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1.
Various natural environments have been examined for the presence of antibiotic-resistant bacteria and/or novel resistance
mechanisms, but little is known about resistance in the terrestrial deep subsurface. This study examined two deep environments
that differ in their known period of isolation from surface environments and the bacteria therein. One hundred fifty-four
strains of bacteria were isolated from sediments located 170–259 m below land surface at the US Department of Energy Savannah
River Site (SRS) in South Carolina and Hanford Site (HS) in Washington. Analyses of 16S rRNA gene sequences showed that both
sets of strains were phylogenetically diverse and could be assigned to several genera in three to four phyla. All of the strains
were screened for resistance to 13 antibiotics by plating on selective media and 90% were resistant to at least one antibiotic.
Eighty-six percent of the SRS and 62% of the HS strains were resistant to more than one antibiotic. Resistance to nalidixic
acid, mupirocin, or ampicillin was noted most frequently. The results indicate that antibiotic resistance is common among
subsurface bacteria. The somewhat higher frequencies of resistance and multiple resistance at the SRS may, in part, be due
to recent surface influence, such as exposure to antibiotics used in agriculture. However, the HS strains have never been
exposed to anthropogenic antibiotics but still had a reasonably high frequency of resistance. Given their long period of isolation
from surface influences, it is possible that they possess some novel antibiotic resistance genes and/or resistance mechanisms.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
2.
A tuberculosis model which incorporates treatment of infectives and chemoprophylaxis is presented. The model assumes that
latently infected individuals develop active disease as a result of endogenous re-activation, exogenous re-infection and disease
relapse, though a small fraction is assumed to develop active disease soon after infection. We start by formulating and analyzing
a TB model without any intervention strategy that we extend to incorporate chemoprophylaxis and treatment of infectives. The
epidemic thresholds known as reproduction numbers and equilibria for the models are determined, and stabilities analyzed.
The reproduction numbers for the models are compared to assess the possible community benefits achieved by treatment of infectives,
chemoprophylaxis and a holistic approach of these intervention strategies. The study shows that treatment of infectives is
more effective in the first years of implementation (≈ 10 years) as treatment results in clearing active TB immediately and
there after chemoprophylaxis will do better in controlling the number of infectives due to reduced progression to active TB. 相似文献
3.
Drug resistance is a common problem in the fight against infectious diseases. Recent studies have shown conditions (which we call antiR) that select against resistant strains. However, no specific drug administration strategies based on this property exist yet. Here, we mathematically compare growth of resistant versus sensitive strains under different treatments (no drugs, antibiotic, and antiR), and show how a precisely timed combination of treatments may help defeat resistant strains. Our analysis is based on a previously developed model of infection and immunity in which a costly plasmid confers antibiotic resistance. As expected, antibiotic treatment increases the frequency of the resistant strain, while the plasmid cost causes a reduction of resistance in the absence of antibiotic selection. Our analysis suggests that this reduction occurs under competition for limited resources. Based on this model, we estimate treatment schedules that would lead to a complete elimination of both sensitive and resistant strains. In particular, we derive an analytical expression for the rate of resistance loss, and hence for the time necessary to turn a resistant infection into sensitive (tclear). This time depends on the experimentally measurable rates of pathogen division, growth and plasmid loss. Finally, we estimated tclear for a specific case, using available empirical data, and found that resistance may be lost up to 15 times faster under antiR treatment when compared to a no treatment regime. This strategy may be particularly suitable to treat chronic infection. Finally, our analysis suggests that accounting explicitly for a resistance-decaying rate may drastically change predicted outcomes in host-population models. 相似文献
4.
Twenty-four acid- and bile-tolerant lactobacilli isolates from dairy products were identified and further in vitro characterized for the presence of functional traits potentially useful for probiotic applications, which included desirable and undesirable traits, such as biofilm formation, ability to inhibit intestinal pathogens, antibiotic susceptibility, and enzyme activity. The majority of examined strains were susceptible to certain antimicrobial agents (streptomycin, gentamicin, clindamycin, erythromycin, tetracycline, quinupristin–dalfopristin), except for three strains of Lactobacillus rhamnosus with minimal inhibitory concentration levels for streptomycin higher than the microbiological breakpoints (≥32 μg/mL), which are considered as resistant. Undesirable traits such as α-chymotrypsin or N-acetyl-β-glucosaminidase activities were not detected, but low β-glucuronidase, and moderate and high β-glucosidase activities were recorded in nine strains, which were eliminated from further examination together with three isolates showing unsuitable antibiotic resistance. Of the remaining 12 isolates, 4 (Lactobacillus fermentum 202, Lactobacillus gallinarum 7001, L. rhamnosus 183, and Lactobacillus plantarum L2-1) manifested an outstanding potential to inhibit selected intestinal pathogens in an agar spot test, including Escherichia coli and Salmonella spp., and simultaneously demonstrated strong biofilm-forming capacity. In conclusion, the results of our in vitro experiments showed that the above four strains had a potential probiotic value and met the criteria to be identified as a possible probiotic microorganism, with the necessity of verification through well-designed in vivo experimental, clinical, and technological studies before the strains can be used as probiotics or as starter probiotic cultures. 相似文献
5.
Long-chain (≥ C20) polyunsaturated fatty acids, such as docosahexaenoic acid and eicosapentaenoic acid, are nutritionally important and provide
protection against cardiovascular disease, stroke, and cancer. Structural variants of these compounds may have the potential
to be used as pharmaceuticals. Marine microalgae are the key producers of long-chain polyunsaturated fatty acids in the global
food web. Assuming vast biological and biochemical diversity, we devised a screen to identify microalgae that produce novel
fatty acids. The herbicide metolachlor, an inhibitor of long-chain fatty acid biosynthesis, was used in microcosms containing
field-collected microalgae to identify naturally resistant strains. We show that one diatom, Melosira cf. moniliformis, is naturally resistant to concentrations of metolachlor, which were cytostatic or lethal to all the other microalgae. Gas
chromatography and gas chromatography-mass spectrometry revealed three fatty acids that have not previously been described-18:4
(Δ5,8,11,14), 18:4 (Δ5,9,12,15), and 18:5 (Δ5,8,11,14,17). We propose that this type of screen may be generally applicable
to the search of novel compounds produced by marine microorganisms. 相似文献
6.
Analysis of antibiotic susceptibility and extrachromosomal DNA content of Ruminococcus albus and Ruminococcus flavefaciens 总被引:3,自引:0,他引:3
Seventeen Ruminococcus albus and Ruminococcus flavefaciens strains have been screened for naturally occurring antibiotic resistance, as determined by zones of inhibition from antibiotic disks. These strains were also examined for extrachromosomal DNA content. All strains screened are resistant to low levels (10-200 micrograms/mL) of streptomycin. In contrast to the previously reported data, we have found that R. flavefaciens C-94 is now susceptible to both kanamycin and tetracycline. However, R. flavefaciens FD-1 is not susceptible to kanamycin (minimum inhibitory concentration (MIC) = 40 micrograms/mL). Furthermore, R. albus 8 is resistant to tetracycline (MIC = 40 micrograms/mL), and erythromycin (MIC = 100 micrograms/mL). Six freshly isolated strains showed resistance to tetracycline (35-70 micrograms/mL), and all tetracycline-resistant strains also showed resistance to minocycline. None of these Ruminococcus determinants share homology with the streptococcal tetL, tetM, or tetN determinants. All 17 strains were screened for extrachromosomal DNA content. Nine different techniques for the detection and isolation of extrachromosomal DNA were tested. However, owing to difficulties in demonstrating or isolating plasmid DNA, it has not been possible to determine if these antibiotic resistance genes are plasmid borne. Evidence is presented to suggest that the presence of oxygen may affect the quality of the DNA obtained from Ruminococcus. 相似文献
7.
We examine a generalised SIR model for the infection dynamics of four competing disease strains. This model contains four
previously-studied models as special cases. The different strains interact indirectly by the mechanism of cross-immunity;
individuals in the host population may become immune to infection by a particular strain even if they have only been infected
with different but closely related strains. Several different models of cross-immunity are compared in the limit where the
death rate is much smaller than the rate of recovery from infection. In this limit an asymptotic analysis of the dynamics
of the models is possible, and we are able to compute the location and nature of the Takens–Bogdanov bifurcation associated
with the presence of oscillatory dynamics observed by previous authors.
Received: 5 December 2001 / Revised version: 5 May 2002 / Published online: 17 October 2002
Keywords or phrases: Infection – Pathogen – Epidemiology – Multiple strains – Cross-immunity – Oscillations – Dynamics – Bifurcations 相似文献
8.
Siva Wu Xiaojin Li Manjula Gunawardana Kathleen Maguire Debbie Guerrero-Given Christoph Schaudinn Charles Wang Marc M. Baum Paul Webster 《PloS one》2014,9(7)
Non-typeable Haemophilus influenzae (NTHi) is a common acute otitis media pathogen, with an incidence that is increased by previous antibiotic treatment. NTHi is also an emerging causative agent of other chronic infections in humans, some linked to morbidity, and all of which impose substantial treatment costs. In this study we explore the possibility that antibiotic exposure may stimulate biofilm formation by NTHi bacteria. We discovered that sub-inhibitory concentrations of beta-lactam antibiotic (i.e., amounts that partially inhibit bacterial growth) stimulated the biofilm-forming ability of NTHi strains, an effect that was strain and antibiotic dependent. When exposed to sub-inhibitory concentrations of beta-lactam antibiotics NTHi strains produced tightly packed biofilms with decreased numbers of culturable bacteria but increased biomass. The ratio of protein per unit weight of biofilm decreased as a result of antibiotic exposure. Antibiotic-stimulated biofilms had altered ultrastructure, and genes involved in glycogen production and transporter function were up regulated in response to antibiotic exposure. Down-regulated genes were linked to multiple metabolic processes but not those involved in stress response. Antibiotic-stimulated biofilm bacteria were more resistant to a lethal dose (10 µg/mL) of cefuroxime. Our results suggest that beta-lactam antibiotic exposure may act as a signaling molecule that promotes transformation into the biofilm phenotype. Loss of viable bacteria, increase in biofilm biomass and decreased protein production coupled with a concomitant up-regulation of genes involved with glycogen production might result in a biofilm of sessile, metabolically inactive bacteria sustained by stored glycogen. These biofilms may protect surviving bacteria from subsequent antibiotic challenges, and act as a reservoir of viable bacteria once antibiotic exposure has ended. 相似文献
9.
Heloisa da Silveira Paro Pedro Susilene Maria Tonelli Nardi Maria Izabel Ferreira Pereira Rosangela Siqueira Oliveira Philip Noel Suffys Harrison Magdinier Gomes Amanda Juliane Finardi Eloise Brasil de Moraes Ida Maria Foschiani Dias Baptista Ricardo Luiz Dantas Machado Lilian Castiglioni 《Memórias do Instituto Oswaldo Cruz》2015,110(2):235-248
Drug-resistant tuberculosis (TB) is a growing global threat. Approximately 450,000
people developed multidrug-resistant TB worldwide in 2012 and an estimated 170,000
people died from the disease. This paper describes the sociodemographic,
clinical-epidemiological and bacteriological aspects of TB and correlates these
features with the distribution of anti-TB drug resistance. Mycobacterium tuberculosis
(MT) cultures and drug susceptibility testing were performed according to the BACTEC
MGIT 960 method. The results demonstrated that MT strains from individuals who
received treatment for TB and people who were infected with human immunodeficiency
virus were more resistant to TB drugs compared to other individuals (p < 0.05).
Approximately half of the individuals received supervised treatment, but most
drug-resistant cases were positive for pulmonary TB and exhibited positive acid-fast
bacilli smears, which are complicating factors for TB control programs. Primary
healthcare is the ideal level for early disease detection, but tertiary healthcare is
the most common entry point for patients into the system. These factors require
special attention from healthcare managers and professionals to effectively control
and monitor the spread of TB drug-resistant cases. 相似文献
10.
Antibiotic synergy against biofilm-forming <Emphasis Type="Italic">Pseudomonas aeruginosa</Emphasis> 总被引:1,自引:1,他引:0
Eight antibiotics (aztreonam, ceftazidim, cefoperazon, cefepim, netilmicin, amikacin, ofloxacin and ciprofloxacin) exhibited
antimicrobial activity individually and/or in combinations against 20 wild-type biofilm-forming strains of Pseudomonas aeruginosa. The strains were less susceptible in biofilm; in 10 strains antibiotic synergy was observed for the combination of aztreonam
and ciprofloxacin. Synergy was also demonstrated in the case of β-lactams and aminoglycosides, β-lactams and fluoroquinolones,
aminoglycosides and fluoroquinolones, and for monobactams and β-lactams although the strains were resistant to the individual
antibiotics. Synergism or partial synergism was found with one or more antibiotic combinations against 32.4% of isolates. 相似文献
11.
Peña-Miller R Lähnemann D Schulenburg H Ackermann M Beardmore R 《Bulletin of mathematical biology》2012,74(4):908-934
Using optimal control theory as the basic theoretical tool, we investigate the efficacy of different antibiotic treatment
protocols in the most exacting of circumstances, described as follows. Viewing a continuous culture device as a proxy for
a much more complex host organism, we first inoculate the device with a single bacterial species and deem this the ‘commensal’
bacterium of our host. We then force the commensal to compete for a single carbon source with a rapidly evolving and fitter
‘pathogenic bacterium’, the latter so-named because we wish to use a bacteriostatic antibiotic to drive the pathogen toward
low population densities. Constructing a mathematical model to mimic the biology, we do so in such a way that the commensal
would be eventually excluded by the pathogen if no antibiotic treatment were given to the host or if the antibiotic were over-deployed.
Indeed, in our model, all fixed-dose antibiotic treatment regimens will lead to the eventual loss of the commensal from the
host proxy. Despite the obvious gravity of the situation for the commensal bacterium, we show by example that it is possible
to design drug deployment protocols that support the commensal and reduce the pathogen load. This may be achieved by appropriately
fluctuating the concentration of drug in the environment; a result that is to be anticipated from the theory optimal control
where bang-bang solutions may be interpreted as intermittent periods of either maximal and minimal drug deployment. While such ‘antibiotic pulsing’
is near-optimal for a wide range of treatment objectives, we also use this model to evaluate the efficacy of different antibiotic
usage strategies to show that dynamically changing antimicrobial therapies may be effective in clearing a bacterial infection
even when every ‘static monotherapy’ fails. 相似文献
12.
Bacteriocinogeny and antibiotic resistance of naturally occurring strains of Streptococcus mutans 总被引:1,自引:0,他引:1
We studied bacteriocinogenies and antibiotic resistances of naturally occurring strains of Streptococcus mutans isolated from different sources. It was found that naturally occurring strains from humans and rats were distinguished by their bacteriocin susceptibilities and production. We had a few incidences of tetracycline resistant strains only among those isolated from rats. It is quite interesting that none of the resistant strains we collected produced bacteriocins. 相似文献
13.
For an infecting bacterium the human body provides several potential ecological niches with both internally (e.g. host immunity) and externally (e.g. antibiotic use) imposed growth restrictions that are expected to drive adaptive evolution in the bacterium, including the development of antibiotic resistance. To determine the extent and pattern of heterogeneity generated in a bacterial population during long-term antibiotic treatment, we examined in a monoclonal Mycobacterium tuberculosis infection antibiotic resistant mutants isolated from one patient during a 9-years period. There was a progressive accumulation of resistance mutations in the infecting clone. Furthermore, apparent clonal sweeps as well as co-existence of different resistant mutants were observed during this time, demonstrating that during treatment there is a high degree of dynamics in the bacterial population. These findings have important implications for diagnostics and treatment of drug resistant tuberculosis infections. 相似文献
14.
15.
S. Özmen Toğay A. Çelebi Keskin L. Açık A. Temiz 《Journal of applied microbiology》2010,109(3):1084-1092
Aim: To determine the virulence genes, antibiotic resistance and plasmid profiles of 16 Enterococcus faecium and 68 Enterococcus faecalis strains isolated from various naturally fermented foods. Methods and Results: The presence of virulence genes (agg2, gelE, cylM, cylB, cylA, espfs, espfm, efaAfs, efaAfm, cpd, cop, ccf, cad) and also the genes vanA and vanB were investigated by polymerase chain reaction (PCR). Antibiotic resistance of the isolates was determined by disc diffusion method. Most of the tested isolates were positive for virulence genes and resistant to some antibiotics. One of the Ent. faecalis strains isolated from a cheese sample carried the vanA gene and was intermediately resistant to vancomycin. The strains usually contained large plasmids, which might harbour acquired antibiotic resistance. Conclusion: The study showed that Ent. faecium and Ent. faecalis strains isolated from naturally fermented Turkish foods may be potential risk factors for consumer health in terms of virulence genes and acquired antibiotic resistance. Significance and Impact of the Study: The results indicate the importance of enterococcal contamination in terms of the safety of some fermented Turkish foods. 相似文献
16.
Uropathogenic strains of E. coli isolated from urine of patients with urinary tract infections were tested for antibiotic sensitivity using bio-Merieux kits
and ATB-UR 5 expression system. The virulence of strains was evaluated by serum bactericidal assay, macrophage “killing” and
bacterial adhesive tests. Survival capability of strains was assessed under starvation in saline. The results showed that
quinolone-resistant uropathogenic strains of E. coli exhibit significantly reduced adhesive potential but relatively high resistance to serum and macrophage bactericidity. In
contrast to laboratory strains, the quinolone-resistant uropathogenic clinical isolate demonstrated increased viability during
starvation in saline. Our study suggests that quinolone-resistant uropathogenic strains are highly adaptable clones of E. coli, which can exhibit compensatory viability potential under unfavorable conditions. The clinical occurrence of such phenotypes
is likely to contribute to the survival, persistence and spread strategy of resistant bacteria. 相似文献
17.
Summary The occurrence and antibiotic resistance of Escherichia coli in tropical seafood was studied. A 3-tube MPN method was used for determining the level of faecal contamination of fresh and processed seafood. Of the 188 samples tested which included finfish, shellfish, water and ice, 155 were positive for the presence of faecal coliforms following incubation at 44.5 °C. However, E. coli was isolated from only 47% of the samples positive for faecal coliforms. The antibiotic resistance of 116 strains isolated from seafood was tested using 14 different antibiotics including ampicillin, cephalothin, chloramphenicol, ciprofloxacin, gentamycin, nalidixic acid, streptomycin and vancomycin. Seven strains were resistant to more than five antibiotics of which one was resistant to eight antibiotics. The multiple drug resistant strains harboured plasmids of varying sizes. Antibiotic susceptibility studies revealed that seafood from India contains multiple antibiotic resistant strains of E. coli which may serve as a reservoir for antibiotic resistance genes in the aquatic environment. All the strains used in this study did not harbour any virulence genes commonly associated with pathogenic E. coli, when tested by polymerase chain reaction (PCR). 相似文献
18.
Summary The uptake of L-tyrosine into wild type and antibiotic resistant strains of Schizosaccharomyces pombe requires an energy source, is initially linear with respect to time, is inhibited by 2,4-dinitrophenol and sodium azide and is saturable. However the initial uptake rates and the amount of L-tyrosine accummulated by antibiotic resistant strains are much less than wild type. Comparison of the kinetic constants of uptake shows that mutant strains have a reduced maximum velocity of uptake compared to wild type and a larger Km.Since the three mutant strains possess a permeability barrier to L-tyrosine as well as being drug resistant this is an indication that antibiotic resistance may be caused by a decrease in plasma membrane permeability. 相似文献
19.
Clinical isolates of Nocardia brasiliensis from Japan were classified into two groups based on their susceptibility to the carbapenem antibiotic, imipenem (IPM). Of
33 strains tested, 10 belonged to an IPM susceptible group, with MIC of from 0.25 to 2 εg/ml and a MIC80 value of 1.5 εg/ml for this antibiotic. The remaining 23 strains belonged to an IPMresistant group with MIC and MIC80 values of 8–16 εg/ml and >16 εg/ml, respectively. The type strain of N. brasiliensis belonged to this resistant group. Analysis of 16S rDNA genes sequences showed that the IPM susceptible group had characteristic
single nucleotide substitutions at positions 103 (T), 381 (A), and 456 (A), in contrast to the IPM resistant group. This grouping,
however, was not associated with their clinical manifestation. 相似文献
20.
Sousa EH Basso LA Santos DS Diógenes IC Longhinotti E Lopes LG Moreira Ide S 《Journal of biological inorganic chemistry》2012,17(2):275-283