Cyclopiazonic acid (CPA) is a mycotoxin produced by various fungal species such as Penicillium sp. Objectives: The aim of this study is to demonstrate that some species of Penicillium synthesize cyclopiazonic acid and to regulate the quantity of cyclopiazonic acid produced by Penicillium sp. contaminated food stuff. Methodology: Thirty-eight food commodity samples were gathered from different parts of Egypt. They discovered and determined the fungal contaminations. Fungi colonies were kept pure and their ability to produce CPA was examined. Applying volatile oils helped to regulate and lower the CPA level. Results: Nineteen of the 38 food samples were found to be contaminated with Penicillium sp., and eleven of the isolates (57.89%) generated CPA. P. commune isolate No. 17 was the most active sample, yielding 340.3 µg/100 ml of CPA in culture media and 0.66 gr/100 ml of dry biomass. The generation of CPA and dry biomass differed significantly (p < 0.05). Clove oil gave the strongest antagonistic activity against P. commune at different concentrations followed by spearmint oil. Significant difference was observed between clove powder concentration and final CPA concentration (p<0.05). 1HNMR and IR showed that pure clove's antifungal component is eugenol. Conclusion: The diversity of biotic control as volatile oils and their effectiveness provide new hope for controlling and reducing cyclopiazonic acid.