Impairment of novel non-coding small RNA00203 inhibits biofilm formation and reduces biofilm-specific antibiotic resistance in Acinetobacter baumannii. - Related Documents




#
Rank
Similarity
Title + Abs.
Year
PMID
012345
904401.0000Impairment of novel non-coding small RNA00203 inhibits biofilm formation and reduces biofilm-specific antibiotic resistance in Acinetobacter baumannii. Small RNAs (sRNAs) are post-transcriptional regulators of many biological processes in bacteria, including biofilm formation and antibiotic resistance. The mechanisms by which sRNA regulates the biofilm-specific antibiotic resistance in Acinetobacter baumannii have not been reported to date. This study aimed to investigate the influence of sRNA00203 (53 nucleotides) on biofilm formation, antibiotic susceptibility, and expression of genes associated with biofilm formation and antibiotic resistance. The results showed that deletion of the sRNA00203-encoding gene decreased the biomass of biofilm by 85%. Deletion of the sRNA00203-encoding gene also reduced the minimum biofilm inhibitory concentrations for imipenem and ciprofloxacin 1024- and 128-fold, respectively. Knocking out of sRNA00203 significantly downregulated genes involved in biofilm matrix synthesis (pgaB), efflux pump production (novel00738), lipopolysaccharide biosynthesis (novel00626), preprotein translocase subunit (secA) and the CRP transcriptional regulator. Overall, the suppression of sRNA00203 in an A. baumannii ST1894 strain impaired biofilm formation and sensitized the biofilm cells to imipenem and ciprofloxacin. As sRNA00203 was found to be conserved in A. baumannii, a therapeutic strategy targeting sRNA00203 may be a potential solution for the treatment of biofilm-associated infections caused by A. baumannii. To the best of the authors' knowledge, this is the first study to show the impact of sRNA00203 on biofilm formation and biofilm-specific antibiotic resistance in A. baumannii.202337315907
637510.9989Role of ppGpp-regulated efflux genes in Acinetobacter baumannii. OBJECTIVES: Treatment of infections caused by Acinetobacter baumannii nosocomial strains has become increasingly problematic owing to their resistance to antibiotics. ppGpp is a secondary messenger involved in growth control and various stress responses in bacteria. The mechanism for inhibition of antibiotic resistance via ppGpp is still unidentified in various pathogenic bacteria including A. baumannii. Here, we investigated the effects of ppGpp on efflux pump (EP)-related genes in A. baumannii. METHODS: ppGpp-deficient and -complementary strains were constructed by conjugation and we confirmed (p)ppGpp measurements by thin-layer chromatography. We observed that the ppGpp-deficient strain (ΔA1S_0579) showed abnormal stretching patterns by transmission electron microscopy analysis. The MICs of antimicrobial agents for the WT A. baumannii (ATCC 17978), ppGpp-deficient and complementary strains were determined by the Etest and broth dilution assay methods. The expression levels of EP-related genes were determined by quantitative RT-PCR. RESULTS: We observed morphological differences between a ppGpp-deficient strain (ΔA1S_0579) and the WT strain. Dramatic reductions of MICs in the ppGpp-deficient strain compared with the WT were observed for gentamicin (2.6-fold), tetracycline (3.9-fold), erythromycin (4-fold) and trimethoprim (>4-fold). Expression of the EP-related genes abeB (2.8-fold), tet(A) (2.3-fold), adeB (10.0-fold), adeI (9.9-fold), adeJ (11.8-fold) and adeK (14.4-fold) was also decreased in the ppGpp-deficient strain. CONCLUSIONS: This study demonstrates that ppGpp regulates EP-related gene expression in A. baumannii, affecting antibiotic susceptibility. To date, treatment for MDR A. baumannii has had no new antimicrobial agents, so the A1S_0579 gene could be a novel therapeutic target for rational drug design by affecting ppGpp production.202032049284
902020.9989Transcriptome Analysis Reveals the Resistance Mechanism of Pseudomonas aeruginosa to Tachyplesin I. BACKGROUND: Tachyplesin I is a cationic antimicrobial peptide with a typical cyclic antiparallel β-sheet structure. We previously demonstrated that long-term continuous exposure to increased concentration of tachyplesin I can induce resistant Gram-negative bacteria. However, no significant information is available about the resistance mechanism of Pseudomonas aeruginosa (P. aeruginosa) to tachyplesin I. MATERIALS AND METHODS: In this study, the global gene expression profiling of P. aeruginosa strain PA-99 and P. aeruginosa CGMCC1.2620 (PA1.2620) was conducted using transcriptome sequencing. For this purpose, outer membrane permeability and outer membrane proteins (OMPs) were further analyzed. RESULTS: Transcriptome sequencing detected 672 upregulated and 787 downregulated genes, covering Clusters of Orthologous Groups (COGs) of P. aeruginosa strain PA-99 compared with PA1.2620. Totally, 749 differentially expressed genes (DEGs) were assigned to 98 Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways, and among them, a two-component regulatory system, a beta-lactam resistance system, etc. were involved in some known genes resistant to drugs. Additionally, we further attempted to indicate whether the resistance mechanism of P. aeruginosa to tachyplesin I was associated with the changes of outer membrane permeability and OMPs. CONCLUSION: Our results indicated that P. aeruginosa resistant to tachyplesin I was mainly related to reduced entry of tachyplesin I into the bacterial cell due to overexpression of efflux pump, in addition to a decrease of outer membrane permeability. Our findings were also validated by pathway enrichment analysis and quantitative reverse transcription polymerase chain reaction (RT-qPCR). This study may provide a promising guidance for understanding the resistance mechanism of P. aeruginosa to tachyplesin I.202032021330
888330.9989Expression of Meiothermus ruber luxS in E. coli alters the antibiotic susceptibility and biofilm formation. Quorum sensing (QS) and signal molecules used for interspecies communication are well defined in mesophiles, but there is still a plethora of microorganisms in which existence and mechanisms of QS need to be explored, thermophiles being among them. In silico analysis has revealed the presence of autoinducer-2 (AI-2) class of QS signaling molecules in thermophiles, synthesized by LuxS (AI-2 synthase), though the functions of this system are not known. In this study, LuxS of Meiothermus ruber was used for understanding the mechanism and functions of AI-2 based QS among thermophilic bacteria. The luxS gene of M. ruber was expressed in luxS(-) deletion mutant of Escherichia coli. Complementation of luxS resulted in significant AI-2 activity, enhanced biofilm formation, and antibiotic susceptibility. Transcriptome analysis showed significant differential expression of 204 genes between the luxS-complemented and luxS(-) deletion mutant of E. coli. Majority of the genes regulated by luxS belonged to efflux pumps. This elucidation may contribute towards finding novel alternatives against incessant antibiotic resistance in bacteria.Key Points• Expression of luxS in luxS(-)E. coli resulted in increase in biofilm index. • Reduction in the MIC of antibiotics was observed after complementation of luxS. • Downregulation of efflux pump genes was observed after complementation of luxS. • Transcriptome analysis showed that 204 genes were differentially regulated significantly.202032215705
903840.9989Molecular mechanisms of chlorhexidine tolerance in Burkholderia cenocepacia biofilms. The high tolerance of biofilm-grown Burkholderia cepacia complex bacteria against antimicrobial agents presents considerable problems for the treatment of infected cystic fibrosis patients and the implementation of infection control guidelines. In the present study, we analyzed the tolerance of planktonic and sessile Burkholderia cenocepacia J2315 cultures and examined the transcriptional response of sessile cells to treatment with chlorhexidine. At low (0.0005%) and high (0.05%) concentrations, chlorhexidine had a similar effect on both populations, but at intermediate concentrations (0.015%) the antimicrobial activity was more pronounced in planktonic cultures. The exposure of sessile cells to chlorhexidine resulted in an upregulation of the transcription of 469 (6.56%) and the downregulation of 257 (3.59%) protein-coding genes. A major group of upregulated genes in the treated biofilms encoded membrane-related and regulatory proteins. In addition, several genes coding for drug resistance determinants also were upregulated. The phenotypic analysis of RND (resistance-nodulation-division) efflux pump mutants suggests the presence of lifestyle-specific chlorhexidine tolerance mechanisms; efflux system RND-4 (BCAL2820-BCAL2822) was more responsible for chlorhexidine tolerance in planktonic cells, while other systems (RND-3 [BCAL1672-BCAL1676] and RND-9 [BCAM1945-BCAM1947]) were linked to resistance in sessile cells. After sessile cell exposure, multiple genes encoding chemotaxis and motility-related proteins were upregulated in concert with the downregulation of an adhesin-encoding gene (BCAM2143), suggesting that sessile cells tried to escape the biofilm. We also observed the differential expression of 19 genes carrying putative small RNA molecules, indicating a novel role for these regulatory elements in chlorhexidine tolerance.201121357299
904150.9988Spontaneous and evolutionary changes in the antibiotic resistance of Burkholderia cenocepacia observed by global gene expression analysis. BACKGROUND: Burkholderia cenocepacia is a member of the Burkholderia cepacia complex group of bacteria that cause infections in individuals with cystic fibrosis. B. cenocepacia isolate J2315 has been genome sequenced and is representative of a virulent, epidemic CF strain (ET12). Its genome encodes multiple antimicrobial resistance pathways and it is not known which of these is important for intrinsic or spontaneous resistance. To map these pathways, transcriptomic analysis was performed on: (i) strain J2315 exposed to sub-inhibitory concentrations of antibiotics and the antibiotic potentiator chlorpromazine, and (ii) on spontaneous mutants derived from J2315 and with increased resistance to the antibiotics amikacin, meropenem and trimethoprim-sulfamethoxazole. Two pan-resistant ET12 outbreak isolates recovered two decades after J2315 were also compared to identify naturally evolved gene expression changes. RESULTS: Spontaneous resistance in B. cenocepacia involved more gene expression changes and different subsets of genes than those provoked by exposure to sub inhibitory concentrations of each antibiotic. The phenotype and altered gene expression in the resistant mutants was also stable irrespective of the presence of the priming antibiotic. Both known and novel genes involved in efflux, antibiotic degradation/modification, membrane function, regulation and unknown functions were mapped. A novel role for the phenylacetic acid (PA) degradation pathway genes was identified in relation to spontaneous resistance to meropenem and glucose was found to repress their expression. Subsequently, 20 mM glucose was found to produce greater that 2-fold reductions in the MIC of multiple antibiotics against B. cenocepacia J2315. Mutation of an RND multidrug efflux pump locus (BCAM0925-27) and squalene-hopene cyclase gene (BCAS0167), both upregulated after chlorpromazine exposure, confirmed their role in resistance. The recently isolated outbreak isolates had altered the expression of multiple genes which mirrored changes seen in the antibiotic resistant mutants, corroborating the strategy used to model resistance. Mutation of an ABC transporter gene (BCAS0081) upregulated in both outbreak strains, confirmed its role in B. cenocepacia resistance. CONCLUSIONS: Global mapping of the genetic pathways which mediate antibiotic resistance in B. cenocepacia has revealed that they are multifactorial, identified potential therapeutic targets and also demonstrated that putative catabolite repression of genes by glucose can improve antibiotic efficacy.201121781329
890860.9988Characterization and Transcriptome Analysis of Acinetobacter baumannii Persister Cells. Acinetobacter baumannii is a nonfermenting Gram-negative bacillus. A. baumannii resistance is a significant obstacle to clinical infection treatment. The existence of persister cells (persisters) might represent the reason for therapy failure and relapse, and such cells may be the driving force behind rising resistance rates. In this study, A. baumannii ATCC 19606 was used as a target to explore the essential features of A. baumannii persisters. Antibiotic treatment of A. baumannii cultures at 50-fold the minimum inhibitory concentration resulted in a distinct plateau of surviving drug-tolerant persisters. The sensitive bacteria were lysed with ceftazidime, and the nonreplicating bacteria were isolated for transcriptome analysis using RNA sequencing. We analyzed the transcriptome of A. baumannii persisters and identified significantly differentially expressed genes, as well as their enriched pathways. The results showed that both the GP49 (HigB)/Cro (HigA) and DUF1044/RelB toxin/antitoxin systems were significantly increased during the persister incubation period. In addition, the activities of certain metabolic pathways (such as electron transport, adenosine triphosphate [ATP], and the citrate cycle) decreased sharply after antibiotic treatment and remained low during the persister period, while aromatic compound degradation genes were only upregulated in persisters. These results suggest the involvement of aromatic compound degradation genes in persister formation and maintenance. They further provide the first insight into the mechanism of persister formation in A. baumannii.201829902105
904670.9988Burkholderia pseudomallei resistance to antibiotics in biofilm-induced conditions is related to efflux pumps. Burkholderia pseudomallei, the causative agent of melioidosis, has been found to increase its resistance to antibiotics when growing as a biofilm. The resistance is related to several mechanisms. One of the possible mechanisms is the efflux pump. Using bioinformatics analysis, it was found that BPSL1661, BPSL1664 and BPSL1665 were orthologous genes of the efflux transporter encoding genes for biofilm-related antibiotic resistance, PA1874-PA1877 genes in Pseudomonas aeruginosa strain PAO1. Expression of selected encoding genes for the efflux transporter system during biofilm formation were investigated. Real-time reverse transcriptase PCR expression of amrB, cytoplasmic membrane protein of AmrAB-OprA efflux transporter encoding gene, was slightly increased, while BPSL1665 was significantly increased during growth of bacteria in biofilm formation. Minimum biofilm inhibition concentration and minimum biofilm eradication concentration (MBEC) of ceftazidime (CTZ), doxycycline (DOX) and imipenem were found to be 2- to 1024-times increased when compared to their MICs for of planktonic cells. Inhibition of the efflux transporter by adding phenylalanine arginine β-napthylamide (PAβN), a universal efflux inhibitor, decreased 2 to 16 times as much as MBEC in B. pseudomallei biofilms with CTZ and DOX. When the intracellular accumulation of antibiotics was tested to reveal the pump inhibition, only the concentrations of CTZ and DOX increased in PAβN treated biofilm. Taken together, these results indicated that BPSL1665, a putative precursor of the efflux pump gene, might be related to the adaptation of B. pseudomallei in biofilm conditions. Inhibition of efflux pumps may lead to a decrease of resistance to CTZ and DOX in biofilm cells.201627702426
628880.9988Regulation of ofloxacin resistance in Escherichia coli strains causing calf diarrhea by quorum-sensing acyl-homoserine lactone signaling molecules. Escherichia coli is a major pathogen responsible for calf diarrhea. However, it has developed resistance to many antimicrobial drugs for their inappropriate usage. The bacterial quorum sensing system transmits information between bacteria, it's important in regulating bacterial virulence, drug and acid resistance and so on. This system can found in Gram-negative bacteria and operates through acyl-homoserine lactone (AHL) signaling molecules. In this study, a type I quorum sensing AHL, N-Octanoyl-L-Homoserine lactone (C8), was added to E. coli growth medium to investigate its regulatory functions in drug resistance. After screening out the strains of E. coli that showed an obvious regulatory effect to the drug ofloxacin (OFX), transcriptomic sequencing was performed on the E. coli strains from the sub-inhibitory concentration group that concentration plus C8 group, and the control group. It shows that C8 significantly influenced resistance to OFX and the minimum inhibitory concentration of OFX in the tested strain was significantly increased. To Analyze transcriptome sequencing results identified 415 differentially expressed genes between the control and sub-inhibitory concentration groups, of which 201 were up-regulated and 214 were down. There were 125 differentially expressed genes between bacteria treated with a sub-inhibitory concentration of OFX and those treated with C8, of which 102 were up-regulated and 23 were down. Finally, It found that to adding the C8 significantly increased the resistance of tested bacteria to OFX. Data from transcriptome sequencing on differently expressed genes helps to explain how the type I quorum sensing system controls drug resistance in E. coli.202539974163
630090.9988Assessing the role of the RND efflux pump in metronidazole resistance of Helicobacter pylori by RT-PCR assay. INTRODUCTION: Metronidazole is a significant antibiotic used for eradication of Helicobacter pylori infections and it is of notice that metronidazole-resistant clinical isolates have been found in high rates worldwide. While the RND family of efflux pumps plays a central role in drug resistance among Gram-negative bacteria, this is questionable for H. pylori. METHODOLOGY: To understand whether TolC homologues of RND pumps contribute to metronidazole resistance in H. pylori isolates, expression of four TolC homologous genes of five resistant clinical isolates exposed to varying concentrations of metronidazole were evaluated by RT-PCR and transcriptional analysis. RESULTS: The results indicate that excess amounts of metronidazole are able to increase the expression level of these genes at the transcriptional stage. CONCLUSIONS: Therefore, it may be hypothesized that use of metronidazole in H. pyori infection can induce metronidazole resistance. Furthermore, the RND family of efflux pumps may contribute to metronidazole resistance in clinical isolates of H. pylori.201121389587
8887100.9987RpoE is a Putative Antibiotic Resistance Regulator of Salmonella enteric Serovar Typhi. Bacterial antimicrobial resistance has been associated with the up regulation of genes encoding efflux pumps and the down regulation of genes encoding outer membrane proteins (OMPs). Gene expression in bacteria is primarily initiated by sigma factors (σ factors) such as RpoE, which plays an important role in responding to many environmental stresses. Here, we report the first observation that RpoE serves as an antibiotic resistance regulator in Salmonella enteric serovar Typhi (S. Typhi). In this study, we found that the rpoE mutant (ΔrpoE) of S. Typhi GIFU10007 has elevated resistance to several antimicrobial agents, including β-lactams, quinolones, and aminoglycosides. Genomic DNA microarray analysis was used to investigate the differential gene expression profiles between a wild type and rpoE mutant in response to ampicillin. The results showed that a total of 57 genes displayed differential expression (two-fold increase or decrease) in ΔrpoE versus the wild-type strain. The expressions of two outer membrane protein genes, ompF and ompC, were significantly down-regulated in ΔrpoE (six and seven-fold lower in comparison to wild-type strain) and RamA, a member of the efflux pump AraC/XylS family, was up-regulated about four-fold in the ΔrpoE. Our results suggest RpoE is a potential antimicrobial regulator in S. Typhi, controlling both the down regulation of the OMP genes and up-regulating the efflux system.201626742769
5062110.9987sRNA expression profile of KPC-2-producing carbapenem-resistant Klebsiella pneumoniae: Functional role of sRNA51. The emergence of carbapenem-resistant Klebsiella pneumoniae (CRKP) has significant challenges to human health and clinical treatment, with KPC-2-producing CRKP being the predominant epidemic strain. Therefore, there is an urgent need to identify new therapeutic targets and strategies. Non-coding small RNA (sRNA) is a post-transcriptional regulator of genes involved in important biological processes in bacteria and represents an emerging therapeutic strategy for antibiotic-resistant bacteria. In this study, we analyzed the transcription profile of KPC-2-producing CRKP using RNA-seq. Of the 4693 known genes detected, the expression of 307 genes was significantly different from that of carbapenem-sensitive Klebsiella pneumoniae (CSKP), including 133 up-regulated and 174 down-regulated genes. Both the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment and Gene Ontology (GO) analysis showed that these differentially expressed genes (DEGs) were mainly related to metabolism. In addition, we identified the sRNA expression profile of KPC-2-producing CRKP for the first time and detected 115 sRNAs, including 112 newly discovered sRNAs. Compared to CSKP, 43 sRNAs were differentially expressed in KPC-2-producing CRKP, including 39 up-regulated and 4 down-regulated sRNAs. We chose sRNA51, the most significantly differentially expressed sRNA in KPC-2-producing CRKP, as our research subject. By constructing sRNA51-overexpressing KPC-2-producing CRKP strains, we found that sRNA51 overexpression down-regulated the expression of acrA and alleviated resistance to meropenem and ertapenem in KPC-2-producing CRKP, while overexpression of acrA in sRNA51-overexpressing strains restored the reduction of resistance. Therefore, we speculated that sRNA51 could affect the resistance of KPC-2-producing CRKP by inhibiting acrA expression and affecting the formation of efflux pumps. This provides a new approach for developing antibiotic adjuvants to restore the sensitivity of CRKP.202438718038
6187120.9987Mechanisms of fluoroquinolone resistance: an update 1994-1998. Fluoroquinolone resistance is mediated by target changes (DNA gyrase and/or topoisomerase IV) and/or decreased intracellular accumulation. The genes (gyrA/gyrB/parC/parE) and proteins of DNA topoisomerase IV show great similarity, both at the nucleotide and amino acid sequence level to those of DNA gyrase. It has been shown that there are hotspots, called the quinolone resistance determining region (QRDR), for mutations within gyrA and parC. Based on the Escherichia coli co-ordinates, the hotspots most favoured for giving rise to decreased susceptibility and/or full resistance to quinolones are at serine 83 and aspartate 87 of gyrA, and at serine 79 and aspartate 83 for parC. Few mutations in gyrB or parE/grlB of any bacteria have been described. Efflux of fluoroquinolones is the major cause of decreased accumulation of these agents; for Staphylococcus aureus, the efflux pump involved in norfloxacin resistance is NorA, and for Streptococcus pneumoniae, PmrA. By analysis of minimum inhibitory concentration (MIC) data derived in the presence and absence of the efflux inhibitor reserpine, it has been shown that up to 50% of ciprofloxacin-resistant clinical isolates of S. pneumoniae may possess enhanced efflux. This suggests that efflux may be an important mechanism of clinical resistance in this species. In Pseudomonas aeruginosa, several efflux operons have been demonstrated genetically and biochemically. These operons are encoded by mex (Multiple EffluX) genes: mexAmexB-oprM, mexCD-OprJ system and mexEF-oprN system. The E. coli efflux pump is the acrAB-tolC system. Both the mar operon and the sox operon can give rise to multiple antibiotic resistance. It has been shown that mutations giving rise to increased expression of the transcriptional activators marA and soxS affect the expression of a variety of different genes, including ompF and acrAB. The net result is that expression of OmpF is reduced and much less drug is able to enter the cell; expression of acrAB is increased, enhancing efflux from the cell.199910553699
9037130.9987Assessment of three Resistance-Nodulation-Cell Division drug efflux transporters of Burkholderia cenocepacia in intrinsic antibiotic resistance. BACKGROUND: Burkholderia cenocepacia are opportunistic Gram-negative bacteria that can cause chronic pulmonary infections in patients with cystic fibrosis. These bacteria demonstrate a high-level of intrinsic antibiotic resistance to most clinically useful antibiotics complicating treatment. We previously identified 14 genes encoding putative Resistance-Nodulation-Cell Division (RND) efflux pumps in the genome of B. cenocepacia J2315, but the contribution of these pumps to the intrinsic drug resistance of this bacterium remains unclear. RESULTS: To investigate the contribution of efflux pumps to intrinsic drug resistance of B. cenocepacia J2315, we deleted 3 operons encoding the putative RND transporters RND-1, RND-3, and RND-4 containing the genes BCAS0591-BCAS0593, BCAL1674-BCAL1676, and BCAL2822-BCAL2820. Each deletion included the genes encoding the RND transporter itself and those encoding predicted periplasmic proteins and outer membrane pores. In addition, the deletion of rnd-3 also included BCAL1672, encoding a putative TetR regulator. The B. cenocepacia rnd-3 and rnd-4 mutants demonstrated increased sensitivity to inhibitory compounds, suggesting an involvement of these proteins in drug resistance. Moreover, the rnd-3 and rnd-4 mutants demonstrated reduced accumulation of N-acyl homoserine lactones in the growth medium. In contrast, deletion of the rnd-1 operon had no detectable phenotypes under the conditions assayed. CONCLUSION: Two of the three inactivated RND efflux pumps in B. cenocepacia J2315 contribute to the high level of intrinsic resistance of this strain to some antibiotics and other inhibitory compounds. Furthermore, these efflux systems also mediate accumulation in the growth medium of quorum sensing molecules that have been shown to contribute to infection. A systematic study of RND efflux systems in B. cenocepacia is required to provide a full picture of intrinsic antibiotic resistance in this opportunistic bacterium.200919761586
4705140.9987Upregulation of outer membrane porin gene ompC contributed to enhancement of azithromycin susceptibility in multidrug-resistant Escherichia coli. The outer membrane (OM) in gram-negative bacteria contains proteins that regulate the passive or active uptake of small molecules for growth and cell function, as well as mediate the emergence of antibiotic resistance. This study aims to explore the potential mechanisms for restoring bacteria to azithromycin susceptibility based on transcriptome analysis of bacterial membrane-related genes. Transcriptome sequencing was performed by treating multidrug-resistant Escherichia coli T28R with azithromycin or in combination with colistin and confirmed by reverse transcription-quantitative PCR (RT-qPCR). Azithromycin enzyme-linked immunosorbent assay (ELISA) test, ompC gene overexpression, and molecular docking were utilized to conduct the confirmatory research of the potential mechanisms. We found that colistin combined with azithromycin led to 48 differentially expressed genes, compared to azithromycin alone, such as downregulation of tolA, eptB, lpxP, and opgE and upregulation of ompC gene. Interestingly, the addition of colistin to azithromycin differentially downregulated the mph(A) gene mediating azithromycin resistance, facilitating the intracellular accumulation of azithromycin. Also, overexpression of the ompC elevated azithromycin susceptibility, and colistin contributed to further suppression of the Mph(A) activity in the presence of azithromycin. These findings suggested that colistin firstly enhanced the permeability of bacterial OM, causing intracellular drug accumulation, and then had a repressive effect on the Mph(A) activity along with azithromycin. Our study provides a novel perspective that the improvement of azithromycin susceptibility is related not only to the downregulation of the mph(A) gene and conformational remodeling of the Mph(A) protein but also the upregulation of the membrane porin gene ompC.IMPORTANCEUsually, active efflux via efflux pumps is an important mechanism of antimicrobial resistance, such as the AcrAB-TolC complex and MdtEF. Also, bacterial porins exhibited a substantial fraction of the total number of outer membrane proteins in Enterobacteriaceae, which are involved in mediating the development of the resistance. We found that the upregulation or overexpression of the ompC gene contributed to the enhancement of resistant bacteria to azithromycin susceptibility, probably due to the augment of drug uptakes caused and the opportunity of Mph(A) function suppressed by azithromycin with colistin. Under the combination of colistin and azithromycin treatment, OmpC exhibited an increased selectivity for cationic molecules and played a key role in the restoral of the antibiotic susceptibility. Investigations on the regulation of porin expression that mediated drug resistance would be important in clinical isolates treated with antibiotics.202438441474
8970150.9987Transcriptomic Analyses to Unravel Cronobacter sakazakii Resistance Pathways. The proliferation of antibiotic usage has precipitated the emergence of drug-resistant variants of bacteria, thereby augmenting their capacity to withstand pharmaceutical interventions. Among these variants, Cronobacter sakazakii (C. sakazakii), prevalent in powdered infant formula (PIF), poses a grave threat to the well-being of infants. Presently, global contamination by C. sakazakii is being observed. Consequently, research endeavors have been initiated to explore the strain's drug resistance capabilities, alterations in virulence levels, and resistance mechanisms. The primary objective of this study is to investigate the resistance mechanisms and virulence levels of C. sakazakii induced by five distinct antibiotics, while concurrently conducting transcriptomic analyses. Compared to the susceptible strains prior to induction, the drug-resistant strains exhibited differential gene expression, resulting in modifications in the activity of relevant enzymes and biofilm secretion. Transcriptomic studies have shown that the expression of glutathione S-transferase and other genes were significantly upregulated after induction, leading to a notable enhancement in biofilm formation ability, alongside the existence of antibiotic resistance mechanisms associated with efflux pumps, cationic antimicrobial peptides, and biofilm formation pathways. These alterations significantly influence the strain's resistance profile.202439272551
9045160.9987Development of Resistance in Escherichia coli ATCC25922 under Exposure of Sub-Inhibitory Concentration of Olaquindox. Quinoxaline1,4-di-N-oxides (QdNOs) are a class of important antibacterial drugs of veterinary use, of which the drug resistance mechanism has not yet been clearly explained. This study investigated the molecular mechanism of development of resistance in Escherichia coli (E. coli) under the pressure of sub-inhibitory concentration (sub-MIC) of olaquindox (OLA), a representative QdNOs drug. In vitro challenge of E. coli with 1/100× MIC to 1/2× MIC of OLA showed that the bacteria needed a longer time to develop resistance and could only achieve low to moderate levels of resistance as well as form weak biofilms. The transcriptomic and genomic profiles of the resistant E. coli induced by sub-MIC of OLA demonstrated that genes involved in tricarboxylic acid cycle, oxidation-reduction process, biofilm formation, and efflux pumps were up-regulated, while genes involved in DNA repair and outer membrane porin were down-regulated. Mutation rates were significantly increased in the sub-MIC OLA-treated bacteria and the mutated genes were mainly involved in the oxidation-reduction process, DNA repair, and replication. The SNPs were found in degQ, ks71A, vgrG, bigA, cusA, and DR76(-)4702 genes, which were covered in both transcriptomic and genomic profiles. This study provides new insights into the resistance mechanism of QdNOs and increases the current data pertaining to the development of bacterial resistance under the stress of antibacterials at sub-MIC concentrations.202033182563
8889170.9987Differences in Gene Expression Profiles between Early and Late Isolates in Monospecies Achromobacter Biofilm. Bacteria of genus Achromobacter are emerging pathogens in cystic fibrosis (CF) capable of biofilm formation and development of antimicrobial resistance. Evolutionary adaptions in the transition from primary to chronic infection were assessed by transcriptomic analysis of successive isolates of Achromobacter xylosoxidans from a single CF patient. Several efflux pump systems targeting antimicrobial agents were upregulated during the course of the disease, whereas all genes related to motility were downregulated. Genes annotated to subsystems of sulfur metabolism, protein metabolism and potassium metabolism exhibited the strongest upregulation. K+ channel genes were hyperexpressed, and a putative sulfite oxidase was more than 1500 times upregulated. The transcriptome patterns indicated a pivotal role of sulfur metabolism and electrical signalling in Achromobacter biofilms during late stage CF lung disease.201728534862
8867180.9987Hfq plays important roles in virulence and stress adaptation in Cronobacter sakazakii ATCC 29544. Cronobacter spp. are opportunistic pathogens that cause neonatal meningitis and sepsis with high mortality in neonates. Despite the peril associated with Cronobacter infection, the mechanisms of pathogenesis are still being unraveled. Hfq, which is known as an RNA chaperone, participates in the interaction with bacterial small RNAs (sRNAs) to regulate posttranscriptionally the expression of various genes. Recent studies have demonstrated that Hfq contributes to the pathogenesis of numerous species of bacteria, and its roles are varied between bacterial species. Here, we tried to elucidate the role of Hfq in C. sakazakii virulence. In the absence of hfq, C. sakazakii was highly attenuated in dissemination in vivo, showed defects in invasion (3-fold) into animal cells and survival (10(3)-fold) within host cells, and exhibited low resistance to hydrogen peroxide (10(2)-fold). Remarkably, the loss of hfq led to hypermotility on soft agar, which is contrary to what has been observed in other pathogenic bacteria. The hyperflagellated bacteria were likely to be attributable to the increased transcription of genes associated with flagellar biosynthesis in a strain lacking hfq. Together, these data strongly suggest that hfq plays important roles in the virulence of C. sakazakii by participating in the regulation of multiple genes.201525754196
6295190.9987Anaerobiosis and Mutations Can Reduce Susceptibility of Pseudomonas aeruginosa to Tobramycin Without Reducing the Cellular Concentration of the Antibiotic. Chronic infections of Pseudomonas aeruginosa are commonly treated with tobramycin. During infections, the bacteria can exist under conditions of oxygen deprivation that render them less susceptible to this antibiotic. The aims of this research were to investigate the genetic basis of tobramycin resistance under anaerobic conditions, and to investigate the effects of anaerobiosis and mutations on the cellular concentration of tobramycin. Ten mutants with lowered susceptibility to tobramycin than wild-type bacteria were evolved from a laboratory reference strain under anaerobic conditions. Mutations were identified by genome sequencing. Mutations had arisen most frequently in the fusA1 gene that encodes elongation factor EF-G1A and in genes involved in twitching motility. Cellular concentrations of tobramycin were then measured. Mutations in fusA1 or absence of the MexXY efflux pump that is associated with tobramycin resistance did not alter the cellular tobramycin concentration under either anaerobic or aerobic conditions. Anaerobic growth reduced the cellular concentration of tobramycin, relative to aerobically grown bacteria, in some but not all of five tested P. aeruginosa isolates. Overall, our findings indicate that anaerobiosis and mutations that reduce aminoglycoside effectiveness do not lower the cellular concentration of antibiotic but instead reduce susceptibility through other mechanisms.202540005562