Evidence for persisters in Staphylococcus epidermidis RP62a planktonic cultures and biofilms. J Med Microbiol

Department of Microbiology and Immunology, Kirksville College of Osteopathic Medicine, A. T. Still University of Health Sciences, Kirksville, MO 63501, USA.
Journal of Medical Microbiology (Impact Factor: 2.25). 03/2011; 60(Pt 7):950-60. DOI: 10.1099/jmm.0.026013-0
Source: PubMed


The pathogenesis of Staphylococcus epidermidis in foreign device-related infections is attributed primarily to its ability to form biofilms on a polymer surface. One mechanism proposed for the survival of organisms in a biofilm is the presence of persister cells. Persister cells survive antibiotic treatment without acquiring heritable antibiotic resistance. This study was conducted to determine if S. epidermidis RP62a growing in planktonic cultures and biofilms could survive as persister cells following treatment with levofloxacin and vancomycin. S. epidermidis RP62a produced a small percentage of persisters (levofloxacin, 3.09×10⁻⁷%; vancomycin, 8.21×10⁻⁵ %) when grown to exponential phase, whereas biofilms contained 28 and 94 % persisters, following exposure to levofloxacin and vancomycin, respectively. The highest percentages of persisters were obtained during stationary phase in planktonic cultures and the lowest percentages of persisters were obtained during mid-exponential phase. An increase in persister number was not due to activation of quorum-sensing regulons. Confocal laser scanning microscopy images of biofilms exposed to levofloxacin demonstrated that the antibiotic was able to kill bacteria throughout the biofilm. Our results suggest that antibiotic tolerance in biofilms and in planktonic cultures of S. epidermidis RP62a is due in part to the presence of persister cells.

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    • "Persisters are dormant, nondividing cells, which are seen to be responsible for most biofilm-associated antibiotic tolerance. Shapiro et al. (2011) reported the same phenomenon in S. epidermidis RP62A (denoted here ATCC 35984), and showed the reduced antibiotic sensitivity of stationary planktonic bacteria . This is of relevance for biofilm sensitivity on nonviable materials such as food of food processing aids, whereas under in vivo conditions, the phagocytes may be able to opsonize and kill persisters (Lewis 2007). "
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    ABSTRACT: To demonstrate different effects of garlic extracts and their main antibiotic substance allicin, as a template for investigations on the antibacterial activity of food ingredients. Staphylococcus epidermidis ATCC 12228 and the isogenic biofilm-forming strain ATCC 35984 were used to compare the activity of allicin against planktonic bacteria and bacterial biofilms. The minimal inhibitory concentration (MIC) and the minimum biofilm inhibitory concentration (MBIC) for pure allicin were identical and reached at a concentration of 12.5 μg/mL. MBICs for standardized garlic extracts were significantly lower, with 1.56 and 0.78 μg/mL allicin for garlic water and ethanol extract, respectively. Biofilm density was impaired significantly at a concentration of 0.78 μg/mL allicin. Viability staining followed by confocal laser scanning microscopy showed, however, a 100% bactericidal effect on biofilm-embedded bacteria at a concentration of 3.13 μg/mL allicin. qRT-PCR analysis provided no convincing evidence for specific effects of allicin on biofilm-associated genes. Extracts of fresh garlic are more potent inhibitors of Staphylococcus epidermidis biofilms than pure allicin, but allicin exerts a unique bactericidal effect on biofilm-embedded bacteria. The current experimental protocol has proven to be a valid approach to characterize the antimicrobial activity of traditional food ingredients.
    Food Science & Nutrition 03/2015; 3(2). DOI:10.1002/fsn3.199
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    • "Since the first report by Bigger in 1944 [1], bacterial persister cells have been described for a number of different species, including Escherichia coli[14], Staphylococcus aureus[14,15], Pseudomonas aeruginosa[16], and Mycobacterium tuberculosis[17,18]. For most of these bacterial species persister cells have also been found in biofilms, which contribute to recalcitrant and/or recurrent infections after antibiotic therapy [4,19-25]. "
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    ABSTRACT: Background Persister cells constitute a subpopulation of dormant cells within a microbial population which are genetically identical but phenotypically different to regular cells. Notably, persister cells show an elevated tolerance to antimicrobial agents. Thus, they are considered to represent a microbial ‘bet-hedging’ strategy and are of particular importance in pathogenic bacteria. Results We studied the ability of the zoonotic pathogen Streptococcus (S.) suis to form multi-drug tolerant variants and identified persister cells dependent on the initial bacterial growth phase. We observed lower numbers of persisters in exponential phase cultures than in stationary growth phase populations. S. suis persister cells showed a high tolerance to a variety of antibiotics, and the phenotype was not inherited as tested with four passages of S. suis populations. Furthermore, we provide evidence that the persister phenotype is related to expression of genes involved in general metabolic pathways since we found higher numbers of persister cells in a mutant strain defective in the catabolic arginine deiminase system as compared to its parental wild type strain. Finally, we observed persister cell formation also in other S. suis strains and pathogenic streptococcal species. Conclusions Taken together, this is the first study that reports multi-drug tolerant persister cells in the zoonotic pathogen S. suis.
    BMC Microbiology 05/2014; 14(1):120. DOI:10.1186/1471-2180-14-120 · 2.73 Impact Factor
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    • "In the present study, biofilms treated with vancomycin or farnesol showed clusters of live (green) and death bacteria (red) but also a sub-population of bacteria with somewhat damaged cell membrane (yellow). Despite the fact that biofilms exposed to vancomycin or farnesol had smaller amounts of biomass, the typical S. epidermidis biofilm high density cell clusters were still detected [35-38]. On the other hand, rifampicin-treated biofilms hardly presented regions of live or somewhat damage cell clusters. "
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    ABSTRACT: Background Staphylococcus epidermidis is the major bacterial species found in biofilm-related infections on indwelling medical devices. Microbial biofilms are communities of bacteria adhered to a surface and surrounded by an extracellular polymeric matrix. Biofilms have been associated with increased antibiotic tolerance to the immune system. This increased resistance to conventional antibiotic therapy has lead to the search for new antimicrobial therapeutical agents. Farnesol, a quorum-sensing molecule in Candida albicans, has been described as impairing growth of several different microorganisms and we have previously shown its potential as an adjuvant in antimicrobial therapy against S. epidermidis. However, its mechanism of action in S. epidermidis is not fully known. In this work we better elucidate the role of farnesol against S: epidermidis biofilms using confocal laser scanning microscopy (CLSM). Findings 24 h biofilms were exposed to farnesol, vancomycin or rifampicin and were analysed by CLSM, after stained with a Live/Dead stain, a known indicator of cell viability, related with cell membrane integrity. Biofilms were also disrupted by sonication and viable and cultivable cells were quantified by colony forming units (CFU) plating. Farnesol showed a similar effect as vancomycin, both causing little reduction of cell viability but at the same time inducing significant changes in the biofilm structure. On the other hand, rifampicin showed a distinct action in S. epidermidis biofilms, by killing a significant proportion of biofilm bacteria. Conclusions While farnesol is not very efficient at killing biofilm bacteria, it damages cell membrane, as determined by the live/dead staining, in a similar way as vancomycin. Furthermore, farnesol might induce biofilm detachment, as determined by the reduced biofilm biomass, which can partially explain the previous findings regarding its role as a possible chemotherapy adjuvant.
    BMC Research Notes 05/2012; 5(1):244. DOI:10.1186/1756-0500-5-244
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