The intrinsic resistance of Escherichia coli to various antimicrobial agents requires ppGpp and sigmas

Greenway, D. L. A.; England, Reg

doi:10.1046/j.1472-765x.1999.00642.x

Cited by 53 publications

(41 citation statements)

References 25 publications

(46 reference statements)

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“…These results also suggest that the morphological change of the B. abortus spoT mutant may be affected by inhibition of ppGpp synthesis, and ppGpp may activate the transcription of one or more genes including b-lactamase production, and affect an as yet uncharacterized regulatory mechanism related to cell morphology. Greenway & England (1999) reported that E. coli able to synthesize ppGpp, either in a RelA-or SpoT-dependent manner, possesses greater resistance to antimicrobial compounds compared with E. coli mutants that cannot produce ppGpp. E. coli mutants showed a higher sensitivity, as demonstrated by MIC values, for b-lactam antibiotics, polymyxin, gentamicin, 1,2-benzisothiazolin-3-one (BIT) and bronopol.…”

Section: Discussionmentioning

confidence: 99%

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Roles of Brucella abortus SpoT in morphological differentiation and intramacrophagic replication

et al. 2005

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The essential mechanisms and virulence factors enabling Brucella species to survive and replicate inside host macrophages are not fully understood. The authors previously reported that a putative guanosine 59-diphosphate 39-diphosphate (ppGpp) mutant (spoT mutant) of Brucella abortus failed to replicate in HeLa cells. The present study showed that the pattern of surface proteins and morphological change of the spoT mutant were different from B. abortus wild-type. B. abortus wild-type changed its morphology upon treatment with ppGpp synthetase I activation inhibitor. In various tests under stress conditions, including nutrient starvation, nitric oxide resistance, acid resistance and antibiotic resistance, the spoT mutant had a lower stress resistance than B. abortus wild-type. Although the spoT mutant has the same smooth phenotype and LPS profile as B. abortus wild-type, it had a higher rate of adherence to macrophages but lower internalization and intracellular replication within macrophages. The spoT mutant did not co-localize with either late endosomes or lysosomes and was almost cleared from the spleens of mice after 10 days, without splenomegaly. RT-PCR was used to detect spoT mRNA from around 10 6 cells incubated in low-pH enriched medium; it showed that the expression of spoT increased after 30 min incubation. The data suggest that SpoT does not contribute to intracellular trafficking of B. abortus, but contributes to the maintenance of bacterial morphology and the physiological adaptation required for intracellular replication. INTRODUCTIONBrucellosis is a major bacterial zoonosis and an important cause of a serious debilitating disease in humans and abortion and sterility in domestic animals. This disease is caused by species of the genus Brucella, classified in the a2 subdivision of Proteobacteria, small Gram-negative and facultative intracellular pathogens that can multiply within professional and non-professional phagocytes (Delrue et al., 2001;Detileux et al., 1990). The genus Brucella consists of seven species according to antigenic variation and primary host: B. melitensis (sheep and goats), B. suis (hogs), B. abortus (cattle), B. ovis (sheep), B. canis (dogs), B. neotomae (wood rats) and B. maris (marine mammals) (Ko & Splitter, 2003). In contrast to other intracellular pathogens, Brucella species do not produce exotoxins, antiphagocytic capsules, thick cell walls, resistance forms or fimbriae and do not show antigenic variation (Finlay & Falkow, 1997).A key aspect of the virulence of Brucella species is their ability to proliferate within professional and nonprofessional phagocytic host cells, therefore successfully bypassing the bactericidal effects of phagocytes. Their virulence and chronic infections are thought to be due to their ability to avoid the killing mechanisms within host cells (Comerci et al., 2001;Ugalde, 1999). Neither virulence factors that allow intracellular survival of Brucella species nor the specific factors that induce such virulence have been elucidated. B. abortus is inte...

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Section: Discussionmentioning

confidence: 99%

“…MICs were measured by using a modified method described previously (Greenway & England, 1999;Mortensen et al, 1986). Antibiotics or biocides were serially diluted twofold in test tubes containing 2 ml final volume Brucella broth, such that the final antibiotic or biocide concentration was reduced from 400 to 0?01 mg ml 21 .…”

Section: Methodsmentioning

confidence: 99%

Roles of Brucella abortus SpoT in morphological differentiation and intramacrophagic replication

et al. 2005

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“…Cell envelope stress responses have been linked to general stress responses (7) and to the overall homeostasis of gram-positive bacteria (18). Moreover, it has been reported that the intracellular concentration of (p)ppGpp is linked to the intrinsic resistance to antimicrobial agents in bacteria (14,19,20,40). TLC analysis of nucleotide extracts clearly indicated that (p)ppGpp accumulates to significantly high levels in OG1RF cells treated with inhibitory concentrations of vancomycin (Fig.…”

Section: E Faecalis Strains Can Mount a Classic Stringent Responsementioning

confidence: 94%

“…Studies have correlated changes in (p)ppGpp levels to the expression of virulence traits, including stress survival (12,20,25,54), biofilm formation (2,25,46), antibiotic resistance (14,19,20,40), and persistence (5,14,20,21,35,42). In some cases, animal models have been used to provide unequivocal evidence of the role of (p)ppGpp in virulence (6,9,10,16,39,46).…”

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confidence: 99%

The Molecular Alarmone (p)ppGpp Mediates Stress Responses, Vancomycin Tolerance, and Virulence inEnterococcus faecalis

Abranches

Martinez²,

Kajfasz³

et al. 2009

J Bacteriol

175

244

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The stringent response is a global bacterial response to stress that is mediated by accumulation of the alarmone (p)ppGpp. In this study, treatment with mupirocin was shown to induce high levels of (p)ppGpp production in Enterococcus faecalis, indicating that this nosocomial pathogen can mount a classic stringent response. In addition, (p)ppGpp was found to accumulate in cells subjected to heat shock, alkaline shock, and inhibitory concentrations of vancomycin. Sequence analysis of the E. faecalis genome indicated that (p)ppGpp synthesis is catalyzed by the bifunctional synthetase/hydrolase RelA and the RelQ small synthase. The (p)ppGpp profiles of ⌬relA, ⌬relQ, and ⌬relAQ strains revealed that RelA is the major enzyme responsible for the accumulation of (p)ppGpp during antibiotic or physical stresses, while RelQ appears to be responsible for maintaining basal levels of alarmone during homeostatic growth. Compared to its parent, the ⌬relA strain was more susceptible to several stress conditions, whereas complete elimination of (p)ppGpp in a ⌬relAQ double mutant restored many of the stress-sensitive phenotypes of ⌬relA. Interestingly, growth curves and time-kill studies indicated that tolerance to vancomycin is enhanced in the ⌬relA strain but diminished in the ⌬relQ and ⌬relAQ strains. Finally, virulence of the ⌬relAQ strain but not of the ⌬relA or ⌬relQ strain was significantly attenuated in the Caenorhabditis elegans model. Taken together, these results indicate that (p)ppGpp pools modulate environmental stress responses, vancomycin tolerance, and virulence in this important nosocomial pathogen.

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“…This operon (3) regulates the expression of a large number of genes, including those coding for at least one broad-specificity efflux pump (the arcAB efflux pump) (30), which are more strongly expressed under conditions of environmental stress (23). This suggests a direct linkage between environmental stresses, such as those occurring in foods and the domestic environment (3), efflux pump expression, and the development of antibiotic resistance (ABR) (12,14,30).…”

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confidence: 99%

Environmental Stress and Antibiotic Resistance in Food-Related Pathogens

McMahon

Moore

et al. 2007

Appl Environ Microbiol

214

140

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This study investigated the possibility that sublethal food preservation stresses (high or low temperature and osmotic and pH stress) can lead to changes in the nature and scale of antibiotic resistance (ABR) expressed by three food-related pathogens (Escherichia coli, Salmonella enterica serovar Typhimurium, and Staphylococcus aureus). The study found that some sublethal stresses significantly altered antibiotic resistance. Incubation at sublethal high temperature (45°C) decreased ABR. Incubation under increased salt (>4.5%) or reduced pH (<5.0) conditions increased ABR. Some of the pathogens continued to express higher levels of ABR after removal of stress, suggesting that in some cases the applied sublethal stress had induced stable increases in ABR. These results indicate that increased use of bacteriostatic (sublethal), rather than bactericidal (lethal), food preservation systems may be contributing to the development and dissemination of ABR among important food-borne pathogens.

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The intrinsic resistance of Escherichia coli to various antimicrobial agents requires ppGpp and sigmas

Cited by 53 publications

References 25 publications

Roles of Brucella abortus SpoT in morphological differentiation and intramacrophagic replication

Roles of Brucella abortus SpoT in morphological differentiation and intramacrophagic replication

The Molecular Alarmone (p)ppGpp Mediates Stress Responses, Vancomycin Tolerance, and Virulence inEnterococcus faecalis

Environmental Stress and Antibiotic Resistance in Food-Related Pathogens

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