Introduction to MDR and MDR-TB. Types of MDR, History and Diagnostic methods, Antibiotics used and their Mechanism, Mechanism of resistance towards Antibiotics by the bacteria and Future Technologies

1. MULTI-DRUG RESISTANCE
IN MYCOBACTERIUM SP.
PRESENTED BY- PARTH, ANJALI, ANAMKIA, ARCHALA, MANISHA, KIRTI

2. INTRODUCTION TO MDR
◦ Ability of a cell to resist or withstand excessive, lethal doses of more than 1 drug used against
nonresistant cells
◦ The primary mechanisms that give rise to MDR include:
(1) Modification of drugs; their inactivation by enzymes of the target cell
(2) Mutations or post-translational modification of the cellular targets
(3) In bacteria, increased cell wall and outer membrane impermeability to drugs
(4) Active efflux of drugs by membrane-bound multidrug efflux transporters

3. MDR IN BACTERIA
1. Streptococcus pneumonia- dual resistance to penicillin and erythromycin
2. Enterobacteriaceae- resistance to antibiotics, including ampicillin, chloramphenicol,
kanamycin, streptomycin, tetracycline, and trimethoprim
3. Neisseria gonorrhoeae- Fluoroquinolone resistance is associated with resistance to
penicillin and tetracycline
4. Mycobacterium tuberculosis- resistance to isoniazid, rifampin, ethambutol, and
streptomycin
5. Staphylococcus aureus- resistance to penicillin, erythromycin, clindamycin, tetracycline,
levofloxacin, gentamicin, and trimethoprim,
MDR IN PARASITES
• The most common example for MDR against antiparasitic drugs is malaria
• Plasmodium vivax has become chloroquine and sulfadoxine pyrimethamine resistant

4. MDR IN FUNGI
◦ Multidrug resistance in fungi comes from non-pathogenic yeast Saccharomyces cerevisiae, in
which the multidrug-resistant phenotype is referred to as pleiotropic drug resistance or Pdr
◦ Candida species have become resistant under long term treatment with azole preparations
MDR IN VIRUS
o HIV is the most common disease that faced MDR against antivirals, as it mutates rapidly
under monotherapy
o Influenza virus has become increasingly MDR; first to amantadines, then to neuraminidase
inhibitors such as oseltamivir

5. TYPES OF MDR
◦ MDR (Multidrug-resistant) Acquired non-susceptibility to at least one agent in three or more
antimicrobial categories
◦ XDR (extensively drug-resistant) Non-susceptibility to at least one agent in all but two or
fewer antimicrobial categories, such as resistance to the first-line
agents isoniazid and rifampicin, to a fluoroquinolone and to at least one of the three-second-
line parenteral drugs (i.e. amikacin, kanamycin or capreomycin)
◦ PDR (Pan-drug-resistant) Defined as non-susceptibility to all agents in all antimicrobial
categories. ‘resistant to all antimicrobials routinely tested’ and ‘resistant to all antibiotic classes
available for empirical treatment

6. INTRODUCTIO
N TO MDR-TB
MDR-TB caused by
strain of mycobacterium
tuberculosis , the
bacteria when develop
resistance to
antimicrobial drug and
does not respond to
both isoniazid and
rifampicin (two most
powerful anti tb drug)
Single isoniazid or
rifampicin resistance is
not MDR-TB

7. DRUG RESISTANT TB- GLOBAL SITUATION
◦ Globally in 2016, there were an estimated 4.1% of new cases and 19% of previously treated
cases with MDR-TB
◦ Drug resistance surveillance data show that an estimated 240 000 people died from MDR-TB
in 2016
◦ In spite of increased testing, the number of MDR-TB cases detected in 2016 only reached 153
000
◦ In 2016, 8 000 patients with extensively drug-resistant TB (XDR-TB) were reported worldwide.
To date, 123 countries have reported at least one XDR-TB case. On average, an estimated
6.2% of people with MDR-TB have XDR-TB

9. CLASSIFICATION OF DRUG
Depending upon the effectiveness and side effects, drugs are classified into the following 3
groups
◦ First line drug – are most effective and with lowest toxicity
Includes-isoniazid and rifampicin , streptomycin , ethambutol
◦ Second line drug – less effective and show more toxic effect
Includes – p-amino salicylic acid ,fluoroquinolones
◦ Third line drug – are least effective and are most toxic
Includes- amikacin, kanamycin, capreomycin, viomycin, Cycloserine

10. DIAGNOSIS AND MODE
OF ACTION OF
MYCOBACTERIUM SP.

11. ◦ Devastating effect on society
◦ On March 24, 1882, Dr. Robert Koch announced the discovery
of Mycobacterium tuberculosis, the bacteria that causes
tuberculosis (TB)
◦ Johann Schoenlein coined the term “tuberculosis” in the 1834
◦ 100 years ago one in five of the population was destined to
die of tuberculosis
◦ Families suffer psychologically, socially and economically
◦ TB is highly stigmatized, especially in Women
◦ Chopin, Keats, the Brontes, Kafka and D.H. Lawrence all
from the Disease
TUBERCULOSIS IN HISTORY

12. ◦ Mycobacteria retain the primary stain even after exposure to decolorizing acid- alcohol, hence the term
“acid-fast bacilli” (AFB)
◦ Ziehl-Neelsen Fluorescence
◦ M. tuberculosis bacilli can be found singly, in clumps or in clusters
DIAGNOSIS OF TB BY MICROSCOPY

13. ◦ New definition in 2007:
◦ "person with al least one smear-positive sample (1AFB is sufficient) out of a total of two
examined
◦ The definition can be applied to countries performing microscopy under satisfactory
quality assurance programs
SMEAR MICROSCOPY

14. ADVANTAGES AND LIMITATIONS OF
SMEAR MICROSCOPY
ADVANTAGES
◦ Rapid
◦ Robust
◦ Cheap
◦ Accessible to the majority of patients
◦ Does not require extensive infrastructure
Limitations
◦ Low sensitivity: 104-105 bacilli/ml.
◦ Detects both dead and viable bacilli.
◦ Does not distinguish tubercle bacilli from
other mycobacteria.

15. ADVANTAGES AND LIMITATIONS OF
CULTURE
ADVANTAGES
◦ Detects small numbers of bacilli/ml,
depending on the techniques used
◦ Improves case detection: often
microscopy
◦ Provides definitive diagnosis
◦ Confirms diagnosis of TB
◦ Allows species identification
◦ Allows DST and drug resistance
◦ Allows epidemiological studies surveys
LIMITATIONS
◦ High cost
◦ Slow growth of M. tuberculosis: delays
results
◦ More sensitive to technical deficiencies
◦ Greater need for infrastructure:
1. qualified staff
2. equipment
3. additional safety measures

16. NATIONAL TUBERCULOSIS PROGRAM
(NTP)
◦ The NTP s a joint effort of the government and community which aims to achieve TB control
at country level
◦ The objectives of the NTP are:
-to reduce mortality, morbidity and disease transmission and avoid the development of drug
resistance;
-in the long term, to eliminate the suffering caused by TB

17. PULMONARY TB
◦ Diagnosing pulmonary TB – TB that affects the lungs – can be difficult, and several tests are usually needed.
◦ X-ray Helps to look for changes in the appearance of lungs that are suggestive of TB
◦ Samples of phlegm will also often be taken and checked for the presence of TB bacteria
◦ These tests are important in helping to decide the most effective treatment
EXTRAPULMONARY-TB
Several tests can be used to confirm suspected extrapulmonary TB, which is TB outside the lungs
These tests include:
1. CT scan, MRI scan or ultrasound scan of the affected part of the body
2. endoscopy – the endoscope can be inserted through a natural opening, such as your mouth, or through a
small cut made in your skin
3. laparoscopy if there's a need to check other parts of your body
urine and
4. blood tests
5. biopsy – a small sample of tissue or fluid is taken from the affected area and tested for TB bacteria
6. Lumbar puncture; a small sample of cerebrospinal fluid (CSF) is taken from the base of your spine. CSF is
fluid that surrounds the brain

18. TESTING FOR LATENT TB
◦ Latent TB – Infected with TB bacteria, but do not have any symptoms
◦ Need to have a test if been in close contact with someone known to have active TB disease
involving the lungs
◦ Or if recently spent time in a country where TB levels are high
◦ If you've just moved to the UK from a country where TB is common, you should be given
information and advice about the need for testing. Your GP may suggest having a test when
you register as a patient

19. MANTOUX TEST
◦ Widely used test for latent TB
◦ Injecting a small amount of a substance called PPD tuberculin into the skin of your forearm, called the
tuberculin skin test (TST)
◦ If you have a latent TB infection, your skin will be sensitive to PPD tuberculin and a small, hard red bump
will develop at the site of the injection, usually within 48 to 72 hours of having the test
◦ If you have a very strong skin reaction, you may need a chest X-ray to confirm whether you have active
TB disease
◦ If you do not have a latent infection, your skin will not react to the Mantoux test
◦ However, as TB can take a long time to develop, you may need to be screened again at a later stage
◦ If you've had the BCG vaccination, you may have a mild skin reaction to the Mantoux test. This does not
necessarily mean you have latent TB

20. INTERFERON GAMMA RELEASE ASSAY (IGRA)
◦ The interferon gamma release assay (IGRA) is a
blood test for TB that's becoming more widely
available
◦ The IGRA may be used to help diagnose latent
TB:
1. if you have a positive Mantoux test
2. if you previously had the BCG vaccination – the
Mantoux test may not be reliable in these
cases
3. as part of your TB screening if you've just
moved to the UK from a country where TB is
common

21. OLD AND NEW DRUGS INVOLVED
First – line antituberculosis drugs - oral drugs
◦ Isoniazid (INH)
◦ Rifampicin (RIF)
◦ Ethambutol (EMB)
◦ Streptomycin (SM)
Newly developed drugs
◦ Bedaquiline
◦ Pretomanid and delamanid
◦ SQ109
◦ Linezolid
◦ Clofazimine
Second – line antituberculosis drugs – sub divided
into-
o Fluoroquinolones -
◦ Ofloxacin (OFX)
◦ Levofloxacin (LEV)
◦ Moxifloxacin (MOX)
◦ Ciprofloxacin (CIP)
o Injectable antituberculosis drugs -
◦ Kanamycin (KAN)
◦ Amikacin (AMK)
◦ Capreomycin (CAP)

23. ISONIAZID (INH)
◦ Introduced in 1952
◦ One of the most effective and specific antituberculosis drug
◦ Prodrug; activated by catalase-peroxidase enzyme coded by katG
gene
◦ Active INH products are targeted by enzymes, fatty acid enoyl acyl
carrier protein (ACP) reductase A (InhA) and
beta ketoacyl ACP synthase (KasA)
◦ Active against metabolically active replicating bacilli
◦ Mode of action - inhibit mycolic acid synthesis most effectively in
dividing cells

24. RIFAMPICIN (RIF)
◦ Introduce in 1972; excellent sterilizing activity
◦ Active against non-growing bacilli
◦ Mode of action- Binds to β-
subunit of RNA polymerase (rpoB), the
enzyme responsible for transcription and expression
of mycobacterial genes
◦ Leads to inhibition of the bacterial transcription activity due to
conformational changes determining low affinity for the drug

25. ETHAMBUTOL
◦ Ethambutol (EMB) (dextro – 2,2' - (ethylenediimino)di- 1 –
butanol), which is an essential first- line drug
◦ Common side effects - dizziness, blurred vision, nausea, loss
of appetite, breathlessness
◦ EMB is an inhibitor of mycobacterial Arabinosyl
transferases, which involved in the polymerization reaction
of arabinogalactan, an essential component of the
mycobacterial cell wall
◦ Mutation in the embCAB operon are responsible for resistance
to EMB
Probable mechanism of action

26. Drugs Drug mode of action Gene Target enzyme
pyrazinamide Disrupts plasma membrane and energy
metabolism (inhibits pantothenate and CoA
synthesis)
pncA pyrazinamidase
streptomycin Inhibits protein synthesis rpsL
rrs
gidB
Ribosomal protein S12
16s rRNA
7- methyltransferase
fluoroquinolones Introduce negative supercoils in DNA
molecules
gyrA
gyrB
DNA gyrase
Kanamycin/
amikacin
Inhibits protein synthesis rrs 16S rRNA
Capreomycin/
viomycin
Inhibits protein synthesis rrs
tlyA
16S rRNA
rRNA methyltransferase
Ethionamide Disrupt cell wall biosynthesis by inhibition of
mycolic acid synthesis
InhA
ethA
ethR
Fatty acid enoyl acyl carrier protein reductase
A
Flavin monooxygenase
Transcriptional repressor

27. BEDAQUILINE
◦ First FDA approved TB drug in almost 40
years
◦ Bedaquiline (TMC207) is highly active;
against both growing and non growing
mycobacterial populations
◦ Inhibits the proton pump of
mycobacterial ATP synthase
◦ Side effects – headache, dizziness,
malaise, joint pain, QT prolongation and
increases in liver enzymes

28. DELAMANID
◦ Pro- drug that need to be activated by M. tuberculosis
◦ Delamanid is active against non- replicating bacteria
◦ Delamaind is nitro- imidazo- oxazole derivative that inhibits the
biosynthesis of methoxy- mycolic acid and keto- mycolic acid,
which are mycobacterial cell wall components
◦ Mutation in one of the five coenzyme F420genes (fgd1, ddn,
fbiA, fbiB, and fbiC) are associated with resistance to delamanid

29. PRETOMANID
◦ It is a prodrug activated by deazaflavin- dependent nitro reductase (Ddn)
◦ Pretomanid (PA-824) is highly active against both growing and non - growing M. tuberculosis
◦ The mechanism of action has been found to be inhibition of cell wall lipid biosynthesis and protein synthesis
◦ PA- 824 also acts directly as an nitric acid donor
◦ Mutation in ddn and fgd1 , both of which are involve in F420 coenzyme biosynthesis, are found
in mutants resistant to pretomanid

30. SQ109 (N- GERANYL-N'-(2-ADAMANTYL)ETHANE
–1,2-DIAMINE)
◦ Derived from high throughput screening of EMB (Ethambutol) analogues
◦ SQ109 is active against replicating and non – replicating bacilli
◦ Inhibits CW-synthesis and targets MmpL3, a transporter of trehalose monomycolate involved in mycolic acid
incorporation to the CW
◦ Site of action of SQ109 and its analogues, MenA, MenG targeting can affect respiration/electron transfer,
PMF collapse lead to decreased ATP biosynthesis, reduction in PMF/ATP - powered transporters (e.g.,
MmpL3), increased TMM accumulation, and decreased cell wall biosynthesis

31. CLOFAZIMINE
◦ Clofazimine (CFZ) is conventionally used for leprosy treatment
◦ Mechanism : unclear, but it appears that the bacterium ineffective
attempts to metabolize drug lead to cycle (redox cycle), which
generate toxic reactive oxygen species within the bacteria, may
target the bacterium's outer membrane by inhibiting respiratory
chain and ion transporters
◦ The inhibition of energy production through inhibiting NDH-
2 (NADH dehydrogenase) and
membrane disruption, which could lead to the inhibition of
potassium(k) uptake and subsequent reduction in ATP production
◦ Mutation in a transcriptional regulator Rv0678 lead to
upregulation of efflux pump MmpL3 and cause resistance to CFZ

32. MECHANISMS OF RESISTANCE TOWARDS
FIRST, SECOND, THIRD AND NEW CLASS ANTI-
TB DRUGS
Isoniazid
Pyrazinamide
Rifampicin
Ethambutol
Fluoroquinolones
Aminoglycosides (Streptomycin,
Kanamycin/Amikacin)
D-Cycloserine/Terizidone
Para-aminosalicylic Acid
Bedaquiline
Pretomanid
Delamanid
SQ109
Clofazimine

34. ISONIAZID
1. KatG S315 Mutations- encoding a catalase-peroxidase
◦ Most common mutation in codon 315 in INH-resistant strains, 50-90%
◦ Do not completely eliminate catalase activity, and have limited effect on fitness and virulence
◦ INH-resistant strains due to katG deletion or mutations that lead to complete loss of catalase
activity causing high-level resistance may cause loss of virulence
2. Mutations in promoter region of mabA(fabG1)/inhA operon- encoding a mycolic acid
biosynthetic pathway enzyme
◦ Overexpression of InhA or by mutations at the InhA active site
◦ Usually associated with low-level resistance (MIC 0.2–1 lg/ml) and do not cause loss of
virulence
◦ Less frequent than katG mutations. and also confer cross-resistance ethionamide (ETH)

35. 3. AhpC mutations
◦ Over-expression of alkyl hydroperoxide reductase (AhpC) increases the MIC of INH for
smegmatis
◦ AhpC gene alterations may be a factor in INH resistance in certain M. tuberculosis strains
4. KasA mutations- encodes a β-ketoacyl-ACP synthase
◦ Nucleotide and amino-acid sequence changes at codons 66 (GAT→AAT), 269
312 (GGC→AGC) and 413 (TTC→TTA) of the KasA gene have been postulated to be
mutations associated with isoniazid resistance
◦ Originally in isoniazid-resistant, but not in isoniazid-susceptible M. tuberculosis isolates

36. PYRAZINAMIDE
1. pncA gene mutations- encodes for pyrazinamidase/nicotinamidase
◦ Highly diverse and scattered along the gene; unique to PZA resistance
◦ Most PZA-resistant M. tuberculosis strains (72–99%) have mutations in pncA
◦ Some PZA-susceptible strains were reported to have non-synonymous mutations in pncA
that cause low-level resistance
2. Ribosomal protein S1 (RpsA) mutations- involved in trans-translation
◦ RpsA target mutations are usually associated with low-level PZA resistance (MIC 200– 300
lg/ml PZA)
◦ 3-base pair “GCC” deletion resulting in the loss of an alanine at amino acid 438 in RpsA in a
low-level PZA-resistant clinical isolate, DHM444
◦ Although there are contradicting results to the above

37. 3. panD mutations- encodes for aspartate decarboxylase
◦ panD involved in the synthesis of β-alanine, a precursor for pantothenate and coenzyme A
biosynthesis
◦ Seen in PZA-resistant M. canettii strains (intrinsically resistant) and some PZA-resistant MDR-TB
strains
◦ M. canettii has mutations in both rpsA48 and panD
4. Some other examples of protein involved in resistance are-
◦ ppsA encoding polyketide synthase involved in phthiocerol dimycocerosate (PDIM) synthesis,
◦ cell division protein FtsH,
◦ TetR family transcriptional regulator (3R)-hydroxyacyl-ACP dehydratase subunit HadC,
◦ phosphate ABC transporter permease protein PstC2
◦ transmembrane transport protein MmpL4
◦ clpC1 (Rv3596c) was identified, encodes an ATP-dependent ATPase

38. RIFAMPICIN
1. rpoB gene mutations
◦ Mutations in 81-bp region of rpoB In about 96% of RMP-resistant M. tuberculosis isolates
◦ Mutation in the rpoB gene at 531 codon (serine to leucine) Highly significant, confers cross-resistance to rifabutin
◦ Mutations at codons 516, 518, 526, and 529 Associated with low-level resistance to RIF and conserved susceptibility to
other rifamycins, e.g., rifabutin or rifalazil
◦ Use of RBT for treating RMP-resistant strains could lead to the development of RMP dependence or enhancement and
potentially worsen the disease due to genetic and epigenetic changes that enhance the fitness and virulence of the
organism
◦ Mutations in rpoC or rpoA could also occur, encoding respectively for α and β' subunits of RNA polymerase
2. Mutations at F514FF, D516V and S522L
◦ They are associated with resistance to RMP but susceptibility to RBT
3. Mutations at E510H, L511P, D516Y, N518D, H526N and L533P
◦ They are not associated with RMP resistance and are found in RMP-susceptible strains

39. ETHAMBUTOL
1. embB and embC mutations-
◦ Cause resistance against ethambutol through restricting the action of drug to cease the biosynthesis
of mycobacterial cell wall
◦ Mutations in embCAB operon, in particular embB, and occasionally embC, are responsible for resistance to
EMB
◦ embCAB genes are organized as an operon; encode Arabinosyl transferases, and synthesis of
arabinogalactan
◦ embB codon 306 mutation is most frequent in clinical isolates resistant to EMB (68%)
◦ Mutations at EmbB306 leads to certain amino acid changes and cause EMB resistance. Other A.A.
substitutions show little effect on EMB resistance
◦ 35% of EMBresistant strains (MIC, 10 lg/ml) show other mechanisms of resistance
2. ubiA mutations- encode for DPPR-synthase involved in CW-synthesis
◦ They have recently been found to cause higher-level EMB resistance in conjunction with embB mutations

40. FLUOROQUINOLONES
Mutations in the quinolone resistance-determining regions (QRDR) in gyrA and gyrB-
1.gyrA mutations-
◦ Most frequent mutation, occurs in a conserved region (codon 74 to 113) of the gyrA gene
◦ Systemic review 1220 FQ-resistant M. tuberculosis isolates were subjected to sequencing of
the (QRDR of gyrA, 780 (64%) were found to have mutations. Of the gyrA mutations, 81% were
inside the QRDR and 19% outside
◦ Mutations at gyrA codons 90, 91 and 94 Present in 54% of the FQ-resistant isolates
(substitutions at amino acid 94 accounted for 37%)
◦ Mutations at positions 74 and 88 Less common.
◦ Mutations at position 80  Might not confer FQ resistance, but may represent non-functional
polymorphisms similar to mutations involving codon 95

41. 2. gyrB mutations-
◦ Occurs in codons 461 to 499
◦ The QRDR of gyrB was sequenced in 534 resistant isolates, only 17 (3%) of which had
mutations. Of the gyrB mutations, only 44% were inside the QRDR.
◦ Generally, but not consistently, associated with lower levels of FQ resistance
◦ Combined gyrA and gyrB mutations could result in a much higher level of resistance,
Asn538lle (GyrB)-Asp94Ala (GyrA) and Ala543Val (GyrB)-Asp94Asn (GyrA)
3. Other efflux pumps that might be at play in FQ resistance include antiporters LfrA and
Tap
4. A recent study in FQ-monoresistant clinical isolates of M. tuberculosis revealed high
levels of efflux pump pstB transcripts in a few of these isolates, suggesting a contribution
of the pump to resistance.

42. AMINOGLYCOSIDES
(STREPTOMYCIN,
KANAMYCIN/AMIKACIN)
◦ Resistance to SM is caused by mutations in the S12 protein encoded by the rpsL gene and 16S rRNA
encoded by the rrs gene
◦ Mutations in rpsL and rrs Principal mechanism of SM resistance, (50% and 20% of SM-resistant strains,
resp.)
◦ Mutations in gidB encoding a conserved 7-methylguanosine (m(7)G) methyltransferase specific for 16S
rRNA 20–30% of SM-resistant strains with low-level resistance
◦ Mutations in the promoter region of whiB7 Contribute to cross-resistance to SM and KM due to increased
expression of the tap efflux gene
◦ Mutations at the 16S rRNA (rrs) position 1400 cause high-level resistance to KM and AMK
◦ Mutations in the promoter region of the eis gene encodes aminoglycoside acetyltransferase and cause
low-level resistance to KM but not to AMK

43. D-CYCLOSERINE/TERIZIDONE
◦ Terizidone is a combination of two molecules of DCS
◦ DCS inhibits the synthesis of cell wall peptidoglycan by blocking the action of D-alanine racemase (Alr) and
D-alanine: D-alanine ligase (Ddl)
1. Mutations in Alr and Ddl regions
◦ Alr is involved in the conversion of L-alanine to D-alanine, which then serves as a substrate for Ddl.
◦ Overexpression of alrA encoding D-alanine racemase from M. smegmatis causes resistance to DCS in M.
bovis bacille Calmette Guerin (BCG)
◦ Overexpression of Alr confers higher resistance to DCS than Ddl overexpression in M. smegmatis,
suggesting that Alr might be the primary target of DCS
◦ However, a recent study suggests that the primary target of DCS in M. tuberculosis is Ddl
◦ Recently reported, cycA encoding D-serine, L- and D-alanine and glycine transporter is involved in the
uptake of D-Cycloserine and is considered defective in M. bovis BCG (natural resistance)

44. PARA-AMINOSALICYLIC ACID
Activates dihydropteroate synthase (DHPS, FolP) and dihydrofolate synthase (DHFS, FolC) to generate a toxic
hydroxy dihydrofolate antimetabolite which inhibits dihydrofolate reductase (DHFR, encoded by dfrA
[Rv2763c])
1. thyA mutations
◦ Mutations in thyA encoding thymidylate synthase, which reduce the utilisation of tetrahydrofolate, were
responsible for resistance in about 37% of PAS-resistant clinical isolates
2. folC and dfrA mutations
◦ Mutations in folC and dfrA have also been found in PAS-resistant strains
◦ Overexpression of the PAS drug-activating enzyme DHFS (FolC) restored sensitivity to PAS in the resistant
strain, while overexpression of the target DHFR caused PAS resistance

45. BEDAQUILINE
◦ Is highly active against M. tuberculosis (MIC 0.03 lg/ml)
◦ Inhibits mycobacterial F1F0 proton adenosine triphosphate (ATP) synthase, a novel target, leading to
ATP depletion
1. Subunit-C mutations in F1-F0 Proton ATP synthase
◦ Resistance is due to mutations in the subunit-C encoded by atpE in the F0 moiety of the mycobacterial
F1F0 proton ATP synthase, which is a key enzyme in ATP synthesis and membrane potential generation
2. Mutations in the transcriptional regulator Rv0678
◦ Recently found and leads to upregulation of efflux pump MmpL5
◦ Cause cross-resistance involving both clofazimine (CFZ) and bedaquiline

46. PRETOMANID
◦ Pretomanid (PA-824) is highly active against both growing and non-growing M. tuberculosis (MIC
0.015–0.25 lg/ml).
◦ Mutations in ddn (Rv3547) encoding deazaflavin-dependent nitroreductase
◦ Mutations in fgd1 (Rv0407) encoding F420-dependent glucose-6-phosphate dehydrogenase
◦ They both are involved in F420 coenzyme biosynthesis and, are found in mutants resistant to
pretomanid
◦ M. canetti is intrinsically resistant to pretomanid, with an MIC of 8 lg/ml

47. DELAMANID
◦ Delamanid (OPC-67683) is a new drug for treatment of MDR-TB in combination with other
drugs
◦ Delamanid inhibits mycolic acid synthesis of M. tuberculosis
◦ It has an MIC of 0.006–0.024 lg/ml, and thus appears to be 20 times more active than
pretomanid
◦ Mutations in one of the five coenzyme F420 genes (fgd1, ddn, fbiA, fbiB and fbiC) are
associated with resistance to delamanid

48. SQ109
◦ SQ109 (N-geranyl-N‘-(2-adamantyl)ethane-1,2-diamine) is active against M. tuberculosis
◦ MIC of 0.5 lg/ml
◦ Inhibits CW-synthesis
◦ Active against drug-susceptible, EMB-resistant and MDR-TB strains
◦ Targets MmpL3, a transporter of trehalose monomycolate involved in mycolic acid incorporation to the
cell-wall core
◦ Mutations in the mmpL3 gene, encoding the transmembrane transporter, are associated with SQ109
resistance

49. CLOFAZIMINE
◦ Clofazimine CFZ, has good activity against mycobacteria, including M. tuberculosis (MIC 0.5–2 lg/ml
◦ Mutations in a transcriptional regulator Rv0678 led to upregulation of efflux pump MmpL5 and caused
resistance to both CFZ and bedaquiline, as well as azole drugs
◦ Mutations in rv0678 are the main mechanism of CFZ resistance
◦ Two new genes, rv1979c and rv2535c, were found to be associated with CFZ resistance

50. REGIMENS TO TREAT MULTIDRUG-RESISTANT
TUBERCULOSIS
◦ Treatment of MDR/ XDR tuberculosis has been challenging because of its prolonged duration,
toxicity, costs and unsatisfactory outcomes
◦ Late 1990s, World Health Organization (WHO) and partners launched “DOTS-Plus” (Directly
Observed Therapy (DOT) for the Treatment of Tuberculosis. It was built upon-
1. sustained political and financial commitment
2. diagnosis of TB by quality ensured sputum smear microscopy
3. standardised short-course anti-TB treatment given under direct and supportive observation
(DOTS)
4. regular uninterrupted supply of high-quality anti-TB drugs
5. standardised recording and reporting

52. Table on innovative ongoing trials aiming to provide a proof-of-concept that treatment of MDR-/XDR-TB can
be significantly shortened and fully oral through combinations of new and old anti-TB drugs

53. CONCLUSION
◦ Therefore, the scale-up of regimens involves all new and old drugs and are useful not only for
surveillance purposes but also to inform treatment choices.
◦ use of modern technology such as sequencing, therapeutic drug monitoring, clinical decision
support systems and digital solutions, even patients experiencing multiple failures and/or
toxicities with unusual and/or more complex resistance profiles could be cured
◦ The ongoing and planned clinical trials will help care providers and offer better, shorter, more
effective and safer regimens to treat people affected by MDR-/XDR-TB while contributing to
elimination of this disease

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