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1.
J Appl Microbiol ; 135(7)2024 Jul 02.
Article in English | MEDLINE | ID: mdl-38991984

ABSTRACT

AIMS: We aimed to identify mechanisms underlying the tolerance of Proteus mirabilis-a common cause of catheter associated urinary tract infection-to the clinically used biocides chlorhexidine (CHD) and octenidine (OCT). METHODS AND RESULTS: We adapted three clinical isolates to grow at concentrations of 512 µg ml-1 CHD and 128 µg ml-1 OCT. Genetic characterization and complementation studies revealed mutations inactivating the smvR repressor and increasing smvA efflux expression were associated with adaptation to both biocides. Mutations in mipA (encoding the MltA interacting protein) were less prevalent than smvR mutations and only identified in CHD adapted populations. Mutations in the rppA response regulator were exclusive to one adapted isolate and were linked with reduced polymyxin B susceptibility and a predicted gain of function after biocide adaptation. Biocide adaptation had no impact on crystalline biofilm formation. CONCLUSIONS: SmvR inactivation is a key mechanism in both CHD and OCT tolerance. MipA inactivation alone confers moderate protection against CHD, and rppA showed no direct role in either CHD or OCT susceptibility.


Subject(s)
Chlorhexidine , Imines , Proteus mirabilis , Pyridines , Proteus mirabilis/drug effects , Proteus mirabilis/genetics , Proteus mirabilis/physiology , Chlorhexidine/pharmacology , Imines/pharmacology , Pyridines/pharmacology , Microbial Sensitivity Tests , Humans , Bacterial Proteins/genetics , Bacterial Proteins/metabolism , Biofilms/drug effects , Biofilms/growth & development , Proteus Infections/microbiology , Mutation , Drug Resistance, Bacterial/genetics , Anti-Infective Agents, Local/pharmacology , Disinfectants/pharmacology , Catheter-Related Infections/microbiology , Urinary Tract Infections/microbiology
2.
J Antimicrob Chemother ; 78(Suppl 2): ii37-ii42, 2023 11 23.
Article in English | MEDLINE | ID: mdl-37995354

ABSTRACT

The COVID-19 pandemic saw unprecedented resources and funds driven into research for the development, and subsequent rapid distribution, of vaccines, diagnostics and directly acting antivirals (DAAs). DAAs have undeniably prevented progression and life-threatening conditions in patients with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. However, there are concerns of antimicrobial resistance (AMR), antiviral resistance specifically, for DAAs. To preserve activity of DAAs for COVID-19 therapy, as well as detect possible mutations conferring resistance, antimicrobial stewardship and surveillance were rapidly implemented in England. This paper expands on the ubiquitous ongoing public health activities carried out in England, including epidemiologic, virologic and genomic surveillance, to support the stewardship of DAAs and assess the deployment, safety, effectiveness and resistance potential of these novel and repurposed therapeutics.


Subject(s)
COVID-19 , Humans , COVID-19/epidemiology , SARS-CoV-2 , Anti-Bacterial Agents/therapeutic use , Pandemics/prevention & control , Antiviral Agents/therapeutic use , Antiviral Agents/pharmacology , Drug Resistance, Bacterial , England/epidemiology
3.
Biochemistry ; 61(11): 1029-1040, 2022 06 07.
Article in English | MEDLINE | ID: mdl-35609188

ABSTRACT

The pharmacodynamic profile of antimicrobial peptides (AMPs) and their in vivo synergy are two factors that are thought to restrict resistance evolution and ensure their conservation. The frog Rana temporaria secretes a family of closely related AMPs, temporins A-L, as an effective chemical dermal defense. The antibacterial potency of temporin L has been shown to increase synergistically in combination with both temporins B and A, but this is modest. Here we show that the less potent temporin B enhances the cooperativity of the in vitro antibacterial activity of the more potent temporin L against EMRSA-15 and that this may be associated with an altered interaction with the bacterial plasma membrane, a feature critical for the antibacterial activity of most AMPs. Addition of buforin II, a histone H2A fragment, can further increase the cooperativity. Molecular dynamics simulations indicate temporins B and L readily form hetero-oligomers in models of Gram-positive bacterial plasma membranes. Patch-clamp studies show transmembrane ion conductance is triggered with lower amounts of both peptides and more quickly when used in combination, but conductance is of a lower amplitude and pores are smaller. Temporin B may therefore act by forming temporin L/B hetero-oligomers that are more effective than temporin L homo-oligomers at bacterial killing and/or by reducing the probability of the latter forming until a threshold concentration is reached. Exploration of the mechanism of synergy between AMPs isolated from the same organism may therefore yield antibiotic combinations with advantageous pharmacodynamic properties.


Subject(s)
Anti-Bacterial Agents , Antimicrobial Cationic Peptides , Anti-Bacterial Agents/chemistry , Antimicrobial Cationic Peptides/chemistry , Bacteria , Cell Membrane/metabolism , Gram-Positive Bacteria
4.
Microbiology (Reading) ; 168(11)2022 11.
Article in English | MEDLINE | ID: mdl-36748532

ABSTRACT

AbstractWith an increase in the number of isolates resistant to multiple antibiotics, infection control has become increasingly important to help combat the spread of multi-drug-resistant pathogens. An important component of this is through the use of disinfectants and antiseptics (biocides). Antibiotic resistance has been well studied in bacteria, but little is known about potential biocide resistance genes and there have been few reported outbreaks in hospitals resulting from a breakdown in biocide effectiveness. Development of increased tolerance to biocides has been thought to be more difficult due to the mode of action of biocides which affect multiple cellular targets compared with antibiotics. Very few genes which contribute towards increased biocide tolerance have been identified. However, the majority of those that have are components or regulators of different efflux pumps or genes which modulate membrane function/modification. This review will examine the role of efflux in increased tolerance towards biocides, focusing on cationic biocides and heavy metals against Gram-negative bacteria. As many efflux pumps which are upregulated by biocide presence also contribute towards an antimicrobial resistance phenotype, the role of these efflux pumps in cross-resistance to both other biocides and antibiotics will be explored.


Subject(s)
Disinfectants , Disinfectants/pharmacology , Bacteria/genetics , Anti-Bacterial Agents/pharmacology , Biological Transport , Drug Resistance, Microbial , Drug Resistance, Bacterial , Microbial Sensitivity Tests
5.
BMC Microbiol ; 22(1): 113, 2022 04 25.
Article in English | MEDLINE | ID: mdl-35468722

ABSTRACT

BACKGROUND: Silver ions have potent broad-spectrum antimicrobial activity and are widely incorporated into a variety of products to limit bacterial growth. In Enterobacteriaceae, decreased silver susceptibility has been mapped to two homologous operons; the chromosomally located cus operon and the plasmid based sil operon. Here we characterised the mechanisms and clinical impact of induced silver tolerance in Klebsiella pneumoniae. RESULTS: In K. pneumoniae carriage of the sil operon alone does not give elevated silver tolerance. However, when exposed to increasing concentrations of silver nitrate (AgNO3), K. pneumoniae strains which contain the sil operon, will preferentially mutate SilS, resulting in overexpression of the genes encoding the RND efflux pump silCBA. Those strains which do not carry the sil operon also adapt upon exposure to increasing silver concentrations through mutations in another two-component regulator CusS. Secondary mutations leading to disruption of the outer membrane porin OmpC were also detected. Both routes result in a high level of silver tolerance with MIC's of >512 mg/L. When exposed to a high concentration of AgNO3 (400 mg/L), only strains that contained the sil operon were able to survive, again through mutations in SilS. The AgNO3 adapted strains were also resistant to killing by challenge with several clinical and commercial silver containing dressings. CONCLUSIONS: This study shows that K. pneumoniae has two possible pathways for development of increased silver tolerance but that the sil operon is preferentially mutated. This operon is essential when K. pneumoniae is exposed to high concentrations of silver. The potential clinical impact on wound management is shown by the increased survivability of these adapted strains when exposed to several silver impregnated dressings. This would make infections with these strains more difficult to treat and further limits our therapeutic options.


Subject(s)
Bacterial Proteins/genetics , Klebsiella pneumoniae , Porins , Ions , Klebsiella pneumoniae/genetics , Microbial Sensitivity Tests , Mutation , Porins/genetics
6.
Appl Environ Microbiol ; 87(10)2021 04 27.
Article in English | MEDLINE | ID: mdl-33674437

ABSTRACT

Octenidine-based disinfection products are becoming increasingly popular for infection control of multidrug-resistant (MDR) Gram-negative isolates. When a waste trap was removed from a hospital and allowed to acclimatize in a standard tap rig in our laboratory, it was shown that Klebsiella pneumoniae, Pseudomonas aeruginosa, and Citrobacter and Enterobacter spp. were readily isolated. This study aimed to understand the potential impact of prolonged exposure to low doses of a commercial product containing octenidine on these bacteria. Phenotypic and genotypic analyses showed that P. aeruginosa strains had increased tolerance to octenidine, which was characterized by mutations in the Tet repressor SmvR. Enterobacter species demonstrated increased tolerance to many other cationic biocides, although not octenidine, as well as the antibiotics ciprofloxacin, chloramphenicol, and ceftazidime, through mutations in another Tet repressor, RamR. Citrobacter species with mutations in RamR and MarR were identified following octenidine exposure, and this is linked to development of resistance to ampicillin, piperacillin, and chloramphenicol, as well as an increased MIC for ciprofloxacin. Isolates were able to retain fitness, as characterized by growth, biofilm formation, and virulence in Galleria mellonella, after prolonged contact with octenidine, although there were strain-to-strain differences. These results demonstrate that continued low-level octenidine exposure in a simulated sink trap environment selects for mutations that affect smvR It may also promote microbial adaptation to other cationic biocides and cross-resistance to antibiotics, while not incurring a fitness cost. This suggests that hospital sink traps may act as a reservoir for more biocide-tolerant organisms.IMPORTANCE Multidrug-resistant (MDR) strains of bacteria are a major clinical problem, and several reports have linked outbreaks of MDR bacteria with bacterial populations in hospital sinks. Biocides such as octenidine are used clinically in body washes and other products, such as wound dressings for infection control. Therefore, increased tolerance to these biocides would be detrimental to infection control processes. Here, we exposed bacterial populations originally from hospital sink traps to repeated dosing with an octenidine-containing product over several weeks and observed how particular species adapted. We found mutations in genes related to biocide and antibiotic susceptibility, which resulted in increased tolerance, although this was species dependent. Bacteria that became more tolerant to octenidine also showed no loss of fitness. This shows that prolonged octenidine exposure has the potential to promote microbial adaptation in the environment and that hospital sink traps may act as a reservoir for increased biocide- and antibiotic-tolerant organisms.


Subject(s)
Anti-Infective Agents/pharmacology , Bacterial Proteins/genetics , Drug Resistance, Bacterial/genetics , Enterobacteriaceae/drug effects , Membrane Transport Proteins/genetics , Pseudomonas aeruginosa/drug effects , Pyridines/pharmacology , Enterobacteriaceae/genetics , Enterobacteriaceae/growth & development , Hospitals , Imines , Mutation , Pseudomonas aeruginosa/genetics , Pseudomonas aeruginosa/growth & development , Waste Disposal, Fluid
7.
Molecules ; 25(24)2020 Dec 18.
Article in English | MEDLINE | ID: mdl-33352963

ABSTRACT

Two new epimeric bibenzylated monoterpenes machaerifurogerol (1a) and 5-epi-machaerifurogerol (1b), and four known isoflavonoids (+)-vestitol (2), 7-O-methylvestitol (3), (+)-medicarpin (4), and 3,8-dihydroxy-9-methoxypterocarpan (5) were isolated from Machaerium Pers. This plant was previously assigned as Machaerium multiflorum Spruce, from which machaeriols A-D (6-9) and machaeridiols A-C (10-12) were reported, and all were then re-isolated, except the minor compound 9, for a comprehensive antimicrobial activity evaluation. Structures of the isolated compounds were determined by full NMR and mass spectroscopic data. Among the isolated compounds, the mixture 10 + 11 was the most active with an MIC value of 1.25 µg/mL against methicillin-resistant Staphylococcus aureus (MRSA) strains BAA 1696, -1708, -1717, -33591, and vancomycin-resistant Enterococcus faecium (VRE 700221) and E. faecalis (VRE 51299) and vancomycin-sensitive E. faecalis (VSE 29212). Compounds 6-8 and 10-12 were found to be more potent against MRSA 1708, and 6, 11, and 12 against VRE 700221, than the drug control ciprofloxacin and vancomycin. A combination study using an in vitro Checkerboard method was carried out for machaeriols (7 or 8) and machaeridiols (11 or 12), which exhibited a strong synergistic activity of 12 + 8 (MIC 0.156 and 0.625 µg/mL), with >32- and >8-fold reduction of MIC's, compared to 12, against MRSA 1708 and -1717, respectively. In the presence of sub-inhibitory concentrations on polymyxin B nonapeptide (PMBN), compounds 10 + 11, 11, 12, and 8 showed activity in the range of 0.5-8 µg/mL for two strains of Acinetobacter baumannii, 2-16 µg/mL against Pseudomonas aeruginosa PAO1, and 2 µg/mL against Escherichia coli NCTC 12923, but were inactive (MIC > 64 µg/mL) against the two isolates of Klebsiella pneumoniae.


Subject(s)
Anti-Bacterial Agents/pharmacology , Benzopyrans/pharmacology , Fabaceae/chemistry , Methicillin-Resistant Staphylococcus aureus/drug effects , Vancomycin-Resistant Enterococci/drug effects , Anti-Bacterial Agents/chemistry , Anti-Bacterial Agents/isolation & purification , Benzopyrans/chemistry , Benzopyrans/isolation & purification , Microbial Sensitivity Tests , Molecular Structure
8.
Article in English | MEDLINE | ID: mdl-31160293

ABSTRACT

The Prestwick library was screened for antibacterial activity or "antibiotic resistance breaker" (ARB) potential against four species of Gram-negative pathogens. Discounting known antibacterials, the screen identified very few ARB hits, which were strain/drug specific. These ARB hits included antimetabolites (zidovudine, floxuridine, didanosine, and gemcitabine), anthracyclines (daunorubicin, mitoxantrone, and epirubicin), and psychoactive drugs (gabapentin, fluspirilene, and oxethazaine). These findings suggest that there are few approved drugs that could be directly repositioned as adjunct antibacterials, and these will need robust testing to validate efficacy.


Subject(s)
Anti-Bacterial Agents/pharmacology , Gram-Negative Bacteria/drug effects , Didanosine/pharmacology , Drug Resistance, Multiple, Bacterial , Ethanolamines/pharmacology , Floxuridine/pharmacology , Gram-Negative Bacteria/genetics , Microbial Sensitivity Tests , Mitoxantrone/pharmacology , Zidovudine/pharmacology
9.
J Antimicrob Chemother ; 73(8): 2003-2020, 2018 08 01.
Article in English | MEDLINE | ID: mdl-29506149

ABSTRACT

Efflux pumps are widely implicated in antibiotic resistance because they can extrude the majority of clinically relevant antibiotics from within cells to the extracellular environment. However, there is increasing evidence from many studies to suggest that the pumps also play a role in biofilm formation. These studies have involved investigating the effects of efflux pump gene mutagenesis and efflux pump inhibitors on biofilm formation, and measuring the levels of efflux pump gene expression in biofilms. In particular, several key pathogenic species associated with increasing multidrug resistance, such as Acinetobacter baumannii, Escherichia coli, Pseudomonas aeruginosa and Staphylococcus aureus, have been investigated, whilst other studies have focused on Salmonella enterica serovar Typhimurium as a model organism and problematic pathogen. Studies have shown that efflux pumps, including AcrAB-TolC of E. coli, MexAB-OprM of P. aeruginosa, AdeFGH of A. baumannii and AcrD of S. enterica, play important roles in biofilm formation. The substrates for such pumps, and whether changes in their efflux activity affect biofilm formation directly or indirectly, remain to be determined. By understanding the roles that efflux pumps play in biofilm formation, novel therapeutic strategies can be developed to inhibit their function, to help disrupt biofilms and improve the treatment of infections. This review will discuss and evaluate the evidence for the roles of efflux pumps in biofilm formation and the potential approaches to overcome the increasing problem of biofilm-based infections.


Subject(s)
Bacteria/growth & development , Bacterial Proteins/physiology , Biofilms/growth & development , Drug Resistance, Multiple, Bacterial , Membrane Transport Proteins/physiology , Anti-Bacterial Agents/pharmacology , Bacterial Proteins/antagonists & inhibitors , Membrane Transport Modulators/pharmacology , Quorum Sensing
10.
Article in English | MEDLINE | ID: mdl-27799211

ABSTRACT

Klebsiella pneumoniae is an opportunistic pathogen that is often difficult to treat due to its multidrug resistance (MDR). We have previously shown that K. pneumoniae strains are able to "adapt" (become more resistant) to the widely used bisbiguanide antiseptic chlorhexidine. Here, we investigated the mechanisms responsible for and the phenotypic consequences of chlorhexidine adaptation, with particular reference to antibiotic cross-resistance. In five of six strains, adaptation to chlorhexidine also led to resistance to the last-resort antibiotic colistin. Here, we show that chlorhexidine adaptation is associated with mutations in the two-component regulator phoPQ and a putative Tet repressor gene (smvR) adjacent to the major facilitator superfamily (MFS) efflux pump gene, smvA Upregulation of smvA (10- to 27-fold) was confirmed in smvR mutant strains, and this effect and the associated phenotype were suppressed when a wild-type copy of smvR was introduced on plasmid pACYC. Upregulation of phoPQ (5- to 15-fold) and phoPQ-regulated genes, pmrD (6- to 19-fold) and pmrK (18- to 64-fold), was confirmed in phoPQ mutant strains. In contrast, adaptation of K. pneumoniae to colistin did not result in increased chlorhexidine resistance despite the presence of mutations in phoQ and elevated phoPQ, pmrD, and pmrK transcript levels. Insertion of a plasmid containing phoPQ from chlorhexidine-adapted strains into wild-type K. pneumoniae resulted in elevated expression levels of phoPQ, pmrD, and pmrK and increased resistance to colistin, but not chlorhexidine. The potential risk of colistin resistance emerging in K. pneumoniae as a consequence of exposure to chlorhexidine has important clinical implications for infection prevention procedures.


Subject(s)
Anti-Bacterial Agents/pharmacology , Chlorhexidine/pharmacology , Colistin/pharmacology , Klebsiella pneumoniae/drug effects , Bacterial Proteins/genetics , Drug Resistance, Bacterial/genetics , Klebsiella pneumoniae/genetics , Microbial Sensitivity Tests , Mutation/genetics , Plasmids/genetics
11.
Bioorg Med Chem ; 25(15): 3971-3979, 2017 08 01.
Article in English | MEDLINE | ID: mdl-28600080

ABSTRACT

A novel series of pyridyl nitrofuranyl isoxazolines were synthesized and evaluated for their antibacterial activity against multiple drug resistant (MDR) Staphylococcus strains. Compounds with piperazine linker between the pyridyl group and isoxazoline ring showed better activity when compared to compounds without the piperazine linker. 3-Pyridyl nitrofuranyl isoxazoline with a piperazine linker was found to be more active than corresponding 2-and 4-pyridyl analogues with MICs in the range of 4-32µg/mL against MDR Staphylococcus strains. The eukaryotic toxicity of the compounds was tested by MTT assay and were found to be non-toxic against both non-tumour lung fibroblast WI-38 and cervical cancer cell line HeLa. The most active pyridyl nitrofuranyl isoxazoline compound showed improved activity against a panel of Staphylococcus strains compared to nitrofuran group containing antibiotic nitrofurantoin.


Subject(s)
Anti-Bacterial Agents/pharmacology , Drug Resistance, Multiple, Bacterial/drug effects , Nitrofurantoin/chemistry , Oxazoles/pharmacology , Staphylococcus aureus/drug effects , Anti-Bacterial Agents/chemistry , Cell Line, Tumor , Humans , Microbial Sensitivity Tests , Oxazoles/chemistry , Spectrum Analysis , Structure-Activity Relationship
12.
Biomed Microdevices ; 18(1): 18, 2016 Feb.
Article in English | MEDLINE | ID: mdl-26846875

ABSTRACT

Antibiotic resistance in urinary tract infections (UTIs) can cause significant complications without quick detection and appropriate treatment. We describe a new approach to capture, concentrate and prepare amplification-ready DNA from antibiotic resistant bacteria in human urine samples. Klebsiella pneumoniae NCTC13443 (bla CTX-M-15 positive) spiked into filtered human urine was used as a model system. Bacteria were captured using anion exchange diaethylaminoethyl (DEAE) magnetic microparticles and concentrated 200-fold within ~3.5 min using a custom, valve-less microfluidic chip. Eight samples were processed in parallel, and DNA was released using heat lysis from an integrated resistive heater. The crude cell lysate was used for real time Recombinase Polymerase Amplification (RPA) of the bla CTX-M-15 gene. The end to end processing time was approximately 15 min with a limit of detection of 1000 bacteria in 1 mL urine.


Subject(s)
Bacterial Proteins/genetics , Drug Resistance, Bacterial/genetics , Klebsiella Infections , Klebsiella pneumoniae/genetics , Polymerase Chain Reaction/methods , Urinary Tract Infections , beta-Lactamases/genetics , Female , Humans , Klebsiella Infections/genetics , Klebsiella Infections/urine , Male , Urinary Tract Infections/genetics , Urinary Tract Infections/urine
13.
Antimicrob Agents Chemother ; 59(7): 3966-72, 2015 Jul.
Article in English | MEDLINE | ID: mdl-25896708

ABSTRACT

The EGD Murray collection consists of approximately 500 clinical bacterial isolates, mainly Enterobacteriaceae, isolated from around the world between 1917 and 1949. A number of these "Murray" isolates have subsequently been identified as Klebsiella pneumoniae. Antimicrobial susceptibility testing of these isolates showed that over 30% were resistant to penicillins due to the presence of diverse blaSHV ß-lactamase genes. Analysis of susceptibility to skin antiseptics and triclosan showed that while the Murray isolates displayed a range of MIC/minimal bactericidal concentration (MBC) values, the mean MIC value was lower than that for more modern K. pneumoniae isolates tested. All Murray isolates contained the cation efflux gene cepA, which is involved in disinfectant resistance, but those that were more susceptible to chlorhexidine were found to have a 9- or 18-bp insertion in this gene. Susceptibility to other disinfectants, e.g., H2O2, in the Murray isolates was comparable to that in modern K. pneumoniae isolates. The Murray isolates were also less virulent in Galleria and had a different complement of putative virulence factors than the modern isolates, with the exception of an isolate related to the modern lineage CC23. More of the modern isolates (41% compared to 8%) are classified as good/very good biofilm formers, but there was overlap in the two populations. This study demonstrated that a significant proportion of the Murray Klebsiella isolates were resistant to penicillins before their routine use. This collection of pre-antibiotic era isolates may provide significant insights into adaptation in K. pneumoniae in relation to biocide susceptibility.


Subject(s)
Anti-Bacterial Agents/pharmacology , Disinfectants/pharmacology , Klebsiella Infections/microbiology , Klebsiella pneumoniae/drug effects , Moths/microbiology , Animals , Biofilms/drug effects , Chlorhexidine/pharmacology , Humans , Klebsiella pneumoniae/pathogenicity , Microbial Sensitivity Tests , Mutagenesis, Insertional , Penicillin Resistance/drug effects , Triclosan/pharmacology , Virulence Factors , beta-Lactamases/genetics
14.
J Antimicrob Chemother ; 70(8): 2209-16, 2015 Aug.
Article in English | MEDLINE | ID: mdl-25904728

ABSTRACT

OBJECTIVES: Colistin resistance in Acinetobacter baumannii has been associated with loss of virulence and a negative impact on isolate selection. In this study, exposure of clinical isolates to suboptimal concentrations of colistin was used to explore the capacity to develop resistance by diverse mechanisms, and whether acquired resistance always reduces fitness and virulence. METHODS: Twelve colistin-susceptible clinical A. baumannii isolates were exposed to a sub-MIC concentration of colistin over 6 weeks with weekly increases in concentration. Stable resistance was then phenotypically investigated with respect to antibiotic/biocide resistance, virulence in Galleria mellonella and growth rate. Putative mechanisms of resistance were identified by targeted sequencing of known resistance loci. RESULTS: Eight A. baumannii isolates acquired resistance to colistin within 1 week with MICs ranging from 2 to >512 mg/L. By 6 weeks 11 isolates were resistant to colistin; this was linked to the development of mutations in pmr or lpx genes. Strains that developed mutations in lpxACD showed a loss of virulence and increased susceptibility to several antibiotics/disinfectants tested. Two of the colistin-resistant strains with mutations in pmrB retained similar virulence levels to their respective parental strains in G. mellonella. CONCLUSIONS: Acquisition of colistin resistance does not always lead to a loss of virulence, especially when this is linked to mutations in pmrB. This underlines the importance of understanding the mechanism of colistin resistance as well as the phenotype.


Subject(s)
Acinetobacter baumannii/drug effects , Acinetobacter baumannii/growth & development , Anti-Bacterial Agents/pharmacology , Colistin/pharmacology , Drug Resistance, Bacterial , Mutation , Animals , DNA, Bacterial/chemistry , DNA, Bacterial/genetics , Genes, Bacterial , Lepidoptera/microbiology , Microbial Sensitivity Tests , Models, Animal , Sequence Analysis, DNA , Serial Passage , Survival Analysis , Virulence
15.
Transfusion ; 55(10): 2390-7, 2015 Oct.
Article in English | MEDLINE | ID: mdl-26033029

ABSTRACT

BACKGROUND: The P-Capt prion reduction filter (MacoPharma) removes prion infectivity in model systems. This independent evaluation assesses prion removal from endogenously infected animal blood, using CE-marked P-Capt filters, and replicates the proposed use of the filter within the UK Blood Services. STUDY DESIGN AND METHODS: Two units of blood, generated from 263K scrapie-infected hamsters, were processed using leukoreduction filters (LXT-quadruple, MacoPharma). Approximately 100 mL of the removed plasma was added back to the red blood cells (RBCs) and the blood was filtered through a P-Capt filter. Samples of unfiltered whole blood, the prion filter input (RBCs plus plasma and SAGM [RBCPS]), and prion-filtered leukoreduced blood (PFB) were injected intracranially into hamsters. Clinical symptoms were monitored for 500 ± 1 day, and brains were assessed for spongiosis and prion protein deposit. RESULTS: In Filtration Run 1, none of the 50 challenged animals were diagnosed with scrapie after inoculation with the RBCPS fraction, while two of 190 hamsters injected with PFB were infected. In Filtration Run 2, one of 49 animals injected with RBCPS and two of 193 hamsters injected with PFB were infected. Run 1 reduced the infectious dose (ID) by 1.467 log (>1.187 log and <0.280 log for leukoreduction and prion filtration, respectively). Run 2 reduced prion infectivity by 1.424 log (1.127 and 0.297 log, respectively). Residual infectivity was estimated at 0.212 ± 0.149 IDs/mL (Run 1) and 0.208 ± 0.147 IDs/mL (Run 2). CONCLUSION: Leukoreduction removed the majority of infectivity from 263K scrapie hamster blood. The P-Capt filter removed a proportion of the remaining infectivity, but residual infectivity was observed in two independent processes.


Subject(s)
Blood Safety , Disinfection , Leukapheresis , PrPSc Proteins , Scrapie/prevention & control , Animals , Blood Safety/instrumentation , Blood Safety/methods , Cricetinae , Disease Models, Animal , Disinfection/instrumentation , Disinfection/methods , Leukapheresis/instrumentation , Leukapheresis/methods , Scrapie/blood
16.
Eur J Pharm Sci ; 192: 106648, 2024 Jan 01.
Article in English | MEDLINE | ID: mdl-37992909

ABSTRACT

Conventional wound infection treatments neither actively promote wound healing nor address the growing problem of antibacterial resistance. Antimicrobial peptides (AMPs) are natural defense molecules, released from host cells, which may be rapidly bactericidal, modulate host-immune responses, and/or act as endogenous mediators for wound healing. However, their routine clinical use has hitherto been hindered due to their instability in the wound environment. Here we describe an electrospun carrier system for topical application of pleurocidin, demonstrating sufficient AMP release from matrices to kill wound-associated pathogens including Acinetobacter baumannii and Pseudomonas aeruginosa. Pleurocidin can be incorporated into polyvinyl alcohol (PVA) fiber matrices, using coaxial electrospinning, without major drug loss with a peptide content of 0.7% w/w predicted sufficient to kill most wound associated species. Pleurocidin retains its activity on release from the electrospun fiber matrix and completely inhibits growth of two strains of A. baumannii (AYE; ATCC 17978) and other ESKAPE pathogens. Inhibition of P. aeruginosa strains (PAO1; NCTC 13437) is, however, matrix weight per volume dependent, with only larger/thicker matrices maintaining complete inhibition. The resulting estimation of pleurocidin release from the matrix reveals high efficiency, facilitating a greater AMP potency. Wound matrices are often applied in parallel or sequentially with the use of standard wound care with biocides, therefore the presence and effect of biocides on pleurocidin potency was tested. It was revealed that combinations displayed additive or modestly synergistic effects depending on the biocide and pathogens which should be considered during the therapy. Taken together, we show that electrospun, pleurocidin-loaded wound matrices have potential to be investigated for wound infection treatment.


Subject(s)
Disinfectants , Wound Infection , Humans , Fish Proteins/pharmacology , Bacteria , Anti-Bacterial Agents/pharmacology , Anti-Bacterial Agents/chemistry , Disinfectants/pharmacology , Wound Infection/drug therapy
17.
ACS Med Chem Lett ; 15(2): 239-249, 2024 Feb 08.
Article in English | MEDLINE | ID: mdl-38352828

ABSTRACT

A new class of amphiphilic molecules, the lipoguanidines, designed as hybrids of guanidine and fatty acid compounds, has been synthesized and developed. The new molecules present both a guanidine polar head and a lipophilic tail that allow them to disrupt bacterial membranes and to sensitize Gram-negative bacteria to the action of the narrow-spectrum antibiotics rifampicin and novobiocin. The lipoguanidine 5g sensitizes Klebsiella pneumonia, Acinetobacter baumannii, Pseudomonas aeruginosa, and Escherichia coli to rifampicin, thereby reducing the antibiotic minimum inhibitory concentrations (MIC) up to 256-fold. Similarly, 5g is able to potentiate novobiocin up to 64-fold, thereby showing a broad spectrum of antibiotic potentiating activity. Toxicity and mechanism studies revealed the potential of 5g to work synergistically with rifampicin through the disruption of bacterial membranes without affecting eukaryotic cells.

18.
ACS Omega ; 9(24): 26030-26049, 2024 Jun 18.
Article in English | MEDLINE | ID: mdl-38911757

ABSTRACT

Antimicrobial resistance has increased rapidly, causing daunting morbidity and mortality rates worldwide. Antimicrobial peptides (AMPs) have emerged as promising alternatives to traditional antibiotics due to their broad range of targets and low tendency to elicit resistance. However, potent antimicrobial activity is often accompanied by excessive cytotoxicity toward host cells, leading to a halt in AMP therapeutic development. Here, we present multivariate analyses that correlate 28 peptide properties to the activity and toxicity of 46 diverse African-derived AMPs and identify the negative lipophilicity of polar residues as an essential physiochemical property for selective antimicrobial activity. Twenty-seven active AMPs are identified, of which the majority are of scorpion or frog origin. Of these, thirteen are novel with no previously reported activities. Principal component analysis and quantitative structure-activity relationships (QSAR) reveal that overall hydrophobicity, lipophilicity, and residue side chain surface area affect the antimicrobial and cytotoxic activity of an AMP. This has been well documented previously, but the present QSAR analysis additionally reveals that a decrease in the lipophilicity, contributed by those amino acids classified as polar, confers selectivity for a peptide to pathogen over mammalian cells. Furthermore, an increase in overall peptide charge aids selectivity toward Gram-negative bacteria and fungi, while selectivity toward Gram-positive bacteria is obtained through an increased number of small lipophilic residues. Finally, a conservative increase in peptide size in terms of sequence length and molecular weight also contributes to improved activity without affecting toxicity. Our findings suggest a novel approach for the rational design or modification of existing AMPs to increase pathogen selectivity and enhance therapeutic potential.

19.
ACS Sens ; 8(3): 1101-1108, 2023 03 24.
Article in English | MEDLINE | ID: mdl-36820613

ABSTRACT

Rapid tests to assess the susceptibility of bacteria to antibiotics are required to inform antibiotic stewardship. We have developed a novel test, which measures changes in the impedance of a 100 nanoliter volume of bacterial suspension to determine an "electrical" minimum inhibitory concentration (eMIC). Two representative strains of Klebsiella pneumoniae, Acinetobacter baumannii, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus were tested against a panel of frontline antibiotics with different modes of action (ciprofloxacin, doxycycline, colistin and imipenem, gentamicin, and ceftazidime). The eMIC measured at 1 h correlated strongly with a standard 24 h microbroth dilution MIC for all combinations of antibiotics and bacteria, allowing strains to be correctly assigned as sensitive or resistant measured in a fraction of the time.


Subject(s)
Anti-Bacterial Agents , Colistin , Anti-Bacterial Agents/pharmacology , Colistin/pharmacology , Bacteria , Ciprofloxacin , Drug Resistance, Microbial
20.
Chem Commun (Camb) ; 59(70): 10504-10507, 2023 Aug 29.
Article in English | MEDLINE | ID: mdl-37644759

ABSTRACT

We determine the efficacy for three known structurally related, membrane active detergents against multidrug resistant and wild type strains of Pseudomonas aeruginosa. Accessible solution state NMR experiments are used to quantify phospholipid headgroup composition of the microbial membranes and to gain molecular level insight into antimicrobial mode of action.


Subject(s)
Detergents , Pseudomonas aeruginosa , Detergents/pharmacology , Betaine , Phospholipids
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