Antibiotic Resistance in Anaerobic Bacteria - Essay Example

 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 (Gardner et al, p415). The first antibiotic discovered was penicillin by Alexander Fleming and he had warned us against the irrational 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 under dose himself and by exposing his microbes to non‐lethal quantities of the drug make them resistant. Here is a hypothetical illustration. Mr. X. has a sore throat. He buys some penicillin and gives himself, not enough to kill the streptococci but enough to educate them to resist penicillin. He then infects his wife. Mrs. X gets pneumonia and is treated with penicillin. As the streptococci are now resistant to penicillin the treatment fails. Mrs. X dies. Who is primarily responsible for Mrs. X’s death?” (Fleming, p88). 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 (Nelson, p 294). The major antibiotic resistant pathogen associated with nosocomial infection is Staphylococcus aureus. It was one of the earlier organisms to develop penicillin resistance. Methicilin was then used against the resistant strains but in the year 1961MRSA (Methycillin-resistant staphylococcus aureus) was detected in Britain. 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.By the 1980s MRSA had spread and became quite common in US hospitals and along with resistance to Methycillin. There was a steady increase in oxacillin (Methycillin) resistant S. aureus in U.S. hospitals in the year 1997 which increased to 26.2%.( Pfaller et al,p1886). Most of these Staphylococcus aureus also showed resistance to tetracycline and erythromycin. Aminoglycoside resistant Staphylococcus aureus had already become common all over the world in the late 1980s( Bawdon et al,p1075).Vancomycin was the only effective antibiotic against Staphylococcus aureus available at that time. However in the year 1996 VRSA (vancomycin resistant staphylococcus aureus) strain was first isolated in Japan and was soon found in hospitals of England, France and by 2002 in US (Bozdogan et al,p864). 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(Xie et al, p13946).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.(Edmond et al, p1126). Figure 1: the timing for market introduction and emergence of resistant strains against certain drugs. Organisms associated with hospital acquired infection are frequently resistant to antibiotics. Major factors responsible for this increased prevalence of resistance are changes in the types of organisms causing nosocomial infection which may further be due to changes in hospital populations and changes in the instrumentation and procedures used in patient care, increasing prevalence of naturally acquired resistance phenomenon and irrational use of antibiotics. Resistance to antibiotics may be considered to be an evolving process which is driven by the selective pressure of excessive use of antibiotics. In the hospital the ICU (intensive care unit) which are crowded by debilitated patients receiving broad spectrum antibiotics, provides the perfect environment for the emergence of antibiotic resistance (Flaherty & Weinstein, p236). According to a study made by Edmond et al in US Hospitals Gram positive organisms contributed for 64% of nosocomial infections while the contribution by Gram negative organisms was 27% and by fungi was 8%. The most common organisms involved in nosocomial infection in US hospitals were Staphylococcus aureus and enterococci and in some cases Candida(Wallace et al,p239).According to the National Nosocomial Infections Surveillance system of different CDCs of USA (center for disease control) Candida spp. are the main cause of nosocomial urinary infections in ICUs (Fridkin et al, p 476).The major nosocomial infections include ventilator associated pneumonia (VAP) caused by Streptococcus pneumoniae and MRSA, drug resistant Pseudomonas aeruginosa and Acinetobacter baumannii ( Trouillet et al, p531).Urinary tract infection caused by ESBL (extended spectrum β lactamase) producing Enterobactriaceae especially Uropathogenic Escherichia coli(UPEC) (Bradford, p934).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 (Caini et al, p7). The causes of such increase in antibiotic resistance may be natural but mainly it is through the irrational use of antibiotics. For example the extensive use of cephalosporins against Gram negative bacilli in the 1970s and 1980s led to the development of pathogens resistant to the earlier generations of cephalosporins. Extensive use of cephalosporin is also responsible for the development of enterococci as a major nosocomial infectant .Similarly in order to treat catheter associated infection caused by coagulase negative Staphylococci vancomycin was used widely leading to the formation of VRE(vancomycin resistant enterococci. Hospitals provide the environment for the accumulation of such antibiotic resistant organisms from patients as well as their spread to normal as well as other patients. Selection of antibiotic resistance follows the classical expression of “survival of the fittest”. But the resistant pathogens are fittest only in the presence of antibiotics. Usage of broad spectrum antibiotics also removes the normal host microbial flora, thus, providing a more suitable place for the resistant pathogens to proliferate. 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. REFERENCES Bawdon et al. "Antibiotic resistance in anaerobic bacteria: molecular biology and clinical aspects." . Rev Infect Dis 1 (1982): 1075-95. Print. Bozdogan, Bülent, Duygu Esel, Cynthia Whitener, Frederick A. Browne, and Peter C. Appelbaum. "Antibacterial susceptibility of a vancomycin-resistant Staphylococcus aureusstrain isolated at the Hershey Medical Center." Journal of Antimicrobial Chemotherapy 52.5 (2003): 864-868. Print. Bradford, Patricia A. "Extended-Spectrum -Lactamases in the 21st Century: Characterization, Epidemiology, and Detection of This Important Resistance Threat."Clinical Microbiology Reviews 14.4 (2001): 933–951. Print. Caini et al. 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