What is multidrug resistance? Umaer Naseer Senior Research Scientist Department of Zoonotic, Water- and Foodborne Infections Norwegian Institute of Public Health
Magiorakos A.P. et al 2012 Definition of multidrug resistance Joint ECDC and CDC definition Acquired non-susceptibility to at least one agent in three or more antimicrobial categories Defined for: Staphylococcus aureus, Enterococcus spp. Enterobacteriales (not Salmonella or Shigella), Pseudomonas aeruginosa and Acinetobacter spp.
Classification of antimicrobials 1. Chemical structures Antibiotics with different basic chemical structures 2. Spectrum of activity The range of bacterial species susceptible to these agents 3. Effect on bacteria Different mechanism of action leading to an endpoint of either inactivation or actual death of the bacteria 4. Mode of action Different antibiotics have different modes of action, owing to the nature of their structure and degree of affinity to certain target sites within bacterial cells 5. Epidemiologically meaningful Bacteria specific categories based on therapeutically relevant groups
Mode of action 1. Inhibitors of nucleic acid synthesis Fluoroquinolones, rifamycins 1 2. Inhibitors of protein synthesis Aminoglycosides, tetracyclines, macrolides, chloramphenicol, lincosamides 5 3. Inhibitors of metabolic pathways Sulfonamides, trimethoprim 3 4. Inhibitors of membrane integrity Polymyxin B 5. Inhibitors of cell wall synthesis Penicillins, Cephalosporins, Vancomycin, Bacitracin 2 Kim Lewis Nature Reviews Drug Discovery 2013
Determining susceptibility to antimicrobial drugs Minimum Inhibitory Concentration (MIC) Broth microdilution ISO standard Series of concentrations to determine the lowest needed to prevent growth of specific organism Disc diffusion Qualitative determination E-test Quantitative determination Disc diffuision E-test
What are we missing? Clinical resistance When a bacterial strain is enable to endure a higher antibiotic concentration then what is achievable in vivo Microbial resistance When a bacterial strain is enable to endure a considerable higher antibiotic concentration then bacteria of the same species
E. Gullberg Bacterial strategies of resistance 1. Decreased uptake Prevention of the AB from reaching its target by reducing its ability to penetrate into the cell 2. Efflux of AB Expulsion of the AB from the cell via general or specialized efflux pumps 2 1 3. Inactivation of AB Inactivation of AB via modification or degradation 4. Modification of target Reducing affinity of AB by structural modification of target 5. By-passing AB By-passing the effect of the antibiotic by applying alternative metabolic pathways 3 5 4
Resistance: intrinsic or acquired Intrinsic Innate ability of a bacterial species to resist activity of a particular antimicrobial agent Acquired When a particular microorganism obtains the ability to resist the activity of a particular antimicrobial agent Mutation of genes involved in normal physiological processes and cellular structures Acquisition of foreign resistance genes
Examples of intrinsic resistance ORGANISMS NATURAL RESISTANCE AGAINST MECHANISM Anaerobic bacteria Aminoglycosides Lack of oxidative metabolism to drive uptake of aminoglycosides Aerobic bacteria Metronidazole Inability to anaerobically reduce drug to its active form Gram-positive bacteria Aztreonam (a beta-lactam) Lack of penicillin binding proteins (PBPs) that bind and are inhibited by this beta lactam antibiotic Gram-negative bacteria Vancomycin Lack of uptake resulting from inability of vancomycin to penetrate outer membrane Klebsiella spp. Ampicillin (a beta-lactam) Production of enzymes (beta-lactamases) that destroy ampicillin before the drug can reach the PBP targets Stenotrophomonas maltophila Imipenem (a beta-lactam) Production of enzymes (beta lactamases) that destroy imipenem before the drug can reach the PBP targets. Lactobacilli and Leuconostoc Vancomycin Lack of appropriate cell wall precursor target to allow vancomycin to bind and inhibit cell wall synthesis Pseudomonas aeruginosa Sulfonamides, trimethoprim, tetracycline, or chloramphenicol Lack of uptake resulting from inability of antibiotics to achieve effective intracellular concentrations Enterococci Aminoglycosides Lack of sufficient oxidative metabolism to drive uptake of aminoglycosides All cephalosporins Lack of PBPs that effectively bind and are inhibited by these beta lactam antibiotics Forbes et al., 1998, Giguere et al., 2006
Mutation driven resistance Hypermutators Selection of mutation by turning off MMR Persistors Withstand increased mutation frequencies by turning off SOSresponse Hitchhiker Extract favorable mutations from mutants Disseminators Vertical transfer of resistance Rodriguez-Rojas et al. 2013
Horizontal gene transfer
Multidrug resistant plasmids Gene Imp aaca4 cata2, catb3 Sul1 dfra19 stra, strb TetA(D) - qacg- Resistance to Imipenem Aminoglycoside Chloramphenicol Sulfonamide Trimethoprime Streptomycin Tetracycline Quaternary ammonium compounds Sam Abraham et al 2016, Shewli Mukerj et al. 2017
Akifumi Yamashita et al. 2014 Plasmidome network analysis Largest Connected Component (LCC) Enterobacteriales (Escherichia, Klebsiella, Salmonella) Plasmids share genes by HGT
Examples of acquired resistance ACQUIRED RESISTANCE RESISTANCE OBSERVED MECHANISM INVOLVED Mutations Mycobacterium tuberculosis resistance to rifamycins Point mutations in the rifampin-binding region of rpob Resistance of many clinical isolates to fluoroquinolones Predominantly mutation of the quinolone-resistancedetermining-regiont (QRDR) of GyrA and ParC/GrlA E. coli, Hemophilius influenzae resistance to trimethoprim Mutations in the chromosomal gene specifying dihydrofolate reductase Horizontal gene transfer Staphylococcus aureus resistance to methicillin (MRSA) Resistance of many pathogenic bacteria against sulfonamides Enterococcus faecium and E. faecalis resistance to vancomycin (VRE) Via acquisition of meca genes which is on a mobile genetic element called staphylococcal cassette chromosome (SCCmec) which codes for penicllin binding proteins (PBPs) that are not sensitive to ß-lactam inhibition Mediated by the horizontal transfer of foreign folp genes or parts of it Via acquisition of one of two related gene clusters VanA and Van B, which code for enzymes that modify peptidoglycan precursor, reducing affinity to vancomycin.
The ESCAPE pathogens E Vancomycin resistant Enterococcus faecium S Methicillin resistant Staphylococcus aureus C Flouroquionolone resistant Campylobacter A Carbapenem resistant Acinetobacter baumannii P Carbapenem resistant Pseudomonas aeruginosa E Carbapenem resistant Enterobacteriales
Cesar A. Arias & Barbara E. Murray 2012 Mechanisms of enterococcal resistance A A A A
Vancomycin resistant enterococci (VRE) 1950s, Usage of vancomycin and teicoplanin MRSA, PRSP 1975 - Avoparcin growth promoter in agriculture 1986 - Single E. faecium clone outbreak (UK) 1990 - Multi-clonal VRE outbreaks (USA) 1989 0 % 1995 26.2 % 1996 48.8% Avoparcin Banned 1997 1990s Norway, Denmark, Iceland (sporadic) 1996-97 Finland (hospital epidemic) 2000-07 Sweden (annually 18-53 cases) 2008 Sweden (618 cases) 2017 Norway (384 cases) Wegener HC et al 2003
Tofteland et al. 2013 Hospital Outbreak of KPC- Producing Klebsiella pneumoniae 15 September 2008 a patient (P1) was admitted to ICU at Sørlandet Hospital Arendal 8 October 2008 tested blood culture positive for KPC producing K. pneumoniae Discharged 21 October 2008 2 20 November 2008 a patient (P2) was admitted to ICU at Sørlandet Hospital Flekkefjord 1 December 2008 tested expectorate positive for KPC producing K. pneumoniae Discharged 16 February 2009 23 October 2008 a patient (P3) was admitted to ICU at Sørlandet Hospital Arendal 15 March 2009 tested urine positive for KPC producing K. pneumoniae Discharged 18 April 2009 Dec08 Jan09
Molecular typing with PFGE K. pneumoniae K. pneumoniae K. pneumoniae K. pneumoniae K. pneumoniae 17 April 2010 a patient (P4) was admitted to ICU at Sørlandet Hospital Arendal tested expectorate positive for KPC producing K. pneumoniae
Outbreak response Faecal screening of all ICU admitted at Sørlandet Hospital Arendal Environmental screening involving sink drains (n=19) and water taps in the ICU the neighbouring post-operative unit, the coronary unit Identified one carrier (P5) Positive for KPC-1 producing K. pneumoniae and Enterobacter asburiae Four environmental samples from sink drains were positive for KPC-1 All four positive for KPC-1 producing K. pneumoniae Two additionally positive for KPC-1 producing E. asburiae
Chromosomal and Plasmid Typing
Summary of the oubreak An outbreak of KPC-1 producing K. pneumoniae and E. asburiae started at Sørlandet Hospital Complex after import of KPC-1 producing K. pneumoniae from Greece in November 2007 Seven cases between November 2007 and April 2010 The outbreak involved three different hospitals as a result of patient exchange between them Epidemiological and molecular data showed that the outbreak was due to clonal spread of a K. pneumoniae strain as well as interspecies plasmid transmission of a 100kb KPC-plasmid (IncFII) betweem two distinct K. pneumoniae strains and intergenus spread to E. asburiae Environmental screening identified a local environmental reservoir. The spread among patients probably occurred as a result of transmission between patients and was prolonged by continuous spread from the environmental source
Multidrug resitant bacteria Have acquired resistance mechanism to thee or more antimicrobial categories MDR bacteria have evolved and are adapted to accumulate a variety of resistance Dissemination of resistant plasmids don t respect species borders Infections with MDR bacteria have increased morbidity and mortality compared to infections with antibiotic susceptible strains Higher risk of ICU admission Higher risk of treatment failure Increased length of hospitalization Increased costs to hospitals