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
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
Antibiotic Resistance
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
Interior of organism
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
Interior of organism
Cell wall
Target siteBinding
Antibiotic
Antibiotics normally bind to specific binding proteins on the bacterial cell surface
Structurally modified antibiotic target site
Interior of organism
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
Interior of organism
Cell wall
Antibiotic
Target siteBindingEnzyme
Inactivating enzymes target antibiotics
Antibiotic inactivation
Interior of organism
Cell wall
Antibiotic
Target siteBindingEnzyme
Enzymebinding
Enzymes bind to antibiotic molecules
Antibiotic inactivation
Interior of organism
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.
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, a
s the
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 Resistance
Environmental Factors
Drug Related Factors
Patient Related Factors
Prescriber Related Factors
Antibiotic Resistance
• 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?
Empirical Microbial Selection
• Can some simple bed side test done to confirm your suspicion?– Microscopy– Gram staining
Empirical Microbial Selection
• Have appropriate clinical specimens been obtained to establish a microbial diagnosis?
Empirical Microbial Selection
• What are the likely etiologic agents for the patient’s illness?
Empirical Microbial Selection
• 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
Empirical Microbial Selection
• 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
Definitive Treatment
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?
Definitive 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