Detection and evaluation of susceptibility to antibiotics in non-hydrogen sulfide-producing antibiotic-resistant soil microbe: Pseudomonas guariconensis. - Related Documents




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473801.0000Detection and evaluation of susceptibility to antibiotics in non-hydrogen sulfide-producing antibiotic-resistant soil microbe: Pseudomonas guariconensis. Antimicrobial resistance in bacteria is a global threat that can make antibacterial treatments ineffective. One well-known method of antibiotic resistance and a common defensive mechanism in many harmful bacteria is the synthesis of endogenous hydrogen sulfide (H(2)S) in bacteria. In this study, soil bacteria were screened using the lead acetate agar test and the triple sugar iron test to determine that they were non-endogenous H(2)S producers. This was further validated by full genome analysis of the identified organism against the gene sequences of H(2)S-producing genes. Antibacterial resistance of the bacteria was phenotypically analyzed using the Kirby-Bauer disk diffusion method. Then, the effect of exogenous H(2)S on the antibiotic-resistant bacteria was checked in sodium sulfide, leading to antibiotic re-sensitization.202538767682
473910.9999Indirect resistance to several classes of antibiotics in cocultures with resistant bacteria expressing antibiotic-modifying or -degrading enzymes. OBJECTIVES: Indirect resistance (IR), the ability of an antibiotic-resistant population of bacteria to protect a susceptible population, has been previously observed for β-lactamase-producing bacteria and associated with antimicrobial treatment failures. Here, we determined whether other resistance determinants could cause IR in the presence of five other classes of antibiotics. METHODS: A test was designed to detect IR and 14 antibiotic resistance genes were tested in the presence of 13 antibiotics from six classes. A bioassay was used to measure the ability of resistance-causing enzymes to decrease the concentration of active antibiotics in the medium. RESULTS: We confirmed IR in the presence of β-lactam antibiotics (ampicillin and mecillinam) when TEM-1A was expressed. We found that bacteria expressing antibiotic-modifying or -degrading enzymes Ere(A), Tet(X2) or CatA1 caused IR in the presence of macrolides (erythromycin and clarithromycin), tetracyclines (tetracycline and tigecycline) and chloramphenicol, respectively. IR was not observed with resistance determinants that did not modify or destroy antibiotics or with enzymes modifying aminoglycosides or degrading fosfomycin. IR was dependent on the resistance enzymes decreasing the concentration of active antibiotics in the medium, hence allowing nearby susceptible bacteria to resume growth once the antibiotic concentration fell below their MIC. CONCLUSIONS: IR was not limited to β-lactamase-producing bacteria, but was also caused by resistant bacteria carrying cytoplasmic antibiotic-modifying or -degrading enzymes that catalyse energy-consuming reactions requiring complex cellular cofactors. Our results suggest that IR is common and further emphasizes that coinfecting agents and the human microflora can have a negative impact during antimicrobial therapy.201626467993
575920.9999The Relationship between Antibiotic Susceptibility and pH in the Case of Uropathogenic Bacteria. Urinary tract infections (UTIs) are common bacterial infections caused mainly by enteric bacteria. Numerous virulence factors assist bacteria in the colonization of the bladder. Bacterial efflux pumps also contribute to bacterial communication and to biofilm formation. In this study, the phenotypic and genetic antibiotic resistance of clinical UTI pathogens such as Escherichia coli, Klebsiella pneumoniae, and Proteus mirabilis were determined by disk diffusion method and polymerase chain reaction (PCR). Following this, different classes of antibiotics were evaluated for their antibacterial activity at pH 5, 6, 7 and 8 by a microdilution method. Gentamicin (GEN) was the most potent antibacterial agent against E. coli strains. The effect of GEN on the relative expression of marR and sdiA genes was evaluated by quantitative PCR. The slightly acidic pH (pH 6) and GEN treatment induced the upregulation of marR antibiotic resistance and sdiA QS activator genes in both E. coli strains. Consequently, bacteria had become more susceptible to GEN. It can be concluded that antibiotic activity is pH dependent and so the artificial manipulation of urinary pH can contribute to a more effective therapy of multidrug resistant bacterial infections.202134943643
474030.9998Resensitization of Multi Drug-Resistant Aeromonas caviae with Exogenous Hydrogen Sulfide Potentiated Antibiotics. Antimicrobial resistance (AMR) is a growing public health threat caused by the widespread overuse of antibiotics. Bacteria with antibiotic resistance may acquire resistance genes from soil or water. Endogenous hydrogen sulfide (H(2)S) production in bacteria confers antibiotic tolerance in many, suggesting a universal defense mechanism against antibiotics. In this study, we isolated and identified soil-based antibiotic-resistant bacteria collected from contaminated areas. An antibiotic-resistant bacterium was identified as non-endogenous-H(2)S-producing, allowing us to examine the effect of exogenous H(2)S on its resistance mechanism. Therefore, we demonstrated that different classes of antibiotic resistance can be reverted by employing H(2)S with antibiotics like ampicillin and gentamicin. Methods like Kirby-Bauer Disk-Diffusion, Scanning Electron Microscopy, and Flow Cytometer analysis were performed to assess the antibacterial activity of H(2)S with ampicillin and gentamicin. The antioxidative efficiency of H(2)S was evaluated using the DCFH-DA (ROS) test, as well as lipid peroxidation, and LDH activity. These were further confirmed with enzymatic and non-enzymatic (SOD, CAT, GST, and GSH) antioxidant studies. These findings support H(2)S as an antibiotic-potentiator, causing bacterial membrane damage, oxidative stress, and disrupting DNA and proteins. Thus, supplying exogenous H(2)S can be a good agent for the reversal of Antibiotic resistance.202439579197
473240.9998A Comparison of Antibiotics' Resistance Patterns of E. coli and B. subtilis in their Biofilms and Planktonic Forms. BACKGROUND: A biofilm refers to a community of microbial cells that adhere to surfaces that are surrounded by an extracellular polymeric substance. Bacteria employ various defence mechanisms, including biofilm formation, to enhance their survival and resistance against antibiotics. OBJECTIVE: The current study aims to investigate the resistance patterns of Escherichia coli (E. coli) and Bacillus subtilis (B. subtilis) in both biofilms and their planktonic forms. METHODS: E. coli and B. subtilis were used to compare resistance patterns in biofilms versus planktonic forms of bacteria. An antibiotic disc diffusion test was performed to check the resistance pattern of biofilm and planktonic bacteria against different antibiotics such as penicillin G, streptomycin, and ampicillin. Biofilm formation and its validation were done by using quantitative (microtiter plate assay) and qualitative analysis (Congo red agar media). RESULTS: A study of surface-association curves of E. coli and B. subtilis revealed that surface adhesion in biofilms was continuously constant as compared to their planktonic forms, thereby confirming the increased survival of bacteria in biofilms. Also, biofilms have shown high resistance towards the penicillin G, ampicillin and streptomycin as compared to their planktonic form. CONCLUSION: It is safely inferred that E. coli and B. subtilis, in their biofilms, become increasingly resistant to penicillin G, ampicillin and streptomycin.202539092644
597750.9998Methods to determine antibiotic resistance gene silencing. The occurrence of antibiotic-resistant bacteria is an increasingly serious problem world-wide. In addition, to phenotypically resistant bacteria, a threat may also be posed by isolates with silent, but intact, antibiotic resistance genes. Such isolates, which have recently been described, possess wild-type genes that are not expressed, but may convert to resistance by activating expression of the silent genes. They may therefore compromise the efficacy of antimicrobial treatment, particularly if their presence has not been diagnosed. This chapter describes the detection of silent resistance genes by PCR and DNA sequencing. A method to detect five potentially silent acquired resistance genes; aadA, bla (OXA-2), strAB, sul1, and tet(A) is described. First, the susceptibility of the isolates to the relevant antibiotics is determined by an appropriate susceptibility testing method, such as E-test. Then the presence of the genes is investigated by PCR followed by agarose gel electrophoresis of the amplification products. If a resistance gene is detected in a susceptible isolate, the entire open-reading frame and promoter sequence of the gene is amplified by PCR and their DNA sequences obtained. The DNA sequences are then compared to those of known resistant isolates, to detect mutations that may account for susceptibility. If no mutations are detected the expression of the gene is investigated by RT-PCR following RNA extraction. The methods described here can be applied to all acquired resistance genes for which sequence and normal expression data are available.201020401584
583660.9998Identification of Pseudomonas aeruginosa genes associated with antibiotic susceptibility. Pseudomonas aeruginosa causes acute and chronic infections in humans and these infections are difficult to treat due to the bacteria's high-level of intrinsic and acquired resistance to antibiotics. To address this problem, it is crucial to investigate the molecular mechanisms of antibiotic resistance in this organism. In this study, a P. aeruginosa transposon insertion library of 17000 clones was constructed and screened for altered susceptibility to seven antibiotics. Colonies grown on agar plates containing antibiotics at minimum inhibitory concentrations (MICs) and those unable to grow at 1/2 MIC were collected. The transposon-disrupted genes in 43 confirmed mutants that showed at least a three-fold increase or a two-fold decrease in susceptibility to at least one antibiotic were determined by semi-random PCR and subsequent sequencing analysis. In addition to nine genes known to be associated with antibiotic resistance, including mexI, mexB and mexR, 24 new antibiotic resistance-associated genes were identified, including a fimbrial biogenesis gene pilY1 whose disruption resulted in a 128-fold increase in the MIC of carbenicillin. Twelve of the 43 genes identified were of unknown function. These genes could serve as targets to control or reverse antibiotic resistance in this important human pathogen.201020953948
474170.9998Detection of antimicrobial resistance-associated proteins by titanium dioxide-facilitated intact bacteria mass spectrometry. Titanium dioxide-modified target plates were developed to enhance intact bacteria analysis by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The plates were designed to photocatalytically destroy the bacterial envelope structure and improve the ionization efficiency of intracellular components, thereby promoting the measurable mass range and the achievable detection sensitivity. Accordingly, a method for rapid detection of antimicrobial resistance-associated proteins, conferring bacterial resistance against antimicrobial drugs, was established by mass spectrometric fingerprinting of intact bacteria without the need for any sample pre-treatment. With this method, the variations in resistance proteins' expression levels within bacteria were quickly measured from the relative peak intensities. This approach of resistance protein detection directly from intact bacteria by mass spectrometry is useful for fast discrimination of antimicrobial-resistant bacteria from their non-resistant counterparts whilst performing species identification. Also, it could be used as a rapid and convenient way for initial determination of the underlying resistance mechanisms.201829719694
584180.9998Isolation and Characterization of a Bacteriophage with Potential for the Control of Multidrug-Resistant Salmonella Strains Encoding Virulence Factors Associated with the Promotion of Precancerous Lesions. BACKGROUND: Antimicrobial-resistant bacteria represent a serious threat to public health. Among these bacteria, Salmonella is of high priority because of its morbidity levels and its ability to induce different types of cancer. AIM: This study aimed to identify Salmonella strains encoding genes linked to the promotion of precancerous lesions and to isolate a bacteriophage to evaluate its preclinical potential against these bacteria. METHODOLOGY: An epidemiological approach based on wastewater analysis was employed to isolate Salmonella strains and detect genes associated with the induction of precancerous lesions. Antimicrobial susceptibility was assessed by the disk diffusion method. A bacteriophage was isolated via the double agar technique, and its morphological characteristics, stability, host range, replication dynamics, and ability to control Salmonella under different conditions were evaluated. The bacteriophage genome was sequenced and analyzed using bioinformatics tools. RESULTS: Thirty-seven Salmonella strains were isolated, seventeen of which contained the five genes associated with precancerous lesions' induction. These strains exhibited resistance to multiple antimicrobials, including fluoroquinolones. A bacteriophage from the Autographiviridae family with lytic activity against 21 bacterial strains was isolated. This phage exhibited a 20 min replication cycle, releasing 52 ± 3 virions per infected cell. It demonstrated stability and efficacy in reducing the Salmonella concentration in simulated gastrointestinal conditions, and its genome lacked genes that represent a biosafety risk. CONCLUSION: This bacteriophage shows promising preclinical potential as a biotherapeutic agent against Salmonella.202439599826
464890.9998Potential of phage cocktails in the inactivation of Enterobacter cloacae--An in vitro study in a buffer solution and in urine samples. The objective of this study was to compare the dynamics of three previously isolated phages for Enterobacter cloacae in order to evaluate their ability to treat urinary tract infections (UTI). The phages genomes, survival, host range, were characterized, and the host-phage dynamics was determined in culture medium and urine samples. The presence of prophages in bacteria, host recovery and development of resistance to phage after treatment was also evaluated. The growth of the E. cloacae was inhibited by the three phages, resulting in a decrease of ≈3 log. The use of cocktails with two or three phages was significantly more effective (decrease of ≈4 log). In urine, the inactivation was still effective (≈2 log). Both phages were considered safe to inactivate the bacteria (no integrase and toxin codifying genes). Some bacteria remained viable in the presence of the phages, but their colonies were smaller than those of the non-treated control and were visible only after 5 days of incubation (visible after 24h in the control). A high bacterial inactivation efficiency with phage cocktails combined with the safety of the phages and their long periods of survival, even in urine samples, paves the way for depth studies, especially in vivo studies, to control urinary tract infection and to overcome the development of resistances by the nosocomial bacterium E. cloacae.201626541317
5760100.9998Downregulation of Klebsiella pneumoniae RND efflux pump genes following indole signal produced by Escherichia coli. BACKGROUND: More than a century has passed since it was discovered that many bacteria produce indole, but research into the actual biological roles of this molecule is just now beginning. The influence of indole on bacterial virulence was extensively investigated in indole-producing bacteria like Escherichia coli. To gain a deeper comprehension of its functional role, this study investigated how indole at concentrations of 0.5-1.0 mM found in the supernatant of Escherichia coli stationary phase culture was able to alter the virulence of non-indole-producing bacteria, such as Pseudomonas aeruginosa, Proteus mirabilis, and Klebsiella pneumoniae, which are naturally exposed to indole in mixed infections with Escherichia coli. RESULTS: Biofilm formation, antimicrobial susceptibility, and efflux pump activity were the three phenotypic tests that were assessed. Indole was found to influence antibiotic susceptibly of Pseudomonas aeruginosa, Proteus mirabilis and Klebsiella pneumoniae to ciprofloxacin, imipenem, ceftriaxone, ceftazidime, and amikacin through significant reduction in MIC with fold change ranged from 4 to 16. Biofilm production was partially abrogated in both 32/45 Pseudomonas aeruginosa and all eight Proteus mirabilis, while induced biofilm production was observed in 30/40 Klebsiella pneumoniae. Moreover, acrAB and oqxAB, which encode four genes responsible for resistance-nodulation-division multidrug efflux pumps in five isolates of Klebsiella pneumoniae were investigated genotypically using quantitative real-time (qRT)-PCR. This revealed that all four genes exhibited reduced expression indicated by 2^-ΔΔCT < 1 in indole-treated isolates compared to control group. CONCLUSION: The outcomes of qRT-PCR investigation of efflux pump expression have established a novel clear correlation of the molecular mechanism that lies beneath the influence of indole on bacterial antibiotic tolerance. This research provides novel perspectives on the various mechanisms and diverse biological functions of indole signaling and how it impacts the pathogenicity of non-indole-producing bacteria.202439182027
4786110.9998Novel Antimicrobial Target in Acinetobacter Baumannii. BACKGROUND: Resistance to multiple drugs is one of the biggest challenges in managing infectious diseases. Acinetobacter baumannii is considered a nosocomial infection. According to the multiple roles of the toxin-antitoxin system, this system can be considered an antimicrobial target in the presence of bacteria. With the impact on bacterial toxin, it can be used as a new antibacterial target. The purpose of this study was to determine the mazEF genes as a potent antimicrobial target in A. baumannii clinical isolates. METHODS: The functionality of mazEF genes was evaluated by qPCR in fifteen A. baumannii clinical isolates. Then, the mazE locus was targeted by peptide nucleic acid (PNA). RESULTS: The results showed a significant difference in the mean number of copies of mazF gene in normal and stress conditions. Also, we found that at a concentration of 15 µM of PNA the bacteria were killed and confirmed by culture on LB agar. CONCLUSIONS: This research is the first step in introducing mazEF TA loci as a sensitive target in A. baumannii. However, more studies are needed to test the effectiveness in vivo. In addition, the occurrence and potential for activation of the TA system, mazEF in other pathogenic bacteria should be further investigated.202235536074
4737120.9998Unprecedented Silver Resistance in Clinically Isolated Enterobacteriaceae: Major Implications for Burn and Wound Management. Increased utilization of inorganic silver as an adjunctive to many medical devices has raised concerns of emergent silver resistance in clinical bacteria. Although the molecular basis for silver resistance has been previously characterized, to date, significant phenotypic expression of these genes in clinical settings is yet to be observed. Here, we identified the first strains of clinical bacteria expressing silver resistance at a level that could significantly impact wound care and the use of silver-based dressings. Screening of 859 clinical isolates confirmed 31 harbored at least 1 silver resistance gene. Despite the presence of these genes, MIC testing revealed most of the bacteria displayed little or no increase in resistance to ionic silver (200 to 300 μM Ag(+)). However, 2 isolates (Klebsiella pneumonia and Enterobacter cloacae) were capable of robust growth at exceedingly high silver concentrations, with MIC values reaching 5,500 μM Ag(+). DNA sequencing of these two strains revealed the presence of genes homologous to known genetic determinants of heavy metal resistance. Darkening of the bacteria's pigment was observed after exposure to high silver concentrations. Scanning electron microscopy images showed the presence of silver nanoparticles embedded in the extracellular polymeric substance of both isolates. This finding suggested that the isolates may neutralize ionic silver via reduction to elemental silver. Antimicrobial testing revealed both organisms to be completely resistant to many commercially available silver-impregnated burn and wound dressings. Taken together, these findings provide the first evidence of clinical bacteria capable of expressing silver resistance at levels that could significantly impact wound management.201526014954
3806130.9997Bioinformatic analysis reveals the association between bacterial morphology and antibiotic resistance using light microscopy with deep learning. Although it is well known that the morphology of Gram-negative rods changes on exposure to antibiotics, the morphology of antibiotic-resistant bacteria in the absence of antibiotics has not been widely investigated. Here, we studied the morphologies of 10 antibiotic-resistant strains of Escherichia coli and used bioinformatics tools to classify the resistant cells under light microscopy in the absence of antibiotics. The antibiotic-resistant strains showed differences in morphology from the sensitive parental strain, and the differences were most prominent in the quinolone-and β-lactam-resistant bacteria. A cluster analysis revealed increased proportions of fatter or shorter cells in the antibiotic-resistant strains. A correlation analysis of morphological features and gene expression suggested that genes related to energy metabolism and antibiotic resistance were highly correlated with the morphological characteristics of the resistant strains. Our newly proposed deep learning method for single-cell classification achieved a high level of performance in classifying quinolone-and β-lactam-resistant strains.202439364166
5080140.9997Rapid screening for antibiotic resistance elements on the RNA transcript, protein and enzymatic activity level. BACKGROUND: The emerging threat posed by antibiotic resistance has affected public health systems all over the world. Surveillance of resistant bacteria in clinical settings and identifying them in mixed cultures is of paramount importance and can contribute to the control of their spreading. Culture-independent monitoring approaches are highly desirable, since they yield results much faster than traditional susceptibility testing. However, many rapid molecular methods like PCR only detect the sole presence of a potential resistance gene, do not provide information regarding efficient transcription, expression and functionality and, in addition, cannot assign resistance genes to species level in mixed cultures. METHODS: By using plasmid-encoded TEM β-lactamase mediated ampicillin resistances as a proof of principle system, we (1) developed a fluorescence in situ hybridization-test (FISH) capable to detect the respective mRNAs, (2) implemented an immunofluorescence test to identify the corresponding proteins and (3) compared these two microscopic tests with an established colorimetric nitrocefin assay to assess the enzymatic activity. RESULTS: All three methods proved to be suitable for the testing of antibiotic resistance, but only FISH and immunofluorescence were able to differentiate between susceptible and resistant bacteria on the single cell level and can be combined with simultaneous species identification. CONCLUSIONS: Fluorescence in situ hybridization and immunofluorescence tests are promising techniques in susceptibility testing since they bridge the gap between the slow, but accurate and sound cultural methods and molecular detection methods like PCR with much less functional relevance.201627663856
5837150.9997The secondary resistome of multidrug-resistant Klebsiella pneumoniae. Klebsiella pneumoniae causes severe lung and bloodstream infections that are difficult to treat due to multidrug resistance. We hypothesized that antimicrobial resistance can be reversed by targeting chromosomal non-essential genes that are not responsible for acquired resistance but essential for resistant bacteria under therapeutic concentrations of antimicrobials. Conditional essentiality of individual genes to antimicrobial resistance was evaluated in an epidemic multidrug-resistant clone of K. pneumoniae (ST258). We constructed a high-density transposon mutant library of >430,000 unique Tn5 insertions and measured mutant depletion upon exposure to three clinically relevant antimicrobials (colistin, imipenem or ciprofloxacin) by Transposon Directed Insertion-site Sequencing (TraDIS). Using this high-throughput approach, we defined three sets of chromosomal non-essential genes essential for growth during exposure to colistin (n = 35), imipenem (n = 1) or ciprofloxacin (n = 1) in addition to known resistance determinants, collectively termed the "secondary resistome". As proof of principle, we demonstrated that inactivation of a non-essential gene not previously found linked to colistin resistance (dedA) restored colistin susceptibility by reducing the minimum inhibitory concentration from 8 to 0.5 μg/ml, 4-fold below the susceptibility breakpoint (S ≤ 2 μg/ml). This finding suggests that the secondary resistome is a potential target for developing antimicrobial "helper" drugs that restore the efficacy of existing antimicrobials.201728198411
5840160.9997Detection of point mutations associated with antibiotic resistance in Pseudomonas aeruginosa. Excessive use of broad-spectrum antibiotics in hospitals has led to the emergence of highly resistant strains of Pseudomonas aeruginosa. To reduce the selection pressure for resistance, it is important to determine the antibiotic susceptibility pattern of bacteria so that hospital patients can be treated with more narrow-spectrum and target-specific antibiotics. This study describes the development of a technique for detecting point muations in the fluoroquinolone resistance-determining region of the gyrA and parC genes as well as the efflux regulatory genes mexR, mexZ and mexOZ that are associated with fluoroquinolone and aminoglycoside resistance. The assay is based on a short DNA sequencing method using multiplex-fast polymerase chain reaction (PCR) and Pyrosequencing for amplification and sequencing of the selected genes. Fifty-nine clinical isolates of P. aeruginosa were examined for mutations in the abovementioned genes. Mutations related to antibiotic resistance were detected in codons 83 and 87 of gyrA and codon 126 of the mexR regulatory gene. Results of this study suggest Pyrosequencing as a substitute for traditional methods as it provides a rapid and reliable technique for determining the antibiotic resistance pattern of a given bacterial strain in <1 h.200919656662
4815170.9997The high prevalence of antibiotic heteroresistance in pathogenic bacteria is mainly caused by gene amplification. When choosing antibiotics to treat bacterial infections, it is assumed that the susceptibility of the target bacteria to an antibiotic is reflected by laboratory estimates of the minimum inhibitory concentration (MIC) needed to prevent bacterial growth. A caveat of using MIC data for this purpose is heteroresistance, the presence of a resistant subpopulation in a main population of susceptible cells. We investigated the prevalence and mechanisms of heteroresistance in 41 clinical isolates of the pathogens Escherichia coli, Salmonella enterica, Klebsiella pneumoniae and Acinetobacter baumannii against 28 different antibiotics. For the 766 bacteria-antibiotic combinations tested, as much as 27.4% of the total was heteroresistant. Genetic analysis demonstrated that a majority of heteroresistance cases were unstable, with an increased resistance of the subpopulations resulting from spontaneous tandem amplifications, typically including known resistance genes. Using mathematical modelling, we show how heteroresistance in the parameter range estimated in this study can result in the failure of antibiotic treatment of infections with bacteria that are classified as antibiotic susceptible. The high prevalence of heteroresistance with the potential for treatment failure highlights the limitations of MIC as the sole criterion for susceptibility determinations. These results call for the development of facile and rapid protocols to identify heteroresistance in pathogens.201930742072
4726180.9997Overcoming Multidrug Resistance in E. coli and Salmonella Isolates from Nile Tilapia: Synergistic Effects of Novel Antibiotic Combinations. Escherichia coli and Salmonella are significant foodborne zoonotic pathogens, causing serious human illness. The rising global prevalence of antimicrobial resistance (AMR) in these species exacerbates their public health risk, complicating the treatment of bacterial infection. This study investigates its prevalence, resistant genes, and treatment strategy against antibiotic-resistant bacteria, focusing on E. coli and Salmonella isolates from Nile tilapia. Prevalence of E. coli and Salmonella was found to be 32 and 22% respectively. Antibiotic susceptibility testing revealed resistance to five antibiotics in E. coli and four in Salmonella. Physiochemical properties of antibiotic resistance genes (ABRGs) indicated that the TetB gene has the highest aliphatic index in both bacteria, suggesting greater stability. All Bla proteins were hydrophobic as indicated by negative GRAVY values, which may contribute to antibiotic efflux or modification of antibiotic targets. Motif analysis identified functional domains, and cellular localization prediction showed that TetA and TetB genes are primarily expressed in the cell membrane. To combat this resistance, a checkerboard method was used to explore novel antibiotic combinations. For E. coli, one synergistic and two additive combinations were identified, while for Salmonella, two synergistic and one additive combination were effective. These results highlight the importance of regularly evaluating antibiotic combinations to combat resistance and preserve antibiotic efficacy.202540581898
3805190.9997De Novo Characterization of Genes That Contribute to High-Level Ciprofloxacin Resistance in Escherichia coli. Sensitization of resistant bacteria to existing antibiotics depends on the identification of candidate targets whose activities contribute to resistance. Using a transposon insertion library in an Escherichia coli mutant that was 2,000 times less susceptible to ciprofloxacin than its parent and the relative fitness scores, we identified 19 genes that contributed to the acquired ciprofloxacin resistance and mapped the shortest genetic path that increased the antibiotic susceptibility of the resistant bacteria back to a near wild-type level.201627431218