Antimicrobial drug resistance

A brief presentation on antibiotic drug resistance.

1. ANTIMICROBIAL DRUG RESISTANCE Presented By: Dr. Manas Kr. Nath, PGT, Deptt. of Pharmacology, SMCH. Moderated By: Dr. (Mrs.) Dolly Roy, Associate Professor, Deptt. of Pharmacology, SMCH.

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3. Objectives Introduction. Definition. Timeline. Factors. Mechanisms. Control strategy. Conclusion. 09-06-2017 3 Department of Pharmacology, SMCH.

4. Introduction Discovery of anti-microbial agents created a new era in the field of Medical Science. Microbes, on the other hand, developed various mechanisms to counter this threat to their existence. Antimicrobial drug resistance is the ability of a microbe to resist the effects of medication which was previously used to treat them. 09-06-2017 4 Department of Pharmacology, SMCH.

5. C ontd .. This is responsible for millions of death worldwide and is considered as a major health concern nowadays. Antimicrobial resistance (AMR) threatens the effective prevention and treatment of an ever-increasing range of infections caused by the microbes. The cost of health care for patients with resistant infections is higher. 09-06-2017 5 Department of Pharmacology, SMCH.

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7. definition Antimicrobial resistance is the ability of a microorganism (like bacteria, viruses, and some parasites) to stop an antimicrobial (such as antibiotics, antivirals and antifungals) from working against it. 09-06-2017 7 Department of Pharmacology, SMCH.

8. Timeline of amr 09-06-2017 8 Department of Pharmacology, SMCH.

9. Factors of amr Antimicrobial Resistance Drug Related Factors Environmental Factors Patient Related Factors Prescriber Related Factors 09-06-2017 9 Department of Pharmacology, SMCH.

10. C ontd .. Environmental Factors Huge populations and overcrowding. Rapid spread due to better transport facilities. Poor sanitation. Increase in community acquired resistance. 09-06-2017 10 Department of Pharmacology, SMCH.

11. C ontd .. Ineffective infection control program. Widespread use of antibiotics in animal husbandry and agriculture and as medicated cleansing products. Release of large quantities of antibiotics into the environment during pharmaceutical manufacturing through inadequate wastewater treatment. 09-06-2017 11 Department of Pharmacology, SMCH.

12. C ontd .. Drug Related Factors Over the counter availability of antimicrobials. Counterfeit and substandard drug causing sub-optimal blood concentration. Irrational fixed dose combination of antimicrobials. Increasing use of antibiotics. 09-06-2017 12 Department of Pharmacology, SMCH.

13. C ontd .. Patient Related Factors Poor adherence of dosage Regimens. Poverty. Lack of sanitation concept. Lack of education. Self-medication. 09-06-2017 13 Department of Pharmacology, SMCH.

14. C ontd .. Prescriber Related Factors Inappropriate use of antibiotics. Increased empiric poly-antimicrobial use. Overuse of antimicrobials. Prolonged use of antimicrobials. Inadequate dosing. Lack of current knowledge and training. 09-06-2017 14 Department of Pharmacology, SMCH.

15. Mechanisms of AMR 09-06-2017 15 Department of Pharmacology, SMCH.

16. C ontd .. A) Intrinsic or Natural. B) Acquired: Genetic Methods: Chromosomal Methods: Mutations. Extra-chromosomal Methods: Plasmids: Transfer of r-Genes from one bacterium to another: Conjugation. Transduction. Transformation. Transfer of r-Genes between plasmids within the bacterium: By Transposons. By Integrons. Biochemical Mechanisms: Production of Antibiotic inactivating enzymes. Preventing drug accumulation within bacterium. Modifying/protecting target site. Use of alternative pathways for Metabolism/Growth. Quorum Sensing. 09-06-2017 16 Department of Pharmacology, SMCH.

17. Intrinsic or Natural resistance Some microbes have always been resistant to certain AMAs. They lack the metabolic process or the target site which is affected by the particular drug. This type of resistance does not pose significant clinical problem. E.g.: Mycobacterium tuberculosis is resistant to tetracyclines. Aerobic organisms are not affected by metronidazole. Gram –ve bacilli are normally unaffected by penicillin G. 09-06-2017 17 Department of Pharmacology, SMCH.

18. Acquired resistance It is the development of resistance by an organism (which was earlier sensitive) due to the use of an AMAs over a period of time. This can happen with any microbes and is a major clinical problem . This type of resistance develops either by gene transfer or by mutation or by modification in biochemical mechanisms . 09-06-2017 18 Department of Pharmacology, SMCH.

19. Genetic Methods CHROMOSOMAL METHODS: MUTATIONS It refers to a stable and heritable change in the DNA structure of the bacterial gene. Spontaneous and random mutations occur in bacterial cells at a frequency of approximately one per million cells. In any population of a microbe few mutant cells are present which require higher concentration of antibiotic for their elimination. 09-06-2017 19 Department of Pharmacology, SMCH.

20. C ontd .. During a course of antibiotic therapy, the resistant bacteria continue to grow and multiply resulting in ‘selection of mutants’ which confer resistance to the antibiotic. Mutants resulting from chromosomal mutations have reduced pathogenicity, except in cases of Mycobacteria (both tuberculosis and leprosy) and Methicillin Resistant Staphylococcus aureus . 09-06-2017 Department of Pharmacology, SMCH. 20

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22. C ontd .. Single step Mutation (Point Mutation) Mutation occurring in a single gene. Rapid emergence with high degree of resistance. E.g. Enterococci to Streptomycin. E. coli and Staphylococci to Rifampin. 09-06-2017 Department of Pharmacology, SMCH. 22

23. C ontd .. Multi step Mutation A number of genetic mutations are involved. Sensitivity to AMAs decrease in a step-wise manner. E.g. Resistance to Erythromycin, Tetracycline & Chloramphenicol. 09-06-2017 Department of Pharmacology, SMCH. 23

24. C ontd .. Extra-chromosomal Methods: Plasmids Plasmids are extra-chromosomal genetic materials serving as vectors for carrying DNA molecule. Plasmids can replicate independently and freely in cytoplasm. Plasmids which carry genes resistant to antibiotics (r-Genes) are called R-plasmids. These r-Genes can get readily transferred from one R-plasmid to another plasmid or to a chromosome. 09-06-2017 24 Department of Pharmacology, SMCH.

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26. C ontd .. Most of the drug resistance encountered in clinical practice is plasmid mediated. Transfer of resistant genes can occur between bacteria of same species or of different species. There are three mechanisms for gene transfer: Conjugation. Transduction. Transformation. 09-06-2017 26 Department of Pharmacology, SMCH.

27. C ontd .. Conjugation It is the main mechanism for transfer of resistance. The conjugative plasmids which contain the transfer r-Genes, make a connecting tube (sex pili) between the two bacteria through which the plasmid itself can pass [ in presence of a Resistance Transfer Factor (RTF)]. This is commonly observed with bacterial population at high density (as in gut  resident micro-flora can serve as reservoir for the resistant genes which can later be transferred to other invading pathogens). 09-06-2017 27 Department of Pharmacology, SMCH.

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29. C ontd .. Transduction This process involves bacteriophages which encloses a plasmid DNA and transfers it to another bacterium of the same species. Usually observed in transmission of resistant genes between strains of staphylococci and streptococci. 09-06-2017 29 Department of Pharmacology, SMCH.

30. C ontd .. Transformation Certain bacteria have the ability to pick up free DNA from the environment (i.e., from a cell belonging to closely related or the same strain), which then gets incorporated in the genome of the bacteria thereby making it resistant. 09-06-2017 Department of Pharmacology, SMCH. 30

31. C ontd .. Transfer of r-Genes between plasmids within the bacterium By Transposons These are DNA segments that cannot self-replicate but can self-transfer between plasmids or from plasmid to chromosome. The donor plasmid containing a transposon having r-Genes co-integrates with the acceptor plasmid  during the process the transposon replicates  the plasmids separate, each containing the r-Gene. E.g., some strains of staphylococci and enterococci  conferring nosocomial infection. 09-06-2017 31 Department of Pharmacology, SMCH.

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33. C ontd .. By Integrons It is a larger mobile DNA unit which can be located on a transposon. Each integron is packed with multiple gene cassettes, each containing a r-Gene attached to a small recognition site. They cannot promote self transfer, but are commonly associated with and work with transposons and conjugative plasmids. Multidrug resistance can be conferred by integrons. 09-06-2017 33 Department of Pharmacology, SMCH.

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35. Biochemical Mechanisms By producing Antibiotic inactivating enzymes Staphylococcus aureus, Neisseria gonorrhoea, Haemophilus influenzae and some enteric Gram negative rods produce β lactamase enzyme which cleaves the β lactam ring thereby inactivating β lactam antibiotics. Some Gram –ve and Gram +ve bacteria inactivates Chloramphenicol by the enzyme chloramphenicol acetyltransferase (plasmid mediated). Inactivation of Aminoglycosides by some Gram –ve and Gram +ve bacteria are mediated by the enzymes acetyltransferases, phospotransferases and adenylyltransferases (plasmid and transposon mediated). 09-06-2017 35 Department of Pharmacology, SMCH.

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37. C ontd .. By preventing drug accumulation within bacterium It is mediated either by promoting efflux or by preventing the influx of the drug. Efflux pumps (chromosomal or plasmid-mediated) are cytoplasmic membrane transport proteins which commonly operates in E. coli, P. aeruginosa, S. typhi, Staph. aureus, Stretpto. pyogenes, Strepto. Pneumoniae , N. gonorrhoeae, mycobacteria and enterococci. 09-06-2017 37 Department of Pharmacology, SMCH.

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39. C ontd .. These efflux pumps are the major mechanism of resistance for tetracyclines, fluoroquinolones and erythromycin. Some Gram –ve bacteria inhibit plasmid mediated synthesis of porin channels, which obstructs the influx of antibiotic agents (ampicillin ). 09-06-2017 39 Department of Pharmacology, SMCH.

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41. C ontd .. By modifying or protecting the target site Ribosomal point mutations for tetracyclines, macrolides and clindamycin. Altered DNA gyrase and topoisomerase for fluoroquinolones. Modified penicillin binding protein (PBPs) in Strepto. pneumoniae leading to penicillin resistance. Point mutation in β subunit of DNA-directed RNA-polymerase confers resistance to Rifampicin by Mycobacterium tuberculosis . 09-06-2017 41 Department of Pharmacology, SMCH.

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43. C ontd .. By use of alternative pathways for Metabolism/Growth Resistance to antibiotics can be conferred by developing an alternative pathway that bypasses the reaction inhibited by the antibiotic. E.g., Sulfonamide resistance occurs from overproduction of PABA. Some enteric organisms evade β lactam antibiotics by overproducing β lactamases. 09-06-2017 Department of Pharmacology, SMCH. 43

44. C ontd .. Quorum Sensing (QS) It is the process by which the microbes communicate with each other and exchange signaling chemicals (autoinducers) which allows the bacterial population to coordinate gene expression for virulence, conjugation, mobility, apoptosis and antibiotic resistance, etc. Any change can only be induced when the microbial colony reaches a critical density (quorum) and a threshold of autoinduction is reached and gene expression starts. 09-06-2017 Department of Pharmacology, SMCH. 44

45. C ontd .. Gram –ve bacteria have been found to contain several chemically distinct classes of QS-signal molecules like AHLs, AIP, AI-2 & AI-3. AI-2 QS-system is also shared by Gram +ve bacteria. Drugs targeting the QS-system may minimize microbial growth and development of antibiotic resistance. 09-06-2017 Department of Pharmacology, SMCH. 45

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47. Strategy to contain AMR Judicious use of Existing Anti-microbial Agents. Development of new Anti–microbial Agents. 09-06-2017 Department of Pharmacology, SMCH. 47

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49. Scenario of Antibiotic development 09-06-2017 Department of Pharmacology, SMCH. 49

50. Newer Approaches Phage Therapy Phage Therapy is the therapeutic use of lytic bacteriophages to treat pathogenic bacterial infections. Bacteriophage therapy can be an important alternative to antibiotics. The success rate was 80–95% with few gastrointestinal or allergic side effects. British studies also demonstrated significant efficacy of phages against Escherichia coli , Acinetobacter spp., Pseudomonas spp. and Staphylococcus aureus . 09-06-2017 Department of Pharmacology, SMCH. 50

51. C ontd .. Quorum Sensing Analogues These agents inhibit the QS system in different bacteria. These include AHL, AIP & AI-2 analogues. 09-06-2017 Department of Pharmacology, SMCH. 51

52. Conclusion Anti microbial resistance is an emerging global threat. Strategies to prevent development of antimicrobial resistance should be devised. Judicious use of antimicrobial agents by health care professionals & general population. Preventing un-judicious use of antibiotics in animal husbandry and farming practices. Avoiding incorporation of antibiotics in commercial cleansing products. Proper pharmaceutical waste management. 09-06-2017 Department of Pharmacology, SMCH. 52

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