Inhibition of indole production increases the activity of quinolone antibiotics against E. coli persisters

Indole works as an interspecies signal molecule to regulate multiple physiological activities, like antibiotic resistance, acid resistance, and virulence. However, the effect of indole on conjugation is unknown. Here, with Escherichia coli SM10λπ as a donor strain that carries a chromosomally integrated conjugative RP4 plasmid, we explored the effect of indole on conjugation of a mobilizable pUCP24T plasmid imparting gentamycin resistance. The results showed that exogenous indole treatment inhibited conjugative transfer of pUCP24T from SM10λπ to recipient strains, Pseudomonas aeruginosa PAO1 and E. coli EC600. Furthermore, raising endogenous indole production through overexpression of TnaA, a tryptophanase, in SM10λπ significantly inhibited both SM10λπ-PAO1 and SM10λπ-EC600 conjugation, whereas deficiency of tnaA reversed the phenotype. Subsequent mechanistic studies revealed that exogenous indole significantly inhibited the expression of mating pair formation gene (trbB) and the DNA transfer and replication gene (trfA), mainly due to the promotion of regulatory genes (korA and korB), and the result was confirmed in tnaA knockout and overexpression strains. Additionally, we found that both extracellular indole production and tnaA expression of SM10λπ were downregulated by ciprofloxacin (CIP). Intriguingly, one-eighth minimum inhibitory concentration of CIP treatment clearly facilitated both SM10λπ-PAO1 and SM10λπ-EC600 conjugation, and indole inhibited CIP-induced conjugation frequency. These data suggest that indole may play a negative role in the process of CIP-induced conjugation. This is the first study to reveal the biological function of indole-inhibiting conjugation and its role in CIP-induced conjugation, which may be developed into a new way of controlling the spread of antibiotic resistance.

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A novel, double mutation in DNA gyrase A of Escherichia coli conferring resistance to quinolone antibiotics.

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.41.1.85 ◽

1997 ◽

Vol 41 (1) ◽

pp. 85-90 ◽

Cited By ~ 31

Author(s):

Q C Truong ◽

J C Nguyen Van ◽

D Shlaes ◽

L Gutmann ◽

N J Moreau

Keyword(s):

Escherichia Coli ◽

Nalidixic Acid ◽

Acid Resistance ◽

Gyra Gene ◽

Double Mutation ◽

E Coli ◽

Quinolone Antibiotics ◽

Gyrase A ◽

Level Resistance ◽

Nalidixic Acid Resistance

A spontaneous Escherichia coli mutant, named Q3, resistant to nalidixic acid was obtained from a previously described clinical isolate of E. coli, Q2, resistant to fluoroquinolones but susceptible to nalidixic acid (E. Cambau, F. Bordon, E. Collatz, and L. Gutmann, Antimicrob. Agents Chemother. 37:1247-1252, 1993). Q3 harbored the mutation Asp82Gly in addition to the Gly81Asp mutation of Q2. The different mutations leading to Gly81Asp, Asp82Gly, and Gly81AspAsp82Gly were introduced into the gyrA gene harbored on plasmid pJSW102, and the resulting plasmids were introduced into E. coli KNK453 (gyrAts) by transformation. The presence of Asp82Gly or Gly81Asp alone led to a low-level resistance to fluoroquinolones but not to nalidixic acid resistance. When both mutations were present, resistance to both nalidixic acid and fluoroquinolones was expressed. Purified gyrases of the different mutants showed similar rates of supercoiling. Dominance of the various gyrA mutant alleles harbored on plasmids was examined. The susceptibility to quinolones associated with wild-type gyrA was always dominant. The susceptibility to nalidixic acid expressed by the Gly81Asp mutant was dominant, while that expressed by the Asp82Gly mutant was recessive. From these results, we hypothesize that some amino acids within the quinolone resistance-determining region of gyrase A are more important for the association of subunits rather than for the activity of the holoenzyme.

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Indole Production Promotes Escherichia coli Mixed-Culture Growth with Pseudomonas aeruginosa by Inhibiting Quorum Signaling

Applied and Environmental Microbiology ◽

10.1128/aem.06396-11 ◽

2011 ◽

Vol 78 (2) ◽

pp. 411-419 ◽

Cited By ~ 74

Author(s):

Weihua Chu ◽

Tesfalem R. Zere ◽

Mary M. Weber ◽

Thomas K. Wood ◽

Marvin Whiteley ◽

...

Keyword(s):

Escherichia Coli ◽

Pseudomonas Aeruginosa ◽

Mixed Culture ◽

Receptor Gene ◽

Enteric Bacteria ◽

Wild Type ◽

Content Type ◽

E Coli ◽

Culture Growth ◽

Indole Production

ABSTRACTIndole production byEscherichia coli, discovered in the early 20th century, has been used as a diagnostic marker for distinguishingE. colifrom other enteric bacteria. By using transcriptional profiling and competition studies with defined mutants, we show that cyclic AMP (cAMP)-regulated indole formation is a major factor that enablesE. coligrowth in mixed biofilm and planktonic populations withPseudomonas aeruginosa. Mutants deficient in cAMP production (cyaA) or the cAMP receptor gene (crp), as well as indole production (tnaA), were not competitive in coculture withP. aeruginosabut could be restored to wild-type competitiveness by supplementation with a physiologically relevant indole concentration.E. colisdiAmutants, which lacked the receptor for both indole andN-acyl-homoserine lactones (AHLs), showed no change in competitive fitness, suggesting that indole acted directly onP. aeruginosa. AnE. colitnaAmutant strain regained wild-type competiveness if grown withP. aeruginosaAHL synthase (rhlIandrhlI lasI) mutants. In contrast to the wild type,P. aeruginosaAHL synthase mutants were unable to degrade indole. Indole produced during mixed-culture growth inhibited pyocyanin production and other AHL-regulated virulence factors inP. aeruginosa. Mixed-culture growth withP. aeruginosastimulated indole formation inE. colicpdA, which is unable to regulate cAMP levels, suggesting the potential for mixed-culture gene activation via cAMP. These findings illustrate how indole, an early described feature ofE. colicentral metabolism, can play a significant role in mixed-culture survival by inhibiting quorum-regulated competition factors inP. aeruginosa.

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Modulation of Gyrase-Mediated DNA Cleavage and Cell Killing by ATP

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.42.5.1022 ◽

1998 ◽

Vol 42 (5) ◽

pp. 1022-1027 ◽

Cited By ~ 12

Author(s):

Tsai-Kun Li ◽

Leroy F. Liu

Keyword(s):

Escherichia Coli ◽

Dna Cleavage ◽

Important Determinant ◽

Dna Gyrase ◽

Bactericidal Action ◽

Atpase Subunit ◽

Fluoroacetic Acid ◽

E Coli ◽

Quinolone Antibiotics ◽

Atp Pool

ABSTRACT An uncoupler of oxidative phosphorylation, 2,4-dinitrophenol, and an aconitase inhibitor, fluoroacetic acid, both of which are known to lower the cellular ATP pool, protected Escherichia colicells from the bactericidal actions of gyrase poisons including quinolone antibiotics, nalidixic acid and ciprofloxacin, and the epipodophyllotoxins VP-16 and VM-26. Using purified E. coliDNA gyrase, we examined the effect of ATP on gyrase-mediated DNA cleavage in the presence of these gyrase poisons. ATP was shown to stimulate gyrase-mediated DNA cleavage from 10- to more than 100-fold in the presence of these gyrase poisons. ADP antagonized the stimulatory effect of ATP. Consequently, gyrase-mediated DNA cleavage induced by gyrase poisons is modulated by the ATP concentration/ADP concentration ([ATP]/[ADP]) ratio. Coumermycin A1, an inhibitor of the ATPase subunit of DNA gyrase, like ADP, also effectively antagonized the stimulatory effect of ATP on gyrase-mediated DNA cleavage induced by gyrase poisons. Furthermore, coumermycin A1, like DNP and fluoroacetic acid, also protected cells from the bactericidal action of gyrase poisons. In the aggregate, our results are consistent with the notion that the [ATP]/[ADP] ratio, through its modulatory effect on the gyrase-mediated DNA cleavage, is an important determinant of cellular susceptibility to gyrase poisons.

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Effect of Subinhibitory Concentrations of Antibiotics on Intrachromosomal Homologous Recombination in Escherichia coli

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00358-09 ◽

2009 ◽

Vol 53 (8) ◽

pp. 3411-3415 ◽

Cited By ~ 60

Author(s):

Elena López ◽

Jesús Blázquez

Keyword(s):

Escherichia Coli ◽

Homologous Recombination ◽

Dna Sequences ◽

Sos Response ◽

E Coli ◽

Homologous Sequences ◽

Sos Induction ◽

Quinolone Antibiotics ◽

Subinhibitory Concentrations ◽

Sublethal Concentrations

ABSTRACT Subinhibitory concentrations of some antibiotics, such as fluoroquinolones, have been reported to stimulate mutation and, consequently, bacterial adaptation to different stresses, including antibiotic pressure. In Escherichia coli, this stimulation is mediated by alternative DNA polymerases induced via the SOS response. Sublethal concentrations of the fluoroquinolone ciprofloxacin have been shown to stimulate recombination between divergent sequences in E. coli. However, the effect of ciprofloxacin on recombination between homologous sequences and its SOS dependence have not been studied. Moreover, the possible effects of other antibiotics on homologous recombination remain untested. The aim of this work was to study the effects of sublethal concentrations of ciprofloxacin and 10 additional antibiotics, including different molecular families with different molecular targets, on the rate of homologous recombination of DNA in E. coli. The antibiotics tested were ciprofloxacin, ampicillin, ceftazidime, imipenem, chloramphenicol, tetracycline, gentamicin, rifampin (rifampicin), trimethoprim, fosfomycin, and colistin. Our results indicate that only ciprofloxacin consistently stimulates the intrachromosomal recombinogenic capability of homologous sequences in E. coli. The ciprofloxacin-based stimulation occurs at concentrations and times that apparently do not dramatically compromise the viability of the whole population, and it is dependent on RecA and partially dependent on SOS induction. One of the main findings of this work is that, apart from quinolone antibiotics, none of the most used antibiotics, including trimethoprim (a known inducer of the SOS response), has a clear side effect on homologous recombination in E. coli. In addition to the already described effects of some antibiotics on mutagenicity, DNA transfer, and genetic transformability in naturally competent species, the effect of increasing intrachromosomal recombination of homologous DNA sequences can be uniquely ascribed to fluoroquinolones, at least for E. coli.

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Genotype, Serotype, and Antibiotic Resistance of Sorbitol-Negative Escherichia coli Isolates from Feedlot Cattle†

Journal of Food Protection ◽

10.4315/0362-028x-72.1.28 ◽

2009 ◽

Vol 72 (1) ◽

pp. 28-36 ◽

Cited By ~ 11

Author(s):

MOUSSA S. DIARRA ◽

KARINE GIGUÈRE ◽

FRANÇOIS MALOUIN ◽

BRIGITTE LEFEBVRE ◽

SUSAN BACH ◽

...

Keyword(s):

Escherichia Coli ◽

Virulence Genes ◽

Growth Promotion ◽

Tetracycline Resistance ◽

Feedlot Cattle ◽

Antibiotic Resistant ◽

E Coli ◽

Arginine Dihydrolase ◽

Stx1 Gene ◽

Indole Production

Rectal fecal samples from 80 steers receiving Rumensin, Revalor-S, and Liquamycin alone or in combination for growth promotion and disease prevention were examined for the presence of non-O157:H7 Shiga toxin–producing Escherichia coli. All isolates were identified with the API 20E test, virulence genes were detected with a PCR assay, and antibiotic susceptibilities were determined with the Sensititre system. Of the 153 E. coli isolates recovered 126 (82.3%) were sorbitol negative. Isolates were classified into 14 biochemical E. coli groups; 51.6% were negative for arginine dihydrolase, ornithine decarboxylase, sorbitol, and saccharose reactions but positive for lysine decarboxylase, indole production, and rhamnose reactions. Twenty-one O:H serotypes were detected in the 153 E. coli isolates. The most frequent serotypes were O2:H42 (49.7% of isolates), O49:NM (13.7%), O?:H25 (9.2%), and O10:NM (7.2%). One isolate of E. coli O172:H25 and one of E. coli O157: H39 were found. The stx1 gene was found in the two E. coli O98:H25 isolates. The eaeA and e-hlyA genes were detected in 21, 14, and 10 isolates of serotypes O49:NM, O?:H25, and O10:NM, respectively, and in each isolate of serotype O156:H25 and O172:H25. Four E. coli O132:H18 isolates were multiresistant to ampicillin, chloramphenicol, kanamycin, streptomycin, and sulfisoxazole. Tetracycline resistance due to the tet(B) gene was observed in 74 of the 76 E. coli O2:H42 isolates. Except for one isolate, all tetracycline-resistant isolates were negative for the virulence genes eaeA and e-hlyA or stx1. Pulsed-field gel electrophoresis typing revealed that the tetracycline-resistant serotypes were genetically diverse. Our data illustrate that cattle are a potential source of some atypical antibiotic-resistant E. coli isolates that harbor virulence genes.

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PROBLEMS IN THE RECOVERY AND IDENTIFICATION OF ENTEROPATHOGENIC ESCHERICHIA COLI FROM FOODS1

Journal of Milk and Food Technology ◽

10.4315/0022-2747-37.6.350 ◽

1974 ◽

Vol 37 (6) ◽

pp. 350-356 ◽

Cited By ~ 8

Author(s):

Ira J. Mehlman ◽

Nicholas T. Simon ◽

Arvey C. Sanders ◽

Joseph C. Olson

Keyword(s):

Escherichia Coli ◽

Nitrate Reduction ◽

Future Research ◽

Decarboxylase Activity ◽

Lauryl Sulfate ◽

Critical Factors ◽

Macconkey Agar ◽

E Coli ◽

Recent Outbreak ◽

Indole Production

During a recent outbreak of gastroenteritis associated with serogroup 0124:B17 of Escherichia coli, various problems complicated recovery and identification of the pathogen. Standard methods for E. coli were of limited value because of atypical behavior of isolates. Two modified recovery procedures have been presented. For rapid lactose fermenters, pre-enrichment in MacConkey broth with subsequent transfer to lauryl sulfate tryptose broth and incubation at 44 C is recommended. For slow lactose fermenters, pre-enrichment in nutrient broth with subsequent transfer to Mossel's enteric enrichment broth and incubation at 41.5 C is tentatively proposed. Isolation agars include Levine's eosin methylene blue for lactose fermenters and MacConkey agar for non-lactose fermenters. The merits of a direct streak are considered. To facilitate rapid differentiation of E. coli from closely related Enterobacteriaceae within 3 days a modified Lundbeck procedure is offered. Isolates are first screened for H2S formation, indole production, arabinose fermentation, urease and ONPG-ase. Secondary characterization based on results of the indole and TSI reactions includes Voges-Proskauer test (22 C), lysine decarboxylase activity, KCN tolerance, and fermentation of adonitol, cellobiose, sorbitol, or glucose. Confirmation by gram-reaction nitrate reduction, and cytochrome oxidase activity is required to differentiate from members of other families. Critical factors of serological analysis are stressed. Prospects for future research are discussed.

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Comparison of β-Glucuronidase and Indole-Based Direct Plating Methods for Enumerating Escherichia coli in Artificially Inoculated Ground Meats

Journal of Food Protection ◽

10.4315/0362-028x-53.11.933 ◽

1990 ◽

Vol 53 (11) ◽

pp. 933-935 ◽

Cited By ~ 2

Author(s):

ELON W. FRAMPTON ◽

LAWRENCE RESTAINO ◽

NANCY BLASZKO

Keyword(s):

Escherichia Coli ◽

Ground Beef ◽

Plate Count ◽

Most Probable Number ◽

Probable Number ◽

E Coli ◽

Glucuronidase Activity ◽

Plate Count Agar ◽

Significant Difference ◽

Indole Production

Peptone tergitol glucuronide (PTG) agar containing 4-methylumbelliferyl-β-D glucuronide (MUG) (for β-glucuronidase activity), the Holbrook, Anderson, Baird-Parker (HABP) method (for detecting indole production), and the standard 3-tube most probable number (MPN) method were compared with plate count agar (PCA) for enumerating three strains of unstressed Escherichia coli artificially inoculated into ground beef and chicken at 1–6 × 106 cells/g. No significant difference (P>0.05) was determined between PTG agar and PCA in the recovery of E. coli. The MPN method enumerated a significantly greater (P<0.05) number of E. coli cells than PCA. Compared with PCA, the HABP method recovered a significantly lower (P<0.05) number of E. coli cells from chicken, whereas no significant difference (P>0.05) was obtained with ground beef. When combining all data from chicken and beef, the recovery of E. coli cells by the HABP method was also significantly lower (P<0.05). Overall, based on the enumeration of E. coli on PCA, the HABP method, PTG agar, and MPN method recovered 57, 102, and 144%, respectively.

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Identification of IbeR as a Stationary-Phase Regulator in MeningiticEscherichia coliK1 that Carries a Loss-of-Function Mutation inrpoS

Journal of Biomedicine and Biotechnology ◽

10.1155/2009/520283 ◽

2009 ◽

Vol 2009 ◽

pp. 1-13 ◽

Cited By ~ 8

Author(s):

Feng Chi ◽

Ying Wang ◽

Timothy K. Gallaher ◽

Chun-Hua Wu ◽

Ambrose Jong ◽

...

Keyword(s):

Stationary Phase ◽

Stress Resistance ◽

Parent Strain ◽

Regulatory Gene ◽

Loss Of Function ◽

Signal Molecule ◽

Two Dimensional Gel Electrophoresis ◽

E Coli ◽

Survival Studies ◽

Indole Production

IbeRis a regulator present in meningiticEscherichia colistrain E44 that carries a loss-of-function mutation in the stationary-phase (SP) regulatory generpoS. In order to determine whether IbeR is an SP regulator in E44, two-dimensional gel electrophoresis and LC-MS were used to compare the proteomes of a noninvasive ibeR deletion mutant BR2 and its parent strain E44 in the SP. Four up-regulated (TufB, GapA, OmpA, AhpC) and three down-regulated (LpdA, TnaA, OpmC) proteins in BR2 were identified when compared to E44. All these proteins contribute to energy metabolism or stress resistance, which is related to SP regulation. One of the down-regulated proteins, tryptophanase (TnaA), which is regulated by RpoS in otherE. colistrains, is associated with SP regulation via production of a signal molecule indole. Our studies demonstrated that TnaA was required for E44 invasion, and that indole was able to restore the noninvasive phenotype of thetnaAmutant. The production of indole was significantly reduced in BR2, indicating thatibeRis required for the indole production viatnaA. Survival studies under different stress conditions indicated that IbeR contributed to bacteria stress resistance in the SP. Taken together, IbeR is a novel regulator contributing to the SP regulation.

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