Drug Repurposing for Candidate SARS-CoV-2 Main Protease Inhibitors by a Novel In Silico Method.

The SARS-CoV-2 outbreak caused an unprecedented global public health threat, having a high transmission rate with currently no drugs or vaccines approved. An alternative powerful additional approach to counteract COVID-19 is in silico drug repurposing. The SARS-CoV-2 main protease is essential for viral replication and an attractive drug target. In this study, we used the virtual screening protocol with both long-range and short-range interactions to select candidate SARS-CoV-2 main protease inhibitors. First, the Informational spectrum method applied for small molecules was used for searching the Drugbank database and further followed by molecular docking. After in silico screening of drug space, we identified 57 drugs as potential SARS-CoV-2 main protease inhibitors that we propose for further experimental testing.

Clinical determinants for the recovery of fungal and mezlocillin-resistant pathogens from bile specimens.

We conducted a retrospective analysis of all bile specimens obtained for routine cultures from January 1995 through December 1999 at our tertiary care hospital. Results of microbiologic testing were linked to clinical parameters gathered by means of chart review. A total of 722 isolates were cultured from 345 of 454 bile specimens obtained from 288 individual patients. Prior receipt of a >7-day course of antibiotics (odds ratio [OR], 5.7), extensive leukocytosis (leukocyte count, >20,000 cells/microL) on admission (OR, 7.8), endoscopic or percutaneous biliary manipulation during the previous 14 days (OR, 2.9), and treatment in an internal medicine ward (OR, 2.5) were independent factors significantly associated (Pless-than-or-eq, slant.05) with recovery of Candida species from bile specimens. Culture of mezlocillin-resistant bacteria from bile specimens was independently associated with the specimen having been obtained >1 week after admission (OR, 3.8), lack of history of endoscopic biliary drainage (OR, 3.2), and high serum aspartate aminotransferase levels (>72 U/L) on admission (OR, 2.6). Prospective studies are warranted to evaluate accordingly adjusted empiric therapies for biliary infections.

In vitro activity of mezlocillin, meropenem, aztreonam, vancomycin, teicoplanin, ribostamycin and fusidic acid against Borrelia burgdorferi.

The in vitro susceptibility profile of Borrelia burgdorferi is not yet well defined for several antibiotics. Our study explored the in vitro susceptibility of B. burgdorferi to mezlocillin, meropenem, aztreonam, vancomycin, teicoplanin, ribostamycin and fusidic acid. Minimal inhibitory concentrations (MICs) and minimal borreliacidal concentrations (MBCs) were measured using a standardised colorimetric microdilution method and conventional subculture experiments. MIC values were lowest for mezlocillin (MIC(90), < or =0.06 mg/l) and meropenem (MIC(90), 0.33 mg/l). Vancomycin (MIC(90), 0.83 mg/l) was less effective in vitro. Borreliae proved to be resistant to aztreonam (MIC(90), >32 mg/l), teicoplanin (MIC(90), 6.6 mg/l), ribostamycin (MIC(90), 32 mg/l), and fusidic acid (MIC(90), >4 mg/l). The mean MBCs resulting in 100% killing of the final inoculum after 72 h of incubation were lowest for mezlocillin (MBC, 0.83 mg/l). This study gathered further data on the in vitro susceptibility patterns of the B. burgdorferi complex. The excellent in vitro effectiveness of acylamino-penicillin derivatives and their suitability for the therapy of Lyme disease is emphasised.

Characterization of an In vitro-selected amoxicillin-resistant strain of Helicobacter pylori.

An amoxicillin-resistant (Amox(r)) strain of Helicobacter pylori was selected for by culturing an amoxicillin-sensitive (Amox(s)) strain in increasingly higher concentrations of amoxicillin, resulting in a 133-fold increase in MIC, from 0.03 to 0.06 microg/ml to 4 to 8 microg/ml. This resistance was stable upon freezing for at least 6 months and conferred cross-resistance to seven other beta-lactam antibiotics. beta-Lactamase activity was not detected in this Amox(r) strain; however, analysis of the penicillin-binding protein (PBP) profiles generated from isolated bacterial membranes of the Amox(s) parental strain and the Amox(r) strain revealed a significant decrease in labeling of PBP 1 by biotinylated amoxicillin (bio-Amox) in the Amox(r) strain. Comparative binding studies of PBP 1 for several beta-lactams demonstrated that PBP 1 in the Amox(r) strain had decreased affinity for mezlocillin but not significantly decreased affinity for penicillin G. In addition, PBP profiles prepared from whole bacterial cells showed decreased labeling of PBP 1 and PBP 2 in the Amox(r) strain at all bio-Amox concentrations tested, suggesting a diffusional barrier to bio-Amox or a possible antibiotic efflux mechanism. Uptake analysis of (14)C-labeled penicillin G showed a significant decrease in uptake of the labeled antibiotic by the Amox(r) strain compared to the Amox(s) strain, which was not affected by pretreatment with carbonyl cyanide m-chlorophenylhydrazone, eliminating the possibility of an efflux mechanism in the resistant strain. These results demonstrate that alterations in PBP 1 and in the uptake of beta-lactam antibiotics in H. pylori can be selected for by prolonged exposure to amoxicillin, resulting in increased resistance to this antibiotic.

In-vitro susceptibilities of species of the Bacteroides fragilis group to newer beta-lactam agents.

The in-vitro activities of imipenem and four beta-lactam-beta-lactamase inhibitor combinations were tested against 816 strains of the Bacteroides fragilis group, and compared with other anti-anaerobic agents. None of the strains was resistant to metronidazole, and only one was resistant to chloramphenicol. Mezlocillin and piperacillin were moderately active, while clindamycin was the least active. Rates of resistance varied between various species. The new beta-lactam agents tested showed excellent activity; piperacillin-tazobactam and imipenem were the most active. The emergence of strains that are resistant to these agents, observed in this study, suggests there is a need to perform periodic antimicrobial susceptibility tests.

Influence of ciprofloxacin and other antimicrobial drugs on different Escherichia coli strains in continuous-flow cultures under aerobic and anaerobic conditions.

In continuous-flow culture, long generation times and high bacterial counts favour survival of bacteria. A chemotherapeutic agent that achieves a bactericidal effect under these circumstances can therefore be seen as highly effective. In our continuous-flow culture we obtained bactericidal effects with ciprofloxacin 1-2 mg/L, cefotaxime 4 mg/L and mezlocillin 32 mg/L. These effects were seen irrespective of whether conditions were aerobic or anaerobic. There were no significant differences between monocultures and mixed cultures simulating faecal flora with the various Escherichia coli strains tested. Cefotaxime had an initial effect but an increase in counts was then observed as a result of regrowth of E. coli survivor strains in aerobic monoculture and mixed cultures. Mezlocillin was completely bactericidal in monocultures, but regrowth occurred in mixed cultures under anaerobic conditions. Neither the bacterial composition of this culture nor the resistance pattern explained this regrowth. These results were observed in long-term experiments followed for up to 7 days. We conclude that the antibiotics tested are highly effective against E. coli under unfavourable conditions simulating in-vivo situations.

Microflora-associated defense stimulating factors.

Mucosal surfaces are habitats for the physiological microflora and are closely related to the mucosal immune compartment (mucosa-associated lymphoid tissue, MALT). Recently, considerable evidence has accumulated showing that various members of the physiological microflora liberate low molecular weight substances which, apparently, are essential for the adequate immune response of the host. Antibiotic decontamination (e.g. of the BALB/c mouse gastrointestinal tract) results in a lack of generation of immunopriming microbial substances leading to immunosuppression. Biochemical analysis of the microbial substances revealed reproducible chromatographic fractions which selectively influence maturation, proliferation and activation of mononuclear immune cells.

Evaluation of 500 gram negative isolates to determine the number of major susceptibility interpretation discrepancies between the Vitek and MicroScan Walkaway for 9 antimicrobial agents.

Although the Vitek and MicroScan Walkaway are two of the most commonly used automated antimicrobial susceptibility test systems, few studies have been performed comparing discrepancies between these systems. In this study, 500 Gram negative clinical isolates were tested against ampicillin, ampicillin/sulbactam, ticarcillin, ticarcillin/clavulanate, imipenem, ciprofloxacin, norfloxacin, mezlocillin, and piperacillin to determine the number of major interpretation discrepancies between the two systems. The 500 isolates consisted of 100 isolates each of Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus mirabilis and Enterobacter species. Each isolate was tested simultaneously in both systems using the same standardized inoculum. Eighty-four major discrepancies occurred, of which 48 were reproducible. The reproducible discrepancy rate, for the 4,500 isolate/antimicrobic combinations tested, was 48 of 4500 (1.06%). The rate for individual antimicrobics varied from 17 of 500 (3.4%) for ampicillin to no discrepancies for ticarcillin or ciprofloxacin. Of the 48 reproducible discrepancies, 44 (92%) were Vitek resistant, MicroScan susceptible. Fifteen (31%) of the Vitek and 21 (44%) of the MicroScan results were confirmed by broth microdilution. Disk diffusion results were in agreement with 15 (31%) of the Vitek and 21 (44%) of the MicroScan results. Twelve (25%) of the broth microdilution and 12 (25%) of the disk diffusion results were intermediate. The broth microdilution and disk diffusion results for the 48 isolates with reproducible discrepancies were in agreement more often with MicroScan. However, there was less very major error comparing the Vitek results for these isolates to the broth microdilution and disk diffusion. Overall, the result of this evaluation indicate that the number of major interpretation discrepancies between the two systems is minimal for the isolate/antimicrobic combinations tested.

Comparison of the pharmacokinetic and pharmacodynamic activity of piperacillin and mezlocillin.

STUDY OBJECTIVE: To compare serum bactericidal activity over time and pharmacokinetics resulting from single doses of piperacillin (PIP) and a single dose of mezlocillin (MEZ). DESIGN: Open-label, randomized, three-way crossover study. SETTING: Hartford Hospital Clinical Research Center. PATIENTS: Nine healthy volunteers. INTERVENTIONS: Subjects received single doses of PIP 3 and 4 g/70 kg, and a single dose of MEZ 5 g/70 kg. MEASUREMENTS AND MAIN RESULTS: Test organisms were two clinical isolates of Pseudomonas aeruginosa. Pharmacodynamic analysis revealed that PIP 4 g had 2- to 3-fold higher peak serum bactericidal activity at the end of infusion and 4- to 5-fold higher activity at 0.5 hour than did MEZ 5 g, and also provided approximately 1 hour additional activity over MEZ 5 g. Pharmacokinetic analysis revealed that serum concentrations resulting from PIP 4 g remained above the minimum inhibitory concentration of our test strains almost twice as long as MEZ 5 g. CONCLUSION: Since mezlocillin 5 g every 8 hours is currently proving to be effective at many institutions, and since piperacillin 4 g demonstrates superior pharmacokinetic and pharmacodynamic activity, we believe that piperacillin 4 g every 8 hours could be used instead, with resulting cost savings.

[Immunomodulating effects of antibiotics influencing digestive flora]. / Effets immunomodulateurs des antibiotiques influençant les flores digestives.

Mucosal surfaces are habitats of the physiological microflora and are closely related to the mucosal immune compartment (mucosa-associated lymphoid tissue, MALT). Recently, considerable evidence has been accumulated showing that various members of the physiological microflora liberate low molecular weight peptides which, apparently, are essential for adequate immune responses of the host. Antibiotic decontamination (e.g. of the BALB/c-mouse intestinal tract) results in a lack of generation of immunopriming microbial peptides leading to immunosuppression. Biochemical analysis of the peptides revealed reproducible chromatographic fractions which selectively influence maturation, proliferation, and activation of lymphatic cells.

Enterococcus faecalis: in vitro activity of antimicrobial drugs, singly and combined, with and without defibrinated human blood, against high-level-gentamicin-resistant isolates.

Teicoplanin (4 micrograms/ml) combined with 4 micrograms/ml of ampicillin, mezlocillin, and piperacillin, respectively, proved more efficacious than vancomycin (4 micrograms/ml) combined with the three beta-lactam antibiotics against three representative clinical isolates of Enterococcus faecalis that showed high-level-gentamicin resistance (HLGR). In the presence of 65% (v/v) of fresh defibrinated human blood, teicoplanin (4 micrograms/ml) alone afforded significant bactericidal activity, but failed to completely sterilize assay tube contents, whereas teicoplanin combined with any of the three beta-lactam antibiotics consistently and completely killed HLGR E. faecalis inocula.

Beta-lactam antibiotics inhibit agonist-stimulated platelet calcium influx.

beta-lactam antibiotics cause platelet dysfunction with reversible agonist-receptor inhibition, irreversible [14C]-penicillin binding, and inhibition of agonist-stimulated elevation in cytosolic Ca2+ ([Ca2+]i), occurring after 24 h exposure in vitro and after in vivo treatment. We investigated beta-lactam antibiotic-induced inhibition of rises in [Ca2+]i stimulated by thrombin, sodium arachidonate or A23187 to determine whether Ca2+ influx or intracellular release was primarily affected. The mean rise in [Ca2+]i, measured with fura-2-AM, was inhibited 43.7-84.1% by penicillin when the extracellular Ca2+ concentration ([Ca2+]e) was 1 mM, but was significantly less inhibited when [Ca2+]e was < 1 microM. NiCl2 (2 mM), that blocks Ca2+ influx, caused inhibition comparable to penicillin. MnCl2 (1 mM), that quenches the intracellular fura-2 signal, significantly decreased the rise in 1 mM [Ca2+]i when [Ca2+]e was 1 mM, but did not increase the inhibition caused by penicillin. Penicillin did not inhibit the rise in [Ca2+]i stimulated by inositol-1,4,5-trisphosphate or GTP gamma S. Therefore, beta-lactam antibiotics inhibit agonist-induced elevations of [Ca2+]i primarily through inhibition of Ca2+ influx, which probably accounts for the irreversible inhibition of platelet function seen after prolonged in vitro or in vivo treatment.

Use of pharmacodynamic concepts in developing a cost-effective dosing method for piperacillin.

Because they were almost always used in combination with an aminoglycoside, piperacillin and mezlocillin were considered therapeutic alternatives at Hartford Hospital, a 900-bed teaching facility. To determine an appropriate comparative dose, the bactericidal activities of 5 gm of mezlocillin and 4 gm and 3 gm of piperacillin were compared. The results demonstrated that 4 gm of piperacillin possessed stronger bactericidal activity than either 3 gm of piperacillin or 5 gm of mezlocillin. Hartford Hospital has since approved an antibiotic management program using 4 gm of piperacillin every 8 hours, thereby reducing the daily cost of antibiotic therapy. The modified program offers the hospital measurable cost savings without jeopardizing the quality of care.

Patterns of multiple resistance to antibiotics in gram-negative bacteria demonstrated by factor analysis.

Principal component analysis was used to demonstrate the main associations between patterns of resistance to antibiotic drugs in 670 gram-negative bacteria consecutively isolated from blood cultures over a period of two years. Six factors were derived, which accounted for 84% of the total variance of the original matrix. Each factor represented an association between resistance to certain antibiotics as follows: factor 1: aztreonam, third generation cephalosporins and aminoglycosides; factor 2: first and second generation cephalosporins; factor 3: tetracycline and chloramphenicol; factor 4: ampicillin and ureidopenicillins; factor 5: trimethoprim/sulfamethoxazole; factor 6: fluoroquinolones. On two-way analysis of variance the difference in the factor scores was significant between bacteria for all factors except factor 5. The difference in factor scores between community and hospital acquired strains was significant only for factors 1, 2 and 6. Only the score of factor 6 showed a clear trend to increase with time during the two-year study period. Patients who were treated with antibiotics prior to bacteremia had higher scores for all factors, the difference being most marked in patients treated with fluoroquinolones. Factor analysis can be used to describe phenotypic associations between resistance to antibiotics, and the factor score used to compare groups of isolates and to demonstrate temporal and other trends.

Antibacterial and mezlocillin-enhancing activity of pure human pancreatic fluid.

The majority of deaths in severe pancreatitis are the result of superinfection of necrotic tissue. The pathogen most commonly responsible for such infections is Escherichia coli. Antibiotic prophylaxis would appear a logical precaution. The antibacterial drugs of choice should possess two basic characteristics: they must be active against the flora responsible for the infections and must be capable of penetrating into the pancreas at adequate minimum inhibitory concentrations (MICs). Mezlocillin--which is active against E. coli--has been shown to possess the latter requisite, but achieving therapeutic concentrations requires administration at high doses. In the present study, pure human pancreatic fluid showed properties similar to those observed in the dog against E. coli (bacterial colony growth 100 times lower than in a control culture) and produced a 75% reduction in mezlocillin MICs against this organism. These enhancing characteristics might make the commonly used doses sufficient for prophylactic purposes.

Antimicrobial activity of isepamicin (SCH21420, 1-N-HAPA gentamicin B) combinations with cefotaxime, ceftazidime, ceftriaxone, ciprofloxacin, imipenem, mezlocillin and piperacillin tested against gentamicin-resistant and susceptible gram-negative bacilli and enterococci.

Isepamicin, formerly SCH21420 or 1-N-HAPA gentamicin B, is an aminoglycoside that was tested alone or in combination with one of seven broad spectrum drugs against 80 clinical isolates. Half of the strains were gentamicin-resistant but only one isolate (1.3%) was resistant to isepamicin. The broadest spectrum comparison drugs tested alone (ciprofloxacin at 3.8% resistance and imipenem at 5.0% resistance) were associated with the lowest synergy rates when combined with isepamicin. The rank order of synergy (complete or partial) was; cefotaxime = ceftazidime = ceftriaxone = mezlocillin = piperacillin (75% to 80%) greater than imipenem (66%) greater than ciprofloxacin (38%). Isepamicin/ampicillin combinations produced synergistic killing of those enterococci not having high-grade resistance to gentamicin or kanamycin. Enterococcus faecium strains were also refractory to isepamicin/ampicillin synergy. Isepamicin appears to be widely useable against gentamicin-resistant gram-negative bacilli either alone or combined with most commonly used broad spectrum beta-lactams.