Resistance to antibiotics

Resistance to antimicrobial agents is of concern as it is well known that bacterial resistance to antibiotics can develop. Many bacteria already derive some nonspecific resistance to biocides through morphological features such as thek cell wall. Bacterial populations present as part of a biofilm have achieved additional resistance owkig to the more complex and thicker nature of the biofilm. A system contaminated with a biofilm population can requke several orders of magnitude more chlorine to achieve control than unassociated bacteria of the same species. A second type of resistance is attributed to chemical deactivation of the biocide. This deactivation resistance to the strong oxidising biocides probably will not occur (27). 

The phenomenon of bacterial resistance to antibiotics was already known by the pioneers of the era of antibiotics, like Paul Ehrlich, who coined the term selective toxicity as the basic principle of antimicrobial therapeutics, as well as Gerhard Domagk, the inventor of the sulfonamide drugs, and Sir Alexander Fleming, the discoverer of the penicillins. When penicillin G was introduced into clinical practice in 1944, as many as 5% of the isolates of Staphylococcus aureus were resistant to penicillin, while 5 years later the percentage was 50%. 

Lambert PA (2005) Bacterial resistance to antibiotics modified target sites. Adv Drug Deliv Rev 29 1471-1485... 

Bacterial resistance to antibiotics has been recognized since the first drugs were introduced for clinical use. The sulphonamides were introduced in 1935 and approximately 10 years later 20% of clinical isolates of Neisseria gonorrhoeae had become resistant. Similar increases in sulphonamide resistance were found in streptococci, coliforms and other bacteria. Penicillin was first used in 1941, when less than 1 % of Staphylococcus aureus strains were resistant to its action. By 1947,3 8% of hospital strains had acquired resistance and currently over 90% of Staph, aureus isolates are resistant to penicillin. Increasing resistance to antibiotics is a consequence of selective pressure, but the actual incidence of resistance varies between different bacterial species. For example, ampicillin resistance inEscherichia coli, presumably under similar selective pressure as Staph, aureus with penicillin, has remained at a level of 30-40% for mai years with a slow rate of increase. Streptococcus pyogenes, another major pathogen, has remained susceptible to penicillin since its introduction, with no reports of resistance in the scientific literature. Equally, it is well recognized that certain bacteria are unaffected by specific antibiotics. In other words, these bacteria have always been antibiotic-resistant. 

Several factors are known to influence biocidal activity these include the period of contact, biocide concentration, pH, temperature, the presence of oigartic matter and the nature and condition of the microorgartisms being treated. Bacterial resistance to antibiotics is a well-established phenomenon and has been widely studied for luar years. By contrast, the mechanisms of insusceptibility to non-antibiotic chemical agents are less well understood. 

Strains of Streptomyces isolated from a range of nrban, agricnltnral, and forest soils isolated on a standard medinm displayed resistance to antibiotics that were well established in clinical practice. Resistance was fonnd among all classes of antibiotics, and a distnrbing nnmber of isolates were resistant to between 5 and 10 of them (D Costa et al. 2006). 

It has been shown (Smith et al. 1978) that in enteric bacteria carrying thermosensitive plasmids coding for the utilization of citrate and for resistance to antibiotics, rates of transmission were negligible at 37°C but appreciable at 23°C—a temperature more closely approaching that which prevails in natural ecosystems. 

A gene reporter refers to a fragment of DNA, which encodes a product that allows the selection of the clones, which express it. Examples of gene reporters useful for this purpose are those, which encode resistance to antibiotics or heavy metals or enzymes such as xylE or the same sox proteins. 

Another problem is bacterial resistance to antibiotics. As doctors have treated people with the available antibiotics that medicinal chemistry devised in the past, they have selected for strains of bacteria that are resistant to those antibiotics. There is now a race against time by medicinal chemists to devise new antibiotics that will work against the resistant organisms. If we do not succeed, many bacterial infections that we thought had been cured will emerge again as major threats to our health and life. 

Spratt BG Resistance to antibiotics mediated by target alterations. Science 1994 264 388-393. 

Espersen F Resistance to antibiotics used in dermatological practice. Br J Dermatol 1998 139(suppl53) 4-8. 

Enterococcus faecalis (generally not as resistant to antibiotics as Enterococcus faea um)... 

E faedum (generally more resistant to antibiotics than faecalis)... 

Bacterial resistance to antibiotics is an emerging public health crisis. The prevalence of pathogens resistant to currently available antibiotics continues to grow annually. Two million patients in the U.S. acquire an infection during a hospital stay and approximately 90,000 of these patients die each year as a result of the infection [1]. More than 70% of hospital-acquired infections are now resistant to... 

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