Phenotypic and Genotypic Characterization of Metallo-Beta-Lactamase and Extended-Spectrum Beta-Lactamase among Enterobacteria Isolated at National Public Health Laboratory of Brazzaville

The improper use of antimicrobials against infectious diseases has allowed microorganisms to develop defense mechanisms that give them insensitivity to these agents. All bacteria are concerned by this phenomenon. This work aimed to assess prevalence of beta-lactamase produced by enterobacterial isolates. Then, disc diffusion, double disc synergy test (DDST) and combined disc test (CDT) were respectively used for antimicrobial resistance, detection of Extended-Spectrum Beta-Lactamases (ESBL) and Metallo-Beta-Lactamases (MBL). bla genes were detected by PCR. A total of 132 enterobacterial strains were studied. Resistance to antibiotic families was observed with a greater frequency than 50%. Gentamicin was the least active beta-lactam antibiotic, with a resistance rate of 88%. 40.9% of strains show an ESBL phenotype and 16.6% were MBL. An overall prevalence of 74% (40/54) and respectively rates of 29.6%, 27.7% and 16.7% for blaSHV, blaCTX and blaTEM genes were observed. SHV, CTX, CTX/SHV/TEM, CTX/TEM, SHV/TEM and CTX/SHV were different ESBL genotypes observed. ESBL-producing enterobacteria isolation worried about the future of antimicrobial therapy in the Republic of Congo. This is a public health problem that requires careful monitoring and implementation of a policy of rational antibiotics use.

Biosynthesis of trialkyl-substituted aromatic polyketide NFAT-133 involves unusual P450 monooxygenase-mediating aromatization and a putative metallo-beta-lactamase fold hydrolase

The bacterial trialkyl-substituted aromatic polyketides are structurally featured with the unusual aromatic core in the middle of polyketide chain such as TM-123(1),veramycin A(2),NFAT-133(3)and benwamycin I(4),which were discovered from Streptomyces species and demonstrated with antidiabetic and immunosuppressant activities.Though the biosynthetic pathway of 1-3 was reported as a type I polyketide synthase(PKS),the PKS assembly line was interpreted inconsistently,and it remains a mystery how the compound 3 was generated.Herein,the PKS assembly logic of 1-4 was revised by site-mutagenetic analysis of the PKS dehydratase domains.Based on gene deletion and complementation,the putative P450 monooxygenase nftE1 and metallo-beta-lactamase(MBL)fold hydrolase nftF1 were verified as essential genes for the biosynthesis of 1-4.The absence of nftE1 led to abolishment of 1-4 and accumulation of new products(5-8).Structural elucidation reveals 5-8 as the non-aromatic analogs of 1,suggesting the NftE1-catalyzed aromatic core formation.Deletion of nftF1 resulted in disappearance of 3 and 4 with the compounds 1 and 2 unaffected.As a rare MBL-fold hydrolase from type I PKSs,NftF1 potentially generates the compound 3 through two strategies:catalyze premature chain-offloading as a trans-acting thioesterase or hydrolyze the lactone-bond of compound 1 as an esterase.

Virtual screening and high-throughput testing of L1 metallo-β-lactamase inhibitor

As a zinc-dependent enzyme, metal-β-lactamase L1 contributes to the development of β-lactam antibiotic resistance. The metal-β-lactamase inhibitor can restore the efficacy of β-lactam antibiotics, and its development has attracted much attention. In the present study, we used four widely-used virtual screening programs to screen 7035 small molecules to identify potential L1 inhibitors, and a high-throughput experimental model of L1 inhibitors was established. In this high-throughput testing model, the inhibition rate of 163 compounds on L1 exceeded 40%. The results of virtual screening of 7035 small molecules using the following four programs showed that among the top 1.35% of the compounds, their hit rates were ranked as Schr?dinger’s(5.26%), DS(1.05%), and Sybyl-x 2.0(1.05%), and Smina(2.11%).