"Penbritin"-A New Broad-spectrum Antibiotic

Breaching the Barrier: Genome-Wide Investigation into the Role of a Primary Amine in Promoting E. coli Outer-Membrane Passage and Growth Inhibition by Ampicillin

Gram-negative bacteria are problematic for antibiotic development due to the low permeability of their cell envelopes. To rationally design new antibiotics capable of breaching this barrier, more information is required about the specific components of the cell envelope that prevent the passage of compounds with different physiochemical properties. Ampicillin and benzylpenicillin are β-lactam antibiotics with identical chemical structures except for a clever synthetic addition of a primary amine group in ampicillin, which promotes its accumulation in Gram-negatives. Previous work showed that ampicillin is better able to pass through the outer membrane porin OmpF in Escherichia coli compared to benzylpenicillin. It is not known, however, how the primary amine may affect interaction with other cell envelope components. This study applied TraDIS to identify genes that affect E. coli fitness in the presence of equivalent subinhibitory concentrations of ampicillin and benzylpenicillin, with a focus on the cell envelope. Insertions that compromised the outer membrane, particularly the lipopolysaccharide layer, were found to decrease fitness under benzylpenicillin exposure, but had less effect on fitness under ampicillin treatment. These results align with expectations if benzylpenicillin is poorly able to pass through porins. Disruption of genes encoding the AcrAB-TolC efflux system were detrimental to survival under both antibiotics, but particularly ampicillin. Indeed, insertions in these genes and regulators of acrAB-tolC expression were differentially selected under ampicillin treatment to a greater extent than insertions in ompF. These results suggest that maintaining ampicillin efflux may be more significant to E. coli survival than full inhibition of OmpF-mediated uptake. IMPORTANCE Due to the growing antibiotic resistance crisis, there is a critical need to develop new antibiotics, particularly compounds capable of targeting high-priority antibiotic-resistant Gram-negative pathogens. In order to develop new compounds capable of overcoming resistance a greater understanding of how Gram-negative bacteria are able to prevent the uptake and accumulation of many antibiotics is required. This study used a novel genome wide approach to investigate the significance of a primary amine group as a chemical feature that promotes the uptake and accumulation of compounds in the Gram-negative model organism Escherichia coli. The results support previous biochemical observations that the primary amine promotes passage through the outer membrane porin OmpF, but also highlight active efflux as a major resistance factor.

Potentiation of Vancomycin: Creating Cooperative Membrane Lysis through a "Derivatization-for-Sensitization" Approach

Gram-negative bacteria, especially the ones with multidrug resistance, post dire challenges to antibiotic treatments due to the presence of the outer membrane (OM), which blocks the entry of many antibiotics. Current solutions for such permeability issues, namely lipophilic-cationic derivatization of antibiotics and sensitization with membrane-active agents, cannot effectively potentiate the large, globular, and hydrophilic antibiotics such as vancomycin, due to ineffective disruption of the OM. Here, we present our solution for high-degree OM binding of vancomycin via a hybrid "derivatization-for-sensitization" approach, which features a combination of LPS-targeting lipo-cationic modifications on vancomycin and OM disruption activity from a sensitizing adjuvant. 10⁶- to 10⁷-fold potentiation of vancomycin and 20-fold increase of the sensitizer's effectiveness were achieved with a combination of a vancomycin derivative and its sensitizer. Such potentiation is the result of direct membrane lysis through cooperative membrane binding for the sensitizer-antibiotic complex, which strongly promotes the uptake of vancomycin and adds to the extensive antiresistance effectiveness. The potential of such derivatization-for-sensitization approach was also supported by the combination's potent in vivo antimicrobial efficacy in mouse model studies, and the expanded application of such strategy on other antibiotics and sensitizer structures.

Predictive compound accumulation rules yield a broad-spectrum antibiotic

Most small molecules are unable to rapidly traverse the outer membrane of Gram-negative bacteria and accumulate inside these cells, making the discovery of much-needed drugs against these pathogens challenging. Current understanding of the physicochemical properties that dictate small-molecule accumulation in Gram-negative bacteria is largely based on retrospective analyses of antibacterial agents, which suggest that polarity and molecular weight are key factors. Here we assess the ability of over 180 diverse compounds to accumulate in Escherichia coli. Computational analysis of the results reveals major differences from the retrospective studies, namely that the small molecules that are most likely to accumulate contain an amine, are amphiphilic and rigid, and have low globularity. These guidelines were then applied to convert deoxynybomycin, a natural product that is active only against Gram-positive organisms, into an antibiotic with activity against a diverse panel of multi-drug-resistant Gram-negative pathogens. We anticipate that these findings will aid in the discovery and development of antibiotics against Gram-negative bacteria.

Pharmacology and chemotherapy of ampicillin--a new broad-spectrum penicillin

The pharmacology and chemotherapy of a new penicillin, 6[D(-)-alpha-aminophenylacetamido] penicillanic acid, are described. It is non-toxic, is absorbed orally and is distributed throughout the body in a manner similar to other penicillins. It is eliminated unchanged from the body in high concentrations in the bile and urine. Almost all of the antibiotic can be accounted for in the urine and intestinal contents 2 hr after intramuscular administration but not after oral administration. It is concluded that the antibiotic is not metabolized within the body. Studies with infected animals show that it is as effective as the existing oral penicillins against Staphylococcus pyogenes Smith (penicillin sensitive), Streptococcus pyogenes Group A and Diplococcus pneumoniae. It is ineffective against penicillin-resistant Staphylococci. When tested in mice infected with the gram-negative organisms, Salmonella tryphimurium and Klebsiella pneumoniae, it was considerably more active than tetracycline and chloramphenicol.

Disposition kinetics, renal clearance and excretion of ampicillin after oral administration in goats

Disposition kinetics, renal clearance and urinary excretion of ampicillin were determined after oral administration of 10 mg/kg in 8 goats. Peak plasma concentration 1.86 +/- 0.14 mumol/l was attained at 117 +/- 11 min after oral administration. Half-time of absorption was 28.7 +/- 5.8 minutes and that of elimination was 135 +/- 15 minutes. Total area under plasma concentration versus time curve was 9.16 +/- 0.97 mumol.h/l. Total body clearance of ampicillin was 52.1 +/- 4.2 and renal clearance was 0.07 +/- 0.008 ml/min.kg. The renal handling of ampicillin involved glomerular filtration and back diffusion.

Plasma concentration and disposition of antimicrobial agents in the dog

Although there is sufficient information on the pharmacology and therapeutic application of the antimicrobial drugs to permit their effective use, they are still often misused in canine practice. This paper collates the data on drug dose rate/plasma concentration relationships observed in dogs after the administration of specific members of the major antimicrobial drug groups and on the possible impact of drug disposition (distribution and elimination) on therapeutic effect. Some information gleaned from studies in other animal species is added.

Ampicillin levels in human bile in the presence of biliary tract disease

Ampicillin levels were measured in the serum and in the bile from both the gall bladder and the common bile duct in patients undergoing surgery for biliary tract diseases. In patients with radiologically non-functioning gall bladders ampicillin was either not present or its concentration was lower than normal. Therapeutic levels were present in the common bile duct of all patients except those with obstruction of the common bile duct. Hence ampicillin fails appreciably to penetrate the obstructed viscus in obstructive biliary tract disease, and it is unlikely to be effective in treating infection associated with this.

Effect of Ampicillin on E. Coli of Swine Origin

The in vitro susceptibility of 103 cultures of E. coli isolated from scouring and nonscouring pigs, and four cultures of Salmonella isolated from a case of necrotic enteritis was tested against Ampicillin contained in nutrient broth at concentrations of 0, 0.1, 1.0 and 5.0 uG per ml. of the medium. All but three cultures of E. coli were found to be susceptible to 5.0 uG/ml., all Salmonella isolates were also susceptible to this concentration of the antibiotic. Susceptibility of E. coli was also tested by plating dilutions of fecal samples obtained from either a scouring or a nonscouring pig, with E.M.B. agar containing 0, 0.1, 1.0, 2.5, 5.0 and 10.0 uG Ampicillin per ml. of the medium. No difference in the growth of E. coli was observed at 0, 0.1 and 1.0 uG concentrations. The three higher concentrations of the antibiotic inhibited the growth of E. coli proportional to the amount of Ampicillin in each concentration.Ampicillin proved very effective in alleviating the symptoms of hemorrhagic enteritis in a 11-week old pig. The disappearance of scours was associated with the replacement of the previously existing sero-biotypes of fecal E. coliwith another aberrant type of E.coli which produced H(2)S. No Ampicillin resistant strains of E. coli emerged following treatment of the animal with this antibiotic.