The Causes of the Development of Antimicrobial Resistance - Essay Example

Antibiotics are antimicrobial medications that kills or slows down the growth of micro-organisms. The term is derived from the Greek word “anti” meaning against and “bios” meaning life. The US National Library of Medicine defines antibiotics as powerful medicines that fight microbial infections by either stopping them from reproducing or terminate them. However, they are not effective against viruses). A large number of antibiotics are available but they all work in either of the two ways- a microbicidal antibiotic which kills the microorganism and microbistatic antibiotic. The former class includes antibiotics like the β lactams (penicillin, penicillin derived antibiotics, carbapenems,cephalosporins, vancomycin) and most aminoglycosides especially against Gram negative organisms but not against Gram positive and anaerobic micro-organisms.The other class of antibiotics, the microbistatic, include antibiotics that prevent the micro-organisms from multiplying by interfering with their protein production, DNA replication and other metabolic pathways. Tetracycline, sulphonamides, trimethoprim and most microbicidal antibiotics at low concentration are few examples of the microbistatic group. The first antibiotic to be discovered was penicillin derived from the Penicillium mold. It was discovered by Alexander Fleming in 1928.Later on the development of synthetic penicillin broadened the spectrum of activity and at the same time enhanced the efficacy of these drugs. However, with the emergence of resistant bacterial strains the usefulness of penicillins have been limited in the recent years. Methicillin is a narrow spectrum β lactam antibiotic which was developed in 1959 by Beechman in order to treat penicillin resistant Gram positive organisms like Staphylococcus aureus. In the 1960s and 1970s it proved so efficient against Staphylococcus aureus that it was extensively used and even sprayed in the wards of hospitals to control Staphylococcal infection in new born.( Elek SD, Fleming PC. A new technique for the control of hospital cross infection. Lancet 1960;ii:569–72). Methicillin resistant isolates though present were not notably troublesome because of the emergence and prevalence of microbial resistance especially MRSA( methicillin resistant staphylococcus aureus) in hospitals. The major antibiotic resistant pathogen associated with nosocomial infection. It was reported that there was an increase in the number of fatal cases of sepsis from 4% in 1991 to 37% in 1999 in UK due to MRSA and to USA by the 1980s (4). Aminoglycoside resistant Staphylococcus aureus had already become common all over the world in the late 1980s( 5) strain was first isolated in Japan and was soon found in hospitals of England, France and by 2002 in US(6). However, recently in the year 2011 a modified form of vancomycin, engineered for Dual D-Ala-D-Ala and D- Ala-D-Lac binding showed potent antimicrobial activity against VRSA.(  7.). Vancomycin resistance was also seen in enterococci in a species dependent manner-3% of Enterococcus faecalis and 50% of Enterococcus faecium showed resistance to Vancomycin.(8). Alexander Fleming had warned us against the irrartional use of antibiotics stating “The time may come when penicillin can be bought by anyone in the shops. Then there is the danger that the ignorant man may easily underdose himself and by exposing his microbes to non‐lethal quantities of the drug make them resistant” (2) However it is not only the irrational use of the drugs that causes antibiotic resistance but there are reports of the naturally occurring resistance. According to an experiment conducted by Joshua and Esther Lederberg in 1952, penicillin-resistant strains of bacteria developed much more before the start of penicillin in medicinal practices. Joshua Lederberg and his student Zinder also demonstrated the pre-existence of Steptomycin resistance strains.( 3) The causes of the development of antimicrobial resistance includes selective pressure-survival and proliferation of resistant strains when treatment with antibiotics kills susceptible micro-organisms in a microbial population; mutation-mutations may arise during the process of replication which may help the organism to survive in presence of a particular antibiotics; irrational use- selection of certain resistant strains may be exacerbated due to inappropriate usage and inadequate dosage of antibiotics; gene transfer-microbes can transfer genes among themselves and transfer of the R plasmid may contribute to resistant properties to susceptible cells; heavy use of antibiotics in hospitals-in order to treat critically ill patients heavy usage of antibiotics is done, however, this might lead to the selection of antibiotic resistant pathogens and the patient may act as a reservoir for antimicrobial resistant micro-organisms Hospital acquired infections which are now popularly called as nosocomial infections are most often caused by organisms resistant to antimicrobial agents. The frequency of its occurrence has become a source of concern to most clinicians and epidemiologists all over the world. The propensity of these pathogens to develop resistance to the current antimicrobial drugs has made things challenging for most clinicians.(1) However in the 1970s nosocomial infection was not regarded as a high priority but after major outbreaks of the epidemic MRSA occurred in Kettering ) nosocomial infection especially due to MRSA or other ESBL became a major concern. Since then EMRSA has affected most hospitals in UK as well as US (8). According to the National Nosocomial Infections Surveillance system of different CDCs of USA (center for disease conrol) Candida spp. are the main cause of nosocomial urinary infections in ICUs (14). Other common nosocomial infections include ventilator associated pneumonia (VAP) caused by Streptococcus pneumoniae and MRSA, drug resistant Pseudomonas aeruginosa and Acinetobacter baumannii(10), Urinary tract infection caused by ESBL (extended spectrum β lactamase) producing Enterobactriaceae especially Uropathogenic Escherichia coli(UPEC), vascular access-related bacteremia and surgical wounds infection (11).Such nosocomial infections caused by multidrug resistant organisms are usually associated with prolonged and challenging medical care, complications and costly therapies. In the year 2004 in Hungary 6485 such cases arose out of which one-third patients died in hospital. MRSA was the most common and frequent (almost 52.2%) pathogen reported but after 2007 nosocomial infections because of MRSA has stabilized. Rather, there is an increase in the cases caused by multi-drug resistance gram negative bacteria within 2005-2010(13.) Today nosocomial infection is given an immense importance with National Guidelines for controlling MRSA published in 1998(). According to this hospitals that do not have incidents of MRSA should try and maintain that and hospitals where MRSA is endemic should try and concentrate resources on sensitive areas like the ICU . However according to Thompson’s article the current general hospital intensive care ward is the most susceptible site for nosocomial infection by resistant pathogens as these are crowded by debilitated patients receiving broad spectrum antibiotics, provides the perfect environment for the emergence of antibiotic resistance.( 12) The patients in hospitals are immuno-compromised and are mostly subjected to broad spectrum antibiotics and exposed to resistant pathogens. This account for the different global outbursts in nosocomial infections associated with resistant pathogens over the past decades and definitely will be haunting clinicians and medical practitioners in the years to come. Read More