Bubonic plague, TB , Malaria,hiv have affected significant number of hyman beings and caused mortality and morbidity Adult humans contains 1014 cells, only 10% are human – the rest are bacteriaAntibiotic use promotes Darwinian selection of resistant bacterial speciesBacteria have efficient mechanisms of genetic transfer – this spreads resistanceBacteria double every 20 minutes, humans every 30 yearsDevelopment of new antibiotics has slowed – resistant microorganisms are increasing
Antimicrobial agents were viewed as miracle cure when introduced into clinical practice. However it became evident rather soon after the discovery of penicillin that resistance develops quickly terminating the miracle. This serious development is ever present with each new antimicrobial agents and threatens end of antimicrobial area. Today even major class of antibiotics are resistant
If this can be achieved, the microorganism is considered susceptible to the antibiotic. If an inhibitory or bactericidal concentration exceeds that which can be achieved safely in vivo, then the microorganism is considered resistant to that drug. Antibiotic resistance refers to unresponsiveness of microorganism to antimicrobial agents.Susceptible MIC is at a concentration attainable in blood or other appropriate body fluid using usually recommended dosagesResistant MIC is higher than normally attainable levels in body fluidsIntermediate (moderately sensitive, moderately resistant) MIC is between sensitive and resistant levels, may be able to treat with increased dosage
Presence of few mutants not sufficient to produce resistance Single step : E.coli & staph to RifampicinMultistep : erythromycin, tetracyclines, chloramphenicol
The new DNA is then incorporated into the genome of the bacteria which becomes resistant.
They have insertion sequence at end of gene.
They are commonly associates with Transposons.
Commonly operate in E.coli,P.aeruginosa,S.typhi,Staph.aureus,N.gonorroea.
ACYl HOMOSERINE LACTONE,
It remains to be seen if widespread use of antibiotics in syndromic control of LRTI chanfes pattern overtime
Some antibiotics like aminoglycosides and fluoroquinolones do not contain beta-lactam rings. Unfortunately, the bacteria that have acquired NDM-1 have also acquired other resistance factors and most are already resistant to aminoglycosides and fluoroquinolones. The addition of NDM-1 production has the ability to turn these bacteria into true superbugs (bacteria resistant to usually two or more antibiotics) which are resistant to virtually all commonly used antibiotics.
There are two different approaches to managing antibiotic resistance:1.Managing existing resistant pathogens 2.Avoiding future evolution of more resistanceThe first can be done by, in the case of MRSA, improving hygiene in hospitals, screening hospital visitors and isolating patients
COLONIZATION means that the organism is present in or on the body but is not causing illness.Adopt WHO Strategies and PoliciesVaccination is the most logical and effective means to contain resistance by preventing infection in the first place. For ARIs, diarrhoeal diseases and malaria in children, WHO has developed the Integrated Management of Childhood Illness (IMCI). For the treatment of TB, WHO recommends use of the DOTS strategy. Antimicrobial resistance surveillance – another critical tool in the fight against antimicrobial resistance – identifies and tracks resistance trends in specific infections and geographical locations. INFECTION means that the organism is present and is causing illness.
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
History Nobel Lecture, December 11, 1945 Sir Alexander Fleming The Nobel Prize in Physiology or Medicine 1945In his 1945 Nobel Prize lecture, Fleming himself warned ofthe danger of resistance –“It is not difficult to make microbes resistant topenicillin in the laboratory by exposing them toconcentrations not sufficient to kill them, and thesame thing has occasionally happened in the body……and by exposing his microbes to non-lethalquantities of the drug make them resistant.”
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 ResistanceDrug resistance occurs in : BACTERIA—ANTIBIOTIC RESISTANCE Endoparasites Viruses—Resistance to antiviral drugs Fungi Cancer cells
Antibiotic Resistance• The concentration of drug at the site ofinfection must inhibit the organism and alsoremain below the level that is toxic to humancells. GOODMAN & GILMANS THE PHARMACOLOGICAL BASIS OF THERAPEUTICS - 11th Ed. (2006)
Antibiotic ResistanceDefined as micro-organisms that are notinhibited by usually achievable systemicconcentration of an antimicrobial agent withnormal dosage schedule and / or fall in theminimum inhibitory concentration (MIC)range. Antibiotic Resistance (DR) = MIC / MCC > Toxic Plasma Concentration
Myths of Antibiotic Resistance1. 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.
Antibiotic ResistanceSome microorganisms may ‘born’ resistant,some ‘achieve’ resistance by mutation or somehave resistance ‘thrust upon them’ by plasmidsSome are born great, some achieve greatnessor some have greatness thrust upon them
Intrinsic ResistanceIt occurs naturally.1. Lack target : • No cell wall; innately resistant to penicillin2. Innate efflux pumps: • Drug blocked from entering cell or ↑ export of drug (does not achieve adequate internal concentration). Eg. E. coli, P. aeruginosa3. Drug inactivation: • Cephalosporinase in Klebsiella
Acquired resistanceMutations• 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 TransposonsTransposons are sequences of DNAthat can move around differentpositions within the genome of singlecell. The donor plasmid containing theTransposons, co-integrate with acceptorplasmid. They can replicate duringcointegrationBoth plasmids then separate and eachcontains the r-gene carrying thetransposon. Eg ; Staphylococci,Enterococci
Mechanisms of Resistance Gene Transfer IntegronsIntegron is a large mobile DNAcan spread Multidrug resistanceEach Integron is packed withmultiple gene casettes, eachconsisting of a resistance geneattached to a small recognition site.These genes encode severalbacterial functions includingresistance 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 / growthrequirements• By producing an enzyme that inactivates theantibiotic• Quorum sensing
Decreased permeability: Porin Loss Antibiotics normally enter bacterial cells via porin channels in the cell wallAntibiotic Porin channel into organismCell wall Interior of organism
Decreased permeability: Porin Loss New porin channels in the bacterial cell wall do not allow antibiotics to enter the cellsAntibiotic New porin channel into organismCell wall Interior of organism
Efflux pumps• Cytoplasmic membrane transport proteins.• Major mechanism for resistance in Tetracyclines.• Some gram -ve bacteria inhibit the plasmidmediated synthesis of porin channels ,whichobstructs the influx of hydrophilic Penicillinseg.ampicillin ATP Binding Cassette Major facilitator superfamily Multidrug and toxic compound exporter Small multidrug resistance transporters Resistance-nodulation-division
Structurally modified antibiotic target site Antibiotics normally bind to specific binding proteins on the bacterial cell surfaceAntibiotic Binding Target siteCell wall Interior of organism
Structurally modified antibiotic target site Antibiotics are no longer able to bind to modified binding proteins on the bacterial cell surfaceAntibiotic Modified target siteCell wall Changed site: blocked binding Interior of organism
Modification/Protection of the Target siteResistance resulting from altered target sites : Target sites Resistant Antibiotics Ribosomal point mutation Tetracyclines,Macrolides , Clindamycin Altered DNA gyrase Fluoroquinolones Modified penicillin binding Penicillinsproteins (Strepto.pneumonia) Mutation in DNA dependant Rifampicin RNA polymerase (M.tuberculosis)
Antibiotic inactivation Inactivating enzymes target antibioticsAntibioticEnzyme Binding Target site Cell wall Interior of organism
Antibiotic inactivation Enzymes bind to antibiotic moleculesAntibiotic Enzyme bindingEnzyme Binding Target site Cell wall Interior of organism
Antibiotic inactivation Enzymes destroy antibiotics or prevent binding to target sites Antibiotic Antibiotic altered, destroyed binding preventedAntibioticEnzyme Target site Cell wall Interior of organism
By producing enzymes that inactivates antibiotica)Inactivation of b-lactam antibiotics •S. aureus, N. gonorrohoea, H.influenza, Produce b- lactamase which cleaves -lactam ringb)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 resistancePencillins & B Lactamase cleavage of the Blactam ringCephalosporiinsAminoglycosides Modification by phosphorylating, adenylating and acetylating enzymesChloramphenicol Modification by acetylytionErythromycin Change in receptor by methylation of r RNATetracycline Reduced uptake / increased export Active export out of the cell & reduced affinitySulfonamides 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• 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
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 patients 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).
Alternate ApproachesPhage 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:
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 ResistanceDrug Related Environmental Factors Factors Antibiotic Resistance PrescriberPatient Related Related Factors Factors
1. Environmental 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
2. Drug Related• Over the counter availability of antimicrobials• Counterfeit and substandard drug causing sub- optimal blood concentration• Irrational fixed dose combination of antimicrobials Policy• Soaring use of antibiotics Decision at Higher level
3. Patient Related• Poor adherence of dosage Regimens• Poverty• Lack of sanitation concept• Lack of education Patient• Self-medication Counseling,• Misconception 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 Containment Antibiotic Resistance Evolutionary Faulty Use of Process Antibiotics Hospital Acquired Hospital EnvironmentalAntibiotic Resistance Community Acquired Antibiotic Resistance Empirical Use Definitive UseUse of antimicrobials beforepathogen responsible for a particularillness or the susceptibility to aparticular 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)?2 1
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 Treatment1. Can a narrower spectrum agent be substituted for initial empiric drug?
Definitive Treatment (2)1. Is one agent or combination of agents necessary?
Who’s Work? MicrobiologistAdvise the proper and adequate antibiotics with Physician balancing the economy of hospital Pharmacologist
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 hospitals 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 bacteriaSr. Organism Resistance Antibiotic usedNo1 E. Faecalis Penicillin Vancomycin, Ampicillin -SLB2 MRSA Methicillin etc Linezolid , quinpristine, Vancomycin dalfopristine , daptomycin, telavacin3 S. Epidermidis Methicillin Vancomycin + Rifampicin+ Gentamicin4 S. Pneumoniae Penicillin G Ceftriaxone, cefotaxime, Telithromycin MIC>4 Vancomycin + Rifampicin5 C. Jejuni FQ Macrolides, doxycycline, clindamycin
Treatment options for selected highly resistant bacteriaSr. Organism Resistance Antibiotic usedNo6 E. Coli Cotrimoxazole, Fosfomycin, Nitrofurantoin, oral Ertapenum cephalosporins , FQ7 K III Gen Imipenum, Meropenum, Pneumoniae Cephalosporins Colistin & Ceftazidime8 P. aeruginosa Imipenum, Antipseudomal meropenum Aminoglycosides , Colistin, Ceftazidime
In our hospital antibioticsGm +ve bacteria recommended First line Second line • Penicillin • Vancomycin • Oxacillin • Ofloxacin • Amoxy –Clav • Clindamycin • Cephalothin • Clarithromycin • Erythromycin • Linezolid • Cotrimoxazole • Ciprofloxacin • Gentamicin
In our hospital antibioticsGm -ve bacteria recommended First line Second line • Amoxy-clav • Cefta Clav • Gentamicin • Cefipime • Ciprofloxacin • Imipenum • Ceftazidime • Netilimycin • Cefuroxime • Tobramycin • Cefazoline • Amikacin
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
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