short presentation including mechanism of drug resistance for each class of antibiotics in short. Also, includes in general info on drug resistance

1. Mechanism of
Drug Resistance
Presenter-
Dr Nikita Ingale,
JR3
Pharmacology GMCH Nagpur
Guide-
Dr Vijay Motghare
Professor and Head
Pharmacology, GMCH Nagpur

2. History of Drug resistance…
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- Drug resistance was described by Yong et al in a swedish country who acquired an antibiotic resistant
infection during his visit in india
- After he returned to sweden, he identified a resistant strain of klebsiella bearing a novel gene
- New delhi metallo beta lactamase is an enzyme that makes bacteria resistant to broad range beta lacta
m antibiotics and the term ‘superbug’ came into existence

3. What is Drug resistance..???
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- Drug resistance is a global problem, with evolution of microoragnisms that has provided
them block the action of antibiotics
- Antimicrobial agents were viewed as miracle cures when first introduced into clinical
practice
- Drug resistance is the reduction in effectiveness of a medication such as an antimicrobial
or an antineoplastic in treating a disease or condition
- This serious development is present with each new antimicrobial agent and challenges the
humans for development of new drugs
- Today, every major class of antibiotic is associated with the emergence of significant
resistance

4. Drug resistance
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- 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.
- e.g. gram-negative bacilli are unaffected by
penicillin G
- This type of resistance does not pose a
significant clinical problem.
Natural resistance Acquired resistance
- development of resistance by an organism (which was
sensitive before) due to the use of an AMA over a
period of time.
- Some bacteria get rapid acquisition of resistance
e.g. staphylococci, coliforms, tubercle bacilli.
- Others like Strep. pyogenes and spirochetes have not
developed significant resistance to penicillin despite its
widespread use for > 60 years.
- Pose a significant clinical problem

5. How does drug resistance occur???
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reduced entry of
antibiotic into pathogen
enhanced export of antibiotic
by efflux pumps
alteration of target
proteins
release of microbial enzymes
that alter or destroy the antibiotic

6. Genetic basis of drug resistance
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Mutation Gene transfer
Single step
Multi step
Transduction
Transformation
Conjugation

7. Mutation

8. Mutation -
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- It is a stable and heritable genetic change that occurs spontaneously and randomly among microorganisms
Any sensitive population of a microbe contains a few mutant cells
It requires higher concentration of the AMA for inhibition.
These are selectively preserved and get a chance to proliferate when the sensitive cells are eliminated by the AMA.
in time , sensitive strain gets replaced by a resistant one, as happens when a single antitubercular drug is used.
Vertical transfer of resistance
(slow and usually of lower grade)

9. Gene transfer

10. Gene transfer-
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The resistance causing gene is passed from one organism to the other; is called horizontal transfer of resistance. Rapid
spread of resistance can occur by this mechanism and high level resistance to several antibiotics (multidrug resistance) can
be acquired concurrently.
(i) Conjugation –
- Sexual contact through the formation of a bridge or sex pilus is common among gram-negative bacilli
- The gene carrying the 'resistance' or 'R' factor is transferred only if another 'resistance transfer factor' (RTF) is also
present.
- Conjugation frequently occurs in the colon, here a large variety of gram-negative bacilli come in close contact.
- Chloramphenicol resistance of typhoid bacilli, streptomycin resistance of E. coli, and many others have been traced to
this mechanism.

11. Gene transfer-
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(ii) Transduction
- It is the transfer of gene carrying resistance through the agency of a bacteriophage.
- The R factor is taken up by the phage and delivered to another bacterium which it infects.
- Certain instances of penicillin. erythromycin and chloramphenicol resistance have been found to be phage mediated.
(iii) Transformation
- A resistant bacterium may release the resistance carrying DNA into the medium and this may be imbibed by another
sensitive organism-becoming unresponsive to the drug.
- Resistance once acquired by any or the above mechanisms becomes prevalent due to the selection
pressure or a widely used AMA, i.e. presence of the AMA provides opportunity for the resistant
subpopulation to thrive in preference to the sensitive population

12. Resistant organisms

13. Resistant organisms
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Drug tolerant Drug destroying Drug impermea
ble- The target biomolecule of the
microorganism loses affinity
for a particular AMA
- e.g. certain penicillin-resistant
pneumococcal strains have
altered penicillin binding
proteins.
- Another mechanism is
acquisition of an alternative
metabolic pathway.
e.g. sulfonamide resistant
bact switch over to utilizing.
preformed folic acid in place
of synthesizing it from PABA
- The resistant microbe elaborates
enzyme which inactivates drug
- beta-lactamases are produced
by staphylococci, Haemophilus,
gonococci which inactivate
penicillin G.
- Many hydrophilic antibiotics
gain access into the bacterial
cell through specific channels
formed by protein called porins
- These porins may be lost by the
resistant strains
- e.g. concentration of some
aminoglycosides n tetracyclines
in the resistant gram-negative
bacterial strains has been found
to be much lower than that in
their sensitive counterparts

14. Cross resistance

15. Cross resistance-
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- Acquisition of resistance to one AMA conferring resistance to another AMA, to which the organism has not been
exposed, is called CROSS RESISTANCE
- This is more commonly seen between chemically related drugs
- e.g. resistance to one sulfonamide means resistance to all other sulphonamides
- resistance to one tetracycline means insensitivity to all other tetracyclines
- Resistance to one aminoglycoside may not extend to another
e.g. gentamicin-resistant strains may respond to amikacin.
- Unrelated drugs show partial cross resistance
e.g. tetracyclines and chloramphenicol, erythromycin and lincomycin.

16. Drug resistance to common
Antimicrobial agents

17. Drug resistance to Beta lactam antibiotics-
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- The beta-lactam antibiotics inhibit the transpeptidases so that cross linking of the cell wall does not take place.
- When susceptible bacteria divide in presence of this antibiotics, cell wall deficient (CWD) forms are produced.
Mechanism of resistance–
- Many bacteria are inherently insensitive to PenicillinG because in them PBPs are located deeper under lipoprotein
barrier where PnG is unable to penetrate or have low affinity for PnG.
- The primary mechanism of acquired resistance is production of penicillinase.
- Some resistant bacteria become penicillin tolerant and not penicillin destroying. Their target enzymes are altered to
have low affinity for penicillin, e.g. The methicillin-resistant Staph. aureus (MRSA) have acquired a PBP which has
very low affinity for Beta-lactam antibiotics.

18. Drug resistance to Sulphonamides-
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Sulfonamides, being structural analogues of PABA
inhibit bacterial folate synthase
FolicAcid is not formed and a number of essential metabolic reactions suffer.
Mechanism of resistance–
The resistant mutants either:
(a) produce folate synthase enzyme which has low affinity for sulfonamides or
(b) adopt an alternative pathway in folate metabolism.
When an organism is resistant to one sulfonamide, it is resistant to all other sulfonamides

19. Drug resistance to Quinolones-
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- The FQs inhibit the enzyme bacterial DNA gyrase.
- The DNA gyrase
- The FQs bind to A subunit with high affinity and interfere with its strand cutting and resealing function
Mechanism of resistance–
- Because of the unique mechanism of action, plasmid mediated transferable resistance is less likely.
- Resistance noted so far is due to chromosomal mutation producing a DNA gyrase with reduced affinity for FQs
OR
- due to reduced permeability/increased efflux of these drugs across bacterial membranes.
two A subunits - nicking of DNA
two B subunits - introduces negative supercoils then A subunit reseals it

20. Drug resistance to Aminoglycosides -
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- The aminoglycosides are bactericidal antibiotics
- Binding to ribosomes resulting in inhibition of protein synthesis
- Mechanism of resistance–
- Acquisition of cell membrane bound modifying enzymes which phosphorylate the antibiotic.
- The conjugated aminoglycosides do not bind to the target ribosomes. This is the most important mechanism of.
development of resistance lo aminoglycosides.
- Mutation decreases the affinity of ribosomal proteins and aminoglycosides

21. Drug resistance to Tetracyclines- -
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The tetracyclines are primarily bacteriostatic.
They inhibit protein synthesis by binding to 30S ribosomes in susceptible organisms.
the peptide chain fails to grow.
Mechanism of resistance–
- Resistance to tetracyclines develops slowly in a graded manner.
- the bacteria acquire capacity to pump the drug out.
- Another mechanism is protecting the binding of ribosomal binding site from tetracycline.

22. Drug resistance to Chloramphenicol -
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- Chloramphenicol inhibits bacterial protein synthesis
- It specifically attaches to the 50S ribosome near the acceptor (A) site and prevents peptide bond formation between the
newly attached aminoacid and the nascent peptide chain
Mechanism of resistance–
- Highly chloramphenicol resistant S. typhi have emerged due to transfer of R factor by conjugation.
- Decreased permeability into the resistant bacterial cells and lowered affinity of bacterial ribosome for chloramphenicol are
the other mechanisms of resistance.

23. Drug resistance and common
diseases

24. Chloroquine resistant malaria

25. Chloroquine resistant malaria -
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- Chloroquine-resistance among P vivax has been slow in developing, but P falciparum has acquired significant
resistanceand resistant strains have become prevalent in India
Mechanism of resistance–
- An efflux transporter encoded by the pfcrt (P.f. chloroquine-resistance transporter) gene, has been identified in the
membranes of the acidic vacuoles of CQ-resistant Pf
- It serves to pump out CQ from the vacuoles and thus protects the haeme detoxifying mechanism of the resistant
parasite. This appears to be the most important mechanism of CQ-reistance.
- The pfmdr gene encoded P-glycoprotein is an energy-dependent ABC transporter which confers resistance to many
antimalarials like quinine, meftoquine

26. Drug resistant tuberculosis

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Resistance to antitubercular drugs-
Isoniazid – mutation of the (KatG) gene OR inhA gene, so that the bacilli do not generate the reactive metabolite of INH.
Rifampicin - mutation in the rp0B gene reducing its affinity for the drug.
Pyrazinamide - Resistance develops rapidly if it is used alone, and is mostly due
to mutation in the pncA gene which creates active metabolite pyrazinoic acid
Ethambutol – Resistance develops slowly and is most commonly associated with mutation in embB gene, reducing the
affinity of the target enzyme for drug

28. Multidrug resistant TB-
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- A Multidrug resistant-TB (MDR-TB) case is -
-whose sputum is culture positive for Mycobacterium tuberculosis
-is resistant in vitro to Isoniazid and Rifampicin with or without resistance to other
anti-tb drugs
-based on results from a quality assured certified Culture & Drug Sensitivity Test (DST)
laboratory.

29. Extensively drug resistant TB-
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- An extensively drug resistant tuberculosis (XDR TB) case-
is an MDR-TB case
M. tuberculosis isolate is resistant to at Isoniazid, Rifampicin
Resistant to Fluoroquinolone (ofloxacin, levofloxacin, or moxifloxacin)
Resistant to any Second-line injectable anti-TB drug (kanamycin, amikacin, or capreomycin)
at a quality assured certified C & DST laboratory.
MDR-TB cases that are resistant to at least 4 mo
st effective cidal drugs,
viz. H,R,FQ and one of Km/Am/Cm.

30. Drug resistant anti
retroviral drugs

31. Drug resistant anti-retrovirals-
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- NRTIs – Zidovudine, Didanosine
- various professional bodies and health organizations like WHO and ACO recommended delaying start of ART in
asymptomatic HIV infected subjects untill the CD4 count fell to <350 cells/μL or untill symptoms/opportunistic.
infections appeared.
- strong evidence has emerged after 2013, to show that early institution of ART is associated with better clinical
outcomes in people living with HIV compared to late start ART.
- early damage can be minimized and the prognosis improved by prompt institution of ART.
- early-start ART results in a smaller pool of chronically virus infected CD4 cells and lower chances of drug resistance

32. Can drugs be given inspite of resistance???

33. Dapsone resistant leprosy

34. Dapsone resistant leprosy-
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- When dapsone resistance is encountered in an untreated patient, it is called 'primary', and indicates that the
infection was contacted from a patient harbouring resistant bacilli. Resistance which develops during monotherapy
with dapsone is called 'secondary'
The mechanism of secondary resistance-
- appears to be the same as for M. tuberculosis, i.e. selective propagation of resistant bacilli over time.
- Dapsone resistant M leprae have mutated folate synthase which has lower affinity for dapsone.
- However, the peak serum concentration of dapsone after 100 mg/day dose exceeds MIC for M leprae by nearly
500 times.
- Therefore, dapsone continues to be active against low to moderately resistant
bacilli and the risk of relapse due to dapsone resistance is reported to be only 2-3%.

35. Isoniazid resistance and streptomycin dependance-
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ISONIAZID
RESISTANCE
STREPTOMYCIN
DEPENDANCE
KAT GENE inhA GENE
High dose isoniazid

36. Can drugs be given inspite of resistance???
Yes for Dapsone and Isoniazid !
For low / moderate level r

37. Drug resistant anti
Neoplastic agents

38. Chemotherapy is the primary treatment modality that can achieve cure or prolonged remission in:
Acute leukemias
Wilms tumour
Ewing's sarcoma
Retinoblastoma
Rhabdomyosarcoma
Testicular teratomas
- Tumours often become resistant to any drug that is used repeatedly due to selection of less responsive cells.
- Mutations alter the MDR I gene which increases the concentration of P-glycoprotein (an efflux transporter) on the
surface of cancer cells, resulting in pumping out of the chemotherapeutic agents.
- This mechanism is particularly applicable to natural products like vinca alkaloids, anthracycline antibiotics, taxanes
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39. Overcoming drug
Resistance….

40. Prevention of drug resistance-
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- Control antibiotic usage with correct dose and duration
- No unduly prolonged use of AMAs so that resistant strains will get less chance to preferentially propagate.
- Use combination of AMAs whenever prolonged therapy is undertaken, e.g. tuberculosis, HIV-AIDS.
- Prefer rapidly acting and selective AMAs whenever possible,
broad-spectrum drugs should be used only when a specific one cannot be
determined
- Improve hygiene in hospitals to eliminate dissemination
of resistant organisms
- Develop new antibiotic and new advances like bacteriophage therapy

41. New drug devolopment-
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Penicillin
Penicillin resistant mutants.  Methicillin
Methicillin resistant mutants.  Vancomycin
Vancomycin resistant mutants
Ceftraroline , linezolid

42. Novel mechanism for drugs-
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Tuberculosis –
- Drugs like bedaquiline and delamanid are known to have completely novel mechanism of action
- These are reserve drugs for XDR TB
- New clinicial trials also aims at new 3 month regimen using fluoroquinolones like moxifloxacin, bedaquiline and
isoniazid for tuberulosis…
- Helpful in reducing the long duration for course of treatment

43. drug resistance29-07-2019 43
Km = Kanamycin
Lfx = levofloxacin
Eto = Ethionamide
Cs = Cycloserine
E = Ethambutol
+ Pyridoxine 100mg/day
IP = INTENSIVE PHASE
CP = CONTINUATION PHASE
IP CP
Multidrug resistant TB-

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Cm = capreomycin 1000 mg
Mfx = moxifloxacin 400 mg
High dose H = high dose isoniazid 900 mg
PAS = PAS 12 g
Cfz = clofazimine 200 mg
Lzd = linezolid 600 mg
Amx/ Clv = [875 + 125 mg] amoxicillin + clavulanate tabs morning &
one tab evening
Extensively drug resistant TB-

45. Stewardship program-
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- Antimicrobial stewardship has been defined as “the optimal selection, dosage, and duration of antimicrobial
treatment that results in the best clinical outcome for the treatment or prevention of infection, with minimal toxicity
to the patient and minimal impact on subsequent resistance.
- The goal of antimicrobial stewardship is 3-fold
1]The first goal is to work with health care practitioners to help each patient receive the most appropriate antimicrobial
with the correct dose and duration.
2]The second goal is to prevent antimicrobial overuse, misuse, and abuse.
3]The third goal is to minimize the development of resistance.

46. Insulin resistance-
46
Tolerance Resistance
Pharmacokinetic mechanism
Pharmacodynamic mechanism
siteDrug
No response due to genetic
changes or mutation in the
target
siteDrug
siteDrug
No response due to
autoinduction of drug
No response due to
downregulation of receptors

47. Insulin tolerance???
OR
Insulin resistance???
Remains a question!

48. Summary -
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- Anti microbial resistance is an emerging global threat.
- Strategies to prevent development of antimicrobial resistance should be devised and implication of
stewardship programmes in hospital institutions
- Judicious use of antimicrobial agents by health care professionals & general population obeying 4Ds
of stewardship programme
- Vigorous and intense therapy with 3-4 drugs must be instilled to prevent resistance in notorius health
conditions like tuberculosis and HIV AIDS
- There are certain drugs like dapsone and isoniazid which can be prescribed in spite of low to
moderate resistance by organisms

49. Summary -
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ANTIBIOTIC METHOD OF RESISTANCE
Chloramphenicol Reduce uptake into cell
Tetracycline Active reflex from cell
B-lactam, aminoglycosides,
chloramphenicol
Enzymatic cleavage or modification
to inactive antibiotic molecule
Sulfonamides, Trimethoprim Metabolic bypass of inhibited
reaction
Sulfonamides, Trimethoprim Modification of antibiotic target

50. References -
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- Goodman, L., Gilman, A. and Brunton, L. 13th edition, Goodman & Gilman's manual of pharmacology and therapeuti
cs. Chemotherapy of infectious diseases, New York: McGraw-Hill Medical. P1023-47
- HL Sharma & KK Sharma. Chemotherapy of microbial disease, sharma and sharma’s principles of pharmacology.3rd
edition.hyderabad, Paras Medical Publisher;2017.p699-847
- RNTCP technical and operational guidelines for tuberculosis control in India 2016, central TB division, directorate ge
neral of health services, New Delhi
- www.tbcindia.gov.in
- NNIS System; Division of Healthcare Quality Promotion, National Center for Infectious Diseases, Centers for Diseas
e Control and Prevention, Public Health Service, US Department of Health and Human Services National Nosocomia
l Infections Surveillance (NNIS) System Report, data summary from January 1992 through June 2003, issued August
2003. Am J Infect Control. 2003;31(8):481-498

51. D
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Dr Anisha
Immunomodulators
13/06/19