The Antibiotic Epidemic Antibiotic Resistance

Antibiotic Resistance: Surviving An Uncertain Future

Antibiotic use can damage and weaken a healthy immune system and our reliance on them has been a double-edged sword. In fact, there are many, many powerful plant-based antimicrobials, scientifically tested, that can step up to the plate and help us face the growing threat of resistant bacteria. And you'll find them in this new eBook: The Antibiotic Epidemic: How to Fight Superbugs and Emerging Bacteria with Miracles from Mother Earth. This Ebook Shows You The Many Powerful Plant-based Antimicrobials And Provides Recipes To Help Diminish The Need For Antibiotics. ebooThis can be your guide during the coming antibiotic apocalypse.

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Transfer Of Antibiotic Resistance

Anaerobes acquire and disseminate mobile DNA transfer factors by conjugation, that can harbor antibiotic resistance genes. Opportunities for the rapid disseminate of antibiotic resistance determinants are in the gut flora, as well as in polymicrobial infections. Transfer of resistance genes has been found in the B. fragilis group and in Prevotella, Clostridium, and Fusobacterium spp. (24). Bacterial conjugation, is the most common method of antibiotic resistance genes transmission in anaerobes. The resistance genes are located in DNA transfer factors that can harbor mobile transposons, plasmids and chromosomal elements (144,145). The transfer from one cell to cell of the DNA requires a connector bridge that is encoded by much larger transferable conjugative transposons (144). Two biochemical processes are required for horizontal transmission of the transmissible DNA (145, 146). The conjugative transposons are called Tet elements, because of their ability to harbor a tetracycline...

Antibiotic Resistance And Bacterial Variation

Geriatric medicine has certainly contributed to the growing problem of microbial antibiotic resistance. As a group, elderly patients in hospitals and long-term care facilities (LTCFs) are the major recipients of antibiotics. It has been estimated that among residents of LTCFs approx 40 of prescribed drugs for systemic use are antibiotics (68). A distressing result is the promotion and spread of antibiotic-resistant microorganisms (69). The types and origins of antibiotic-resistant pathogens in LTCFs have been carefully reviewed in a recent publication (70). Information about antibiotic resistance in the population of elderly who reside in LTCFs is probably the most reliable available. As stated in the review article (70), the antibiotic resistant bacteria of greatest concern to geriatricians are 1) p-lactam resistant organisms, especially penicillin-resistant pneumococci and aerobic Gram-negative bacilli resistant to third-generation cephalosporins 2) vanco-mycin-resistant enterococci...

[2 Use of Antibiotic Resistant Transposons for Mutagenesis

The insertion mutation is completely linked to the phenotype of the transposon in genetic crosses. This makes it easy to transfer mutations into new strain backgrounds simply by selecting for transposon-associated antibiotic resistance. 4. It is feasible to screen for transposon insertion mutants after low-level mutagenesis because each mutant that inherits the transposon-associated antibiotic resistance phenotype is likely to have only one insertion. The antibiotic resistance provides a selectable marker for backcrosses to establish that the mutant phenotype is due exclusively to one particular transposon insertion. the insertions are stable and secondary transposon events are eliminated. These mini-transposons must contain the ends of the transposon required for transposition, typically flanking a useful antibiotic-resistance gene. Plasmid delivery systems take advantage of a transposon insertion on a plasmid that is unable to replicate in the recipient cell (i.e., the transposon is...

Molecular Basis for P acnes Resistance

In general, bacteria develop antibiotic resistance by acquiring mobile genetic elements such as plasmids, which can be transferred between strains of a species and even between species in some instances. With tetracyclines and erythromycin, mobile plasmids and transposons encode for pump proteins that efflux antibiotics away from ribosomes, and less commonly resistance is due to enzymatic inactivation 10-12 . In the case of clinically relevant strains of resistant P. acnes, mobile elements have not been found. Rather, point mutations in the genes encoding the 23S rRNA (erythromycin) and the 16S rRNA (tetracycline) have been identified 13-16 .

Which Expression Vector Constitutive or Inducible

The selectable marker(s) encoded by the vector, which will provide antibiotic resistance for obtaining stably transfected cells. One must also decide whether to use constitutively active, inducible, or repressible expression vectors. Although constitutively active vectors are suitable for many purposes, such as characterization of receptor pharmacology, ligand binding, and large-scale receptor purification, inducible or repressible vectors allow one to control expression levels. Inducible vector systems now widely available include those responsive to metals, glucocorticoids, tetracycline, or isopropylthiogalactose (IPTG) (a galactose analog). Most repressible vectors now in use are responsive to tetracycline (8). Since glucocorticoids and metal ions often affect expression of many endogenous genes, we have found the LacSwitch-inducible expression vector system (7) to be very useful for inducible expression of adrenergic receptors in various cell lines. This system has been used in...

[4 Identification of Essential Genes in Bacteria

The arrival of antibiotic-resistance strains of pathogenic bacteria has forced a major push for the development of novel drugs to combat these resistant strains. Identification of essential genes in any bacterial species is an important step for the identification of targets for new generations of

[6 Localized Mutagenesis

Localized mutagenesis can be used to obtain mutants in genes of interest based on linkage to selectable markers. Mutagens diethylsulfate and hydroxylamine are used to obtain predominantly transition mutations in the DNA either by whole chromosomal mutagenesis or mutagenesis of DNA isolated as purified plasmid or packaged in transducing phage particles. Selectable markers can include those based on auxotrophic requirements, carbon or nitrogen source utilization, or antibiotic resistance markers, such as those encoded in transposons.

Aminoglycoside Resistance By Enzymatic Modification

The aminoglycoside modifying enzymes are the most prevalent and clinically relevant mechanism of aminoglycoside antibiotic resistance. They are classified into three major families the aminoglycoside N-acetyltransferases (AACs), the aminoglycoside O-nucleotidyltransferases (ANTs), and the aminoglycoside O-phosphotransferases (APHs) (Figure 3.3). These enzymes act by acetylat-ing, adenylylating, or phosphorylating their target aminoglycosides on selected amino or hydroxyl groups using either acetylCoA or ATP as co-substrates.

Susceptibility Patterns Of Anaerobic Bacteria

The increase in antibiotic resistance among anaerobes generated extensive studies of the mechanisms of resistance and resistance-gene transfer. These investigations brought about more insight into the causes of the rapid development of resistance. The observed resistance patterns to different antibiotics vary among the different groups of organisms as variations in the mechanisms of resistance exist.

Development Of Sequenceready Genomic Frameworks

In the early 1990s, bacterial artificial chromosomes (BACs) became a viable alternative to YACs.10 Contrary to their name, BACs are not really artificial chromosomes per se, but modified bacterial F factors. Although BACs can carry inserts approaching 500 kb in length, insert sizes between 80 and 300 kb are more common.10-12 Most BAC vectors possess traditional plasmid selection features such as an antibiotic resistance gene and a polycloning site within a reporter gene allowing insertional inactivation. BAC clones have several important advantages over YACs. In particular, BACs are considerably less prone to chimerism and insert rearrange-ments.7913 The stability of BAC inserts appears to be due, in part, to F factor genes (parA and parB) that prevent more than one BAC from simultaneously occupying a bacterium.101314 An additional advantage of BAC clones is that they are relatively easy to manipulate and propagate compared with viral- or yeast-based clones. Consequently, BACs have...

Treatment and protection

Antibiotic resistance of some E. tarda isolates from Taiwan was plasmid-mediated (Aoki et al., 1977 Aoki and Kitao, 1981). Aoki et al. (1986) detected 13 transferable R plasmids in E. tarda, two of which encoded for resistance to chloramphenicol, tetracycline and sulphonamide. Subsequent studies showed that 20 of 152 antibiotic-resistant strains of E. tarda possessed transferable antibiotic-resistant R plasmids therefore, the function of some of these structures in the bacterium are unknown (Aoki et al., 1987). When R plasmid resistance to tetracycline and sulphonamides occurs, Aoki et al. (1989) recommend that a potentiated sulphonamide at 25 mg kg-1 day-1, oxalinic acid at 12.5 mg kg-1 day-1 or miloxacin at 6.2 mg kg-1 day-1 be fed. Liu and Wang (1986) reported that nearly 92 of E. tarda isolates from the water of eel-culture ponds showed some degree of antibiotic resistance. Edwardsiella tarda has a long history of causing disease in South-East Asian aquaculture, where the pathogen...

Topics For Further Study

Chemotherapeutic control of E. tarda and E. ictaluri is a problem, because they have transmissible R plasmids, which enhance antibiotic resistance. Educating and encouraging aquaculturists to practise health maintenance and to apply drugs properly and only when necessary will slow the evolution of resistance to commonly used drugs. New therapeutics must be developed for aquaculture to avoid overdependence on one specific drug.

Antimicrobialresistant Microorganisms

Strategies to prevent and control the emergence and spread of antimicrobial-resistant microorganisms have been developed. These include optimal use of antimicrobial prophylaxis for surgical procedures optimizing choice and duration of empirical therapy improving antimicrobial prescribing patterns by physicians monitoring and providing feedback regarding antibiotic resistance formulating and using practice guidelines for antibiotic usage developing a system to detect and report trends in antimicrobial resistance ensuring that caregivers respond rapidly to the detection of antimicrobial resistance in individual patients incorporating the importance of controlling antimicrobial resistance into the institutional mission and climate increasing compliance with basic infection control policies and procedures and developing a plan for identifying, transferring, discharging, and readmitting patients colonized or infected with specific antimicrobial-resistant microorganisms.80

Eliminated Eliminated

Apoptosis is frequently induced in experimental systems by a defined signal, such as ionizing radiation, dexamethasone, or camptothecin. In these cases, it is important to differentiate between first-round transcriptional targets of the inducing agents and subsequent knock-on effects. This can be accomplished by inclusion of a protein synthesis inhibitor (cycloheximide), but it is important to generate representations from both cycloheximide-treated and untreated controls to ensure that identified transcripts are not artefacts of treatment with the inhibitor. In some systems, apoptosis can result from the expression of an exogenous transgene, which can either be inducible or show constitutive expression. Appropriate controls include the preparation of representations from vector-only transfectants, with or without inducing agents. Control representations can then be mixed in the Driver to prevent the cloning of unwanted transcripts such as antibiotic resistance marker (e.g., Neo).

[5 Isolation of Transposon Insertions

Most transposons have low target-site specificity, allowing insertions in many sites throughout the bacterial genome. Antibiotic-resistant transposons are particularly useful genetic tools because the antibiotic resistance provides a selectable marker within the transposon. This chapter will focus on antibiotic-resistant transposons transposons derived from Tn10. A few of the applications of antibiotic resistant transposon insertions are summarized in Chapter 2. pools can then be used to transfer the transposon insertions into a new strain background by selection for the transposon-associated antibiotic resistance, in this case tetracycline resistance. Assuming a random distribution of insertion of the transposon throughout the genome, roughly 1 in 2000 of the mutants will have an insertion in any given nonessential gene. The desired mutants can thus be obtained by selection for a particular pheno-type, or by screening through several thousand independent tetracycline-resistant...

Treatment and prophylaxis

Used as feed additives or added directly to the water to prevent and treat vibriosis. In Japan, ampicillin, chloramphenicol, nalidixic acid derivatives, nitrofuran derivatives, sulphonamides and trimethoprim have been routinely used to treat vibriosis (Aoki et al, 1984). However, the use of these compounds has resulted in drug resistant strains (Watanabe et al., 1971 Shotts et al, 1976 Aoki et al, 1977, 1979, 1980 Hayashi et al, 1982 Toranzo et al, 1984). Tetracycline resistant isolates were recovered from cultured ayu (Plecoglossus altivelis), up until 1977, when the use of this antibiotic was discontinued. Analysis of the resistance profile of V. anguillarum recovered since 1978 has shown that only one isolate was resistant to tetracycline (Aoki et al, 1984), demonstrating a correlation between the use of tetracycline and the appearance of resistance. Molecular and genetic analysis show that the genes encoding antibiotic resistance were often found in plasmids. Furthermore, in some...

The Eukaryotic Vectors

Monogenic vectors are the simplest form of expression plasmids. Briefly, they consist of a single transcription unit containing a strong promoter (SV40, CMV or RSV) for high-level constitutive expression in a large variety of mammalian cell lines, a series of unique restriction sites for insertion of the gene of interest, and a polyadenylation signal and site for transcriptional termination. They also generally contain a sequence responsible for mRNA stabilization (P-globin intron, for instance). Examples of monogenic vectors used for expression of adrenergic receptors include pSVL (11), pRK5 (12), pBC12BI (7), pCMV4 (10), or pSG5 (13). By themselves, such vectors allow transient expression only. Generation of stable transfectants requires cotransfection with a second vector carrying an antibiotic resistance gene. In contrast to monogenic vectors, bigenic vectors are designed to allow both transient and stable transfection. This feature is owing to the fact that these plasmids contain...

Resistance And Aminoglycoside Evolution

Antibiotic resistance (both endogenous and acquired) is an important determining factor in the historical development of the aminoglycosides as therapeutic agents. After streptomycin was introduced for the treatment of tuberculosis, it was found that bacterial resistance to the drug often developed this was shown to be due to spontaneous mutants arising during the course of therapy with the antibiotic, although the biochemical mechanism was not known at the time. Kanamycin, the first useful DOS aminoglycoside, was isolated in Japan in 1957 and rapidly became an antibiotic of choice in that country. However, the appearance of strains resistant to both streptomycin and kanamycin increasingly interfered with their therapeutic use in addition, hospital infections of Pseudomonas aeruginosa, a bacterium that is naturally less susceptible to antibiotics, were on the rise. A major breakthrough came with the discovery of a novel class of 2-DOS compounds, the gentamicins.34 These are extremely...

Relaxed Control In Gene Expression

Heavy metals) Usually antibiotic resistance used as dominant selectable marker (q.v. plasmid vectors) Enables host to cause disease. Specifically refers to those plasmids encoding direct virulence functions (e.g. toxin synthesis, tumor induction), but also applies to indirect functions such as antibiotic resistance (which increases virulence by making host resistant to medical treatments)

Pinocytosis See viropexis

Plasmids Genetic elements composed of double-stranded circular DNA which replicate separately from the bacterial chromosome within the bacterial cell wall. Some can induce their direct transmission to other bacteria, although they differ from viruses in having no extracellular infective particle. Some plasmids are under stringent control and as little as one copy is replicated per genome. Others, under more relaxed control, replicate many copies per cell. They may carry genetic determinants which can be translocated from the plasmid to the bacterial chromosome. Some of these determinants mediate antibiotic resistance. See also episomes.

Chloroplast Transformation

Chloroplast transformation. (A) Small leaf sections are biolistically bombarded with DNA fragments containing the aadA spectinomycin-resistance gene flanked by regions of homology to the chloroplast genome at both the 5 - and 3 -ends. (B) After four weeks on a medium containing spectinomycin, the leaf discs are bleached due to the inhibition of chloroplast protein synthesis. Successfully transformed chloroplasts initially grow as undifferentiated green calluses, which will, in the presence of appropriate growth hormones, produce shoots. (C) Spectinomycin-positive leaf segments are exposed to spectinomycin and streptomycin. The presence of the aadA gene confers broad-spectrum antibiotic resistance. Both antibiotics are therefore used to ensure that spontaneous spectinomycin-resistance mutants have not arisen. The three leaf fragments on the right-hand side of the plate have become bleached in the presence of both antibiotics because they are spontaneous spectinomycin...

Nmr In The Design Of Aminoglycoside Mimetics

The growing problem of antibiotic-resistant bacterial infections creates a need for new antibiotics.101 Aminoglycosides are one of the critical classes of antibiotics that have seen a reduction in clinical utility due to antibiotic resistance. NMR impinges upon the design of aminoglycoside mimetics for RNA targeted drug therapies in two major ways. First, the characterization of the structural and physical properties that govern aminoglycoside binding, resistance, specificity, and mode of action via NMR and other biophysical techniques has helped to motivate and to guide the development of both RNA- and ribosome-targeted drugs via rational design. Second, adapting NMR methodology traditionally used in protein-targeted drug design for RNA aids in the design of RNA-directed therapeutics. We focus on the development of small molecules targeted at the decoding region of the ribosomal A-site, highlighting a few studies that are representative of work in the field. With the goal of...

Immediate

In hospital and health department laboratories, various infectious agents are monitored for changes in bacterial resistance to antibiotics or antigenic composition. The detection of penicillinase-producing Neisseria gonorrhea in the United States through surveillance activities has provided critical information for the proper treatment of gonorrhea (CDC 1976). The National Nosocomial Infection Surveillance System monitors the occurrence of hospital-acquired infections, including changes in antibiotic resistance. Surveillance of influenza monitors the continual change in the influenza virus structure, information vital to vaccine formulation (Emori et al. 1991).

Dna Cloning

In 1973 scientists discovered that restriction enzymes, DNA ligase, and bacterial plasmids could be used to clone DNA molecules. Plasmids are small (about 4,000 base pairs, also expressed as 4.0 kilo base pairs or 4 Kbp) circular minichromosomes that occur naturally in bacteria and are often exchanged between cells by passive diffusion. When a bacterium acquires a new plasmid, it is said to have been transfected. For bacteria, the main advantage to swapping plasmids is that they often carry antibiotic resistance genes, so that a cell sensitive to ampicillin can become resistant simply by acquiring the right plasmid.

Bacterial Properties

Bacteria with multiple antibiotic resistance (e.g., methi-cillin-resistant 5. aureus MRSA , 5. epidermidis, and van-comycin-resistant enterococci VRE ) can be associated with significant SSI problems. In particular, staphylococci, with their natural virulence, present an important hazard if inappropriate prophylaxis is used.

Bh3216

Through a series of analyses such as a BLAST2 search, clustering analysis by the single linkage method examining all CDSs identified in the B. halodurans C-125 and B. subtilis genomes (8166 CDSs), and multiple alignment, 18 CDSs were grouped into the category of antiporter- and transporter-related protein genes in the C-125 genome. In this analysis, five CDSs were found to be candidates for Na + H * antiporter genes (BH1316, BH1319, BH2844, BH2964 and BH3946). However, no gene encoding antibiotic-resistance proteins in the C-125 were found, whereas the B. subtilis genome has nine different ones. Eleven genes for multidrug-resistant proteins were identified in the C-125 genome, 6 fewer than in B. subtilis. A non-alkaliphilic mutant strain (mutant 38154) derived from B. halodurans C-125, which is useful as a host for cloning genes related to alkaliphily has been isolated and characterized (Kudo et al. 1990). A 3.7-kb DNA fragment (pALK fragment) from the parent strain restored the...

Cosmid Vectors

The only DNA requirements for in vitro packaging into X phage are the presence of two cos sites that are separated by 37-51 kbp of intervening sequence. Cosmids were developed in light of this observation, and are simply plasmids that contain a X phage cos site (Collins and Briining, 1978). Figure 3.14 shows the overall architecture of a cosmid vector and a cloning scheme for the insertion of foreign DNA. As plasmids, cosmids contain an origin of replication and a selectable marker. Cosmids also possess a unique restriction enzyme recognition site into which DNA fragments can be ligated. After the packaging reaction has occurred, the newly formed X particles are used to infect E. coli cells. The DNA is injected into the bacterium like normal X DNA and circularizes through complementation of the cos ends. The lack of other X sequences means, however, that X infection will not proceed beyond this stage. The circularized DNA will, however, be maintained in the E. coli cell as a plasmid....

Bubonic Plague

Bubonic Plague Resistance

In 1971, the plague bacillus was renamed Y. pestis, in honor of Alexandre Yersin. At least three naturally occurring varieties of Y. pestis are known today. All three varieties cause virulent infections in humans and most mammals. The microbe can remain viable for many months in the congenial microclimate of rodent warrens. Its life span in putrefying corpses is limited to a few days, but it may survive for years in frozen cadavers. Thus, local outbreaks depend on the state of rodent communities and the means used to dispose of the bodies of plague victims. During the 1980s and 1990s, the World Health Organization recorded more than 18,000 cases of plague in 24 countries more than half were in Africa. In the United States, the disease was reported in 13 states. By the end of the 1990s, epidemiologists were warning that cases of plague were actually increasing throughout the world and that the disease should be classified as a re-emerging disease. Until the late 1990s, the plague...