Microbial resistance, antibiotics

Lactam Antibiotics Microbial Resistance to Drugs Quinolones... 

Even during the very early days of the widespread use of antibiotics, microbial resistance was never very far behind. Long-term use (ten days or more) of a single antibiotic will select for bacteria not only resistant to that specific antibiotic but to others as well. Even without long-term use of antibiotics, resistance within hospital... 

Microbial Resistance to Drugs. Table 2 Antibiotic modifying enzymes [2, 3]... 

Otitis media is most common in children between 6 months and 2 years of age but can occur in all age groups, including adults. By 12 months of age, 75% of children have had at least one episode of otitis media, and up to 20% have recurrent infections.3,4 At least 13 million antibiotic prescriptions are written annually in the United States for otitis media, resulting in 2 billion in direct costs.5 Many risk factors (Table 69-1) predispose children to otitis media and can be associated with microbial resistance, such as day-care attendance, prior antibiotic exposure, and age younger than 2 years.3,4,6... 

Watchful waiting and safety-net antibiotic prescriptions are approaches being used more frequently to attenuate microbial resistance and avoid unnecessary adverse events and costs of antibiotics. Observation is practiced extensively in Europe and involves monitoring for 48 to 72 hours after diagnosing AOM to see if spontaneous resolution will occur. Observation or delayed antibiotic therapy should be considered only in otherwise healthy children without recurrent disease (Fig. 69-1) and only if proper follow-up and good communication exist between clinicians and the parent/caregiver.4,5,16... 

Microbial resistance to established organic antibiotics is a potentially serious problem and provides an impetus for the development of novel antimicrobial metal compounds. The potency of Ag(I) ions is well known—but how does Ag(I) kill a bacterium Much current attention is focused on Bi(III) on account of its ability to kill Helicobacter pylori, an organism which prevents ulcers from healing. Bis-muth(III) chemistry has many unusual features a variable coordination number, strong bonds to alkoxide ligands, the stereochemical role of its 6s2 lone pair, facile formation of polymers, and dual hard and soft character. 

The emergence of microbial antibiotic drug resistance was speeded by the indiscriminate use of antibiotics in humans and livestock. Exposure to very low concentrations of antibiotic in meat or milk may have provided a path whereby human pathogens could eventually evolve high-level antibiotic drug resistance. Recently some strains of enterococcus and tuberculosis have developed resistance to all known antibiotic drugs. Inappropriate use of antibiotics is very common, and it accelerates the development of resistance in pathogens. 

Choose the best answer for the following. The emergence of microbial antibiotic drug resistance... 

Prepackaged topical antibacterial preparations that contain multiple antibiotics are available in fixed dosages well above the therapeutic threshold. These formulations offer the advantages of efficacy in mixed infections, broader coverage for infections due to undetermined pathogens, and delayed microbial resistance to any single component antibiotic. 

Microbial resistance to antibiotics can develop by which of the following mechanisms ... 

Furthermore, esters of tylosin such as AIV (14) inhibited protein synthesis and bound to tylosin-resistant ribosomes [77], These results illustrate the dynamics of microbial resistance as antibiotics are developed to combat microorganisms which are continually evolving and acquiring new means of blocking the actions of antibiotics. 

Answer A- Microbial resistance to fluoroquinolones is increasing, and some strains of Streptococcus pneumoniae are now resistant to ciprofloxacin. The mechanism can involve changes in the structure of topoisomerase IV, one of the targets of fluoroquinolones, which inhibit nucleic acid synthesis. Pneumococcal resistance to penicillins is also increasing via changes in penicillin-binding proteins (PBPs). The other mechanisms listed underlie microbial resistance to other antibiotics as follows sulfonamides (choice B), macrolides (choice C), extended-spectrum penicillins (choice D), and beta-lactams (choice E). 

The use of higher plants and their preparations to treat infections is an age-old practice and in times past possibly the only method available. Interest in plants with antimicrobial properties has revived because of the current problems associated with the use of penicillin and other antibiotics. Therapy with several types of antibiotics is frequently accompanied by side effects and microbial resistance. It is currently accepted that the accumulation of secondary metabolites in plants can be a consequence of requirements for chemical defense against microorganisms. Research carried out in the chemical and biological sciences has resulted in much evidence concerning the defensive role of natural products. 

In a number of cases, microbial resistance is mediated by the production of bacterial enzymes that attack the antibiotic molecule, changing its structure to an inactive form. This can lead to a so-called inoculum effect, in which a susceptible antibiotic is apparently less potent when larger numbers of bacteria are present in the medium than when fewer cells are employed. The more bacteria that are present, the more antibiotic-destroying enzyme that is present, and the more antibiotic that is required to overcome this to achieve the desired response. An antibiotic that is not enzyme modified is comparatively free of inoculum effects. 

Microbial resistance Microbial resistance to antibiotics in feeds is not harmful per se, but may create a public health hazard if the resistance interferes with the control of a given microorganism, especially a pathogen, in animals or humans ... 

The mechanisms of microbial resistance to antibiotics are generally due to alterations of the antibiotic s target site, enzymatic inactivation of the antibiotic, cell impermeability, reduced cellular uptake, or increased efflux of antibiotic from cells [218]. The occurrence of these mechanisms in macrolide-resistant organisms has been reviewed [219-221]. The most widespread mechanism is modification of the macrolide s ribosomal... 

---