Antimicrobial Resistance

ANTIMICROBIAL RESISTANCE

Antimicrobial resistance results in increased morbidity, mortality, and cost of health care. Prevention of the emergence of resistance and the dissemination of resistant microorganisms will reduce these adverse effects and their attendant costs. Appropriate antimicrobial stewardship that includes optimal selection, dose, and duration of treatment, as well as control of antibiotic use, will prevent or slow the emergence of resistance among microorganisms. A comprehensively applied infection control program will interdict the dissemination of resistant strains.

Stuart Levy, MD proposed a provocative hypothesis: the intensity of antibiotic use in a population may be the most important factor in selection of resistance. Moreover, there may be a “threshold” for such selection that may differ for an individual, as compared to a population, and from one population to another. This may explain why, in intensive-care units, where there is usually a small population undergoing intensive antibiotic therapy or prophylaxis, resistance tend to be more common, pathogens are more often multiply resistant, and spread within the population is more likely. The same concept might explain resistance problems in the poultry manufacturing industry and in other setting where antibiotic use is intensive within a small and confined population. [1]

The Prevention of Antimicrobial Resistance In Hospital

The 1990s is the era of multidrug resistance. Some bacteria causing several kinds of human infectious diseases are resistant to multiple antibiotics and are continuing to increase. Resistant infections confront and thwart the treatment of some patients in the community as well as in the hospital. Major resistant hospital organisms include Staphylococcus aureus, enterococcus, Klebsiella, Enterobacter, Escherichia coli, Pseudomonas and more recently Acinetobacter. Multidrug resistant bacteria causing community acquired infections include pneumococcus, gonococcus, Mycobacterium tuberculosis, group A streptococci and E. coli. [See : NFID]

It therefore is recommended that hospitals, large and small, with and without perceived problems of bacterial resistance to antimicrobials, do the following :

1. Establish a system for monitoring bacterial resistance and antibiotic usage.
2. Establish practice guidelines and other institutional policies to control the use of antibiotics, and respond to data from the monitoring system.
3. Adopt the recommendations of the Centers for Disease Control and Prevention’s (CDC) “guidelines for Isolation Precautions in Hospitals” as concerns the isolation of patients colonized or infected with resistant microorganisms.
4. Utilize hospital committees to develop local policies and to evaluate and adopt, as appropriate, guidelines from state advisory boards and national societies.
5. Recognize that the financial well-being of the institution and the health of its patients are at stake be accountable for the implementation and enforcement of policies adopted by hospital committees.
6. By measuring outcomes, evaluate the effectiveness of the policies that are put in place.

The Joint Commission on the Accreditation of Healthcare Organizations, or a similar review organization skilled in oversight functions, should take into account the priority hospitals give to antimicrobial resistance; policies, procedures, and measurements hospitals put into place; and evidence of ongoing review of data to judge the effectiveness of the plan.

Recommendations for future studies to examine. Means to prevent and reduce the development and dissemination of antimicrobial resistance :

1. The development and testing of protocols for measuring the effect of a variety of antimicrobial usage controls is recommended for use in multiple hospitals to determine the most effective ways to prevent and reduce antimicrobial resistance in specific species to specific antimicrobial.
2. Pharmaceutical industry and governmental support for such studies is recommended and encouraged.
3. It is recommended that educational methods, including those that are interactive and computer-based, be developed to improve the appropriateness of antimicrobial prescribing.
4. It is recommended that protocols to evaluate antimicrobial resistance include the ability to relate resistance rates to the “defined drug density” (the amount of antimicrobial used per geographyc area per unit time).
5. The transfer of resistance determinants in situ in a patient population is very poorly understood. First, the genetics of resistance transfer, the construction of composite transposons, and the actual mechanism of dissemination of these elements in situ, especially intergeneric transfer within the gram-positive bacteria, all should be studied further.
6. Method for interdicting transfer of resistance requires further study, especially in the behavioral area. Novel approaches to this area are needed.
7. The efficacy of various levels of infection control precaution should be documented by controlled trials.
8. Controlled studies of behavior modification, including novel approaches, to permit the efficient application of recommended guidelines within hospitals are recommended.
9. The efficacy of quality improvement approaches to control resistance should be studied.

Microbiologic Diagnostic Tests
[Minimum Bactericidal Concentration (MBC) and Minimum Inhibitory Concentration (MIC)]
Descriptions :
Varying concentrations of an antimicrobial are prepared in liquid growth medium or on solid medium. A standard number of organisms are added to each test tube or agar plate in incubated. After the appropriate incubation period, the test tubes or agar plate that contains the lowest concentration of antibiotic that prevents visible growth is considered the MIC. The tubes that demonstrate no growth are then placed onto an antibiotic free agar an incubated for 24 hours. The MBC is the lowest concentration of drug that results in a 99,9 % reductions in the initial bacterial count.

The MIC is quantitative measure of particular drug’s activity against identified bacteria. This allows the comparison of antibiotics in order to choose the antibiotic with the lowest MICs for likely eradication of infection by use of usual doses of an antimicrobial agent. The MBC can determine if the antibiotic will kill the organism (i.e., bactericidal).

Clinical implication :

1. Although useful in selecting the antimicrobial agent, MICs are not reliable predictors of success or failure of drug therapy.
2. Susceptible organism are those with the lowest MICs that will be effectively treated by the antimicrobial.
3. Moderately susceptible organism are those less likely to be effectively treated and should therefore be treated with maximum doses of the antimicrobial.
4. Resistant organism are those with high MICs to the tested antimicrobial suggesting probable failure of treatment.

Guidelines for Testing Bacterial Pathogens for Antimicrobial Resistance

A major role of the clinical microbiology laboratory is to provide antimicrobial susceptibility testing data on bacterial isolates to guide clinicians in their choice of anti-infective therapy. Susceptibility testing data can serve both as guide to therapy and, in some instances, as an initial means of strain typing for investigations of potential outbreaks of infection.
The guidelines for testing bacterial pathogens for antimicrobial resistance are shown in table. This guide is adapted from The National Committee for Clinical Laboratory Standards Document M100S6 for initial susceptibility testing and reporting of antimicrobial agents for several bacterial pathogen groups . (Not all drugs should be reported routinely).


)*Laboratories may screen for penicillin resistance in pneumococci by using a 1 μg oxacillin disk. Organisms with zone diameters of ≥20 mm are considered susceptible to all β-lactam drugs. Isolates with zona diameters of ≤19mm should be tested by minimum inhibitory concentration method against both penicillin and cefotaxime or ceftriaxone, especially if the organism is causing invasive disease.

by Andi Surya Amal,SSi,Apt,MKes
e.mail : suryaamal88@gmail.com

Reference :

1. Shlaes DM. et al. “Society for Healthcare Epidemiology of America and Infectious Diseases Society of America Joint Committee on the Prevention of Antimicrobial Resistance: Guidelines for the Prevention of Antimicrobial Resistance in Hospitals”. Infection Control and Hospital Epidemiology, Vol. 18 No. 4, 1997, 275-291
2. Boh LE. Clinical Clerkship Manual. Applied Therapeutics, Inc, Vancouver, Washington, 1996, 5-57,
3. National Committee for Clinical Laboratory Standards Document M100S6 for initial susceptibility testing and reporting of antimicrobial agents for several bacterial pathogen groups.
4. National Foundation for Infectious Diseases

(Please see on the video below; why antimicrobial resistance is a serious problem in both the hospital and community settings. And then, do we have any solution ?)