Efficacy of antimicrobial peptide P113 oral health care products on the reduction of oral bacteria number and dental plaque formation in a randomized clinical assessment

Background/purpose

Dental plaque is the main cause leading to the dental caries and periodontal diseases. The main purpose of this study was to test the efficacy of oral spray containing the antimicrobial peptide P-113 on the reduction of oral bacteria number and dental plaque formation in a randomized clinical assessment.

Materials and methods

This study was divided into two parts. In Part A, we investigated the user experiences with the P-113 containing oral spray. In part B, 14 subjects in the experimental group used the P-113-containing oral spray, while 14 subjects in the control group used a placebo without the P-113 in a 4-week clinical trial. Participants were asked to use the P-113-containing oral spray or placebo 3 times per day and 5 times per use. Moreover, 3 check-ups and 2 washouts were carried out to evaluate the DMFT score, dental plaque weight, dental plaque index, and gingival index.

Results

In part A, up to 91.8% of the subjects in the experimental group were satisfied with the use of the P-113-containing oral spray. In part B, based on our PacBio SMRT sequencing platform and DADA2 analysis, the numbers of Streptococcus and Porphyromonas in the experimental group were lower than those in the control group. In addition, decreased dental plaque weight, dental plaque index, and gingival index were all observed in the experimental group.

Conclusion

The P-113-containing oral spray has the potential to reduce the dental caries and periodontal disease-related bacteria and to control the dental plaque formation.

Microneedles as a potential platform for improving antibiotic delivery to bacterial infections

Bacterial infections are mainly managed by the administration of antibiotics, which are either cytotoxic or cytostatic to microbes. In some cases, it is inconvenient to treat infections caused by bacteria using the traditional oral route for antibiotic administration. This can be due to the limited oral bioavailability of antibiotics, their gastrointestinal tract (GIT) adverse effects, and the increased possibility of the appearance of resistant strains. In addition, the fact that many populations are needle-phobic restricts the switch from the oral to the parenteral route. Furthermore, poor drug permeation throughout the stratum corneum of topically applied antibiotics causes low systemic bioavailability. Therefore, microneedles (MNs) have emerged as viable medicinal devices for the delivery of antibiotics, either for local or systemic effects. MNs represent a minimally invasive, painless way of administration that can be self-administered by the patient without the need of medical professionals. This review has specifically focused on MNs as a promising approach for the delivery of antibiotics; it has discussed the different types of MNs, their advantages, and possible limitations for the delivery of antibiotics. Recent studies on the incorporation of antibiotics into various types of MNs, either for topical or transdermal delivery are highlighted, and finally, we present the conclusion and future perspectives.

Novel nickel(II) phthalocyanine/reduced graphene oxide: an electrochemical sensing platform for analysis of hydroquinone and chloramphenicol in environmental samples

Novel tetra-2-(biphenyl-4-yl)-1,3-benzoxazol-carboxamide nickel(II) phthalocyanine (NiTBPBXCAPc) and rGO were confirmed using FT-IR, UV-vis, XRD, TGA and Raman spectra. The NiTBPBXCAPc and rGO nanocomposite has been developed to detect hydroquinone (HQN) and chloramphenicol (CPC). NiTBPBXCAPc has been examined using cyclic voltammetry (CV), linear sweep voltammetry (LSV), differential pulse voltammetry (DPV) and electrochemical impedance spectroscopy (EIS) analysis. The simultaneous CV analysis of HQN and CPC demonstrated the ability of NiTBPBXCAPc@rGO/GCE to execute simultaneous redox reactions. The voltammetric and amperometric limit of detection for HQN and CPC was determined to be 4.5 and 3.5 nM respectively, with a sensitivity of 0.446 and 0.416 μA M-1 cm-2. The amperometric LOD was observed to be 5 and 4 nM with a sensitivity of 0.235 and 0.288 μA M-1 cm-2. Additionally, the NiTBPBXCAPc@rGO/GC electrode is also used for real sample analysis with outstanding recovery. The long-term storage stability, reusability, and real-world sample analysis of the NiTBPBXCAPc@rGO/GC electrode demonstrated its use in environmental analysis.

Hydrogel-forming microarray patch mediated transdermal delivery of tetracycline hydrochloride

Antibiotic resistance is one of the most serious health problems today and is expected to worsen in the coming decades. It has been suggested that antibiotic administration routes that bypass the human gut could potentially tackle this problem. In this work, an antibiotic hydrogel-forming microarray patch (HF-MAP) system, which can be used as an alternative antibiotic delivery technology, has been fabricated. Specifically, poly(vinyl alcohol)/poly(vinylpyrrolidone) (PVA/PVP) microarray showed excellent swelling properties with >600% swelling in PBS over 24 h. The tips on the HF-MAP were proven to be able to penetrate a skin model which is thicker than stratum corneum. The antibiotic (tetracycline hydrochloride) drug reservoir was mechanically robust and dissolved completely in an aqueous medium within a few minutes. In vivo animal studies using a Sprague Dawley rat model showed antibiotic administration using HF-MAP achieved a sustained release profile, in comparison with animals receiving oral gavage and intravenous (IV) injection, with a transdermal bioavailability of 19.1% and an oral bioavailability of 33.5%. The maximum drug plasma concentration for HF-MAP group reached 7.40 ± 4.74 μg/mL at 24 h, whereas the drug plasma concentration for both oral (5.86 ± 1.48 μg/mL) and IV (8.86 ± 4.19 μg/mL) groups peaked soon after drug administration and had decreased to below the limit of detection at 24 h. The results demonstrated that antibiotics can be delivered by HF-MAP in a sustained manner.

Novel N-doped carbon dots derived from citric acid and urea: fluorescent sensing for determination of metronidazole and cytotoxicity studies

Blue emitting nitrogen-doped carbon dots were synthesized using citric acid and urea through the hydrothermal method, and the fluorescence quantum yield was 35.08%. We discovered that N-CDs featured excellent robust fluorescence stability and chemical resistance. For metronidazole detection, our N-CDs exhibited quick response time, high selectivity and sensitivity, and low cytotoxicity. Specifically, our N-CDs could detect metronidazole in the linear range of 0-179 μM, and the LOD was 0.25 μM. Furthermore, metronidazole efficaciously quenches the fluorescence of N-CDs, possibly owing to the inner filter effect. Lastly, we have employed our N-CDs to detect metronidazole in commercial metronidazole tablets with high accuracy. Overall, the newly prepared fluorescence sensor, N-CDs, demonstrated a huge potential to detect metronidazole in a simple, efficient, sensitive, and rapid manner.

Evaluation of in-vitro colistin susceptibility and clinical profile of carbapenem resistant Enterobacteriaceae related invasive infections

PURPOSE

To determine the colistin susceptibility. To compare E-test vs broth-microdilution (BMD) method for invasive carbapenem resistant Enterobacteriaceae (CRE) infections. To study treatment options for the CRE. To analyze the clinical profile and outcome of CRE infections.

METHODS

Antimicrobial susceptibility testing was performed for 100 invasive CRE isolates. Gradient diffusion and BMD methods were performed to determine colistin MICs. Essential agreement (EA), categorical agreement (CA), very major error (VME), and major error (ME) were worked out between BMD method and E-test. The clinical profile of patients was analyzed.

RESULTS

The majority of the patients suffered from bacteremia [47(47%)]. Klebsiella pneumoniae was the most common organism isolated overall as well as among bacteremic isolates. 9(9%) CRE isolates were colistin resistant by BMD of which six were Klebsiella pneumoniae. There was 97% CA between E-test and BMD. EA was 68%. VME was found in three out of nine colistin resistant isolates. No ME was found. Among the other antibiotics tested for CRE isolates, the highest susceptibility was seen to tigecycline [43(43%)] followed by amikacin [19 (19%)]. The most common underlying condition was post solid organ transplantation [36(36%)]. A higher survival rate was seen among non-bacteremic CRE infections (58.49%) than bacteremic CRE infections (42.6%). Four out of nine patients with colistin resistant CRE infections survived and had a satisfactory outcome.

CONCLUSION

Klebsiella pneumoniae was the most common organism causing invasive infection. Survival rates were higher in non-bacteremic CRE infections than bacteremic infections. Good CA was seen between E-test and BMD for colistin susceptibility, but the EA was poor. VME was more common than ME when E-tests were used for colistin susceptibility testing resulting in false susceptibility. Tigecycline and aminoglycosides are possible adjunct drugs for the treatment of invasive CRE infections.

Resistance to Critical Important Antibacterials in Staphylococcus pseudintermedius Strains of Veterinary Origin

Staphylococcal infections represent a challenge in companion animals and hospitalized patients. This study aimed to assess the resistance of Staphylococcus pseudintermedius isolates, against a broad panel of antibacterials, including exclusive to human medicine. A total of 40 S. pseudintermedius were collected from clinical specimens of dogs (n = 31) and cats (n = 5). All strains were tested for 20 antibacterials, namely 14 Critical Important and eight Highly Important Antibacterials (CIA and HIA, respectively), indicative for 18 antimicrobial classes. All strains were susceptible to seven antibiotics (daptomycin, fosfomycin, fusidic acid, linezolid, quinupristin-dalfopristin, teicoplanin/vancomycin, tigecycline). The highest resistance was against penicillin (97.5% Confidence Interval [CI]: 83.8-100.0), whereas the lowest against telavancin (2.5%, CI: 0.0-16.2). Resistance versus Highest Priority CIA was observed, namely against macrolides (70.0, CI: 52.1-84.3), quinolones (62.5, CI: 44.5-78.3), 5th generation cephalosporins (7.5, CI: 1.3-21.6), and glycopeptides (2.5%, CI: 0.0-14.2). Among High Priority CIA, strains were resistant only to aminoglycosides (65.0, CI: 47.0-80.4) and ansamycins (12.5, CI: 3.8-28.1). We observed the highest resistance against veterinary medicine antibacterials, but there was also resistance against antibacterials exclusive to human medicine, namely ceftaroline (7.5, CI: 1.0-23.8) and telavancin. S. pseudintermedius zoonotic potential and its rate of acquisition of new resistance should encourage surveillance on a broad spectrum of antibacterials.

Assessing Clinical Potential of Old Antibiotics against Severe Infections by Multi-Drug-Resistant Gram-Negative Bacteria Using In Silico Modelling

In the light of increasing antimicrobial resistance among gram-negative bacteria and the lack of new more potent antimicrobial agents, new strategies have been explored. Old antibiotics, such as colistin, temocillin, fosfomycin, mecillinam, nitrofurantoin, minocycline, and chloramphenicol, have attracted the attention since they often exhibit in vitro activity against multi-drug-resistant (MDR) gram-negative bacteria, such as Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii. The current review provides a summary of the in vitro activity, pharmacokinetics and PK/PD characteristics of old antibiotics. In silico modelling was then performed using Monte Carlo simulation in order to combine all preclinical data with human pharmacokinetics and determine the probability of target (1-log kill in thigh/lung infection animal models) attainment (PTA) of different dosing regimens. The potential of clinical efficacy of a drug against severe infections by MDR gram-negative bacteria was considered when PTA was >95% at the epidemiological cutoff values of corresponding species. In vitro potent activity against MDR gram-negative pathogens has been shown for colistin, polymyxin B, temocillin (against E. coli and K. pneumoniae), fosfomycin (against E. coli), mecillinam (against E. coli), minocycline (against E. coli, K. pneumoniae, A. baumannii), and chloramphenicol (against E. coli) with ECOFF or MIC90 ≤ 16 mg/L. When preclinical PK/PD targets were combined with human pharmacokinetics, Monte Carlo analysis showed that among the old antibiotics analyzed, there is clinical potential for polymyxin B against E. coli, K. pneumoniae, and A. baumannii; for temocillin against K. pneumoniae and E. coli; for fosfomycin against E. coli and K. pneumoniae; and for mecillinam against E. coli. Clinical studies are needed to verify the potential of those antibiotics to effectively treat infections by multi-drug resistant gram-negative bacteria.

Boswellic Acids as Effective Antibacterial Antibiofilm Agents

Boswellic acids are biologically active pentacyclic terpenoid compounds derived from Boswellia sp. plants. Extracts containing these acids have a number of positive effects on human health, especially in the treatment of inflammation, arthritis, or asthma. With increasing resistance to common antibiotics, boswellic acid-containing extracts could serve as an alternative or work in synergy with commonly available preparations. This study aims to determine the effect of boswellic acids on suspension cells and biofilms of Staphylococcus epidermidis, Enterococcus faecalis, and Escherichia coli. The antimicrobial and antibiofilm effect found was compared with commonly available antibiotics to control these undesirable microorganisms. The synergistic effect of boswellic acids and common antibiotics on the growth of these microorganisms was also determined. All tested microorganisms showed a positive additive effect of antibiotics and boswellic acid extract. The most significant effect was found in Enterococcus faecalis ATCC 29212 in a combination of 0.2 × MIC80 erythromycin (0.2 mg/L) and 0.8 × MIC80 boswellic acid extract (16 mg/L).

Convergent phenotypic evolution towards fosfomycin collateral sensitivity of Pseudomonas aeruginosa antibiotic-resistant mutants

The rise of antibiotic resistance and the reduced amount of novel antibiotics support the need of developing novel strategies to fight infections, based on improving the use of the antibiotics we already have. Collateral sensitivity is an evolutionary trade-off associated with the acquisition of antibiotic resistance that can be exploited to tackle this relevant health problem. However, different works have shown that patterns of collateral sensitivity are not always conserved, thus precluding the exploitation of this evolutionary trade-off to fight infections. In this work, we identify a robust pattern of collateral sensitivity to fosfomycin in Pseudomonas aeruginosa antibiotic-resistant mutants, selected by antibiotics belonging to different structural families. We characterize the underlying mechanism of the collateral sensitivity observed, which is a reduced expression of the genes encoding the peptidoglycan-recycling pathway, which preserves the peptidoglycan synthesis in situations where its de novo synthesis is blocked, and a reduced expression of fosA, encoding a fosfomycin-inactivating enzyme. We propose that the identification of robust collateral sensitivity patterns, as well as the understanding of the molecular mechanisms behind these phenotypes, would provide valuable information to design evolution-based strategies to treat bacterial infections.

Phytochemical and pharmacological anti-diabetic properties of bilberries (Vaccinium myrtillus), recommendations for future studies

Nowadays, extensive attention has focused on dietary constituents that may be valuable for treating, eating, and preventing diabetes. Numerous studies have shown that anthocyanin's are one of the most important nutritional factors associated with diabetes. Anthocyanin's are the leading group of water-soluble pigments in the plant kingdom, and they are generally available in some human diet in fruits, vegetables, cereals, beans. Amongst, bilberries (Vaccinium myrtillus), is one of the essential sources for dietary anthocyanin consumption containing vast amounts of anthocyanin's, making them the main plant in the treatment and prevention of diabetes. Although the bilberries have other valuable properties such as anti-cancer, anti-inflammatory, and antioxidant, the main focus of the present study is to present the effects of bilberries (V. myrtillus) on the prevention and treatment of diabetes.

Nanobiotic formulations as promising advances for combating MRSA resistance: susceptibilities and post-antibiotic effects of clindamycin, doxycycline, and linezolid

Antimicrobial activity and post-antibiotic effects (PAEs) are both important parameters in determination of the dosage regimen of antimicrobial agents. In the present study, antimicrobial activity and PAEs of clindamycin, doxycycline, linezolid, and their nanobiotic formulations were evaluated against two methicillin resistant Staphylococcus aureus clinical isolates (MRSA) encoded (MRSA-S1 and MRSA-S2). Nanobiotic formulations increased the susceptibility of MRSA isolates by 4-64 folds as compared to their conventional ones. The PAE values were determined after exposure of MRSA isolates for 1 h to 10× the MICs of the tested antibiotics. The duration of PAEs were recorded after bacterial growth in Mueller Hinton broth (MHB) free from antibiotic has been restored. The PAE values for MRSA-S1 were 2.5 h for the conventional antibiotics. However, the PAEs for nanobiotics were 4 h for both clindamycin and linezolid, while 3 h for doxycycline. For MRSA-S2, linezolid and linezolid nanobiotics PAEs were 3 h. PAEs of clindamycin and clindamycin nanobiotics were 3.75 h and 4 h, respectively. Doxycycline and doxycycline nanobiotics revealed the same PAEs patterns of 3.5 h. The findings of the current study may positively influence the pharmacodynamics of the antibiotics and consequently the dosage regimen of nanobiotics as well as on their clinical outcome.

Prescribing Patterns for Upper Respiratory Tract Infections: A Prescription-Review of Primary Care Practice in Quetta, Pakistan and the Implications

Background: To identify and address the potential overuse of antibiotics, it is important to ascertain the prescribing practices of physicians. We, therefore, conducted this prescription analysis to document URTI-specific antibiotic prescription frequency in a public primary healthcare setting of Quetta city, Pakistan.

Methods: A retrospective record review was conducted of all prescriptions for URTIs in Combined Military Hospital, Quetta from 1 March to 31st May 2021. The Mann-Whitney U and Jonckheere–Terpstra test was used to evaluate the association between the tendencies of a different group of prescribers. p-value of <0.05 was of statistical significance.

Results: Over the 3 months, 50,705 prescriptions were screened and analyzed according to the established inclusion and exclusion criteria. A total of 4,126 (8.13%) URTI prescriptions met the inclusion criteria, of which 2,880 (69.80%) prescriptions contained antibiotics. Among all antibiotics, penicillins (Amoxicillin + Clavulanate) were the most prescribed antibiotic, constituting 1,323 (45.9%) of total antibiotics prescribed for all cases, followed by the Macrolide group 527 (18.2%). The Jonckheere–Terpstra test revealed a statistically significant association between the status of the prescriber and the diagnosis (p = 0.002). Furthermore, a moderate positive trend was reported with specialists being more competent in antibiotic prescribing based on their diagnosis, followed by postgraduates and house officers (τ = 0.322).

Conclusion: The prescribing patterns for the management of URTIs in the hospital were inconsistent with current guidelines. Strict adherence to guidelines must be ensured and antibiotic prescribing for URTIs should be discouraged.

How to Combat Gram-Negative Bacteria Using Antimicrobial Peptides: A Challenge or an Unattainable Goal?

Antimicrobial peptides (AMPs) represent a promising and effective alternative for combating pathogens, having some advantages compared to conventional antibiotics. However, AMPs must also contend with complex and specialised Gram-negative bacteria envelops. The variety of lipopolysaccharide and phospholipid composition in Gram-negative bacteria strains and species are decisive characteristics regarding their susceptibility or resistance to AMPs. Such biological and structural barriers have created delays in tuning AMPs to deal with Gram-negative bacteria. This becomes even more acute because little is known about the interaction AMP–Gram-negative bacteria and/or AMPs’ physicochemical characteristics, which could lead to obtaining selective molecules against Gram-negative bacteria. As a consequence, available AMPs usually have highly associated haemolytic and/or cytotoxic activity. Only one AMP has so far been FDA approved and another two are currently in clinical trials against Gram-negative bacteria. Such a pessimistic panorama suggests that efforts should be concentrated on the search for new molecules, designs and strategies for combating infection caused by this type of microorganism. This review has therefore been aimed at describing the currently available AMPs for combating Gram-negative bacteria, exploring the characteristics of these bacteria’s cell envelop hampering the development of new AMPs, and offers a perspective regarding the challenges for designing new AMPs against Gram-negative bacteria.

Allogenous Selection of Mutational Collateral Resistance: Old Drugs Select for New Resistance Within Antibiotic Families

Allogeneous selection occurs when an antibiotic selects for resistance to more advanced members of the same family. The mechanisms of allogenous selection are (a) collateral expansion, when the antibiotic expands the gene and gene-containing bacterial populations favoring the emergence of other mutations, inactivating the more advanced antibiotics; (b) collateral selection, when the old antibiotic selects its own resistance but also resistance to more modern drugs; (c) collateral hyper-resistance, when resistance to the old antibiotic selects in higher degree for populations resistant to other antibiotics of the family than to itself; and (d) collateral evolution, when the simultaneous or sequential use of antibiotics of the same family selects for new mutational combinations with novel phenotypes in this family, generally with higher activity (higher inactivation of the antibiotic substrates) or broader spectrum (more antibiotics of the family are inactivated). Note that in some cases, collateral selection derives from collateral evolution. In this article, examples of allogenous selection are provided for the major families of antibiotics. Improvements in minimal inhibitory concentrations with the newest drugs do not necessarily exclude “old” antibiotics of the same family of retaining some selective power for resistance to the newest agents. If this were true, the use of older members of the same drug family would facilitate the emergence of mutational resistance to the younger drugs of the family, which is frequently based on previously established resistance traits. The extensive use of old drugs (particularly in low-income countries and in farming) might be significant for the emergence and selection of resistance to the novel members of the family, becoming a growing source of variation and selection of resistance to the whole family. In terms of future research, it could be advisable to focus antimicrobial drug discovery more on the identification of new targets and new (unique) classes of antimicrobial agents, than on the perpetual chemical exploitation of classic existing ones.

Multifunctional Nanofibrous Dressing with Antimicrobial and Anti-Inflammatory Properties Prepared by Needle-Free Electrospinning

An active wound dressing should address the main goals in wound treatment, which are improved wound healing and reduced infection rates. We developed novel multifunctional nanofibrous wound dressings with three active ingredients: chloramphenicol (CAM), beta-glucan (βG) and chitosan (CHI), of which βG and CHI are active nanofiber-forming biopolymers isolated from the cell walls of Saccharomyces cerevisiae and from shrimp shells, respectively. To evaluate the effect of each active ingredient on the nanofibers' morphological features and bioactivity, nanofibers with both βG and CHI, only βG, only CHI and only copolymers, polyethylene oxide (PEO) and hydroxypropylmethylcellulose (HPMC) were fabricated. All four nanofiber formulations were also prepared with 1% CAM. The needle-free NanospiderTM technique allowed for the successful production of defect-free nanofibers containing all three active ingredients. The CAM-containing nanofibers had a burst CAM-release and a high absorption capacity. Nanofibers with all active ingredients (βG, CHI and CAM) showed a concentration-dependent anti-inflammatory activity, while maintaining the antimicrobial activity of CAM. The promising anti-inflammatory properties, together with the high absorption capacity and antimicrobial effect, make these multifunctional nanofibers promising as dressings in local treatment of infected and exuding wounds, such as burn wounds.

Fosfomycin therapeutic drug monitoring in real-life: development and validation of a LC-MS/MS method on plasma samples

Individualization of fosfomycin dosing based on therapeutic drug monitoring (TDM) of plasma concentrations could reduce drug-related adverse events and improve clinical outcome in complex clinical conditions. Quantification of fosfomycin in plasma samples was performed by a rapid ultraperformance liquid chromatography mass spectrometry method. Sample preparation involved protein precipitation with [¹³C₃]-fosfomycin benzylamine salt as internal standard. The calibration curve ranged from 2 to 800 mg/L. Within- and between-day precision and accuracy, sensitivity, selectivity, dilution integrity, recovery were investigated and the results met the acceptance criteria. In patients, multiple drug dosing (every 6 or 8 hours) or in continuous administration were adopted, resulting in a large interpatient variability in drug concentrations (from 7.4 mg/L and 644.6 mg/L; CV: 91.1%). In critical care patient setting TDM can represent an important tool to identify the best fosfomycin dosing in single patients, taking into consideration clinical characteristics, infection sites and susceptibility of the treated pathogens.

A genome-wide analysis of Escherichia coli responses to fosfomycin using TraDIS-Xpress reveals novel roles for phosphonate degradation and phosphate transport systems

Background

Fosfomycin is an antibiotic that has seen a revival in use due to its unique mechanism of action and efficacy against isolates resistant to many other antibiotics. In Escherichia coli, fosfomycin often selects for loss-of-function mutations within the genes encoding the sugar importers, GlpT and UhpT. There has, however, not been a genome-wide analysis of the basis for fosfomycin susceptibility reported to date.

Methods

Here we used TraDIS-Xpress, a high-density transposon mutagenesis approach, to assay the role of all genes in E. coli involved in fosfomycin susceptibility.

Results

The data confirmed known fosfomycin susceptibility mechanisms and identified new ones. The assay was able to identify domains within proteins of importance and revealed essential genes with roles in fosfomycin susceptibility based on expression changes. Novel mechanisms of fosfomycin susceptibility that were identified included those involved in glucose metabolism and phosphonate catabolism (phnC-M), and the phosphate importer, PstSACB. The impact of these genes on fosfomycin susceptibility was validated by measuring the susceptibility of defined inactivation mutants.

Conclusions

This work reveals a wider set of genes that contribute to fosfomycin susceptibility, including core sugar metabolism genes and two systems involved in phosphate uptake and metabolism previously unrecognized as having a role in fosfomycin susceptibility.

Rapid and Accurate Detection of Escherichia coli and Klebsiella pneumoniae Strains Susceptible/Resistant to Cotrimoxazole through Evaluation of Cell Elongation

Trimethoprim-sulfamethoxazole is a well-known antibiotic that inhibits folic acid synthesis, a topic of renewed interest. Since resistant strains are increasingly more common, an early and accurate discrimination of susceptibility may assure confident therapy. Two morphological assays were performed in Escherichia coli (n = 50; 27 non-susceptible) and Klebsiella pneumoniae (n = 52; 18 non-susceptible). First, the strains were incubated with the CLSI breakpoint of cotrimoxazole for 150 min, which induced cell lengthening in the susceptible strains. Second, the bacteria were incubated with mitomycin C (MMC) (0.5 mg/L) for 120 min to induce a SOS-linked cell enlargement higher than that obtained by cotrimoxazole alone. When cotrimoxazole was added 30 min before MMC, the inhibition of folic acid synthesis in the susceptible strain resulted in the suppression of MMC-induced extra elongation. In the non-susceptible strains, folic acid synthesis continued despite the antibiotic, so that the MMC-induced extra cell lengthening could not be impeded. Whereas the first assay resulted in five false negatives and four false positives of resistance, the results of the second assay matched those of the conventional antibiogram. This simple morphological procedure is performed in 2 h and 45 min and may allow a rapid selection of useful and relatively inexpensive therapy, thereby preserving the newer broad-spectrum antibiotics.

Determination of residues of pesticides, anabolic steroids, antibiotics, and antibacterial compounds in meat products in Oman by liquid chromatography/mass spectrometry and enzyme-linked immunosorbent assay

BACKGROUND AND AIM

Meat is a rich source of many nutrients and plays a vital role in human life however, meat safety is one of the top priorities of great concern for consumers today. More than 90% of human exposure to harmful materials is due to consumption of contaminated meat products. This study was designed to compare four valid analytical methods for the determination of organochlorine pesticides 2,4 D (2,4-dichlorophenoxyacetic acid), dichlorodiphenyldichloroethylene/dichlorodiphenyltrichloroethane, alachlor, organophosphate, anabolic steroids (progesterone, testosterone, and estrogen), antibiotics (tetracycline, sulfonamides, gentamycin, and cephalexin), antibacterial compounds (Macrolide, ß-Lactam, Chloramphenicol, Sulphur drugs, and Gentamicin) residues in 135 beef, buffalo, and sheep meat samples (fresh, frozen meats, minced, and sausage samples) of local, regional, and international brands available in Omani markets.

MATERIALS AND METHODS

Triplicate meat samples from each brand within each species were extracted with acetonitrile and purified with acetonitrile-saturated n-hexane to remove all impurities. To dry the sample after heating, the residue was passed across a Sep-Pak C18 cartridge for sample cleaning before gas chromatography (GC) (Brand GCMS-QP2010 Plus) coupled with different detectors, including a mass spectrometer or GC-electron capture detector (GC-ECD). Liquid chromatography/mass spectrometry (LC-MS) was also employed for the quantification of the residues in meat products. Enzyme-linked immunosorbent assay (ELISA) kits were employed to assess veterinary drug residues, anabolic steroids, and pesticides. The CHARM II instrument was employed to detect chloramphenicol, gentamicin, sulfa-drug, ß-lactam, and macrolide residues in meat and meat product samples.

RESULTS

A thin-layer chromatographic (TLC) method should be considered as another method of choice to determine concentrations of veterinary drugs and anabolic steroids. The TLC results were validated by LC-MS. The three described methods permit the multi-residue analysis of anabolic steroid residue levels of 0.06-1.89 ppb in meat product samples. There were three violative residues of anabolic steroids in red meat products that were above the maximum residue limits (MRLs). Although, the levels of organochlorine pesticides and antibiotic concentrations in meat products were below the MRLs, the long-term consumption is considered a health hazard and will affect the wellbeing of consumers.

CONCLUSION

The four techniques (GC, high-performance liquid chromatography, ELISA and CHARM II) provided results that were reliable and precise for the detection of chessssmical residues in meat and meat products.

Intertwined Carbon Nanotubes and Ag Nanowires Constructed by Simple Solution Blending as Sensitive and Stable Chloramphenicol Sensors

Chloramphenicol (CAP) is a harmful compound associated with human hematopathy and neuritis, which was widely used as a broad-spectrum antibacterial agent in agriculture and aquaculture. Therefore, it is significant to detect CAP in aquatic environments. In this work, carbon nanotubes/silver nanowires (CNTs/AgNWs) composite electrodes were fabricated as the CAP sensor. Distinguished from in situ growing or chemical bonding noble metal nanomaterials on carbon, this CNTs/AgNWs composite was formed by simple solution blending. It was demonstrated that CNTs and AgNWs both contributed to the redox reaction of CAP in dynamics, and AgNWs was beneficial in thermodynamics as well. The proposed electrochemical sensor displayed a low detection limit of up to 0.08 μM and broad linear range of 0.1-100 μM for CAP. In addition, the CNTs/AgNWs electrodes exhibited good performance characteristics of repeatability and reproducibility, and proved suitable for CAP analysis in real water samples.

Anti-Endotoxin 9-Meric Peptide with Therapeutic Potential for the Treatment of Endotoxemia

Inflammatory reactions activated by lipopolysaccharide (LPS) of gram-negative bacteria can lead to severe septic shock. With the recent emergence of multidrug-resistant gram-negative bacteria and a lack of efficient ways to treat resulting infections, there is a need to develop novel anti-endotoxin agents. Antimicrobial peptides have been noticed as potential therapeutic molecules for bacterial infection and as candidates for new antibiotic drugs. We previously designed the 9-meric antimicrobial peptide Pro9-3 and it showed high antimicrobial activity against gram-negative bacteria. Here, to further examine its potency as an anti-endotoxin agent, we examined the antiendotoxin activities of Pro9-3 and elucidated its mechanism of action. We performed a dye-leakage experiment and BODIPY-TR cadaverine and limulus amebocyte lysate assays for Pro9-3 as well as its lysine-substituted analogue and their enantiomers. The results confirmed that Pro9-3 targets the bacterial membrane and the arginine residues play key roles in its antimicrobial activity. Pro9-3 showed excellent LPS-neutralizing activity and LPS-binding properties, which were superior to those of other peptides. Saturation transfer difference-nuclear magnetic resonance experiments to explore the interaction between LPS and Pro9-3 revealed that Trp³ and Tlr⁷ in Pro9-3 are critical for attracting Pro9-3 to the LPS in the gram-negative bacterial membrane. Moreover, the anti-septic effect of Pro9-3 in vivo was investigated using an LPS-induced endotoxemia mouse model, demonstrating its dual activities: antibacterial activity against gram-negative bacteria and immunosuppressive effect preventing LPS-induced endotoxemia. Collectively, these results confirmed the therapeutic potential of Pro9-3 against infection of gram-negative bacteria.

Bacteriocins as a new generation of antimicrobials: toxicity aspects and regulations

In recent decades, bacteriocins have received substantial attention as antimicrobial compounds. Although bacteriocins have been predominantly exploited as food preservatives, they are now receiving increased attention as potential clinical antimicrobials and as possible immune-modulating agents. Infections caused by antibiotic-resistant bacteria have been declared as a global threat to public health. Bacteriocins represent a potential solution to this worldwide threat due to their broad- or narrow-spectrum activity against antibiotic-resistant bacteria. Notably, despite their role in food safety as natural alternatives to chemical preservatives, nisin remains the only bacteriocin legally approved by regulatory agencies as a food preservative. Moreover, insufficient data on the safety and toxicity of bacteriocins represent a barrier against the more widespread use of bacteriocins by the food and medical industry. Here, we focus on the most recent trends relating to the application of bacteriocins, their toxicity and impacts.

N-Hydroxysuccinimide crosslinked graphene oxide–gold nanoflower modified SPE electrode for sensitive detection of chloramphenicol antibiotic

Here we introduce a composite material that consists of graphene oxide (GO) sheets crosslinked with N-hydroxysuccinimide (NHS) and functionalized with gold nanoflowers (AuNFs). Furthermore, a screen printed electrode (SPE) modified with the introduced composite is electrochemically reduced to obtain an SPE/rGO–NHS–AuNFs electrode for sensitive and selective determination of chloramphenicol (CAP) antibiotic drug. The morphological structure of the as-prepared nanocomposite was characterized by scanning electron microscopy, energy-dispersive X-ray spectroscopy, cyclic voltammetry, Fourier-transform infrared spectroscopy and electrochemical impedance spectroscopy. The proposed sensor demonstrated excellent performance with a linear concentration range of 0.05 to 100 μM and a detection limit of 1 nM. The proposed electrode offers a high level of selectivity, stability, reproducibility and a satisfactory recovery rate for electrochemical detection of CAP in real samples such as blood serum, poultry feed, milk, eggs, honey and powdered milk samples. This further demonstrates the practical feasibility of the proposed sensor in food analysis.

Here we introduce a composite material that consists of graphene oxide (GO) sheets crosslinked with N-hydroxysuccinimide (NHS) and functionalized with gold nanoflowers (AuNFs).

Geographical distribution and antibiotics susceptibility patterns of toxigenic Vibrio cholerae isolates from Kisumu County, Kenya

Background

Multiple drug resistance has become a major threat to the treatment of cholera. Recent studies in Kenya have described the epidemiology, especially the risk factors, of cholera; however, there is little information on the phenotypic and drug susceptibility patterns of Vibrio cholerae (V. cholerae) in outbreaks that in the recent past have occurred in western Kenya.

Aim

To characterise and determine the antibiotics’ susceptibility profiling of toxigenic V. cholerae isolates from Kisumu County.

Setting

The project was conducted in Kisumu County, Kenya.

Methods

A total of 119 V. cholerae O1, biotype El Tor, isolates collected during 2017 cholera outbreak in Kisumu County were used for this study. The samples were cultured on thiosulphate-citrate-bile salts sucrose (TCBS) agar and biochemical tests were carried out using standard procedures. Susceptibility tests were conducted by using various conventional antibiotics against standard procedures.

Results

Of the 119 isolates, 101 were confirmed to be V. cholerae belonging to serotypes Inaba and Ogawa, with Inaba being the predominant serotype (73.95%). The isolates were susceptible to ciprofloxacin (100%), ofloxacin (100%), gentamycin (100%), doxycycline (99%), ceftriaxone (99%) and streptomycin (96.04%) antimicrobials, and resistant to erythromycin (53.47%), amoxicillin (64.4%), nalidixic acid (83.2%) and ampicillin (89.11%), with high resistance to cotrimoxazole (99%) and tetracycline (97%).

Conclusion

Vibrio cholerae was resistant to multiple antibiotics, including those commonly used in the management of cholera. Taken together, there is a need to carry out regular surveillance on antimicrobial drug resistance during outbreaks.

Efficient preparation of nitrogen-doped fluorescent carbon dots for highly sensitive detection of metronidazole and live cell imaging

Herein, nitrogen-doped carbon dots (N-CDs) emitting blue fluorescence were prepared using L-tartaric acid and triethylenetetramine through a simple and quick microwave-assisted method. The synthesized N-CDs displayed excitation-dependent fluorescence behavior, and their maximum excitation and emission wavelengths were 350 and 425 nm, respectively. The obtained N-CDs, which featured excellent fluorescence properties with a high fluorescence quantum yield of 31%, were applied to detect metronidazole (MNZ), which can effectively quench the fluorescence intensity of N-CDs due to the inner filter effect. This phenomenon was used as basis to develop a label-free fluorescent method for rapid MNZ determination, with the limit of detection of 0.22 μM and corresponding linear range of 0.5-22 μM. Hence, we had established a fluorescence method for MNZ detection and applied it to detect MNZ in real samples with satisfactory results. Finally, N-CDs with superior biocompatibility were applied for cell imaging and MNZ detection by the changes in fluorescence intensity.

A war of attrition against antibiotic resistance: Current strategies try to keep antibiotic resistance at bay and further encourage research to produce genuinely novel antibacterials

To fight antibiotic resistance, novel drugs are urgently needed. Regulatory agencies are addressing the economic problems and offer new incentives for developing new antibiotics.

Characterization of KPC-Producing Serratia marcescens in an Intensive Care Unit of a Brazilian Tertiary Hospital

Serratia marcescens has emerged as an important opportunistic pathogen responsible for nosocomial and severe infections. Here, we determined phenotypic and molecular characteristics of 54 S. marcescens isolates obtained from patient samples from intensive-care-unit (ICU) and neonatal intensive-care-unit (NIUC) of a Brazilian tertiary hospital. All isolates were resistant to beta-lactam group antibiotics, and 92.6% (50/54) were not susceptible to tigecycline. Furthermore, 96.3% showed intrinsic resistance to polymyxin E (colistin), a last-resort antibiotic for the treatment of infections caused by MDR (multidrug-resistant) Gram-negative bacteria. In contrast, high susceptibility to other antibiotics such as fluoroquinolones (81.5%), and to aminoglycosides (as gentamicin 81.5%, and amikacin 85.2%) was found. Of all isolates, 24.1% were classified as MDR. The presence of resistance and virulence genes were examined by PCR and sequencing. All isolates carried KPC-carbapenemase (bla_KPC) and extended spectrum beta-lactamase bla_TEM genes, 14.8% carried bla_OXA–1, and 16.7% carried bla_{CTX–M–1group} genes, suggesting that bacterial resistance to β-lactam antibiotics found may be associated with these genes. The genes SdeB/HasF and SdeY/HasF that are associated with efflux pump mediated drug extrusion to fluoroquinolones and tigecycline, respectively, were found in 88.9%. The aac(6′)-Ib-cr variant gene that can simultaneously induce resistance to aminoglycoside and fluoroquinolone was present in 24.1% of the isolates. Notably, the virulence genes to (i) pore-forming toxin (ShlA); (ii) phospholipase with hemolytic and cytolytic activities (PhlA); (iii) flagellar transcriptional regulator (FlhD); and (iv) positive regulator of prodigiosin and serratamolide production (PigP) were present in 98.2%. The genetic relationship among the isolates determined by ERIC-PCR demonstrated that the vast majority of isolates were grouped in a single cluster with 86.4% genetic similarity. In addition, many isolates showed 100% genetic similarity to each other, suggesting that the S. marcescens that circulate in this ICU are closely related. Our results suggest that the antimicrobial resistance to many drugs currently used to treat ICU and NIUC patients, associated with the high frequency of resistance and virulence genes is a worrisome phenomenon. Our findings emphasize the importance of active surveillance plans for infection control and to prevent dissemination of these strains.

Rough-type and loss of the LPS due to lpx genes deletions are associated with colistin resistance in multidrug-resistant clinical Escherichia coli isolates not harbouring mcr genes

The emergence of multidrug-resistant Escherichia coli has become a great challenge in treating nosocomial infections. The polymyxin antibiotic colistin is used as a ‘last-line’ therapy for such strains, but resistance to colistin is increasingly emerging all over the world. In this study, we investigated lipopolysaccharides (LPS) of colistin-resistant isolates and examined mutations in lpx genes in strains not harbouring mcr genes. We examined 351 clinical E. coli isolates with 38 showing reduced susceptibility to colistin. These isolates were collected from different clinical specimens including blood, urine, and wounds, but no stool. After confirmation of the isolates via a BD Phoenix-100 system (Becton Dickinson, USA), we performed antimicrobial susceptibility tests to characterize the resistance pattern of these isolates to different classes of antibiotics, using the disk diffusion test. The Minimum Inhibitory Concentration (MIC) of colistin was determined using E-test strips. The presence of mobile colistin resistance (mcr-1 and mcr-2) genes was tested for all isolates. LPS (including lipid A) were extracted from all isolates and associated lpx genes analyzed by PCR and sequencing. Among the 38 clinical E. coli isolates with reduced susceptibility to colistin, 52% were resistant to colistin. The MICs of colistin ranged from 0.5 μg/ml to ˃256 μg/ml. Within the 20 colistin-resistant strains, six isolates carried the mcr-1 gene, but not mcr-2. Heterologous expression of the mcr-1 gene in susceptible E. coli DH5α increased the MIC of colistin by eight-fold. The remaining 14 isolates, were negative for both mcr genes. Six isolates were further negative for LPS production and five showed rough LPS phenotypes. Here we present evidence that loss of LPS or lipid A-deficiency can lead to colistin-resistance in clinical E. coli isolates not harbouring mcr genes.

Antibiotic drug discovery: Challenges and perspectives in the light of emerging antibiotic resistance

Amid a rising threat of antimicrobial resistance in a global scenario, our huge investments and high-throughput technologies injected for rejuvenating the key therapeutic scaffolds to suppress these rising superbugs has been diminishing severely. This has grasped world-wide attention, with increased consideration being given to the discovery of new chemical entities. Research has now proven that the relatively tiny and simpler microbes possess enhanced capability of generating novel and diverse chemical constituents with huge therapeutic leads. The usage of these beneficial organisms could help in producing new chemical scaffolds that govern the power to suppress the spread of obnoxious superbugs. Here in this review, we have explicitly focused on several appealing strategies employed for the generation of new chemical scaffolds. Also, efforts on providing novel insights on some of the unresolved questions in the production of metabolites, metabolic profiling and also the serendipity of getting "hit molecules" have been rigorously discussed. However, we are highly aware that biosynthetic pathway of different classes of secondary metabolites and their biosynthetic route is a vast topic, thus we have avoided discussion on this topic.

Combinations of early generation antibiotics and antimicrobial peptides are effective against a broad spectrum of bacterial biothreat agents

The misuse of infectious disease pathogens as agents of deliberate attack on civilians and military personnel is a serious national security concern, which is exacerbated by the emergence of natural or genetically engineered multidrug resistant strains. In this study, the therapeutic potential of combinations of an antibiotic and a broad-spectrum antimicrobial peptide (AMP) was evaluated against five bacterial biothreats, the etiologic agents of glanders (Burkholderia mallei), melioidosis (Burkholderia pseudomallei), plague (Yersinia pestis), tularemia (Francisella tularensis), and anthrax (Bacillus anthracis). The therapeutics included licensed early generation antibiotics which are now rarely used. Three antibiotics and one 24- amino acid AMP were selected based on MIC assay data. Combinations of the AMP and tigecycline, minocycline, or novobiocin were screened for synergistic activity by checkerboard MIC assay. The combinations each enhanced the susceptibility of several strains. The tetracycline-peptide combinations increased the sensitivities of Y. pestis, F. tularensis, B. anthracis and B. pseudomallei, and the novobiocin-AMP combination augmented the sensitivity of all five. In time-kill assays, down-selected combinations of the peptide and minocycline or tigecycline enhanced killing of B. anthracis, Y. pestis, F. tularensis, and Burkholderia mallei but not B. pseudomallei. The novobiocin-AMP pair significantly reduced viability of all strains except B. mallei, which was very sensitive to the antibiotic alone. The results suggested that antibiotic-AMP combinations are useful tools for combating diverse pathogens. Future studies employing cell culture and animal models will utilize virulent strains of the agents to investigate the in vivo availability, host cytotoxicity, and protective efficacy of these therapeutics.

Dextran Microparticulate Inhalable Dry Powder for the Treatment of Cystic Fibrosis and Mucopolysaccharidosis

BACKGROUND

Cystic Fibrosis (CF) is a genetic disease which affects the patient's lungs, pancreas, liver, kidney and intestine and lacks sulfatase enzyme, leading to mucopolysaccharidosis. Colistin sulfate acts by interacting with phospholipids of bacterial cell membranes. Sulfatase enzyme reduces the high levels of sulfated glycosaminoglycans and glycolipids by the hydrolysis of sulfate esters in lysosome.

OBJECTIVE

The aim of the present investigation was to prepare and evaluate dextran microparticulate inhalable dry powder for the efficient targeting of colistin sulfate at affected area of lung without causing the side effects in the treatment of CF and mucopolysaccharidosis.

METHODS

Microparticulate dry powder was prepared by the lyophilization method and evaluated for particle size, % yield, % drug content, solid state characterization, in-vitro lung deposition study, and in-vitro drug release study.

RESULTS

Particle size, % yield and % drug content were found to be 4.03 ± 0.196 µm, 94.02 % and 99.45 ± 0.015% respectively. Bulk density, tapped density, hausner's ratio, carr's index and angle of repose of optimized batch were found to be 0.216 ± 0.025 g/cm³, 0.236 ± 0.035 g/cm³, 1.09 ± 0.026, 8.47 ± 0.025 % and 26.10 ± 0.029˚ respectively. A fine particle fraction, fine particle dose, mass median aerodynamic diameter, geometric standard deviation and emitted dose were found to be 66.78%, 16.45 mg, 4.89 µm, 1.32 and 246.33 mg respectively. The % CDR of optimized batch was found to be 96.12 ± 0.049 % at 24 h.

CONCLUSION

Based on the obtained results, we conclude that dextran microparticulate inhalable dry powder might be suitable carrier for the delivery of colistin sulfate and sulfatase in combination via pulmonary route for the treatment of cystic fibrosis and mucopolysaccharidosis.

Multiple signal amplification chemiluminescence immunoassay for chloramphenicol using functionalized SiO2 nanoparticles as probes and resin beads as carriers

A novel, rapid and convenient competitive immunoassay for ultrasensitive detection of chloramphenicol residues in shrimp and honey was established combined with flow injection chemiluminescence. The carboxylic resin beads were used as solid phase carriers to load with more coating antigen due to their larger specific surface area and good biocompatibility. The surface of the silica dioxide nanoparticles was modified with aldehyde group to combine with more horseradish peroxidase and the chloramphenicol antibody. There was a competitive process between the chloramphenicol in solution and the immobilized coating antigen to combine with the limited binding site of antibody to form the immunocomplex. Silica dioxide nanoparticles played an important role in enhancing chemiluminescence signal, because the horseradish peroxidase on SiO₂ effectively catalyzed the system of luminol-PIP-H₂O₂. Under optimal conditions, the chemiluminescence intensity decreased linearly with the logarithm of the chloramphenicol concentration in the range of 0.0001 to 100 ng mL^-1 and the detection limit (3σ) was 0.033 pg mL^-1. This immunosensor demonstrated acceptable stability, high specificity and reproducibility. The horseradish peroxidase-silica dioxide nanoparticle-chloramphenicol antibody complex successfully prepared in this article was firstly applied to the detection of chloramphenicol, and had extremely important meanings for the application of nanoparticles and enzymatic catalysis in the field of chemiluminescence.

Characterization of the genomically encoded fosfomycin resistance enzyme from Mycobacterium abscessus

Mycobacterium abscessus belongs to a group of rapidly growing mycobacteria (RGM) and accounts for approximately 65-80% of lung disease caused by RGM. It is highly pathogenic and is considered the prominent Mycobacterium involved in pulmonary infection in patients with cystic fibrosis and chronic pulmonary disease (CPD). FosM is a putative 134 amino acid fosfomycin resistance enzyme from M. abscessus subsp. bolletii that shares approximately 30-55% sequence identity with other vicinal oxygen chelate (VOC) fosfomycin resistance enzymes and represents the first of its type found in any Mycobacterium species. Genes encoding VOC fosfomycin resistance enzymes have been found in both Gram-positive and Gram-negative pathogens. Given that FosA enzymes from Gram-negative bacteria have evolved optimum activity towards glutathione (GSH) and FosB enzymes from Gram-positive bacteria have evolved optimum activity towards bacillithiol (BSH), it was originally suggested that FosM might represent a fourth class of enzyme that has evolved to utilize mycothiol (MSH). However, a sequence similarity network (SSN) analysis identifies FosM as a member of the FosX subfamily, indicating that it may utilize water as a substrate. Here we have synthesized MSH and characterized FosM with respect to divalent metal ion activation and nucleophile selectivity. Our results indicate that FosM is a Mn2+-dependent FosX-type hydrase with no selectivity toward MSH or other thiols as analyzed by NMR and mass spectroscopy.

Phage-Antibiotic Combination Treatments: Antagonistic Impacts of Antibiotics on the Pharmacodynamics of Phage Therapy?

Bacteria can evolve resistance to antibiotics. Even without changing genetically, bacteria also can display tolerance to antibiotic treatments. Many antibiotics are also broadly acting, as can result in excessive modifications of body microbiomes. Particularly for antibiotics of last resort or in treating extremely ill patients, antibiotics furthermore can display excessive toxicities. Antibiotics nevertheless remain the standard of care for bacterial infections, and rightly so given their long track records of both antibacterial efficacy and infrequency of severe side effects. Antibiotics do not successfully cure all treated bacterial infections, however, thereby providing a utility to alternative antibacterial approaches. One such approach is the use of bacteriophages, the viruses of bacteria. This nearly 100-year-old bactericidal, anti-infection technology can be effective against antibiotic-resistant or -tolerant bacteria, including bacterial biofilms and persister cells. Ideally phages could be used in combination with standard antibiotics while retaining their anti-bacterial pharmacodynamic activity, this despite antibiotics interfering with aspects of bacterial metabolism that are also required for full phage infection activity. Here I examine the literature of pre-clinical phage-antibiotic combination treatments, with emphasis on antibiotic-susceptible bacterial targets. I review evidence of antibiotic interference with phage infection activity along with its converse: phage antibacterial functioning despite antibiotic presence.

Antiseptic Effect of Ps-K18: Mechanism of Its Antibacterial and Anti-Inflammatory Activities

Recently, bioactive peptides have attracted attention for their therapeutic applications in the pharmaceutical industry. Among them, antimicrobial peptides are candidates for new antibiotic drugs. Since pseudin-2 (Ps), isolated from the skin of the paradoxical frog Pseudis paradoxa, shows broad-spectrum antibacterial activity with high cytotoxicity, we previously designed Ps-K18 with a Lys substitution for Leu18 in Ps, which showed high antibacterial activity and low toxicity. Here, we examined the potency of Ps-K18, aiming to develop antibiotics derived from bioactive peptides for the treatment of Gram-negative sepsis. We first investigated the antibacterial mechanism of Ps-K18 based on confocal micrographs and field emission scanning electron microscopy, confirming that Ps-K18 targets the bacterial membrane. Anti-inflammatory mechanism of Ps-K18 was investigated by secreted alkaline phosphatase reporter gene assays and RT-PCR, which revealed that Ps-K18 activates innate defense via Toll-like receptor 4-mediated nuclear factor-kappa B signaling pathways. Moreover, we investigated the antiseptic effect of Ps-K18 using a lipopolysaccharide or Escherichia coli K1-induced septic shock mouse model. Ps-K18 significantly reduced bacterial growth and inflammatory responses in the septic shock model. Ps-K18 showed low renal and liver toxicity and attenuated lung damage effectively. This study suggests that Ps-K18 is a potent peptide antibiotic that could be applied therapeutically to Gram-negative sepsis.

Using Colistin as a Trojan Horse: Inactivation of Gram-Negative Bacteria with Chlorophyllin

Colistin (polymyxin E) is a membrane-destabilizing antibiotic used against Gram-negative bacteria. We have recently reported that the outer membrane prevents the uptake of antibacterial chlorophyllin into Gram-negative cells. In this study, we used sub-toxic concentrations of colistin to weaken this barrier for a combination treatment of Escherichia coli and Salmonella enterica serovar Typhimurium with chlorophyllin. In the presence of 0.25 µg/mL colistin, chlorophyllin was able to inactivate both bacteria strains at concentrations of 5-10 mg/L for E. coli and 0.5-1 mg/L for S. Typhimurium, which showed a higher overall susceptibility to chlorophyllin treatment. In accordance with a previous study, chlorophyllin has proven antibacterial activity both as a photosensitizer, illuminated with 12 mW/cm2, and in darkness. Our data clearly confirmed the relevance of the outer membrane in protection against xenobiotics. Combination treatment with colistin broadens chlorophyllin's application spectrum against Gram-negatives and gives rise to the assumption that chlorophyllin together with cell membrane-destabilizing substances may become a promising approach in bacteria control. Furthermore, we demonstrated that colistin acts as a door opener even for the photodynamic inactivation of colistin-resistant (mcr-1-positive) E. coli cells by chlorophyllin, which could help us to overcome this antimicrobial resistance.

Meat and Fish as Sources of Extended-Spectrum β-Lactamase-Producing Escherichia coli, Cambodia

We compared extended-spectrum β-lactamase-producing Escherichia coli isolates from meat and fish, gut-colonized women, and infected patients in Cambodia. Nearly half of isolates from women were phylogenetically related to food-origin isolates; a subset had identical multilocus sequence types, extended-spectrum β-lactamase types, and antimicrobial resistance patterns. Eating sun-dried poultry may be an exposure route.

Meta-transcriptomics reveals a diverse antibiotic resistance gene pool in avian microbiomes

BACKGROUND

Antibiotic resistance is rendering common bacterial infections untreatable. Wildlife can incorporate and disperse antibiotic-resistant bacteria in the environment, such as water systems, which in turn serve as reservoirs of resistance genes for human pathogens. Anthropogenic activity may contribute to the spread of bacterial resistance cycling through natural environments, including through the release of human waste, as sewage treatment only partially removes antibiotic-resistant bacteria. However, empirical data supporting these effects are currently limited. Here we used bulk RNA-sequencing (meta-transcriptomics) to assess the diversity and expression levels of functionally viable resistance genes in the gut microbiome of birds with aquatic habits in diverse locations.

RESULTS

We found antibiotic resistance genes in birds from all localities, from penguins in Antarctica to ducks in a wastewater treatment plant in Australia. Comparative analysis revealed that birds feeding at the wastewater treatment plant carried the greatest resistance gene burden, including genes typically associated with multidrug resistance plasmids as the aac(6)-Ib-cr gene. Differences in resistance gene burden also reflected aspects of bird ecology, taxonomy, and microbial function. Notably, ducks, which feed by dabbling, carried a higher abundance and diversity of resistance genes than turnstones, avocets, and penguins, which usually prey on more pristine waters.

CONCLUSIONS

These transcriptome data suggest that human waste, even if it undergoes treatment, might contribute to the spread of antibiotic resistance genes to the wild. Differences in microbiome functioning across different bird lineages may also play a role in the antibiotic resistance burden carried by wild birds. In summary, we reveal the complex factors explaining the distribution of resistance genes and their exchange routes between humans and wildlife, and show that meta-transcriptomics is a valuable tool to access functional resistance genes in whole microbial communities.

High rate of colistin and fosfomycin resistance among carbapenemase-producing Enterobacteriaceae in Turkey

When the problem with carbapenem-resistant Enterobacteriaceae (CRE) increases, the older antimicrobial agents such as colistin and fosfomycin are used for the treatment of these infections. In this study, the broth microdilution method for colistin and the agar dilution method for fosfomycin were used for a total of 147 multidrug-resistant (MDR) or extensively drug-resistant (XDR) strains of CRE. The study included Klebsiella pneumoniae (91.16%), Escherichia coli (7.48%), Enterobacter cloacae (0.68%), and Serratia marcescens (0.68%). All these strains produce various types of carbapenemase, including OXA-48, NDM, and KPC. Some of these strains also have three different carbapenemase mechanisms, including OXA-48 (78.23%), NDM (2.04%), and KPC (0.68%) or OXA-48 and NDM (10.88%), or OXA-48 and KPC (0.68%). About 76.19% of the strains and 67.35% of the strains were resistant for colistin and fosfomycin, respectively. A total of 21 out of 35 colistin-susceptible strains were found to be susceptible to fosfomycin. This study showed that the resistance rates of colistin and fosfomycin are high. The MDR and XDR strains of CRE are spreading in our region and thus a monitoring system for CRE should be followed. Moreover, the applicability of antimicrobial stewardship programs should be increased in all inpatient and outpatient settings.