β-lactam resistance represents a worldwide problem and a serious challenge for antimicrobial treatment. Hence this research was conducted to recognize several mechanisms mediating β-lactam resistance in E. coli and K. pneumoniae clinical isolates collected from Mansoura University hospitals, Egypt. A total of 80 isolates, 45 E. coli and 35 K. pneumoniae isolates, were collected and their antibiotic susceptibility was determined by the Disc diffusion method followed by phenotypic and genotypic detection of extended-spectrum β-lactamases (ESBLs), AmpC β-lactamase, carbapenemase enzymes. The outer membrane protein porins of all isolates were analyzed and their genes were examined using gene amplification and sequencing. Also, the resistance to complement-mediated serum killing was estimated. A significant percentage of isolates (93.8%) were multidrug resistance and showed an elevated resistance to β-lactam antibiotics. The presence of either ESBL or AmpC enzymes was high among isolates (83.75%). Also, 60% of the isolated strains were carbapenemase producers. The most frequently detected gene of ESBL among all tested isolates was blaCTX-M-15 (86.3%) followed by blaTEM-1 (81.3%) and blaSHV-1 (35%) while the Amp-C gene was present in 83.75%. For carbapenemase-producing isolates, blaNDM1 was the most common (60%) followed by blaVIM-1 (35%) and blaOXA-48 (13.8%). Besides, 73.3% and 40% of E. coli and K. pneumoniae isolates respectively were serum resistant. Outer membrane protein analysis showed that 93.3% of E. coli and 95.7% of K. pneumoniae isolates lost their porins or showed modified porins. Furthermore, sequence analysis of tested porin genes in some isolates revealed the presence of frameshift mutations that produced truncated proteins of smaller size. β-lactam resistance in K. pneumoniae and E. coli isolates in our hospitals is due to a combination of β-lactamase activity and porin loss/alteration. Hence more restrictions should be applied on β-lactams usage to decrease the emergence of resistant strains.

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Aim: The present study aims to evaluate the occurrence and characterize E. coli in meat and meat products marketed in Egypt based on their antimicrobial-resistance pattern and production of enterotoxins. Methods: A total of 250 meat samples, categorized as 80 fresh beef, 85 ground beef and 85 beef burger purchased from supermarkets and butchers' shops were used for isolation of E. coli. All isolates were screened for antimicrobial susceptibility. Plasmid profile analyses were done. Polymerase chain reactions were performed for detection of enterotoxin-encoding genes (astA, eaeA, stx1 and stx2). Results: Twenty-five samples were isolated and identified as E. coli. 14 isolates were multidrug resistant. Plasmids isolation from all isolates revealed that 76% of these isolates harbored plasmids. astA gene was amplified in 7 isolates (28%). Eight (32%) isolates harbored eaeA gene. However, none of the isolates harbored stx1 or stx2 genes. Analysis of multiple drug resistant isolates revealed a significant relation between multiple drug resistance and both astA and eaeA. Conclusion: The study confirmed the prevalence of enterotoxin genes (astA and eaeA) in E. coli isolated from meat product and the association between the presence of these genes and multiple drug resistant phenomena.