Risk factors for acquisition of extended spectrum beta lactamase producing Escherichia coli and Klebsiella pneumoniae in North-Indian hospitals

Multidrug resistance and production of extended spectrum β-lactamases (ESBLs) by enteric gram negative rods in hospitals and community continue to be a matter of scientific concern. This retrospective study was executed to assess the prevalence of ESBL-producing Escherichia coli and Klebsiella pneumoniae at two North Indian hospitals and to determine the risk factors associated with the acquisition of these organisms. A total of 346 bacterial isolates were obtained. Of these, 48.27% (n = 167) were confirmed to be ESBL producers while 51.73% (n = 179) were non ESBL-producers. Among the ESBL producers, 55.69% (n = 93) were E. coli and 44.31% (n = 74) were K. pneumoniae. ESBL producing isolates showed co-resistance to multitude of antibiotics tested. Length of hospital stay (>3 days) and previous exposure to antibiotics were found as significant risk factors (p = 0.01 and 0.02) associated with the acquisition of ESBL-producing E. coli and K. pneumoniae isolates. Imipenem and meropenem can be suggested as drugs of choice in our study.     

Interaction of CTX-M-15 enzyme with cefotaxime: a molecular modelling and docking study

Extended-spectrum β-lactamases (ESBLs) are the bacterial enzymes that make them resistant to advanced-generation cephalosporins. CTXM enzymes (the most prevalent ESBL-type) target cefotaxime. Aims of the study were: Modelling of CTX-M enzyme from bla(CTX-M) sequences of clinical Escherichia coli isolatesDocking of cefotaxime with modelled CTX-M enzymes to identify amino acid residues crucial to their interaction To hypothesize a possible relationship between 'interaction energy of the docked enzyme-antibiotic complex' and 'minimum inhibitory concentration (MIC) of the antibiotic against the bacteria producing that enzyme'. Seven E. coli strains of clinical origin which were confirmed as PCR-positive for bla(CTX-M) were selected for the study. C600 cells harboring cloned bla(CTX-M) were tested for ESBL-production by double-disk-synergy test. BLAST analysis confirmed all the bla(CTX-M) genes as blaCTX-M-15. Four of the 7 strains were found to be clonally related. Modelling was performed using Swiss Model Server. Discovery Studio 2.0 (Accelrys) was used to prepare Ramachandran plots for the modelled structures. Ramachandran Z-scores for modelled CTX-M enzymes from E. coli strains D8, D183, D253, D281, D282, D295 and D296 were found to be -0.449, 0.096, 0.027, 0.043, 0.032, -1.249 and -1.107, respectively. Docking was performed using Hex 5.1 and the results were further confirmed by Autodock 4.0. The amino acid residues Asn 104, Asn132, Gly 227, Thr 235, Gly 236, and Ser237 were found to be responsible for positioning cefotaxime into the active site of the CTX-M-15 enzyme. It was found that cefotaxime MICs for the CTX-M-15-producers increased with the increasing negative interaction energy of the enzyme-antibiotic complex.     

Molecular interaction of investigational ligands with human brain acetylcholinesterase

Alzheimer's disease, a neurodegenerative disorder continues to be an area of investigation by the international researchers’ fraternity. Despite all the ongoing efforts, the effective set of promising cholinesterase inhibitors available in the market for patients’ use is limited. Furthermore, the currently available drugs could provide only a palliative type of treatment instead of providing a complete cure or foolproof prevention. Hence, design/discovery of fresh drug molecules as acetylcholinesterase (AChE) inhibitors still remains an urgent requirement. The drug discovery platform, MCULE in the “structure-based virtual screening” (SBVS) mode was used for high throughput ligand screening of over five million structures targeted against the AChE catalytic site. A stepwise query was made for the SBVS input. The number of hits was narrowed down in consecutive succession via varied filtration criteria as AutoDock-Vina rankings, MCULE toxicity filtration, exclusion of ligands having less than four H-bond acceptors, filtration by ΔG cutoff, rule-of-five violation and SWISS ADME profiling. This was followed by holistic analysis of all the results, thereby leading to one promising ligand. The screened out drug molecule, MCULE-5872671137-0-1 exhibited a robust interaction with the AChE catalytic site involving 20 amino acid residues, an acceptable binding free energy of −10.2 kcal/mol in addition to a favorable SWISS ADME-profie showing no harmful effects on the human body. It can be carefully stated that the molecule, MCULE-5872671137-0-1, which is chemically (3S)-N-{4-[(4-chlorophenyl)sulfanyl]phenyl}-3-hydroxypyrrolidine-1-carboxamide could function as a significant “seed” ligand for future design of potent AChE inhibitors and/or novel neuro drugs built upon the seed-scaffold.