Mechanism of antibiotic resistance Dr.Siriwoot Sookkhee Ph.D (Biopharmaceutics) Department of Microbiology Faculty of Medicine, Chiang Mai University
Antibiotic resistance Cross-resistance : resistance in a group of drugs which closely related structure Co-resistance : concomitant resistance in a different group of drugs due to the different mechanisms or genes Multidrug resistance (MDR) : resistance in 1/3 of empiric drugs Extensive, extensively or extremely drug resistant (XDR) : resistance at least 1 drug in each group of empiric drug
Pan-drug resistance Pan-drug resistance (PDR) : resistant in all tested empiric drugs
Sources of resistance Intrinsic resistance : natural or spontaneous resistance insensitive Stenotrophomonas maltophilia Intrinsic resistance to carbapenem Sensitive to ceftazidime, fluoroquinolone, sulphonamide
Sources of resistance Acquired resistance : imported resistant genes - Mutational resistance : vertical gene transfer - Transmissible resistance : horizontal gene transfer - Plasmid borne resistance : rapid resistance - Chromosomal resistance : slow resistance
Drug target modification Alternation of protein target mutation of PBPs gene change of penicillin binding protein reduction of β-lactam binding
Resistance of MRSA : - alteration of PBP2s - staphylococcal cassette chromosome mec or SCCmec (meca gene) - correlated with hospital/community acquired infection
Altering the target receptor for the antibiotic to reduce or block its binding ANTIBIOTIC CELL WALL RECEPTOR CYTOPLASM Bacteria alters the shape of target receptor
Modification of peptidoglycan structural in VRE High level resistant genes : vana, vanb and vand Enterococcus faecalis, Enterococcus faecium D-alanyl-D-alanine D-alanyl-D-lactate
Gram Positive Cell Wall PEPTIDE CROSS-BRIDGE TEICHOIC ACID PEPTIDOGLYCAN LIPOTEICHOIC ACID CELL WALL CELL MEMBRANE
Gram Positive Cell Wall TP TP TP CELL WALL CYTOPLASM
v v Mechanism of Action VANCOMYCIN CELL WALL CYTOPLASM
VRE - Resistant mechanism Enterococcus spp. VRE v D-Alanine v D-Alanine D-Alanine D-Lactate
Vancomycin intermediate resistance (VISA) Thickening of peptidoglycan level Difficult to drug penetration
Heterogenous vancomycin intermediate resistance (hvisa) 1 intermediate resistant cell 999,999 susceptible cells antibiotic Survive and multiply die Predominate with intermediate resistant cells Change the susceptibility, zone diameter, MIC
Target alteration on ribosome Macrolides, lincosamides, streptogramine (MLS) : posttranslational modification at ribosome subunit 50s i.e. methylation
Alteration of DNA synthesis Mutation of gyra Alteration of DNA gyrase Reduction of drug binding Increase of drug MIC for inhibiting bacteria
Alteration of cell membrane structure Porin : protein structure at cell membrane responsible to import small drug molecule i.e. beta lactam and quinolone Porin encoding gene is not expressed in Pseudomonas aeruginosa Imipenem cannot import into cell Imipenem resistance
Preventing the entry of the antibiotic into the bacteria ANTIBIOTIC TRANSPORT PROTEIN PERIPLASM CYTOPLASM Altering transport (carrier) proteins in the cytoplasmic membrane
Preventing the entry of the antibiotic into the bacteria ANTIBIOTIC PORIN PERIPLASM Altering porins in the outer membrane of a bacterium CYTOPLASM
Expression of drug efflux pumps Drug efflux pumps : responsible to export drug decrease drug intracellular concentration Multidrug efflux pump : multidrug transporter involved the resistance of all drugs except polymyxin (colistin)
Actively transporting the antibiotic out of bacteria ANTIBIOTIC TRANSPORT PROTEIN NEW TRANSPORT PROTEIN PERIPLASM Producing a new transport molecule in the cytoplasmic membrane CYTOPLASM
Drug inactivation / modification Structural translocation : Aminoglycosides, macrolides by enzymes involved the group translocation - phosphoryltransferases - nucleotidyltransferases - Adenylyltransferases - acetyltransferases reduction of drug binding cannot inhibit bacterial protein synthesis
Drug inactivation / modification Structural translocation : Chloramphenicol by enzymes involved the transacetylase acetyl group hydroxyl group reduction of drug binding cannot inhibit bacterial protein synthesis
Drug inactivation by hydrolysis Beta lactamase can hydrolyze beta lactam ring Inactive drug (Penicilloic acid) Beta lactam cannot kill bacteria
Drug inactivation by hydrolysis ereb expression in Escherichia coli Erythromycin esterase II production Hydrolysis lactone ring of erythromycin
Producing an enzyme capable of destroying the antibiotic ANTIBIOTIC PERIPLASM ENZYME CYTOPLASM
Producing an enzyme capable of destroying the antibiotic INACTIVATED ANTIBIOTIC ANTIBIOTIC PERIPLASM ENZYME CYTOPLASM
Mechanism of Resistance to β-lactams Porin channels Efflux system PBPs B-lactamases The Gram Negative Cell Wall
Why Test for β-lactamases? Smart use/ Appropriate therapy Breakpoints do not reliably detect new β-lactamases Infection control Identify drugs causing resistance
-LACTAMASE 1. Class A β-lactamase 1.1 Extended spectrum β-lactamase or ESBL Hydrolyze - penicillins - cephalosporin 1 st, 2 nd, 3 th - monobactams Can be inactivated by beta lactamase inhibitors, clavulanic acid, tazobactam, sulbactam Active Inactive
CLSI Screening Test E. coli ceftazidime 22 mm cefotaxime 27 mm Detect key hole phenomenon
Combination Disc Method CLSI Approved Method Combination discs Test cefotaxime and ceftazidime +/- clavulanate > 5 mm zone increase CAZ/CLA CTX/CLA CAZ CTX
Commercial methods E-test : ceftazidime, cefotaxime (MIC 8 times) cefotaxime cefotaxime + clavulanate
Class A carbapenemase Hydrolyze - penicillins - cephalosporin - carbapenem Can be inactivated by beta lactamase inhibitors, clavulanic acid, tazobactam, sulbactam KPC enzymes : carbapenem-resistant Klebsiella pneumoniae
Class B β-lactamase : Metallo carbapenemase or class B carbapenemase or metalloenzymes Can be inhibited by EDTA Cause of high-level carbapenem resistance Pseudomonas aeruginosa, Acinetobacter baumannii
New Delhi Metallo or NDM enzyme Found in 2009 in Klebsiella pneumoniae isolated from Swedish patient at India : Superbug organism multidrug resistance to all drugs except colistin, phosphomycin, tigecycline Klebsiella pneumoniae and Escherichia coli : community-acquired pathogens
Class C β-lactamase : AmpC β-lactamases cannot be inactivated by clavulanic acid or EDTA but can be inactivated by cloxacillin, oxacillin
Class D β-lactamase : Oxacillinase or OXA-type carbapenemase can be inactivated by NaCl Found in multidrug-resistant Acinetobacter baumannii
Macrolide resistance Intrinsic resistance : hydrophobic macrolide have low permeability through outer membrane (Gram -ve) Acquired resistance - ribosomal modification - efflux pump - enzyme inactivation0
Aminoglycoside resistance Enzymatic modification of drug - high level resistance - genes encoding resistance located in plasmids - gene transfer occurs across species Reduced uptake or decreased permeability of bacterial cell wall
Tetracyclines resistance mechanism predominate: efflux and ribosomal protection bacteria survived producing an enzyme to destroy or inactivate the antibiotic blocking tetracyclines from binding to the ribosome (http://student.ccbcmd.edu)
Quinolones resistance mechanism Changes in protein targets - DNA gyrase - Topoisomerase IV Reduction in the accumulation - decrease in permeability - increase in active efflux system DNA gyrase and topoisomerase IV protection - qnr gene
Sulfonamides resistance mechanism altering the target site for the antibiotic to reduce or block its binding altered dihydropteroate synthase or dihydrofolate reductase