Antibiotics, Antibiotics Resistance, Action of Antibiotics, Mechanism of Antibiotics Resistance, Generation of Antibiotics

1. ANTIBIOTICS RESISTANCE!
THE SILENT TSUNAMI
ERASMUS EXCHANGE STUDENT
AHMAD ALI
_______________________________________________________________
DEPARTMENT OF MOLECULAR GENETICS
UNIVERSITY OF ALEXANDRA IOAN CUZA, IASI
ROMANAIA
PROJECT
PRESENTED TO
PROF DR. SIMON DUNCA
APPLICATION OF MICROBIAL BIOTECHNOLOGY

2. OBJECTIVES:
 Background
Why antibacterial resistance is a concern?
 How antibacterials works?
 Mechanisms of resistance to antibacterials
Generation of antibiotics
Conclusion
References

3. ANTIBIOTIC RESISTANCE!
 The ability of bacteria and other micro-organisms to with stand to an antibiotics and
inhibit the antibiotics at the site of infection called antibiotics resistance.
 In 1945 Fleming himself warned of the danger of resistance – According to him
““It is not difficult to make microbes resistant to penicillin in the laboratory by exposing
them to concentrations not sufficient to kill them, and the same thing has occasionally
happened in the body.
OR
by exposing his microbes to non-lethal quantities of the drug make them resistant.”

4. HISTORY OF RESISTANCE
 Throughout history there has been a continual battle
between human beings and multitude of micro-organisms
that cause infection and disease.
 Penicillin was successful in controlling bacterial infections
among World War II soldiers.
 However, shortly thereafter, penicillin resistance became
a substantial clinical problem.
 In response, new beta-lactam antibiotics were discovered,
developed, and deployed, restoring confidence.
 Figure in next slide show the variation and increase in the
antibiotic resistance

5. ANTIBIOTIC RESISTANCE CRISIS

6. WHY RESISTANCE IS A CONCERN! THREAT
 Resistant organisms lead to treatment failure
 Increased mortality
 Resistant bacteria may spread in Community
 Low level resistance can go undetected
 Added burden on healthcare costs
 Threatens to return to pre-antibiotic era
 Selection pressure

7. A COMPLEX GLOBAL CHALLENGE!THREAT TO HUMANITY
Read Antimicrobial Resistance – A Threat to the World’s Sustainable
Development.

8. GLOBAL DISRUPTION OF ANTIBIOTIC-RESISTANT BACTERIA

9. HOW ANTIBIOTICS WORK?
4 Ways Antibiotics Affect
Bacterial Cells:
1. Disrupt cell wall
synthesis
2. Inhibit metabolic
pathway
3. Inhibit protein
synthesis
4. Inhibit DNA
replication

10. HOW THE ANTIBIOTICS DEGRADE THE BACTERIAL CELL
WALL:
 Most bacteria produce a cell wall
that is composed partly of a
macromolecule called peptidoglycan,
itself made up of amino sugars and
short peptides.
 Human cells do not make or need
peptidoglycan.
 Penicillin, one of the first antibiotics
to be used widely, prevents the final
cross-linking step, or
transpeptidation, in assembly of this
macromolecule.
 The result is a very fragile cell wall
that bursts, killing the bacterium.
 No harm comes to the human host
because penicillin does not inhibit
any biochemical process that goes on
within us.

11. INHIBIT METABOLIC PATHWAY
 Bacteria can also be selectively
eradicated by targeting their
metabolic pathways.
 Sulfonamides, such as
sulfamethoxazole, are similar in
structure to para-aminobenzoic acid,
a compound critical for synthesis of
folic acid.
 All cells require folic acid and it can
diffuse easily into human cells.
 But the vitamin cannot enter
bacterial cells and thus bacteria must
make their own.
 The sulfa drugs such as sulfonamides
inhibit a critical enzyme--
dihydropteroate synthase--in this
process.
 Once the process is stopped, the
bacteria can no longer grow.

12. INHIBIT PROTEIN SYNTHESIS
 Another kind of antibiotic—
tetracycline, also inhibits bacterial
growth by stopping protein
synthesis.
 Both bacteria and humans carry out
protein synthesis on structures called
ribosomes.
 Tetracycline can cross the
membranes of bacteria and
accumulate in high concentrations in
the cytoplasm.
 Tetracycline then binds to a single
site on the ribosome--the 30S
(smaller) ribosomal subunit--and
blocks a key RNA interaction, which
shuts off the lengthening protein
chain.
 however, in human cells tetracycline
does not accumulate in sufficient
concentrations to stop protein
synthesis.

13. INHIBIT DNA REPLICATION
 DNA replication must occur in both bacteria and human cells.
 The process is sufficiently different in each that antibiotics such as
ciprofloxacin--a fluoroquinolone notable for its activity against the anthrax
bacillus--can specifically target an enzyme called DNA gyrase in bacteria.
 This enzyme relaxes tightly wound chromosomal DNA, there by allowing
DNA replication to proceed.
 But this antibiotic does not affect the DNA gyrases of humans and thus,
again, bacteria die while the host remains unharmed.

14. MECHANISMS OF RESISTANCE
 The abilities of bacterial organisms to utilize the various strategies to resist
antimicrobial compounds are all genetically encoded.
 Intrinsic resistance: is that type of resistance which is naturally coded and
expressed by all (or almost all) strains of that particular bacterial species. An
example of instrinsic resistance is the natural resistance of anaerobes to
aminoglycosides and Gram-negative bacteria against vancomycin.
 Acquired resistance: Changes in bacterial genome through mutation or
horizontal gene acquisition,on the other hand, may consequently lead to a
change in the nature of proteins expressed by the organism.
 Such change may lead to an alteration in the structural and functional
features of the bacteria involved, which may result in changes leading to
resistance against a particular antibiotic.
 In fact, several different mechanisms may work together to confer
resistance to a single antimicrobial agent.

15. STRATEGY 1: PREVENTING ACCESS OF ANTIMICROBIAL MOLECULE
 Antimicrobial compounds almost always require access
into the bacterial cell to reach their target site where
they can interfere with the normal function of the
bacterial organism.
 Porin channels are the passageways by which these
antibiotics would normally cross the bacterial outer
membrane.
 Some bacteria protect themselves by prohibiting these
antimicrobial compounds from entering past their cell
walls. For example, a variety of Gram-negative bacteria
reduce the uptake of certain antibiotics, such as
aminoglycosides and beta lactams, by modifying the cell
membrane porin channel frequency, size, and
selectivity.
 Prohibiting entry in this manner will prevent these
antimicrobials from reaching their intended targets that,
for aminoglycosides and beta lactams, are the
ribosomes and the penicillin-binding proteins (PBPs),
respectively.
 This strategy have been observed in: Pseudomonas
aeruginosa against imipenem (a beta-lactam antibiotic).
 Many Gram-negative bacteria against aminoglycosides.
 Many Gram-negative bacteria against quinolones.

16. STRATEGY 2: MODIFICATION OF THE ANTIMICROBIAL TARGET/ BY MODIFICATION OR
DEGRADATION
 Some resistant bacteria evade antimicrobials by
reprogramming or camouflaging critical target sites to
avoid recognition.
 Therefore, in spite of the presence of an intact and active
antimicrobial compound, no subsequent binding or
inhibition will take place.
Bacterial Resistance Due To Target Site Modification:
1. Alteration in penicillin-binding protein (PBPs) leading
to reduced affinity of beta-lactam antibiotics.
i,e (Methicillin-Resistant Staphylococcus aureus, S.
pneumoniae, Neisseria gonorrheae, Group A
streptococci, Listeria monocytogenes).
2. A classic example is the hydrolytic deactivation of the
beta-lactam ring in penicillins and cephalosporins by the
bacterial enzyme called beta lactamase. The inactivated
penicilloic acid will then be ineffective in binding to
PBPs (penicllin binding proteins), thereby protecting the
process of cell wall synthesis.
This strategy has also been observed in:
 Enterobacteriaceae against chloramphenicol (acetylation).
 Gram negative and Gram positive bacteria against
aminoglycosides (phosphorylation, adenylation, and
acetylation).

17. 3. ELIMINATING ANTIMICROBIAL AGENTS FROM THE CELL WITH EXPULSION VIA
EFFLUX PUMPS.
 To be effective, antimicrobial agents must also
be present at a sufficiently high concentration
within the bacterial cell.
 Some bacteria possess membrane proteins
that act as an export or efflux pump for certain
antimicrobials, extruding the antibiotic out of
the cell as fast as it can enter.
 This results in low intracellular concentrations
that are insufficient to elicit an effect.
 Some efflux pumps selectively extrude specific
antibiotics such as macrolides, lincosamides,
streptogramins and tetracyclines, whereas
others (referred to as multiple drug resistance
pumps) expel a variety of structurally diverse
anti-infectives with different modes of action.
 Staphylococcus aureus and Streptococcus
pneumoniae against fluoroquinolones.

18. GENERATION OF ANTIBIOTICS
 Generation term comes only in case of Penicillins and Cephalosporins
(Beta lactam antibiotics) and depending on their action on the cell wall
of gram positive and gram negative bacteria.
 They are classified by using terms ‘ Broad spectrum’ and ‘Narrow
spectrum’ antibiotics.
1st Generation Antibiotics:
 Have a narrow spectrum of clinical use (this means there are only a
few organisms that they are able to successfully treat with this class of
penicillin) .
 Good for common gram-positive bacteria that cause ear and throat
infections, venereal diseases of gonorrhea and syphilis.
 A very high number of the drugs in this group are resistant to
organisms that produce penicillinase.

19. 2ND AND 3RD GENERATION ANTIBIOTICS
 2nd generation antibiotics have an extended or Intermediate
spectrum of clinical use (Some gram +ve and gram-ve).
 Not very effective against penicillinase producing organisms
 3rd generation antibiotics are broad spectrum and the effective
against both gram positive and gram negative bacteria.
 However their optimum activity is against gram negative bacteria. not
resistant to penicillinase-producing organisms.
 4th Generation Antibiotics are extended spectrum antibiotics.
 They are not resistant to Beta lactamase producing microorganisms.
 5th Generation antibiotics are Extended spectrum Antibiotics.
 Cephtaroline : Pneumonia, skin and soft tissue infection.
 Cephtobiprole: Methicillin resistant Staphylococcus aureus.

20. A DILEMMA
 We need a much greater understanding of the
specific microorganisms that cause disease, their
biology and their interactions with the host.
 There is a need to move from broad-spectrum
empirical therapy that is no longer effective in the
resistance era to the more personalized approach
of the emerging narrow-spectrum era.

21. CONCLUSION
 The importance and value of antibiotics cannot be
overestimated; we are totally dependent on them for the
treatment of infectious diseases.
 The best practice can be that doctors and health care
centres should provide their patients places that are
resistance-free by taking strict measures in infection
control and antibiotic use.
 There is no perfect antibiotic, and once the most
appropriate uses of any new compound are identified, it is
essential that prescription of the antibiotic be restricted to
those uses.

22. REFERENCES
1. World Health Organization. 2014. Antimicrobial Resistance: Global Report
on Surveillance 2014. WHO, Geneva Switzerland. http://www
.who.int/drugresistance/documents/surveillancereport/en/.
2. Cosgrove SE. 2006. The relationship between antimicrobial resistance and
patient outcomes: mortality, length of hospital stay, and health care costs.
Clin Infect Dis 42(Suppl 2): S82–S89.
3. DiazGranados CA, Zimmer SM, Klein M, Jernigan JA. 2005. Comparison of
mortality associated with vancomycin-resistant and vancomycinsusceptible
enterococcal bloodstream infections: a meta-analysis. Clin Infect Dis
41:327–333.
4. Antibiotic Resistance Threats in the United States. Centers for Disease
Control and Prevention, 2013. CDC, Atlanta, GA.
http://www.cdc.gov/drugresistance/threat-report -2013/index.html.
5. The Review on Antimicrobial Resistance. 2014. Antimicrobial Resistance:
Tackling a Crisis for the Future Health and Wealth of Nations. http://amr-
review.org.
6. Sengupta S, Chattopadhyay MK, Grossart HP. The multifaceted roles of
antibiotics and antibiotic resistance in nature. Front Microbial. 2013; 4:47.

23. REFERENCES
7). Spellberg B, Gilbert DN. The future of antibiotics and resistance: a tribute to a career of
leadership by John Bartlett. Clin Infect Dis. 2014; 59 (suppl 2):S71–S75.
8). Gould IM, Bal AM. New antibiotic agents in the pipeline and how they can overcome microbial
resistance. Virulence. 2013;4(2):185–191.
9). Centers for Disease Control and Prevention, Office of Infectious Disease Antibiotic resistance
threats in the United States, 2013. Apr, 2013. Available
at: http://www.cdc.gov/drugresistance/threat-report-2013.
10). Publichealthonline.gwu.edu/content/, mechanisms-of-antibiotic-resistance.png
11). Wilson DN. 2014. Ribosome-targeting antibiotics and mechanisms of bacterial resistance.
Nat Rev Microbiol 12:35–48.
12). Ramirez MS, Tolmasky ME. 2010. Aminoglycoside modifying enzymes. Drug Resist Update
13:151–171.
13). Hollenbeck BL, Rice LB. 2012. Intrinsic and acquired resistance mechanisms in
enterococcus. Virulence 3:421–433.
14). Schwarz S, Kehrenberg C, Doublet B, Cloeckaert A. 2004. Molecular basis of bacterial
resistance to chloramphenicol and florfenicol. FEMS Microbiol Rev 28:519–542.
15). Abraham EP, ChainE.1940.An enzyme from bacteria able to destroy penicillin. Nature
146:837.
16). D’Costa VM, King CE, Kalan L, Morar M, Sung WW, Schwarz C, Froese D, Zazula G,
Calmels F, Debruyne R, Golding GB, Poinar HN, Wright GD. 2011. Antibiotic resistance
is ancient. Nature 477:457–461.