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

Synthesis of a tetralone derivative of ampicillin to control ampicillin-resistant Staphylococcusaureus

Due to the rapid emergence of antibiotic resistant new bacterial strains and new infections, there is an urgent need for novel or newly modified and efficient alternatives of treatment. However, conventional antibiotics are still used in therapeutic settings but their efficacy is uncertain due to the rapid evolution of drug resistance. In the present study, we have synthesized a new derivative of conventional antibiotic ampicillin using SN2-type substitution reaction. NMR and mass analysis of the newly synthesized derivative of ampicillin confirmed it as ampicillin-bromo-methoxy-tetralone (ABMT). Importantly, ABMT is revealed to have efficient activity against Staphylococcus aureus (S. aureus) with a MIC value of 32 μg ml-1 while ampicillin was not effective, even at 64 μg ml-1 of concentration. Electron microscopy results confirmed the membrane-specific killing of S. aureus at 1 h of treatment. Additionally, molecular docking analysis revealed a strong binding affinity of ABMT with β-lactamase via the formation of a closed compact bridge. Our findings, avail a new derivative of ampicillin that could be a potential alternative to fight ampicillin-resistant bacteria possibly by neutralizing the β-lactamase action.

The influence of pH and dissolved organic carbon on the ecotoxicity of ampicillin and clarithromycin

The impacts of water chemistry properties including pH and dissolved organic carbon (DOC) on the ecotoxicity of active pharmaceutical ingredients (APIs) are increasingly evident. These impacts are a result of alterations in API bioavailability: pH regulates the bioavailability of many ionizable APIs via chemical speciation, whereas DOC interacts with several APIs to inhibit the APIs from traversing the membrane system of organisms. In this study, we examined the influences of pH and DOC on the bioavailability of ampicillin (AMP) and clarithromycin (CLA) with the help of a bioavailability model. The effects on bioavailability were quantified by ecotoxicity observed in cyanobacteria growth inhibition tests with Microcystis aeruginosa PCC7806. The median effect concentration (96 h-EC50total) of AMP increased by 5-fold when pH raised from 7.4 to 9.0, suggesting the zwitterionic AMP+/- species being higher in bioavailability than the negatively charged AMP- species. CLA ecotoxicity showed no significant pH-dependency, suggesting CLA+ and CLA0 species to be equally bioavailable, albeit it correlated significantly with M. aeruginosa growth rate in negative controls. In addition, DOC demonstrated no significant effects on the ecotoxicity of AMP or CLA. Overall, together with earlier results on ciprofloxacin, our data show that bioavailability relations with pH and DOC are variable among different antibiotics. Factors other than chemical speciation alone could play a role in their bioavailability, such as their molecular size and polarity.

Palladium-Catalyzed Heck Cyclization with P(O)H Compounds to Construct Phosphinonyl-Azaindoline and -Azaoxindole Derivatives

We report herein a concise method for the construction of phosphinonyl-azaindoline and -azaoxindole derivatives via a palladium-catalyzed cascade cyclization with P(O)H compounds. Various H-phosphonates, H-phosphinates, and aromatic secondary phosphine oxides are all tolerated under the reaction conditions. Furthermore, the phosphinonyl-azaindoline isomer families such as 7-, 5-, and 4-azaindolines could be synthesized in moderate to good yields.

Overcoming intrinsic resistance in gram-negative bacteria using small molecule adjuvants

Gram-negative bacteria are intrinsically resistant to many classes of antibiotics, predominantly due to the impermeability of the outer membrane and the presence of efflux pumps. Small molecule adjuvants that circumvent these resistance mechanisms have the potential to expand therapeutic options for treating Gram-negative infections to encompass antibiotic classes that are otherwise limited to treating Gram-positive infections. Adjuvants that effect increased antibiotic permeation, either by physical disruption of the outer membrane or through interference with synthesis, transport, or assembly of membrane components, and adjuvants that limit efflux, are discussed as potential avenues to overcoming intrinsic resistance in Gram-negative bacteria.

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.

Iron-Catalyzed Intermolecular Amination of Benzylic C(sp3)-H Bonds

A catalytic system for intermolecular benzylic C(sp³)-H amination is developed utilizing 1,2,3,4-tetrazole as a nitrene precursor via iron catalysis. This method enables direct installation of 2-aminopyridine into the benzylic and heterobenzylic position. The method selectively aminates 2° benzylic C(sp³)-H bond over the 3° and 1° benzylic C(sp³)-H bonds. Experimental studies reveal that the C(sp³)-H amination undergoes via the formation of a benzylic radical intermediate. This study reports the discovery of new method for 2-pyridine substituted benzylamine synthesis using inexpensive, biocompatible base metal catalysis that should have wide application in the context of medicinal chemistry and drug discovery.

Efficient Photon Extraction in Top-Emission Organic Light-Emitting Devices Based on Ampicillin Microstructures

The desire to enhance the efficiency of organic light-emitting devices (OLEDs) has driven to the investigation of advanced materials with fascinating properties. In this work, the efficiency of top-emission OLEDs (TEOLEDs) is enhanced by introducing ampicillin microstructures (Amp-MSs) with dual phases (α-/β-phase) that induce photoluminescence (PL) and electroluminescence (EL). Moreover, Amp-MSs can adjust the charge balance by Fermi level (E_F ) alignment, thereby decreasing the leakage current. The decrease in the wave-guided modes can enhance the light outcoupling through optical scattering. The resulting TEOLED demonstrates a record-high external quantum efficiency (EQE) (maximum: 68.7% and average: 63.4% at spectroradiometer; maximum: 44.8% and average: 42.6% at integrating sphere) with a wider color gamut (118%) owing to the redshift of the spectrum by J-aggregation. Deconvolution of the EL intensities is performed to clarify the contribution of Amp-MSs to the device EQE enhancement (optical scattering by Amp-MSs: 17.0%, PL by radiative energy transfer: 9.1%, and EL by J-aggregated excitons: 4.6%). The proposed TEOLED outperforms the existing frameworks in terms of device efficiency.

Biomarkers Predicting Tissue Pharmacokinetics of Antimicrobials in Sepsis: A Review

The pathophysiology of sepsis alters drug pharmacokinetics, resulting in inadequate drug exposure and target-site concentration. Suboptimal exposure leads to treatment failure and the development of antimicrobial resistance. Therefore, we seek to optimize antimicrobial therapy in sepsis by selecting the right drug and the correct dosage. A prerequisite for achieving this goal is characterization and understanding of the mechanisms of pharmacokinetic alterations. However, most infections take place not in blood but in different body compartments. Since tissue pharmacokinetic assessment is not feasible in daily practice, we need to tailor antibiotic treatment according to the specific patient’s pathophysiological processes. The complex pathophysiology of sepsis and the ineffectiveness of current targeted therapies suggest that treatments guided by biomarkers predicting target-site concentration could provide a new therapeutic strategy. Inflammation, endothelial and coagulation activation markers, and blood flow parameters might be indicators of impaired tissue distribution. Moreover, hepatic and renal dysfunction biomarkers can predict not only drug metabolism and clearance but also drug distribution. Identification of the right biomarkers can direct drug dosing and provide timely feedback on its effectiveness. Therefore, this might decrease antibiotic resistance and the mortality of critically ill patients. This article fills the literature gap by characterizing patient biomarkers that might be used to predict unbound plasma-to-tissue drug distribution in critically ill patients. Although all biomarkers must be clinically evaluated with the ultimate goal of combining them in a clinically feasible scoring system, we support the concept that the appropriate biomarkers could be used to direct targeted antibiotic dosing.

Fluorescence Imaging and Photodynamic Inactivation of Bacteria Based on Cationic Cyclometalated Iridium(III) Complexes with Aggregation-Induced Emission Properties

Antibacterial photodynamic therapy (PDT) is one of the emerging methods for curbing multidrug-resistant bacterial infections. Effective fluorescent photosensitizers with dual functions of bacteria imaging and PDT applications are highly desirable. In this study, three cationic and heteroleptic cyclometalated Ir(III) complexes with the formula of [Ir(CˆN)₂ (NˆN)][PF₆ ] are prepared and characterized. These Ir(III) complexes named Ir(ppy)₂ bP, Ir(1-pq)₂ bP, and Ir(2-pq)₂ bP are comprised of three CˆN ligands (i.e., 2-phenylpyridine (ppy), 1-phenylisoquinoline (1-pq), and 2-phenylquinoline (2-pq)) and one NˆN bidentate co-ligand (bP). The photophysical characterizations demonstrate that these Ir(III) complexes are red-emitting, aggregation-induced emission active luminogens. The substitution of phenylpyridine with phenylquinoline isomers in the molecules greatly enhances their UV and visible-light absorbance as well as the photoinduced reactive oxygen species (ROS) generation ability. All three Ir(III) complexes can stain both Gram-positive and Gram-negative bacteria efficiently. Interestingly, even though Ir(1-pq)₂ bP and Ir(2-pq)₂ bP are constitutional isomers with very similar structures and similar ROS generation ability in buffer, the former eradicates bacteria much more effectively than the other through white light-irradiated photodynamic inactivation. This work will provide valuable information on the rational design of Ir(III) complexes for fluorescence imaging and efficient photodynamic inactivation of bacteria.

Facilitating Compound Entry as a Means to Discover Antibiotics for Gram-Negative Bacteria

It has been over half a century since the last class of antibiotics active against the most problematic Gram-negative bacteria was approved by the Food and Drug Administration (FDA). The major challenge with developing antibiotics to treat these infections is not drug-target engagement but rather the inability of most small molecules to traverse the Gram-negative membranes, be retained, and accumulate within the cell. Despite an abundance of lead compounds, limited understanding of the physicochemical properties needed for compound accumulation (or avoidance of efflux) in Gram-negative bacteria has precluded a generalizable approach for developing Gram-negative antibiotics. Indeed, in many instances, despite years of intensive derivatization efforts and the synthesis of hundreds of compounds aimed at building in Gram-negative activity, little or no progress has been made in expanding the spectrum of activity for many Gram-positive-only antibiotics. In this Account, we describe the discovery and successful applications of a promising strategy for enhancing the accumulation of Gram-positive-only antibiotics as a means of imbuing compounds with broad-spectrum activity.Utilizing a prospective approach examining the accumulation in Escherichia coli for more than 180 diverse compounds, we found that small molecules have an increased likelihood to accumulate in E. coli when they contain an ionizable Nitrogen, have low Three-dimensionality, and are Rigid. Implementing these guidelines, codified as the "eNTRy rules" and assisted by web application www.entry-way.org, we have facilitated compound entry and systematically built Gram-negative activity into Gram-positive-only antibiotics. Though each antibiotic will have case-specific considerations, we describe a set of important criteria to consider when selecting candidate Gram-positive-only antibiotics for conversion to Gram-negative-active versions via the eNTRy rules. As detailed herein, using this blueprint the spectrum of activity was expanded for three antibiotic classes that engage three different biological targets: DNA gyrase inhibitor 6DNM, FabI inhibitor Debio-1452, and FMN riboswitch inhibitor Ribocil C. In each scenario, the eNTRy rules guided the synthesis of key analogues predisposed to accumulate in Gram-negative bacteria leading to compounds that display antibiotic activity (minimum inhibitory concentrations (MIC) ≤8 μg mL^-1) against E. coli and other Gram-negative ESKAPE pathogens. While the eNTRy rules will continue to be refined and enhanced as more accumulation data is gathered, on the basis of these collective results and on other examples not covered herein it is clear that the eNTRy rules are actionable for the development of novel broad-spectrum antibiotics from Gram-positive-only compounds. By enabling the prediction of compound accumulation, the eNTRy rules should facilitate the process of discovering and developing novel antibiotics active against Gram-negative bacteria.

The Antibiotic Resistome: A Guide for the Discovery of Natural Products as Antimicrobial Agents

The use of life-saving antibiotics has long been plagued by the ability of pathogenic bacteria to acquire and develop an array of antibiotic resistance mechanisms. The sum of these resistance mechanisms, the antibiotic resistome, is a formidable threat to antibiotic discovery, development, and use. The study and understanding of the molecular mechanisms in the resistome provide the basis for traditional approaches to combat resistance, including semisynthetic modification of naturally occurring antibiotic scaffolds, the development of adjuvant therapies that overcome resistance mechanisms, and the total synthesis of new antibiotics and their analogues. Using two major classes of antibiotics, the aminoglycosides and tetracyclines as case studies, we review the success and limitations of these strategies when used to combat the many forms of resistance that have emerged toward natural product-based antibiotics specifically. Furthermore, we discuss the use of the resistome as a guide for the genomics-driven discovery of novel antimicrobials, which are essential to combat the growing number of emerging pathogens that are resistant to even the newest approved therapies.

History of penicillin

The history of penicillin was shaped by the contributions of numerous scientists. The ultimate result was the discovery of the mould Penicillium's antibacterial activity and the subsequent development of penicillins, the most widely used antibiotics. Following an accidental discovery of the mould, later identified as Penicillium rubens, as the source of the antibacterial principle (1928) and the production of a pure compound (1942), penicillin became the first naturally derived antibiotic. There is anecdotal evidence of ancient societies using moulds to treat infections and of awareness that various moulds inhibited bacterial growth. However, it is not clear if Penicillium species were the species traditionally used or if the antimicrobial substances produced were penicillin. In 1928, Alexander Fleming was the first to discover the antibacterial substance secreted by the Penicillium mould and concentrate the active substance involved, giving it the name penicillin. His success in treating Harry Lambert's streptococcal meningitis, an infection until then fatal, proved to be a critical moment in the medical use of penicillin. Many later scientists were involved in the stabilisation and mass production of penicillin and in the search for more productive strains of Penicillium. Among the most important were Ernst Chain and Howard Florey, who shared with Fleming the 1945 Nobel Prize in Physiology or Medicine.

Direct Antimicrobial Susceptibility Testing on Clinical Urine Samples by Optical Tracking of Single Cell Division Events

With the increasing prevalence of antibiotic resistance, the need to develop antimicrobial susceptibility testing (AST) technologies is urgent. The current challenge has been to perform the antibiotic susceptibility testing in short time, directly with clinical samples, and with antibiotics over a broad dynamic range of clinically relevant concentrations. Here, a technology for point-of-care diagnosis of antimicrobial-resistant bacteria in urinary tract infections, by imaging the clinical urine samples directly with an innovative large volume solution scattering imaging (LVSi) system and analyzing the image sequences with a single-cell division tracking method is developed. The high sensitivity of single-cell division tracking associated with large volume imaging enables rapid antibiotic susceptibility testing directly on the clinical urine samples. The results demonstrate direct detection of bacterial infections in 60 clinical urine samples with a 60 min LVSi video, and digital AST of 30 positive clinical samples with 100% categorical agreement with both the clinical culture results and the on-site agar plating validation results. This technology provides opportunities for precise antibiotic prescription and proper treatment of the patient within a single clinic visit.

Ampicillin sodium: Isolation, identification and synthesis of the last unknown impurity after 60 years of clinical use

Ampicillin, discovered in 1958, was the first broad spectrum semisynthetic penicillin introduced into the market. Despite its wide use not all the impurities have been identified to date. Herein, the last unknown impurity present in commercially available medicines was isolated and identified. This impurity that accounts up to 0.8 in area % by HPLC (EP 10.0) in the Reference Listed Drugs (RLD) was characterized and identified to be the 16-keto penicillin G. The structure was confirmed by comparison with a chemically synthesized sample. The determination of the Relative Response Factor (RRF) of the impurity respect to the parent drug allowed to recalculate the real amount that is consistently below the reporting threshold.

Iron-Catalyzed Amination of Strong Aliphatic C(sp3)-H Bonds

A concept for intramolecular denitrogenative C(sp³)-H amination of 1,2,3,4-tetrazoles bearing unactivated primary, secondary, and tertiary C-H bonds is discovered. This catalytic amination follows an unprecedented metalloradical activation mechanism. The utility of the method is showcased with the short synthesis of a bioactive molecule. Moreover, an initial effort has been embarked on for the enantioselective C(sp³)-H amination through the catalyst design. Collectively, this study underlines the development of C(sp³)-H bond functionalization chemistry that should find wide application in the context of drug discovery and natural product synthesis.

Noggin Inhibits IL-1β and BMP-2 Expression, and Attenuates Cartilage Degeneration and Subchondral Bone Destruction in Experimental Osteoarthritis

Osteoarthritis (OA) is a chronic inflammatory and progressive joint disease that results in cartilage degradation and subchondral bone remodeling. The proinflammatory cytokine interleukin 1 beta (IL-1β) is abundantly expressed in OA and plays a crucial role in cartilage remodeling, although its role in the activity of chondrocytes in cartilage and subchondral remodeling remains unclear. In this study, stimulating chondrogenic ATDC5 cells with IL-1β increased the levels of bone morphogenetic protein 2 (BMP-2), promoted articular cartilage degradation, and enhanced structural remodeling. Immunohistochemistry staining and microcomputed tomography imaging of the subchondral trabecular bone region in the experimental OA rat model revealed that the OA disease promotes levels of IL-1β, BMP-2, and matrix metalloproteinase 13 (MMP-13) expression in the articular cartilage and enhances subchondral bone remodeling. The intra-articular injection of Noggin protein (a BMP-2 inhibitor) attenuated subchondral bone remodeling and disease progression in OA rats. We also found that IL-1β increased BMP-2 expression by activating the mitogen-activated protein kinase (MEK), extracellular signal-regulated kinase (ERK), and specificity protein 1 (Sp1) signaling pathways. We conclude that IL-1β promotes BMP-2 expression in chondrocytes via the MEK/ERK/Sp1 signaling pathways. The administration of Noggin protein reduces the expression of IL-1β and BMP-2, which prevents cartilage degeneration and OA development.

Addition of ethylamines to the phenols of bithionol and synthetic retinoids does not elicit activity in gram-negative bacteria

Our labs have demonstrated the activity of bithionol and synthetic retinoids against methicillin-resistant Staphylococcus aureus (MRSA), as well as their membrane-acting mechanism of action. However, the compounds lack activity in gram-negative species. Herein, we apply a known strategy for converting gram-positive agents into broad-spectrum therapies: addition of an alkylamine. By appending an alkylamine to the phenols of these known membrane disruptors, we test whether this approach is applicable to our compounds. Ultimately, biological testing in four MRSA strains and three gram-negative species showed abolished or diminished activity in all our analogs compared to their parent compounds and no gram-negative activity. Thus, we find that alkylamines would not elicit broad-spectrum activity from bithionol or CD437 derivatives.

Aliphatic C-H Oxidations for Late-Stage Functionalization

The atomistic change of C( sp³)-H to C( sp³)-O can have a profound impact on the physical and biological properties of small molecules. Traditionally, chemical synthesis has relied on pre-existing functionality to install new functionality, and directed approaches to C-H oxidation are an extension of this logic. The impact of developing undirected C-H oxidation reactions with controlled site-selectivity is that scientists gain the ability to diversify complex structures at sites remote from existing functionality, without having to carry out individual de novo syntheses. This Perspective offers a historical view of why, as recently as 2007, it was thought that the differences between aliphatic C-H bonds of the same bond type (for example, 2° aliphatic) were not large enough to distinguish them preparatively with small-molecule catalysis in the absence of directing groups or molecular recognition elements. We give an account of the discovery of Fe(PDP)-catalyzed non-directed aliphatic C-H hydroxylations and how the electronic, steric, and stereoelectronic rules for predicting site-selectivity that emerged have affected a shift in how the chemical community views the reactivity among these bonds. The discovery that site-selectivity could be altered by tuning the catalyst [i.e., Fe(CF₃-PDP)] with no changes to the substrate or reaction now gives scientists the ability to exert control on the site of oxidation on a range of functionally and topologically diverse compounds. Collectively, these findings have made possible the emerging area of late-stage C-H functionalizations for streamlining synthesis and derivatizing complex molecules.

Manganese-catalysed benzylic C(sp3)-H amination for late-stage functionalization

Reactions that directly install nitrogen into C-H bonds of complex molecules are significant because of their potential to change the chemical and biological properties of a given compound. Although selective intramolecular C-H amination reactions are known, achieving high levels of reactivity while maintaining excellent site selectivity and functional-group tolerance remains a challenge for intermolecular C-H amination. Here, we report a manganese perchlorophthalocyanine catalyst [MnIII(ClPc)] for intermolecular benzylic C-H amination of bioactive molecules and natural products that proceeds with unprecedented levels of reactivity and site selectivity. In the presence of a Brønsted or Lewis acid, the [MnIII(ClPc)]-catalysed C-H amination demonstrates unique tolerance for tertiary amine, pyridine and benzimidazole functionalities. Mechanistic studies suggest that C-H amination likely proceeds through an electrophilic metallonitrene intermediate via a stepwise pathway where C-H cleavage is the rate-determining step of the reaction. Collectively, these mechanistic features contrast with previous base-metal-catalysed C-H aminations and provide new opportunities for tunable selectivities.

Chromatographic Methods for Quantitative Determination of Ampicillin, Dicloxacillin and Their Impurity 6-Aminopenicillanic Acid

Two accurate, precise and sensitive high-performance thin layer chromatography (HPTLC) and high-performance liquid chromatography (HPLC) methods were developed for assay of ampicillin (AMP) and dicloxacillin (DX) in the presence of their impurity, 6-aminopenicillanic acid (APA). Method (A) is HPTLC method; using silica gel HPTLC F254 plates as a stationary phase with methanol: chloroform: acetic acid (1:9: 0.2, by volume) as a developing system. All the bands were scanned at 220 nm. Method (B) is reversed phase- HPLC which depended on isocratic elution using C18 column and mobile phase consisting of acetonitrile: water (60:40, v/v), pH adjusted to 4 with orthophosphoric acid, at a flow rate of 1 mL min-1 and ultraviolet detection at 240 nm. The proposed methods were validated as per ICH guidelines and their linearity was evident in the ranges of 0.5-2 μg band-1, 0.4-2 μg band-1 and 0.2-1.2 μg band-1 for method (A) and 5-40 μg mL-1, 5-40 μg mL-1 and 2-16 μg mL-1 for method (B) for AMP, DX and APA, respectively. The proposed methods were successfully used for assay of AMP and DX in pure form and in pharmaceutical formulation where no interference from the excipients was detected.

The challenge of converting Gram-positive-only compounds into broad-spectrum antibiotics

Multidrug resistant Gram-negative bacterial infections are on the rise, and there is a lack of new classes of drugs to treat these pathogens. This drug shortage is largely due to the challenge of finding antibiotics that can permeate and persist inside Gram-negative species. Efforts to understand the molecular properties that enable certain compounds to accumulate in Gram-negative bacteria based on retrospective studies of known antibiotics have not been generally actionable in the development of new antibiotics. A recent assessment of the ability of >180 diverse small molecules to accumulate in Escherichia coli led to predictive guidelines for compound accumulation in E. coli. These "eNTRy rules" state that compounds are most likely to accumulate if they contain a nonsterically encumbered ionizable Nitrogen (primary amines are the best), have low Three-dimensionality (globularity ≤ 0.25), and are relatively Rigid (rotatable bonds ≤ 5). In this review, we look back through 50+ years of antibacterial research and 1000s of derivatives and assess this historical data set through the lens of these predictive guidelines. The results are consistent with the eNTRy rules, suggesting that the eNTRy rules may provide an actionable and general roadmap for the conversion of Gram-positive-only compounds into broad-spectrum antibiotics.

The behavioral effects of antibiotic treatment on the snail Biomphalaria glabrata

Schistosomiasis is a detrimental neglected tropical disease that is transmitted by Planorbid snails. Understanding the transmission and control of this disease requires an extensive understanding of these intermediate hosts, which is only achieved by the effective rearing and study of species such as Biomphalaria glabrata. This species is the intermediate host for Schistosoma mansoni in the New World, and is also the main model for studying schistosomes in mollusks. Antibiotics are used routinely in B. glabrata tissue culture, and occasionally on live snails. Here we show that standard doses of three common antibiotics (penicillin, streptomycin and gentamicin) drastically diminish the activity of healthy B. glabrata, but that treated snails recover rapidly when placed in fresh water. Ampicillin treated snails did not show altered activity. We suggest that researchers keep these apparent toxicities in mind if a need for antibiotic treatment of live Planorbid snails arises.

Potential of saprophage Diptera to acquire culturable livestock-associated antibiotic-resistant bacteria

The increasing prevalence of antibiotic resistance among bacteria is one of the most intractable challenges in 21st-century public health. Dipterans that associate with livestock, livestock waste products and cadavers have the potential to acquire livestock-associated antibiotic-resistant bacteria (LA-ARB) and transmit them to humans. In this study, piglet cadavers were used to attract saprophage dipterans from the environment and those dipterans were sampled for the presence of LA-ARB. In the first trial, culturable microbes resistant to both aminoglycoside and β-lactam antibiotics were found in all cadavers and masses of dipteran larvae, and in three-quarters of adult dipterans. In the second trial, over 130 culturable bacterial colonies resistant to β-lactams were isolated from the cadavers, larval and adult dipterans. Over 100 of those colonies were coliform or metabolically similar bacteria. Adult dipterans carried β-lactam resistant staphylococci, whereas those bacterial types were absent from larval dipterans and cadavers, suggesting they were picked up from elsewhere in the environment. This research indicates that LA-ARB are ubiquitous in pig farms, and dipterans have the potential to carry medically important microbes. Further research is encouraged to determine the extent to which dipterans acquire microbes from animal agriculture relative to other environments.

Circular dichroism spectroscopy: An efficient approach for the quantitation of ampicillin in presence of cloxacillin

Ampicillin exhibited a negative and a positive cotton effects on the circular dichroism (CD) spectra in the wavelength range of 200-280nm. Cloxacillin showed a positive cotton band peaking at 228nm. Three sensitive, precise and accurate CD spectroscopic methods have been developed for the determination of ampicillin and cloxacillin. Method A was used for the determination of ampicillin in presence of cloxacillin by measuring ellipticity at 206nm. Method B and C were employed to determine ampicillin and cloxacillin based on evaluation of ellipticity at 233nm and 228nm, respectively. Methods A, B and C showed linearity in the concentration range of 10-40μgmL(-1), 5-40μgmL(-1) ampicillin and 10-80μgmL(-1) cloxacillin, respectively. The method A was successfully applied to the determination of ampicillin in commercial dosage forms containing equivalent amount of cloxacillin.

Impact of maternal intrapartum antibiotics, method of birth and breastfeeding on gut microbiota during the first year of life: a prospective cohort study

OBJECTIVE

Dysbiosis of the infant gut microbiota may have long-term health consequences. This study aimed to determine the impact of maternal intrapartum antibiotic prophylaxis (IAP) on infant gut microbiota, and to explore whether breastfeeding modifies these effects.

DESIGN

Prospective pregnancy cohort of Canadian infants born in 2010-2012: the Canadian Healthy Infant Longitudinal Development (CHILD) Study.

SETTING

General community.

SAMPLE

Representative sub-sample of 198 healthy term infants from the CHILD Study.

METHODS

Maternal IAP exposures and birth method were documented from hospital records and breastfeeding was reported by mothers. Infant gut microbiota was characterised by Illumina 16S rRNA sequencing of faecal samples at 3 and 12 months.

MAIN OUTCOME MEASURES

Infant gut microbiota profiles.

RESULTS

In this cohort, 21% of mothers received IAP for Group B Streptococcus prophylaxis or pre-labour rupture of membranes; another 23% received IAP for elective or emergency caesarean section (CS). Infant gut microbiota community structures at 3 months differed significantly with all IAP exposures, and differences persisted to 12 months for infants delivered by emergency CS. Taxon-specific composition also differed, with the genera Bacteroides and Parabacteroides under-represented, and Enterococcus and Clostridium over-represented at 3 months following maternal IAP. Microbiota differences were especially evident following IAP with emergency CS, with some changes (increased Clostridiales and decreased Bacteroidaceae) persisting to 12 months, particularly among non-breastfed infants.

CONCLUSIONS

Intrapartum antibiotics in caesarean and vaginal delivery are associated with infant gut microbiota dysbiosis, and breastfeeding modifies some of these effects. Further research is warranted to explore the health consequences of these associations.

TWEETABLE ABSTRACT

Maternal #antibiotics during childbirth alter the infant gut #microbiome.

LC-MS/MS measurement of ampicillin residue in swine tissues at 5 days after in-feed administration

We assessed ampicillin (ABPC) concentrations of kidney, muscle and intestine after a 5-day withdrawal period in 2 male and a female young Large White pigs fed the diet containing ABPC (ABPC medicated feed, 24 mg/kg/day) for a week. The ABPC residues were measured with liquid chromatography-tandem mass spectrometry, and the mean recoveries and quantitation limits ranged from 91.8 to 97.2% and from 0.1 to 0.12 ng/g, respectively. The residual ABPC concentrations were ≤1.18 ng/g for the muscle, ≤0.53 ng/g for the kidney and ≤1.93 ng/g for the intestine, suggesting below the Japanese provisional maximum residue limits. These results reveal that the analytical method is developed for residual ABPC and that the withdrawal period is appropriate.

High-throughput sequencing reveals the incomplete, short-term recovery of infant gut microbiota following parenteral antibiotic treatment with ampicillin and gentamicin

The infant gut microbiota undergoes dramatic changes during the first 2 years of life. The acquisition and development of this population can be influenced by numerous factors, and antibiotic treatment has been suggested as one of the most significant. Despite this, however, there have been relatively few studies which have investigated the short-term recovery of the infant gut microbiota following antibiotic treatment. The aim of this study was to use high-throughput sequencing (employing both 16S rRNA and rpoB-specific primers) and quantitative PCR to compare the gut microbiota of nine infants who underwent parenteral antibiotic treatment with ampicillin and gentamicin (within 48 h of birth), 4 and 8 weeks after the conclusion of treatment, relative to that of nine matched healthy controls. The investigation revealed that the gut microbiota of the antibiotic-treated infants had significantly higher proportions of Proteobacteria (P = 0.0049) and significantly lower proportions of Actinobacteria (P = 0.00001) (and the associated genus Bifidobacterium [P = 0.0132]) as well as the genus Lactobacillus (P = 0.0182) than the untreated controls 4 weeks after the cessation of treatment. By week 8, the Proteobacteria levels remained significantly higher in the treated infants (P = 0.0049), but the Actinobacteria, Bifidobacterium, and Lactobacillus levels had recovered and were similar to those in the control samples. Despite this recovery of total Bifidobacterium numbers, rpoB-targeted pyrosequencing revealed that the number of different Bifidobacterium species present in the antibiotic-treated infants was reduced. It is thus apparent that the combined use of ampicillin and gentamicin in early life can have significant effects on the evolution of the infant gut microbiota, the long-term health implications of which remain unknown.

Antibiotics suppress Cyp3a in the mouse liver by reducing lithocholic acid-producing intestinal flora

We previously demonstrated that ciprofloxacin (CPX), a new quinolone antibiotic, suppresses Cyp3a in the mouse liver by reducing the hepatic level of lithocholic acid (LCA) produced by intestinal flora. The present study investigated the possibility that other antibiotics with antibacterial activity against LCA-producing bacteria also cause a decrease in the LCA level in the liver, leading to reduced expression of Cyp3a11. While the mRNA expression of Cyp3a11 in the liver was significantly reduced when SPF mice were administered antibiotics such as ampicillin, CPX, levofloxacin, or a combination of vancomycin and imipenem, no significant changes were observed after antibiotic treatment of GF mice lacking intestinal flora. LCA-producing bacteria in the feces as well as the hepatic level of the taurine conjugate of LCA were significantly reduced in the antibiotic-treated SPF mice, suggesting that the decrease in Cyp3a11 expression can be attributed to the reduction in LCA-producing intestinal flora following antibiotic administration. These results suggest that the administration of antibiotics with activity against LCA-producing bacteria can also cause a decrease in the LCA level in humans, which may lower CYP3A4 expression. The intestinal flora are reported to be altered not only by drugs, such as antibiotics, but also by stress, disease, and age. The findings of the present study suggest that these changes in intestinal flora could modify CYP expression and contribute to the individual differences in pharmacokinetics.

Formulation development and in vitro and in vivo evaluation of membrane-moderated transdermal systems of ampicillin sodium in ethanol: pH 4.7 buffer solvent system

The objective of the present study was to develop membrane-moderated transdermal systems of ampicillin sodium and to evaluate them with respect to various in vitro and in vivo parameters. The membrane-type transdermal systems were prepared using a drug with various antinucleant polymers-hydroxypropyl methylcellulose (HPMC), methylcellulose (MC), cellulose acetate phthalate, chitosan, sodium alginate (SA), and sodium carboxymethylcellulose-in an ethanol: pH 4.7 buffer volatile system by the solvent evaporation technique with HPMC as the rate-controlling membrane for all the systems. The swelling properties of the polymers were studied, and drug-polymer interaction studies were performed. The patches were subjected to various physicochemical studies, in vitro release studies, permeation studies, and skin irritation studies. The best patch among the formulations was selected for further in vivo studies. Compared to the other patches, SA exhibited the highest moisture content at 16%; a 21% moisture uptake was found with MC. The release and permeation of the drug from the SA patch was found to be the maximum. The in vivo study of the SA patch exhibited a peak plasma concentration C(max) of 126 microg/mL at T(max) 4 hours. Hence, it can be concluded that hydrophilic ampicillin sodium can be developed as a transdermal delivery system with SA that is an alternative to intravenous administration and has minimal adverse effects.

ACTIVITY OF AMPICILLIN IN VITRO COMPARED WITH OTHER ANTIBIOTICS

Comparative tests in vitro for antibacterial activity were carried out with ampicillin, tetracycline, and chloramphenicol using 673 clinical isolates of Gram-negative bacilli and Streptococcus faecalis. Further comparative tests were also carried out with ampicillin, chloramphenicol, colistin sulphate, colistin methane sulphonate, cycloserine, kanamycin, nitrofurantoin, polymyxin, streptomycin, and tetracycline, using groups of 20 strains of each of the main species selected at random from the total number of isolates. Of the total number of isolates a higher percentage was inhibited by ampicillin than by tetracycline or chloramphenicol. Ampicillin showed particularly high activity against certain species of bacteria and displayed an antibacterial spectrum not shown by any of the other antibiotics tested.

FURTHER PHARMACOLOGY AND CHEMOTHERAPY OF CLOXACILLIN

In concentrations greatly in excess of therapeutic blood levels cloxacillin has a slight hypotensive action. As with other antibiotics, it sometimes causes diarrhoea in rabbits but, in doses up to 200 mg/kg, it does not have a teratogenic effect on the rabbit foetus. Cloxacillin is distributed throughout the body. High concentrations are found only in the liver and kidney, these reflecting the high concentrations in the bile and urine respectively. It differs from other penicillins investigated in that there appears to be little or no renal tubular secretion as demonstrated in experiments on the hen. Cloxacillin is excreted as the unchanged drug and as an active metabolite in the urine and bile. After oral administration it is metabolized in the caecum giving a penicillin which differs from the urinary metabolite and which has a greater antibiotic action against Sarcina lutea than the parent penicillin. The activity of the caecal metabolite against resistant and sensitive strains of Staphylococcus, however, remains similar to that of cloxacillin. Against infections due to resistant and sensitive Staphylococcus in animals cloxacillin is active by both the oral and subcutaneous routes and it is more effective orally than an equal subcutaneous dose of methicillin.

Pharmacokinetics and distribution of ticarcillin-clavulanic acid (Timentin) in experimental animals

The pharmacokinetics and distribution of ticarcillin and clavulanic acid were studied in rats and rabbits after intravenous coadministration of the compounds. The elimination half-lives for ticarcillin and clavulanic acid were similar in both rats (ticarcillin, 0.22 h; clavulanic acid, 0.24 h) and rabbits (ticarcillin, 0.38 h; clavulanic acid, 0.31 h). Both compounds distributed widely throughout rat tissues, and the patterns of distribution were similar to those observed for other beta-lactams. Values for penetration into rat pleural, peritoneal, and subcutaneous fluids calculated from the equation (AUCfluid/AUCserum) X 100, where AUC is the area under the concentration-time curve, were between 83 and 93% for ticarcillin and 86 and 103% for clavulanic acid. Values for penetration into tissue cages in rabbits were 139% +/- 45% for ticarcillin and 109% +/- 22% for clavulanic acid. The penetration of clavulanic acid into rabbit cerebrospinal fluid was higher (P less than 0.05) (4.0% +/- 0.61%) than that of ticarcillin (1.3% +/- 0.53%). Overall, the results show that ticarcillin and clavulanic acid distribute readily throughout body tissues and fluids and predict that the penicillin and beta-lactamase inhibitor would be present together at sites of infection.