Medical oral microbiology I – lecture (ZLLM0421p)

1. Medical oral microbiology I – lecture (ZLLM0421p) Antibiotics III (mechanisms of resistance, factors of resistance) Ondřej Zahradníček zahradnicek@fnusa.cz

2. Resistance of microbes to antimicrobial agents Primary resistance: all strains of a given species are resistant. Example: b-lactam antibiotics have no effect to mycoplasmas, that have no cell wall. Secondary resistance: mutants that are not susceptible are formed, and at selection pressure of the antibiotic they start to be majority. (Escherichia may be susceptible to ampicillin, but in recent times resistant strains are more frequent than before)

3. http://www.nearingzero.net/screen_res/nz149.jpg

4. Mechanisms of resistance I Microbe disables entrance of antibiotic into the cell Microbe causes active efflux of an antibiotic from the cell Microbe changes the target receptor or offers a false receptor to the antibiotic Microbe subdues metabolic changes that disable the common effect of the antibiotic in the usual target structure Microbe splits the antibiotic enzymatically (e. g. a b-lactamase splits b-lactam antibiotics) New mechanisms are found all the time…

5. http://www.powerpak.com/index.asp?show=lesson&page=courses/10132/lesson.htm&lsn_id=10132http://www.powerpak.com/index.asp?show=lesson&page=courses/10132/lesson.htm&lsn_id=10132

6. Mechanisms of resistance II: mutual differences Some of them are coded on chromosomes Some are coded onplasmids, and plasmids may be transmitted intra- or interspecies Some are like „either - or“, so antibiotics either do, or do not function, and if they do not function, even elevated dosage of antibiotics is no help In some other resistance may be overcome by elevation of antibiotic dose (especially in aminoglycosides and fluoroquinolones) In the second case, the phenotypic testing is more difficult than in the first one

7. http://www.adrian.edu/chemistry/th/Somelinks/Spages/jtessmer/why.phphttp://www.adrian.edu/chemistry/th/Somelinks/Spages/jtessmer/why.php

8. Efflux (active expulsion of antibiotics out)

9. A stronger quinolone (ciprofloxacin) is still effective, but the weaker one (norfloxacin) already not. But even at using the stronger it is necessary to be careful! www.microbes-edu.org/etudiant/antibio3.html.

10. Mechanisms of resistance in b-lactam antibiotics b-lactam antibiotics are the most commonly used antibiotics, so their resistance factors require more detailed description Change of penicillin binding proteins, (PBP), for example in strains of MRSA Production of b-lactamases, for example: Staphylococcal penicillinases Penicillinases of Enterobacteriaceae family Cephalosporinases of various microbes Extended-spectre b-lactamases Decreased membrane permeability

11. b-lactamases There exist many types of them, they may have effect against all or majority, or just some of b-lactam antibiotics They may be code chromosomally or on plasmids Basic principle is always splitting of the b-lactamic circle

12. TEM-1 b-lactamase of E. coli

13. Change of PBP (penicillin binding proteins) http://www.proteinexpert.com/RD-services/Protein-engineering.php

14. Resistance – survey As we have seen, there exist lots of mechanisms of resistance, and also many possibilities of genetic coding of them So it is not possible to consider them „all the same“: Some are epidemiologically important, some of them are not Some only concern one antibiotic, some of them the whole group or several groups Some can be overcome by elevated dosing of an antibiotic (so it is rather a quantitative switch – „worse effect“, common in aminoglycosides) In some of the it is „either-or“. In such case resistance cannot be solved by higher doses

15. Transmission of resistance http://www.mja.com.au/public/issues/177_06_160902/col10836_fm.html

16. Transmission of genes for resistance by different ways www.scq.ubc.ca/?p=410

17. Selection of resistant strains www.answers.com/topic/antibiotic-resistance-gif.

18. Another reason for lack of in vivo effect at in vivo effectivity: bacteria in a biofilmBad effect of antibiotics may be used here by Charge of the adhered cells Decreases multiplication of bacteria Mechanisms of intercellular signalisation (quorum sensing) Influence of host immunity response Various other influences

19. Solution Think about the real possibility, that (especially in some types of infection) bacteria exist not just in planctonic form, but also as biofilm (especially in some types of infections) To use combinations of antibiotics Besides MIC, also make tests for MBEC, and not only to individual antibiotics, but also to combinations Use other treatment than just antibiotics (catheter exchange, local treatment etc.)

20. Epidemiologically important strains (MRSA etc.) Common causative agents of nosocomial infections Complication of hospitalisation, complication of operations, deterioration of health status, death of hospitalised people Enormous costs of treatment Medialisation of problematic following panic (often not constructive) They are used also in politics  http://www.bloggerheads.com/anne_milton/2005/04/superbugs-and-super-anne.html

21. Medialisation concerns mostly MRSA http://tahilla.typepad.com/petsmrsa/bella_moss_media_national_papers/index.html

22. Medialisation of these topics It concerns some types (especially MRSA) Often it influences healthcare staff People have often fear of MRSA, but they omit other also important resistances (VRE, ESBL, MLS resistance of staphylococci) Similar situation exist also in some other microbial diseases („flesh-eating streptococci“, „mad cows“, „bird flu“ – they often have their common names)

23. The fear is often abused but commercial sector that offers „surely MRSA-proof“ kits www.healthtec.co.uk/mrsa.htm

24. Fear of the public (including healthcare staff, e. g. nurses) should be converted to be more constructive actions (behaviour that really leads to decrease of risky behaviour in relation with the disease) on the other hand, any non-constructive panic, that follows in pressure for non-reasonable examination of persons that are not in risk, useless use of pharmacotherapy etc., should be eliminated

25. MRSA, or bird flu? www.whale.to/b/bird_flu_h.html.

26. VRE (vancomycin resistant enterococci) http://www.morgenwelt.de/typo3temp/5ce14d39b5.jpg

27. Enterococci – characteristics Enterococci are primarily resistant to lots of antibiotics (including all cephalosporins, but also macrolides, lincosamids, worse effect of V-penicillin) Enterococcus faecium (less pathogenous, but more resistant than E. faecalis) is also primarily resistant to ampicillin Treatment may be done using co-trimoxazole, tetracycline, quinolones. Glycopeptides (vancomycin, teicoplanin) are a reserve. The problem is if even such reserve antibiotics do not function; and just this is a problem in VRE strains.

28. VRE in Brno In Institute of microbiology of St. Ann‘s faculty hospital, we have individual cases of VRE More common presence of VRE strains is seen in Brno-Bohunice faculty hospital Probable reason: VRE are common in patients with cancer of lymphatic cells, and in Brno these patients are mostly present in Bohunice hospital

29. Drugs of choice are linezolid (ZYVOXID) and quinupristin/dalfopristin (SYNERCID) www.aic.cuhk.edu.hk/web8/enterococcus_faecium.htm

30. Meticilin resistant staphylococci (MRSA) www.daikoh.net/service/creansysytem.html

31. History of MRSA Originally also staphylococci were susceptible to penicillin, soon they started to be resistant by action of penicillinase Methicillin was firstly used in 1960, something later also oxacillin and nafcillin (because of various reasons many countries rather use oxacillin or nafcillin than methicillin) First epidemic outbreak of MRSA was seen in 1963, but then the MRSA ratio was 0.4 %. In 1973 it was already 10 % and 2004 even 43 % (data from the U. S.) The resistance problem is based on change of „penicillin binding proteins“

32. MRSA as a problem of today‘s medicine More seniors of in population Use of treatment influencing immunity Using of intravenous catheters and implants inside body Use (and abuse) of antibiotics All this are determining factors that influence risk of (not only) MRSA

33. MRSA is not more virulent than any other strain of S. aureus Although many people would not believe it, as to the ability of a bacterium to cause the disease (virulence), average MRSA strains are quite the same as all the average other golden staphylococci. • Resistance to oxacillin is not a special virulence factor. These strains are not more, but also not less virulent than other strains. www.metrowestcleangear.com/MRSA.htm

34. Staphylococcus aureus (MRSA) www.aic.cuhk.edu.hk/web8/mrsa.htm

35. Not all MRSA strains are the same There exist big differences between MRSA strains There exist a population of so called EMRSA – epidemic MRSA, these are common as nosocomial strains. They use to be polyresistant and e. g. resistance to erytromycin is commonly combined to the resistance to lincosamids On the other hand, there exist also so called community strains of MRSA, that are usually quite susceptible to many common (non-b-lactam) antibiotics. In Central Europe these strains are (good luck) more common than EMRSA stains.

36. Actual situation in Brno There exist individual cases of MRSA in all hospitals, sometimes including out-patients Good luck, big epidemiological outbreaks are not common, especially because of common knowledge concerning necessity of keeping rules for care for MRSA patients Some strains are well effective against other antibiotics, only some strains are polyresistant

37. Golden staphylococcus www.sanger.ac.uk/Info/Press/2004/040624.shtml

38. MRSA – management Antistaphylococcal vaccination Elimination of nasal carriership of golden staphylococcus (only in indicated persons, e. g. prior to surgery) Actions leading to decrease of infection of venous catheters Less frequent use of dialysation canulas Actions leading to less catheter infections, especially in patients with haemodialysis and peritoneal dialysis According to www.ndt-educational.org/goldsmithslide.asp

39. Reporting and strain identification All suspicious strains of MRSA should be well checked and in case of real positivity they are reported to clinical station and also to hospital epidemiology A part of communication between microbiology and department is consultation of treatment of infection, that should be suitable and have sufficient duration, it is a real infection and not just colonisation In case of a MRSA finding on a ward, the measures should be taken that lead to prevent transmission of infection to other patients

40. What treatment? In community strains of MRSA it is possible to use non-b-lactam antibiotics, if the strain is susceptible in vitro (macrolides, tetracyclins, co-trimoxazole) In polyresistant strains it is necessary to glycopeptidic antibiotics (vankomycin, teicoplanin). That also means not using these antibiotics for common infections to keep them effective against serious infections In case of resistance to glycopeptides, or their contraindication caused by bad status of the patient, it is possible to use linezolid or some other newer drugs (quinu-/dalfopristin)

41. Examination for MRSA In indicated patients, examination is mostly done as nasal and perineal swab, eventually also wound swab, swab of tracheostomia etc. (it depend on the individual patient) In such patients, also regular screening during all hospitalisation is usually performed Indicated patients = patients, that have history of MRSA, they come from wards with MRSA, or they come for some „risky type surgeries“

42. MRSA in Europe 2014 http://ecdc.europa.eu/en/activities/surveillance/EARS-Net/database/Pages/maps_report.aspx

43. VISA and VRSA These are golden staphylococci intermediary resistant (I) or completely resistant (R) to vancomycin, eventually also teicoplanin They start to occur since 1997 Until now rare in Europe, a something more frequent in the USA Genes for resistance probably acquired from enterococci Should not be underestimated, although not seen commonly in recent Europe Solution: let glycopeptides as reserve antibiotics for indicated cases only

44. From MRSA to VRE and VRSA www.ndt-educational.org/goldsmithslide.asp

45. MLSB resistance www.szu.cz/cem/zpravy/zpr0306/klinda.htm

46. Characteristics of MLSB resistances It is shared resistance to macrolides, lincosamids and streptogramin B. In concerns namely staphylococci, but similar resistance patterns can be also seen in various species of streptococci Not all strains resistant to erytromycin has this shared resistance. Especially community strains of golden staphylococci have commonly just an isolated resistance to erytromycin In some cases it is an induced type of a resistance: erytromycin induces resistance to lincomycin or clindamycin. In that case none of them should be used

47. Extended spectre b-lactamases (ESBL) http://www.kbc-zagreb.hr/index.php?link=klinike_i_zavodi&action=21&id=2

48. ESBL – extended spectre b-lactamases b-lactamases TEM, SHV, CTX etc. they are seen mostly in Enterobacteriae family:Klebsiella pneumoniae, Escherichia coli, but sometimes also in G– non-fermenters there exist many types of them genes for them are in plasmids, mutations are frequent, new variants occur Among b-lactam antibiotics, only carbapenems remain effective Metalo-b-lactamase they are seen in G– non-fermenters they are active also against carbapenems susceptible are monobactams (azthreonam) rare in Enterobacteriaceae family

49. Inductors and selectors of b-lactamases Production of some b-lactamases may be induced by use of an antibiotic (inductor). An example of an inductor is co-amoxicillin More dangerous than inductors are selectors: quite effective antibiotics, that kill the susceptible part of population, and only highly resistant (polyresistant) strains would remain. Example: 3rd generation cephalosporins. Decrease of their use led to decrease of ESBL positive strains in all hospitals where tried

50. Consumption of cephalosporins vs. ESBL www.medscape.com/viewarticle/413080_31