antibiotic resistance

Problem of Antibiotic Resistance & Rational use of antibiotics

Dr. Naser Tadvi Associate Prof., Pharmacology

Objectives

• What is antimicrobial resistance • Why antibacterial resistance is a concern • How antibacterials work • Mechanisms of resistance to antibacterials • Indian scenario • NDM-1• Strategies to contain resistance • Treatment of some resistant bacterial infections • Summary

Introduction

• Throughout history there has been a continual battle between human beings and multitude of micro-organisms that cause infection and disease

In his 1945 Nobel Prize lecture, Fleming himself warned of the danger of resistance –

“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… …and by exposing his microbes to non-lethal quantities of the drug make them resistant.”

History Nobel Lecture, December 11, 1945

Sir Alexander FlemingThe Nobel Prize in Physiology or Medicine 1945

Timeline of Antibiotic Resistance

Why resistance is a concern

• 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

Drug resistance occurs in :

BACTERIA—ANTIBIOTIC RESISTANCE Endoparasites Viruses—Resistance to antiviral drugs Fungi Cancer cells

Drug Resistance

• The concentration of drug at the site of infection must inhibit the organism and also remain below the level that is toxic to human cells.

GOODMAN & GILMAN'S THE PHARMACOLOGICAL BASIS OF THERAPEUTICS - 11th Ed. (2006)

Antibiotic Resistance


Defined as micro-organisms that are not

inhibited by usually achievable systemic

concentration of an antimicrobial agent with

normal dosage schedule and / or fall in the

minimum inhibitory concentration (MIC)

range. Antibiotic Resistance (DR) = MIC / MCC > Toxic Plasma Concentration

Myths of Antibiotic Resistance

1. Drugs (antibiotics) cause organisms antibiotic resistant.

2. Antibiotic resistant organisms are more virulent

Truth

• Antibiotics select out the resistant strain

• Faulty use of antibiotics or widespread use of antibiotics increases the probability of such selection.

• Antibiotic resistant strains appear to be more virulent because we cannot kill them or stop their growth.

Mechanisms of action of antibiotics

Mechanism Antibiotic Resistance

Intrinsic (Natural) Acquired

Genetic Methods

Chromosomal Methods Mutations

Extra chromosomal Methods Plasmids


Some microorganisms may ‘born’ resistant,

some ‘achieve’ resistance by mutation or some

have resistance ‘thrust upon them’ by plasmids

Some are born great, some achieve greatness

or some have greatness thrust upon them

Intrinsic Resistance

1. Lack target : • No cell wall; innately resistant to penicillin

2. Innate efflux pumps:• Drug blocked from entering cell or ↑ export

of drug (does not achieve adequate internal concentration). Eg. E. coli, P. aeruginosa

3. Drug inactivation: • Cephalosporinase in Klebsiella

It occurs naturally.

Acquired resistance

Mutations• It refers to the change in DNA structure of the

gene.• Occurs at a frequency of one per ten million cells.• Eg.Mycobacterium.tuberculosis,Mycobacterium

lepra , MRSA. • Often mutants have reduced susceptibility

Plasmids • Extra chromosomal genetic elements can replicate

independently and freely in cytoplasm.• Plasmids which carry genes resistant ( r-genes) are called R-

plasmids.• These r-genes can be readily transferred from one R-plasmid to

another plasmid or to chromosome.• Much of the drug resistance encountered in clinical practice is

plasmid mediated

Mechanisms of Resistance Gene Transfer

• 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

Transfer of r-genes from one bacterium to another

Conjugation : Main mechanism for spread of resistance The conjugative plasmids make a connecting tube

between the 2 bacteria through which plasmid itself can pass.

Transduction : Less common method The plasmid DNA enclosed in a bacteriophage is

transferred to another bacterium of same species. Seen in Staphylococci , Streptococci

Transformation : least clinical problem. Free DNA is picked up from the environment (i.e..

From a cell belonging to closely related or same strain.

Mechanisms of Resistance Gene Transfer Transposons

Transposons are sequences of DNA that can move around different positions within the genome of single cell.

The donor plasmid containing the Transposons, co-integrate with acceptor plasmid. They can replicate during cointegration

Both plasmids then separate and each contains the r-gene carrying the transposon. Eg ; Staphylococci,Enterococci

Mechanisms of Resistance Gene Transfer Integrons

Integron is a large mobile DNA can spread Multidrug resistance

Each Integron is packed with multiple gene casettes, each consisting of a resistance gene attached to a small recognition site.

These genes encode several bacterial functions including resistance and virulence.

They cannot promote self transfer

Biochemical mechanisms of antibiotic resistance

• Prevention of drug accumulation in the bacterium

• Modification/protection of the target site

• Use of alternative pathways for metabolic / growth requirements

• By producing an enzyme that inactivates the antibiotic

• Quorum sensing

Decreased permeability: Porin Loss

Interior of organism

Cell wall

Porin channel into organism

Antibiotic

Antibiotics normally enter bacterial cells via porin channels in the cell wall

Decreased permeability: Porin Loss


Cell wall

New porin channel into organism

Antibiotic

New porin channels in the bacterial cell wall do not allow antibiotics to enter the cells

ATP Binding Cassette

Multidrug and toxic compound exporter

Small multidrug resistance transporters

Resistance-nodulation-division

Major facilitator superfamily

Efflux pumps

• Cytoplasmic membrane transport proteins.

• Major mechanism for resistance in Tetracyclines.

• Some gram -ve bacteria inhibit the plasmid mediated synthesis of porin channels ,which obstructs the influx of hydrophilic Penicillins eg.ampicillin

Structurally modified antibiotic target site


Cell wall

Target siteBinding

Antibiotic

Antibiotics normally bind to specific binding proteins on the bacterial cell surface

Structurally modified antibiotic target site


Cell wall

Modified target site

Antibiotic

Changed site: blocked binding

Antibiotics are no longer able to bind to modified binding proteins on the bacterial cell surface

Modification/Protection of the Target site

Resistance resulting from altered target sites :Target sites Resistant Antibiotics

Ribosomal point mutation Tetracyclines,Macrolides, Clindamycin

Altered DNA gyrase FluoroquinolonesModified penicillin binding

proteins (Strepto.pneumonia)Penicillins

Mutation in DNA dependant RNA polymerase (M.tuberculosis)

Rifampicin

Antibiotic inactivation


Cell wall

Antibiotic

Target siteBindingEnzyme

Inactivating enzymes target antibiotics



Cell wall

Antibiotic

Target siteBindingEnzyme

Enzymebinding

Enzymes bind to antibiotic molecules



Cell wall

Antibiotic

Target siteEnzyme

Antibioticdestroyed

Antibiotic altered,binding prevented

Enzymes destroy antibiotics or prevent binding to target sites

By producing enzymes that inactivates antibiotic

a)Inactivation of b-lactam antibiotics• S. aureus, N. gonorrohoea, H.influenza, Produce b-

lactamase which cleaves -lactam ring

b)Inactivation of Chloramphenicol• Inactivated by chloramphenicol acetyltransferase .• Gram-ve (enzyme present constitutively hence higher

resistance) gram +ve bacteria (enzyme is inducible )

c)Inactivation of Aminoglycosides• Inactivated by acetyl, phospho & adenylyl transferases

Present in gram +ve and gram –ve .

Use of alternative pathways for metabolic / growth requirements

• Resistance can also occur by alternate pathway that bypasses the reaction inhibited by the antibiotic.

• Sulfonamide resistance can occur from overproduction of PABA

Drug Mechanism of resistance

Pencillins & Cephalosporiins

B Lactamase cleavage of the Blactam ring

Aminoglycosides Modification by phosphorylating, adenylating and acetylating enzymes

Chloramphenicol Modification by acetylytion

Erythromycin Change in receptor by methylation of r RNA

Tetracycline Reduced uptake / increased export

SulfonamidesActive export out of the cell & reduced affinity of enzymes

Quorum sensing

• Microbes communicate with each other and exchange signaling chemicals (Autoinducers)

• These autoinducers allow bacterial population to coordinate gene expression for virulence, conjugation, apoptosis, mobility and resistance

Why named quorum sensing • Single autoinducer from single microbe is

incapable of inducing any such change• But when its colony reaches a critical density

(quorum), threshold of autoinduction is reached and gene expression starts

• QS signal molecules AHL, AIP, AI-2 & AI-3 have been identified in Gm-ve bacteria

• AI-2 QS –system is shared by GM+ve bacteria also

WHY INHIBIT QUORUM SENSING

Proved to be very potent method for bacterial virulence inhibition.

Several QS inhibitors molecules has been synthesized which include AHL, AIP, and AI-2 analogues

QS inhibitors have been synthesized and have been isolated from several natural extracts such as garlic extract.

QS inhibitors have shown to be potent virulence inhibitor both in in-vitro and in-vivo,using infection animal models.

Indian scenario

Indian scenario

• Lack of community awareness• Availability over the counter • Absence of central monitoring agency • In infants LRTI has taken over IMR due to

diarrhoeal diseases due to use of ORT • S. Pneumoniae fully resistant to cotrimoxazole • Still sensitive to penicillins, macrolides and

fluoroquinolones

Enteric pathogens

• Vibrio cholerae : – resistance to furazolidine, cotrimoxazole, nalidixic

acid – Tetracycline remains effective

• Coliforms – ESBLs , extensive resistance to Beta lactum

antibiotics • Enteric fever

STD

• Penicillin and fluoroquinolone resistance is widespread to gonorhhoea

• Alternate drugs like Azithromycin and cephalosporins should be used

• Syphilis still susceptible to Penicillins

Gram positive Cocci

• Streptococci other than S. Pneumoniae – Resistant to tetracycline and macrolides (40%)– Still sensitive to penicillins

• Staph Aureus– Methicillin resistance 50%-100%– Vancomycin resistance also increasing

Mycobacteria

• Multidrug resistance – Combined resistance to rifampicin and isoniazid

• Extensively drug resistant TB– Additional acquisition of resistance to a

fluroquinolone and one of the three injectable second line drugs (capreomycin, kanamycin and amikacin)

• Steady rise in these patients

What is NDM-1?• NDM-1 stands for New Delhi metallo-beta-

lactamase, an enzyme produced by certain strains of bacteria that have recently acquired the genetic ability to make this compound.

• The enzyme is active against other compounds that beta-lactam ring like penicillins, cephalosporins, and the carbapenems.

• bacteria that produce NDM-1 are resistant to all commonly used beta-lactam antibiotics, including carbapenems.

http://www.medicinenet.com/script/main/art.asp?articlekey=44781


New Delhi metallo-beta-lactamase Why everyone concerned ?

• There are currently no new drugs in the research pipelines that aim to stop NDM-1.To date, some strains of E.coli and Klebseilla pneumoniae are known carriers of the gene, but the gene can be transmitted from one strain of bacteria to another through horizontal gene transfer.

Naming the strain as New Delhi creates controversy

• The gene was named after New Delhi, the capital city of India, as it was first described by Yong et al. in 2009 in a Swedish national who fell ill with an antibiotic-resistant bacterial infection that he acquired in India . The infection was unsuccessfully treated in a New Delhi hospital and after the patient's repatriation to Sweden, a carbapenem-resistant Klebsiella pneumoniae strain bearing the novel gene was identified. The authors concluded that the new resistance mechanism "clearly arose in India, but there are few data arising from India to suggest how widespread it is."

Treatment

• Many NDM-1 strains are resistant to all antibiotics except for colistin.

• Colistin is an older antibiotic that has not been used much in recent decades, because it is somewhat more toxic than other antibiotics.

• A few NDM-1 strains have been sensitive to tigecycline (Tygacil), but this agent should be used cautiously in serious infections because it does not achieve high levels in the bloodstream.

• A few strains have also been sensitive to aztreonam


The spread of NDM-1 can be contained with

• The spread of NDM-1 within health-care facilities can be curbed through strict infection-control measures, including patient isolation and hand washing.

..

Strategy to Contain Resistance

• Develop new antibiotics – Bypass the drug resistance

• Judicious use of the existing antibiotics:– Containment of drug resistance

New Antibiotic Development• Only 15 antibiotics of 167 under development

had a new mechanism of action with the potential to combat of multidrug resistance.

• Lack of incentive for companies to develop antibiotics.

Hope is not exhausted….yet

• Phage therapy• Use of the lytic enzymes found in mucus and

saliva• Agents that target type IIA topoisomerases• Antimicrobial peptides (AMPs), lipopeptides

(AMLPs) target bacterial membranes, making it nearly impossible to develop resistance (bacteria would have to totally change their membrane composition). But th

ey are a long way off, as th

e

research is

still in its

infancy

Phage therapy• Phage Therapy is the therapeutic use of lytic bacteriophages to

treat pathogenic bacteria infections• Bacteriophages are viruses that invade bacterial cells and

disrupt bacterial metabolism and cause the bacterium to lyse.• Bacteriophage therapy is 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.

Efflux Pump Inhibitors:

Alternate Approaches

Some newer antibiotics

• Linezolid: targets 50S ribosome • Tigecycline: targets 30S ribosome • Daptomycin: depolarization of bacterial cell

membrane • Dalbavacin: inhibits cell wall synthesis • Telavacin: inhibition of cell wall synthesis and

disruption of membrane barrier function• Ceftibirole/ ceftaroline: cephalosporins • Iclaprim: inhibits Dihydrofolate reductase

Judicious Use of Antibiotics

• Can only contain antibiotic resistance• Cannot eliminate the possibility of

antibiotic development as resistance is an evolutionary process

Containment of Resistance

• Containment of antibiotic resistance is a multi-pronged program

• Involves all stake holders– Physicans– Patients– Pharmaceuticals

Factors of Antibiotic ResistanceEnvironmental

FactorsDrug Related

Factors

Patient Related Factors

Prescriber Related Factors


• Huge populations and overcrowding

• Rapid spread by better transport facility

• Poor sanitation

• Increases community acquired resistance

• Ineffective infection control program

• Widespread use of antibiotics in animal husbandry and

agriculture and as medicated cleansing products

1. Environmental Factors

• Over the counter availability of antimicrobials

• Counterfeit and substandard drug causing sub-optimal blood concentration

• Irrational fixed dose combination of antimicrobials

• Soaring use of antibiotics

2. Drug Related

Policy Decision at Higher level

• Poor adherence of dosage Regimens

• Poverty

• Lack of sanitation concept

• Lack of education

• Self-medication

• Misconception

3. Patient Related

Patient Counseling, Awareness Program

Prescriber Related

• Inappropriate use of available drugs

• Increased empiric poly-antimicrobial use

• Overuse of antimicrobials

• Inadequate dosing

• Lack of current knowledge and training

Strategy of ContainmentAntibiotic Resistance

Evolutionary Process

Faulty Use of Antibiotics

Hospital Environmental

Empirical Use Definitive Use

Community Acquired Antibiotic Resistance

Hospital Acquired Antibiotic Resistance

Use of antimicrobials before pathogen responsible for a particular illness or the susceptibility to a particular antimicrobial is known

Poor Clinical Practice

• Poor clinical practice that fail to incorporate

the pharmacological properties of

antimicrobials amplify the speed of

development of drug resistance.

Faulty Antibiotic Use

• Antimicrobials are over prescribed• Available without prescription

Over Prescribed Antibiotics

• Clinician should first determine whether antimicrobial therapy is warranted for a given patient

Empirical Microbial Selection

• Is antimicrobial agents indicated on the basis of clinical findings?

Or is it prudent to wait until such clinical findings

become apparent?


• Can some simple bed side test done to confirm your suspicion?– Microscopy– Gram staining


• Have appropriate clinical specimens been obtained to establish a microbial diagnosis?


• What are the likely etiologic agents for the patient’s illness?


• What measures should be taken to protect individuals exposed to the index case to prevent secondary cases (1), and what measures should be implemented to prevent further exposure (2)?

12


• Is there clinical evidence (e.g. from clinical trials) that antimicrobial therapy will confer clinical benefit for the patient?

(Evidence-based medicine)

Definitive Treatment

1. Can a narrower spectrum agent be substituted for initial empiric drug?

Definitive Treatment (2)

1. Is one agent or combination of agents necessary?

Examples

• -lactam + Aminoglycosides• Extended spectum Penicillins + -lactamase

Inhibitors• Anti-tubercular regimen • Anti-leprotic regimen• Co-trimoxazole• Sulphadoxin + pyrimethamine • Artemisinin based Combination Therapy (ACT) in

Malaria


What are the – optimum dose, – route of administration and – duration of therapy?

Definitive treatment

What specific test to identify patients who will not respond to treatment?


What adjunctive measures can be undertaken to eradicate infection?

– Vaccination– Steroid– Drainage of pus– Amputation– Removal of catheter

Who’s Work?

Microbiologist

Physician

Bacterial sensitivity test and find out the possible causes of development Treat Infection

Who’s Work?

Microbiologist

Physician

Pharmacologist

Advise the proper and adequate

antibiotics with balancing the

economy of hospital

Hospital Acquired Drug Resistance• Hospital Antibacterial Policy

• Hospital Antibiogram Hospital specific antibacterial Resistance Pattern

• Identification of potential pathogen most likely to cause infection

• Previous antibacterial therapy

• Prescription auditing

Hospital Antibiotic Policy

• To curb the common misuse and overuse of antibiotics

• Restricts the occurrence of antibacterial resistance among the hospital strains

• Controls the spread of such infections to susceptible and critically ill patients in the hospital and the subsequent infection into the community.

• Saves money for the patient and increases patient satisfaction with decreased side effect.

Hospital Antibiogram

• A periodic summary of antimicrobial susceptibilities of local bacterial isolates submitted to the hospital's clinical microbiology laboratory.

• Used by clinicians to assess local susceptibility rates, as an aid in selecting empiric antibiotic therapy, and in monitoring resistance trends over time within an institution

Treatment options for selected highly resistant bacteria

Sr. No

Organism Resistance Antibiotic used

1 E. Faecalis Penicillin Vancomycin, Ampicillin -SLB2 MRSA Methicillin etc

Vancomycin Linezolid , quinpristine, dalfopristine , daptomycin, telavacin

3 S. Epidermidis Methicillin Vancomycin + Rifampicin+ Gentamicin

4 S. Pneumoniae Penicillin G

MIC>4

Ceftriaxone, cefotaxime, Telithromycin Vancomycin + Rifampicin

5 C. Jejuni FQ Macrolides, doxycycline, clindamycin

Treatment options for selected highly resistant bacteria

Sr. No

Organism Resistance Antibiotic used

6 E. Coli Cotrimoxazole, oral cephalosporins , FQ

Fosfomycin, Nitrofurantoin, Ertapenum

7 K Pneumoniae

III Gen Cephalosporins & Ceftazidime

Imipenum, Meropenum, Colistin

8 P. aeruginosa Imipenum, meropenum

Antipseudomal Aminoglycosides , Colistin, Ceftazidime

In our hospital antibiotics recommended

First line • Penicillin • Oxacillin • Amoxy –Clav • Cephalothin • Erythromycin • Cotrimoxazole • Ciprofloxacin • Gentamicin

Second line • Vancomycin • Ofloxacin • Clindamycin • Clarithromycin • Linezolid

Gm +ve bacteria

First line • Amoxy-clav • Gentamicin • Ciprofloxacin • Ceftazidime • Cefuroxime • Cefazoline • Amikacin

Second line • Cefta Clav • Cefipime • Imipenum• Netilimycin • Tobramycin

In our hospital antibiotics recommended Gm -ve bacteria

• Topical Fusidic acid • Vancomycin • Teicoplanin• Linezolid • Minocycline • Sparfloxacin • Rifampicin

In our hospital antibiotics recommended MRSA

• Piperacillin• Cefaperazone • Amikacin • Ciprofloxacin • Gatifloxacin • Tobramycin • Netilimycin • Cefipime• piperacillin –Tazobactum • Ceftazidime

In our hospital antibiotics recommended P. Aeruginosa

Take Home Message• Target definitive therapy to known pathogen

• Treat infection, not contamination

• Treat infection, not colonization

• Know when to say “no” to Vancomycin, Carbepenems and Cephalosporin IV Generation

• Isolate Pathogen

• Break the chain of contagion – Keep your hands clean.

• Start simple bed side test: Gram stain, microscopy

antibiotic resistance

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