Synthesis of some heterofunctionalized penicillanic acid derivatives and investigation of their biological activities.

6-Substituted amino-penicillanic acid esters were synthesized starting with 6-apa. The compounds containing a 1,3-thiazole- or 1,3-thiazolidinone nucleus linked to the penicillanic acid skeleton via a hydrazino linkage were obtained from 6-apa. The treatment of carbonylamino and carbonothioylamino compounds with 4-chlorophenacyl bromide or ethyl bromoacetate gave 6-bis{4-[1,3-thiazol(idinone)amino]benzoyl}amino derivatives of 6-apa. Benzyl derivatives were synthesized in several steps, starting with 4-aminobenzoyl chloride. The treatment of 4-{[3-benzyl-4-oxo-1,3-thia(oxa)zolidin-2-ylidene]amino}benzoyl chlorides with 6-apa in ethanolic solution produced the 6-[bis(4-{[3-benzyl-4-oxo-1,3-thiazolidin-2-ylidene]amino}benzoyl)amino] derivative of penicillanic acid, while the reaction of the same intermediates in DMF gave the mono-substituted amino derivative of 6-apa. The synthesized compounds were screened for their biological activities, and some of them were found to possess good to moderate antimicrobial activity. Moreover, some of the compounds displayed antiurease, anti-ß-lactamase, and/or antilipase activities.

Structural basis for the ß-lactamase activity of EstU1, a family VIII carboxylesterase.

EstU1 is a unique family VIII carboxylesterase that displays hydrolytic activity toward the amide bond of clinically used ß-lactam antibiotics as well as the ester bond of p-nitrophenyl esters. EstU1 assumes a ß-lactamase-like modular architecture and contains the residues Ser100, Lys103, and Tyr218, which correspond to the three catalytic residues (Ser64, Lys67, and Tyr150, respectively) of class C ß-lactamases. The structure of the EstU1/cephalothin complex demonstrates that the active site of EstU1 is not ideally tailored to perform an efficient deacylation reaction during the hydrolysis of ß-lactam antibiotics. This result explains the weak ß-lactamase activity of EstU1 compared with class C ß-lactamases. Finally, structural and sequential comparison of EstU1 with other family VIII carboxylesterases elucidates an operative molecular strategy used by family VIII carboxylesterases to extend their substrate spectrum.

Antibiofilm Activity of ß-Lactam/ß-Lactamase Inhibitor Combination against Multidrug-Resistant Salmonella Typhimurium.

This study was designed to assess the effect of ß-lactam/ß-lactamase inhibitor combinations on the inhibition of biofilm formation of Salmonella Typhimurium. The anti-planktonic and anti-biofilm activities of ampicillin (AMP), ceftriaxone (CEF), and combination treatments of antibiotics and sulbactam (AMP + SUL and CEF + SUL) were evaluated against antibiotic-sensitive S. Typhimurium ATCC 19585 (STAS) and clinically isolated multidrug-resistant (MDR) S. Typhimurium CCARM 8009 (STMDR). Compared to the control, the minimum inhibitory concentrations (MICs) of AMP against STAS and CEF against STMDR were decreased from 32 to 16 µg/mL and 0.25 to 0.125 µg/mL, respectively, in the presence of SUL. The numbers of STMDR treated with AMP + SUL and CEF + SUL were effectively reduced by more than 2 logs after 4 h of incubation at 37 °C. The ß-lactamase activities of STAS and STMDR treated with AMP and CEF were reduced from 3.3 to 2.6 µmol/min/mL and from 8.3 to 3.4 µmol/min/mL, respectively, in the presence of SUL. The biofilm cell numbers of STAS and STMDR were reduced at all treatments after 24 h of incubation at 37 °C. The biofilm cell numbers of STAS and STMDR were reduced by more than 2 logs in the presence of SUL compared to the AMP and CEF alone. The lowest relative fitness level was 0.6 in STAS treated with AMP + SUL, while no significant differences in the relative fitness were observed in STMDR. This study suggests that ß-lactamase inhibitors (BLIs) could be used for controlling biofilm formation of ß-lactamase-producing multidrug-resistant S. Typhimurium.

Emergence of blaCTX-M-15, blaTEM-169 and blaPER-1 extended-spectrum ß-lactamase genes among different Salmonella enterica serovars from human faecal samples.

BACKGROUND: Broad-spectrum ß-lactams are used for empirical therapy of severe infections with non-typhoid Salmonella serotypes; however, activities of these drugs against the strains producing different ß-lactamase is not so clear. This study investigated the prevalence of ß-lactamase genes among isolates of S. enterica serovars from human faecal samples and determined their diversity in activity against different ß-lactams. METHODS: Antimicrobial resistance of faecal isolates of S. enterica to extended-spectrum cephalosporins was analysed and MIC values were determined for the strains presenting extended-spectrum ß-lactamases (ESBLs) phenotypes. The ß-lactamase genes were identified by PCR and sequencing. ß-lactamase activity of the Salmonella strains exhibiting ESBL phenotype was detected by biological, iodometric, spectrophotometry and nitrocefin assays. RESULTS: Out of 202 S. enterica isolates, ESBLs phenotype was detected among 3.4% (7/202) of the strains. blaTEM-1 and blaCTX-M-15 were among the frequent ß-lactamase genes. Detection of blaTEM-169 in S. enterica serovar Typhimurium and S. enterica serovar Bredeney and blaPER-1 in S. enterica serovar Infantis was a new finding in this experiment. Location of blaCTX-M-15/blaTEM-169/blaPER-1 genes on plasmid was confirmed in a transformation experiment. While crude extracts of the enzymes from each strain showed higher activity against cephalothin and cefotaxime, the lowest activity was detected against ceftazidime. The greatest synergistic activity was seen in a strain of S. enterica that carried blaCTX-M-15 and blaPER-1 genes compared with those presenting blaCTX-M-15/blaTEM-169 or blaCTX-M-15/blaTEM-1 genotypes. CONCLUSIONS: The results show dissemination of ESBLs encoding genes and their combined activity among different serovars of S. enterica that are a threat for future treatment options.

Design, synthesis and biological activities of some 7-aminocephalosporanic acid derivatives.

The treatment of 7-ACA with 4-substituted benzensulfonyl chlorides afforded the compounds containing 4-nitro/aminophenyl sulfonylamino moiety in the cephalosporanic acid skeleton (2, 4). The synthesis of the cephalosporanic acid derivatives containing 1,3-thiazole or 5-oxo-1,3-thiazolidine nucleus and sulfonamide function (8a, 8b, 10) was performed starting from 7-ACA by several steps. The reaction of 7-ACA with [4-(2-fluoro-4-nitrophenyl)piperazin-1-yl]acetyl chloride afforded the corresponding 7-{[4-(2-fluoro-4-nitrophenyl)piperazin-1-yl]acetyl}amino derivative (13). The synthesized compounds were screened for their antimicrobial and antiurease activities. Some of them were found to possess good-moderate antimicrobial activity against the test microorganisms. Compound 5d was observed to have moderate anti-urease activity.