A total of 20 of isolates of lactic acid bacteria (LAB) were selected and screened for antagonistic activity against clinical strains of 30 clinical isolates of extremely drug-resistant (XDR) Acinetobacter baumannii using the well diffusion assay method. Results showed that 50% of the highly LAB strains possessed inhibitory activity against (up to 66%) of the XDR A. baumannii strains tested. The supernatant of the twenty LAB strains was subjected to gas chromatography mass spectrometry (GCMS) revealed that the common compound found in the active isolates against XDR A. baumannii was 3-Isobutyl-2,3,6,7,8,8a-hexahydropyrrolo[1,2-a]pyrazine-1,4-dione, a known potential diketopiperazine group. The molecular docking study against potential antibacterial targets with selected ligands was performed to predict the binding mode of interactions, which is responsible for antibacterial activity. The docking analysis of the potent compounds supported the potential antibacterial activity exhibiting high inhibition constant and binding affinity in silico.
Matched MeSH terms: Drug Resistance, Bacterial/drug effects*
Increased prevalence of methicillin-resistant Staphylococcus aureus (MRSA) has become a major threat to the health sector worldwide due to their virulence, limited therapeutic options and their distribution in both hospital and community settings. Discovery and development of new anti-MRSA agents as alternatives to the very few antibiotics left in the armamentarium are, thus, urgently required. Recently, an efflux mechanism in MRSA has been identified as one of the main contributors of resistance towards various structurally unrelated antibiotics. The potential of reserpine (a phytoalkaloid) as efflux pump inhibitor (EPI) against various microbes remains limited as the concentration needed for inhibition is toxic to humans. This study therefore aimed to evaluate 13 alkaloid compounds as potential inhibitory agents and/or potential EPIs against a panel of three MRSA isolates which not only differ in their susceptibility to vancomycin (amongst the last drugs available to treat serious MRSA infection), but also exhibited active efflux activity. Results indicated berberine's moderate inhibitiory activity against two MRSA isolates scoring a minimum inhibitory concentration (MIC) value of 125 microg/ml. Notable efflux inhibitory activity (ranging from two- to eightfold Ethidium Bromide MIC reduction) meanwhile was detected from quinine, piperine and harmaline using reserpine as the positive control. Findings from this study support the opinion that a vast number of potential phytocompounds with pharmacological potential await discovery. Therapeutic application of these compounds, however, warrants further investigation to ascertain their pharmacodynamics and safety aspects.
Matched MeSH terms: Drug Resistance, Bacterial/drug effects*
Tuberculosis (TB) is described as lethal disease in the world. Resistant to TB drugs is the main reason to have unfavourable outcomes in the treatment of TB. Therefore, new agents to replace existing drugs are urgently needed. Previous reports suggested that InhA inhibitors, an enoyl-ACP-reductase, might provide auspicious candidates which can be developed into novel antitubercular agents. In this review, we explain the role of InhA in the resistance of isoniazid. Furthermore, five classes of InhA inhibitors, which display novel binding modes and deliver evidence of their prosperous target engagement, have been debated.
Matched MeSH terms: Drug Resistance, Bacterial/drug effects
The discovery of antibiotics ought to have ended the issue of bacterial infections, but this was not the case as it has led to the evolution of various mechanisms of bacterial resistance against various antibiotics. The efflux pump remains one of the mechanisms through which organisms develop resistance against antibiotics; this is because organisms can extrude most of the clinically relevant antibiotics from the interior cell environment to the exterior environment via the efflux pumps. Efflux pumps are thought to contribute significantly to biofilm formation as highlighted by various studies. Therefore, the inhibition of these efflux pumps can be a potential way of improving the activity of antibiotics, particularly now that the discovery of novel antibiotics is becoming tedious. Efflux pump inhibitors (EPIs) are molecules that can inhibit efflux pumps; they have been considered potential therapeutic agents for rejuvenating the activity of antibiotics that have already lost their activity against bacteria. However, studies are yet to determine the specific substrates for such pumps; the effect of altered efflux activity of these pumps on biofilm formation is still being investigated. A clear knowledge of the involvement of efflux pumps in biofilm development could aid in developing new agents that can interfere with their function and help to prevent biofilms formation; thereby, improving the outcome of treatment strategies. This review focuses on the novel update of EPIs and discusses the evidence of the roles of efflux pumps in biofilm formation; the potential approaches towards overcoming the increasing problem of biofilm-based infections are also discussed.
Matched MeSH terms: Drug Resistance, Bacterial/drug effects*
The increased Salmonella resistance to quinolones and fluoroquinolones is a public health concern in the Southeast Asian region. The objective of this study is to develop a high resolution melt curve (HRM) assay to rapidly screen for mutations in quinolone-resistant determining region (QRDR) of gyrase and topoisomerase IV genes. DNA sequencing was performed on 62 Salmonella strains to identify mutations in the QRDR of gyrA, gyrB, parC, and parE genes. Mutations were detected in QRDR of gyrA (n = 52; S83F, S83Y, S83I, D87G, D87Y, and D87N) and parE (n = 1; M438I). Salmonella strains with mutations within QRDR of gyrA are generally more resistant to nalidixic acid (MIC 16 > 256 μg/mL). Mutations were uncommon within the QRDR of gyrB, parC, and parE genes. In the HRM assay, mutants can be distinguished from the wild-type strains based on the transition of melt curves, which is more prominent when the profiles are displayed in difference plot. In conclusion, HRM analysis allows for rapid screening for mutations at the QRDRs of gyrase and topoisomerase IV genes in Salmonella. This assay markedly reduced the sequencing effort involved in mutational studies of quinolone-resistance genes.
Matched MeSH terms: Drug Resistance, Bacterial/drug effects
In this study, a series of novel 3-(substituted phenyl)-6,7-dimethoxy-3a,4-dihydro-3H-indeno[1,2-c]isoxazole analogues were synthesized and evaluated for antimycobacterial activity against Mycobacterium tuberculosis (MTB) H(37)Rv and isoniazid resistant M. tuberculosis (INHR-MTB). All the newly synthesized compounds were showing moderate to high inhibitory activities. The compound 6,7-dimethoxy-3-(4-chloro phenyl)-4H-indeno[1,2-c]isoxazole (4b) was found to be the most promising compound, active against MTB H(37)Rv and INHR-MTB with minimum inhibitory concentrations of 0.22 and 0.34 μM.
Matched MeSH terms: Drug Resistance, Bacterial/drug effects*
Carbapenem resistance in Gram-negative pathogens has become a global concern for health workers worldwide. In one of our earlier studies, a Klebsiella pneumoniae-carbapenemase-2 producing strain was induced with meropenem to explore differentially expressed proteins under induced and uninduced conditions. There is, LysM domain BON family protein, was found over 12-fold expressed under the induced state. A hypothesis was proposed that LysM domain protein might have an affinity towards carbapenem antibiotics making them unavailable to bind with their target. Hence, we initiated a study to understand the binding mode of carbapenem with LysM domain protein. MICs of imipenem and meropenem against LysM clone were increased by several folds as compared to NP-6 clinical strain as well as DH5 α (PET-28a KPC-2) clone. This study further revealed a strong binding of both antibiotics to LysM domain protein. Molecular simulation studies of LysM domain protein with meropenem and imipenem for 80 ns has also showed stable structure. We concluded that overexpressed LysM domain under induced condition interacted with carbapenems, leading to enhanced resistance as proved by high MIC values. Hence, the study proved the proposed hypothesis that the LysM domain plays a significant role in the putative mechanism of antibiotics resistance.
Matched MeSH terms: Drug Resistance, Bacterial/drug effects*
A series of twelve dispiropyrrolidines were synthesized using [3+2]-cycloaddition reactions. The synthesized compounds were screened for their antimycobacterial activity against M. tuberculosis H(37)Rv and INH resistant M. tuberculosis strains using agar dilution method, four of them showed good activity with MIC of less than 1 μM. Compound 4'-[5-(4-fluorophenyl)pyridin-3-yl]-1'-methyldispiro[indan-2,2' pyrrolidine-3',2″-indan]-1,3,1″-trione (4b) was found to be the most active with MIC of 0.1215 and 5.121 μM, respectively.
Matched MeSH terms: Drug Resistance, Bacterial/drug effects
Klebsiella pneumoniae is an opportunistic pathogen that is responsible for causing nosocomial and community-acquired infections. Despite its common presence in soil and aquatic environments, the virulence potential of K. pneumoniae isolates of environmental origin is largely unknown. Hence, in this study, K. pneumoniae isolated from the estuarine waters and sediments of the Matang mangrove estuary were screened for potential virulence characteristics: antibiotic susceptibility, morphotype on Congo red agar, biofilm formation, presence of exopolysaccharide and capsule, possession of virulence genes (fimH, magA, ugE, wabG and rmpA) and their genomic fingerprints. A total of 55 strains of K. pneumoniae were isolated from both human-distributed sites (located along Sangga Besar River) and control sites (located along Selinsing River) where less human activity was observed, indicated that K. pneumoniae is ubiquitous in the environment. However, the detection of potentially virulent strains at the downstream of Kuala Sepetang village has suggested an anthropogenic contamination source. In conclusion, the findings from this study indicate that the Matang mangrove estuary could harbor potentially pathogenic K. pneumoniae with risk to public health. More studies are required to compare the environmental K. pneumoniae strains with the community-acquired K. pneumoniae strains.
Matched MeSH terms: Drug Resistance, Bacterial/drug effects*
To reveal whether an increase of CTX-M-15-producing Klebsiella pneumoniae ST11 isolates is due to clonal dissemination across the countries, plasmids (pHK02-026, pM16-13, pIN03-01, and pTH02-34) were extracted from four K. pneumoniae isolates collected in Hong Kong, Malaysia, Thailand, and Indonesia, respectively. Complete sequencing of blaCTX-M-15-carrying plasmids was performed. In addition to the four plasmids, a previously sequenced plasmid (pKP12226) of a K. pneumoniae ST11 isolate from Korea was included in the analysis. While pIN03-01 and pTH02-34, which belonged to the incompatibility group IncX3, showed nearly the same structure, the others of IncF1A or IncFII exhibited very different structures. The number and kinds of antibiotic genes found in the plasmids were also different from each other. Cryptic prophage genes were identified in all five blaCTX-M-15-harboring plasmids from the ST11 isolates; P1-like region in pKP12226, CPZ-55 prophage region in pHK02-026, phage shock operon pspFABCD in pM16-13, and SPBc2 prophage yokD in pIN03-01 and pTH02-34. The plasmids with blaCTX-M-15 in the prevailing K. pneumoniae ST11 isolates in Asian countries might emerge from diverse origins by recombination. The prevalence of CTX-M-15-producing K. pneumoniae ST11 clone in Asian countries is not mainly due to the dissemination of a single strain.
Matched MeSH terms: Drug Resistance, Bacterial/drug effects*
Carbapenem-resistant Enterobacteriaceae (CRE) has been a public health risk in several countries, and recent reports indicate the emergence of CRE in food animals. This study was conducted to investigate the occurrence, resistance patterns, and phylogenetic diversity of carbapenem-resistant E. coli (CREC) from chicken. Routine bacteriology, PCR detection of E. coli species, multiplex PCR to detect carbapenemase-encoding genes, and phylogeny of CRE E. coli were conducted. The results show that 24.36% (19/78) were identified as CREC based on the phenotypic identifications of which 17 were positive for the tested carbapenemases genes. The majority, 57.99% (11/19), of the isolates harbored multiple carbapenemase genes. Four isolates harbored all bla NDM, bla OXA, and bla IMP, and five and two different isolates harbored bla NDM and bla OXA and bla OXA and bla IMP, respectively. The meropenem, imipenem, and ertapenem MIC values for the isolates ranged from 2 μg/mL to ≥256 μg/mL. Phylogenetic grouping showed that the CREC isolates belonged to five different groups: groups A, B1, C, D, and unknown. The detection of CREC in this study shows that it has become an emerging problem in farm animals, particularly, in poultry farms. This also implies the potential public health risks posed by CRE from chicken to the consumers.
Matched MeSH terms: Drug Resistance, Bacterial/drug effects
Nanoparticles (NPs) possessing antibacterial activity represent an effective way of overcoming bacterial resistance. In the present work, we report a novel formulation of a nanoantibiotic formed using Ampicillin/sulbactam (Ams) and a zinc oxide nanoparticle (ZnO NP). 'ZnO NP-Ams' nanoantibiotic formulation is optimized using response surface methodology coupled genetic algorithm approach. The optimized formulation of nanoantibiotic (ZnO NP: 49.9 μg/mL; Ams: 33.6 μg/mL; incubation time: 27 h) demonstrated 15% enhanced activity compared to the unoptimized formulation against K. pneumoniae. The reactive oxygen species (ROS) generation was directly proportional to the interaction time of nanoantibiotic and K. pneumoniae after the initial lag phase of ~18 h as evident from 2'-7'-Dichlorodihydrofluorescein diacetate assay. A low minimum inhibitory concentration (6.25 μg/mL) of nanoantibiotic formulation reveals that even a low concentration of nanoantibiotic can prove to be effective against K. pneumoniae. The importance of nanoantibiotic formulation is also evident by the fact that the 100 μg/mL of Ams and 25 µg of ZnO NP was required individually to inhibit the growth of K. pneumonia, whereas only 6.25 μg/mL of optimized nanoantibiotic formulation (ZnO NP and Ams in the ratio of 49.9: 33.6 in μg/mL and conjugation time of 27 h) was needed for the same.
Matched MeSH terms: Drug Resistance, Bacterial/drug effects
Novel antimicrobial agents are crucial to combat antibiotic resistance in pathogenic bacteria. Choline kinase (ChoK) in bacteria catalyzes the synthesis of phosphorylcholine, which is subsequently incorporated into the cell wall or outer membrane. In certain species of bacteria, phosphorylcholine is also used to synthesize membrane phosphatidylcholine. Numerous human ChoK inhibitors (ChoKIs) have been synthesized and tested for anticancer properties. Inhibition of S. pneumoniae ChoK by human ChoKIs showed a promising effect by distorting the cell wall and retarded the growth of this pathogen. Comparison of amino acid sequences at the catalytic sites of putative choline kinases from pathogenic bacteria and human enzymes revealed striking sequence conservation that supports the potential application of currently available ChoKIs for inhibiting bacterial enzymes. We also propose the combined use of ChoKIs and nanoparticles for targeted delivery to the pathogen while shielding the human host from any possible side effects of the inhibitors. More research should focus on the verification of putative bacterial ChoK activities and the characterization of ChoKIs with active enzymes. In conclusion, the presence of ChoK in a wide range of pathogenic bacteria and the distinct function of this enzyme has made it an attractive drug target. This review highlighted the possibility of "choking" bacterial ChoKs by using human ChoKIs.
Matched MeSH terms: Drug Resistance, Bacterial/drug effects
Multidrug-resistant Streptococcus pneumoniae emerge through the modification of core genome loci by interspecies homologous recombinations, and acquisition of gene cassettes. Both occurred in the otherwise contrasting histories of the antibiotic-resistant S. pneumoniae lineages PMEN3 and PMEN9. A single PMEN3 clade spread globally, evading vaccine-induced immunity through frequent serotype switching, whereas locally circulating PMEN9 clades independently gained resistance. Both lineages repeatedly integrated Tn916-type and Tn1207.1-type elements, conferring tetracycline and macrolide resistance, respectively, through homologous recombination importing sequences originating in other species. A species-wide dataset found over 100 instances of such interspecific acquisitions of resistance cassettes and flanking homologous arms. Phylodynamic analysis of the most commonly sampled Tn1207.1-type insertion in PMEN9, originating from a commensal and disrupting a competence gene, suggested its expansion across Germany was driven by a high ratio of macrolide-to-β-lactam consumption. Hence, selection from antibiotic consumption was sufficient for these atypically large recombinations to overcome species boundaries across the pneumococcal chromosome.
Matched MeSH terms: Drug Resistance, Bacterial/drug effects*
Arsenic is a common contaminant in gold mine soil and tailings. Microbes present an opportunity for bio-treatment of arsenic, since it is a sustainable and cost-effective approach to remove arsenic from water. However, the development of existing bio-treatment approaches depends on isolation of arsenic-resistant microbes from arsenic contaminated samples. Microbial cultures are commonly used in bio-treatment; however, it is not established whether the structure of the cultured isolates resembles the native microbial community from arsenic-contaminated soil. In this milieu, a culture-independent approach using Illumina sequencing technology was used to profile the microbial community in situ. This was coupled with a culture-dependent technique, that is, isolation using two different growth media, to analyse the microbial population in arsenic laden tailing dam sludge based on the culture-independent sequencing approach, 4 phyla and 8 genera were identified in a sample from the arsenic-rich gold mine. Firmicutes (92.23%) was the dominant phylum, followed by Proteobacteria (3.21%), Actinobacteria (2.41%), and Bacteroidetes (1.49%). The identified genera included Staphylococcus (89.8%), Pseudomonas (1.25), Corynebacterium (0.82), Prevotella (0.54%), Megamonas (0.38%) and Sphingomonas (0.36%). The Shannon index value (3.05) and Simpson index value (0.1661) indicated low diversity in arsenic laden tailing. The culture dependent method exposed significant similarities with culture independent methods at the phylum level with Firmicutes, Proteobacteria and Actinobacteria, being common, and Firmicutes was the dominant phylum whereas, at the genus level, only Pseudomonas was presented by both methods. It showed high similarities between culture independent and dependent methods at the phylum level and large differences at the genus level, highlighting the complementarity between the two methods for identification of the native population bacteria in arsenic-rich mine. As a result, the present study can be a resource on microbes for bio-treatment of arsenic in mining waste.
Matched MeSH terms: Drug Resistance, Bacterial/drug effects
The increasing occurrence of hospital-acquired infections and the emerging problems posed by antibiotic-resistant microbial strains have both contributed to the escalating cost of treatment. The presence of infection at the wound site can potentially stall the healing process at the inflammatory stage, leading to the development of a chronic wound. Traditional wound treatment regimes can no longer cope with the complications posed by antibiotic-resistant strains; hence, there is a need to explore the use of alternative antimicrobial agents. Pre-antibiotic compounds, including heavy metal ions and essential oils, have been re-investigated for their potential use as effective antimicrobial agents. Essential oils have potent antimicrobial, antifungal, antiviral, anti-inflammatory, antioxidant and other beneficial therapeutic properties. Similarly, heavy metal ions have also been used as disinfecting agents because of their broad spectrum activities. Both of these alternative antimicrobials interact with many different intracellular components, thereby resulting in the disruption of vital cell functions and eventually cell death. This review will discuss the application of essential oils and heavy metal ions, particularly tea tree oil and silver ions, as alternative antimicrobial agents for the treatment of chronic, infected wounds.
Matched MeSH terms: Drug Resistance, Bacterial/drug effects
Acinetobacter baumannii has emerged as a notorious multidrug-resistant pathogen, and development of novel control measures is of the utmost importance. Understanding the factors that play a role in drug resistance may contribute to the identification of novel therapeutic targets. Pili are essential for A. baumannii adherence to and biofilm formation on abiotic surfaces as well as virulence. In the present study, we found that biofilm formation was significantly induced in an imipenem-resistant (Imp(r)) strain treated with a subinhibitory concentration of antibiotic compared to that in an untreated control and an imipenem-susceptible (Imp(s)) isolate. Using microarray and quantitative PCR analyses, we observed that several genes responsible for the synthesis of type IV pili were significantly upregulated in the Imp(r) but not in the Imp(s) isolate. Notably, this finding is corroborated by an increase in the motility of the Imp(r) strain. Our results suggest that the ability to overproduce colonization factors in response to imipenem treatment confers biological advantage to A. baumannii and may contribute to clinical success.
Matched MeSH terms: Drug Resistance, Bacterial/drug effects