Prezentacja programu PowerPoint · macrolides tetracyclines fluoroquinolones chloramphenicol...
Transcript of Prezentacja programu PowerPoint · macrolides tetracyclines fluoroquinolones chloramphenicol...
Antimicrobial chemotherapy
Prof. Beata M. Sobieszczańska
Department of Microbiology
University of Medicine
Antimicrobials
• Antibiotic is a low molecular substance produced by
microorganisms (molds, bacteria) that at a low
concentration inhibits or kills other microorganisms
• Antimicrobial is any substance of natural, semisynthetic
or synthetic origin that kills or inhibits the growth of
microorganisms but causes little or no damage to the
host
Antimicrobials
• Bacteriostatic = agent that inhibits bacterial growth but
generally do not kill the bacteria
e.g. protein synthesis inhibitors (macrolides,
tetracyclines, streptogramins, lincozamides,
oxazolidinones, chloramphenicol)
• Bactericidal = agent that kills the target bacteria (β-
lactams, glycopeptides, bacitracin, polymyxin,
fluoroquinolones, metronidazole, rifampin)
Drug’s spectrum of activity
Depending on the range of bacterial species
susceptible to antimicrobials – they are classified as:
Narrow spectrum - have limited activity to some bacteria
e.g. GP or GN (e.g. natural penicillins, glycopeptides)
Broad spectrum – are active against both GP and GN
(e.g. amoxycillin, carbapenems, fluoroquinolones)
PAE = post-antibiotic effectIt is a persistence of antibiotic effect observed long after the serum concentration has fallen below the MIC
Strong PAE:
aminoglycosides, clindamycin, macrolides, tetracyclines, rifamycins, streptogramins
Benefit for large, intermittent doses
Weak/absent PAE:
β-lactams; carbapenems –moderate
Benefit from continuous infusion
Sites of action of different antimicrobial agents
Bactericidal - without cell wall osmotic
pressure causes bacteria to burst
Examples:
• All β-lactams
• Glycopeptides
• Bacitracin
• Fosfomycin
Inhibitors of cell wall synthesis
PBP=penicillin binding proteins
(enzymes transpeptidases)
GP susceptible groups of streptococci (except enterococci),
pneumococci, T. pallidum, Actinomyces
Treatment e.g. strep throat, syphilis, pneumonia
Narrow spectrum
GP cocci + penicillinase-producing staphylococci
Treatment e.g. infections caused by MSSA (methicillin sensitive S.
aureus)
Narrow spectrum
Addition of BLIs extends activity to cover β-lactamase-producing
GN rods/bacilli, boarder activity than penicillinase-resistant
penicillins, and activity against anaerobes
Treatment e.g. empiric treatment of polymicrobial infections
Broad spectrum
GP bacteria but limited activity against GN
Treatment e.g. skin/soft tissue infections or surgical prophylaxis
GP + more activity against GN (some β-lactamase-producing Klebsiella
and H. influenzae strains); variable activity against anaerobes
Treatment e.g. mild community-acquired pneumonia (CAP), sinusitis, etc.
GP + expanded GN coverage, but not active against ESBL+ or AmpC+
Treatment e.g. severe infections requiring IV treatment, hospital-acquired
pneumonia (HAP), meningitis etc.
Similar to 3rd generation, but better activity against P. aeruginosa and
Enterobacteriaceae family
Similar to 3rd generation, but activity against MRSA (methicillin-resistant
S. aureus), but not against P. aeruginosa
Restored activity vs GN pathogens that produce β-lactamases
Broadest spectrum of activity
Narrow spectrum of activity vs GN including some P. aeruginosa strains (but
not ESBL– and AmpC-producers)
Monobactams are NOT active against Stenotrophomonas maltophilia
Safe for use in penicillin allergic patients
Broadest spectrum of activity including many GP and GN, and anaerobes
Ertapenem is NOT active vs P. aeruginosa and Acinetobacter spp.
Carbapenems are reserved for severe infections that are polymicrobial and
caused by multidrug resistant pathogens
Cilastatin inhibits renal dehydropeptidases that deactivate imipenem
Bacitracin
Polypeptide antibiotic (mixture of cyclic peptides)
Narrow spectrum; bactericidal
• Inhibits cell wall synthesis of GP bacteria – mostly staphylococci,
streptococci, Corynebacterium, Clostridium
• Used as a topical preparations e.g. ointments
(too toxic to be used parenterally)
• Used to prevent infection from minor abrasions, wounds, bites,
burns etc.
Glycopeptides
Vancomycin, teicoplanin, telavancin, ramoplanin, dalbavancin
Effective against GP bacteria only – but active vs resistant bacteria e.g.
MRSA, HLAR
Narrow spectrum of activity; bactericidal
Inhibit cell wall synthesis
Poor absorption from GIT – orally to treat AAD
Used IV in serious infections caused by GP cocci and other GP bacteria
Fosfomycin
Inhibits bacterial cell wall synthesis by interfering with the enzymes involved
in the formation of peptidoglycan precursors - bactericidal
Effective against many GP and GN bacteria (broad spectrum of activity),
including enterococci irrespective of vancomycin resistance, staphylococci
(irrespective of methicillin resistance), Enterobacteriaceae family, Listeria
monocytogenes, N. gonorrhoea and anaerobes
Pseudomonas, Acinetobacter, Stenotrophomonas, Burkholderia,
S. saprophyticus, M. tuberculosis are intrinsically resistant to fosfomycin
Fosfomycin has an immunomodulatory effects – supress synthesis of
proinflammatory cytokines, enhances bactericidal activity of neutrophils
Penetrates into biofilms
Antimicrobial agents that alter/disrupt the cytoplasmic membrane
bactericidal
Colistin (polymyxin E) used in severe infections caused by MDR GN rods: Pseudomonas, Klebsiella, Acinetobacter, Stenotrophomonas maltophilia, M. tuberculosis, M. intracellulare
BUT: Proteus, Burkholderia, Neisseria, Brucella exhibit intrinsic resistance
Daptomycin (lipopeptide antibiotic) disrupts membrane potential
(depolarization)
Spectrum: GP pathogens (VRE, MRSA etc.), S. pyogenes, S. agalactiae
Used to treat complicated skin/soft tissue infections
Antimicrobial agents that inhibit protein synthesis
These agents prevent bacteria from synthesizing structural proteins and enzymes: alter bacterial ribosome, block translation & cause
faulty protein synthesis
These antibiotics are bacteriostatic or bactericidal depending on concentration
Macrolides Glycylcyclines
Tetracyclines Ketolides
Aminoglycosides Fusidic acid
Spectinomycin Mupirocin
Streptogramins Oxazolidinones
Lincozamides Chloramphenicol
Tetracyclines
• Broad-spectrum: GP & GN bacteria, Rickettsia, Chlamydia, Mycoplasma, spirochetes, some protozoa (malaria)
tetracycline, oxytetracycline, doxycycline, minocycline
• Resistance common
• Primarily used to treat: atypical pneumonia, syphilis, brucellosis, Lyme disease, acne, plague, leptospirosis, anthrax, cholera
Glycylcyclines
Tigecycline – derived from minocycline
Broad-spectrum: GP+GN bacteria including MDR pathogens
GP cocci: staphylococci, enterococci, streptococci - including resistant strains
GN intestinal rods – except Proteus
GN nonfermentive rods e.g. Acinetobacter spp. except Pseudomonas
Obligatory anaerobic – Bacteroides fragilis
Atypical bacteria
Advantage over tetracyclines: active against bacteria resistant to tetracyclines, higher binding affinity, broader spectrum
AminoglycosidesBactericidal – except for staphylococci = static
Active against most GN aerobic bacilli but lack activity against anaerobic & most GP bacteria - except for staphylococci
streptomycin, kanamycin, tobramycin, amikacin, gentamycin
Spectinomycin
Bacteriostatic antibiotic chemically related to aminoglycosides
Its activity is restricted to gonococci
Spectinomycin is given for gonococcal urethritis, cervicitis, proctitis
Macrolideserythromycin, roxithromycin, clarithromycin, azithromycin
mainly affects GP cocci (streptococci, staphylococci, but NOT enterococci) and intracellular pathogens (Mycoplasma, Chlamydia, Legionella); other: Campylobacter, Helicobacter, Borrelia, Treponema, Corynebacterium sp., and some anaerobes (Propionibacterium)
Ketolides (derived from erythromycin)
Bacteriostatic (bactericidal at higher concentrations)
Telithromycin, cethromycin, solithromycin
Active against bacterial strains resistant to macrolides
Lincozamides narrow spectrum
lincomycin, clindamycin
active against GP bacteria (but NOT GN aerobic), and most obligatory anaerobic bacteria, including Bacteroides – but they can induce AAD
Principal therapeutic indications are staphylococcal infections of bones and joints, and anaerobic infections
They are static or cidal depending on concentration, bacterial inoculum and species
StreptograminsA combination of quinupristin & dalfopristin (Synercid) – exhibit dose-dependent cidal activity
Work synergistically to inhibit protein synthesis
Active against: GP cocci (also multi-resistant: VRSA, VRE), modest activity: common respiratory pathogens (Moraxella, Str. pneumoniae,
Mycoplasma, Legionella, Chlamydophila) & anaerobes
OxazolidinonesLinezolid - narrow spectrum of activity: GP bacteria
(staphylococci, streptococci, enterococci, pneumococci –
resistant strains, Listeria, corynebacteria), and certain GN bacteria:
Moraxella, Pasteurella, Bacteroides, also Legionella, M. tuberculosis
but other GN are resistant
Fusidic acidNarrow spectrum of activity: staphylococci (MSSA, MRSA) -treatment skin, eye infections, bone, joints infections – as cream, ointment, eye drops
Activity against other GP (streptococci, enterococci) cocci is poor
Other: anaerobes (Bacteroides fragilis, Clostridium spp.), Neisseria, Bordetella, Corynebacterium
Moderate activity against mycobacteria: M. leprae and certain protozoa (Giardia lamblia, Plasmodium falciparum)
Mupirocin
Bactericidal or static activity depends on concentration
Narrow spectrum of activity: staphylococci + resistant strains, streptococci
Used for topical treatment of superficial skin infections e.g. furuncles, impetigo and eradication of nasal carriage of MRSA (intra-nasally)
Chloramphenicol
GP bacteria: streptococci, staphylococci, enterococci, B. anthracis, Listeria
GN bacteria: H. influenzae, Moraxella, Neisseria, E. coli, Proteus mirabilis, Salmonella, Shigella, Stenotrophomonas matlophilia
Many anaerobic bacteria
Penetrates to CSF
Side effects: fatal aplastic anemia, dose-dependent leucopenia, bone marrow suppression etc. – limit its use
Antimicrobial that interfere with DNA synthesis
bactericidal
Rifampins Fluoroquinolones
Metronidazole Fidaxomicin
Rifamycin (Rifampicin, Rifampin)
Prevent the synthesis of mRNA by inhibiting the RNA polymerase
Effective against some GP & GN bacteria, M. tuberculosis, M. leprae,
Legionella pneumophila
Prophylaxis in e.g. meningococcal meningitis
FluoroquinolonesSynthetic chemicals broad spectrum of activity
Inhibit topoisomerases (DNA gyrases) involved in bacterial nucleic
acid synthesis
Generations:
I – nalidixic acid (GN bacteria) – UTI
II – ciprofloxacin, norfloxacin, ofloxacin
(GN including P. aeruginosa, and S. aureus, some atypical) – UTI,
STD, skin, soft tissue infections, GITI
III – levofloxacin, gatifloxacin, temafloxacin, grepafloxacin, (GP especially pneumococci, GN, atypical) – RTI, GITI
IV – trovafloxacin, moxifloxacin, gemifloxacin (GP, GN, atypical, anaerobes)
Fidaxomicin
Macrocyclic lactone
Inhibits RNA polymerase
Minimally absorbed – active only locally in GTI
Minimal or no activity vs GN bacteria
Bactericidal against C. difficile – better option than vancomycin to treat AAD
Nitroimidazoles
metronidazole, tinidazole
Converted into metabolites that impede bacterial DNA synthesis
An antibiotics active against anaerobic bacteria & certain parasites (Entamoeba histolytica, Trichomonas, Giardia – treatment of bacterial vaginosis)
Competitive antagonistic antibiotics
Synthetic chemicalsInhibitors of metabolic pathways via competitive antagonism include:• Sulphonamides• Trimethoprim• IsoniazidThese all inhibit folic acid biosynthesis
Competitive antagonism - a drug chemically resembles a substrate in a metabolic pathway
Because of their similarity, either the drug or the substrate can bind to the enzyme
While the enzyme is bound to the drug, it is unable to bind to its natural substrate and blocks that step in the metabolic pathway
Sulfonamides & trimethoprim
(TMP-SMX)
Co-trimoxazole is a combination of trimethoprim + sulfamethoxazole (TMP-SMX)
Both of these drugs block enzymes in the bacterial pathway required for the synthesis of tetrahydrofolic acid - a cofactor needed for bacteria to produce nucleic acids
Spectrum - broad:
GP: staphylo, strepto, Listeria, Nocardia,
GN: enteric rods, Stenotrophomonas maltophilia, H. influenzae, Pasteurella, Brucella, Bordetella, Neisseria
Pneumocystis pneumonia
Lipophilic antibiotics Hydrophilic antibiotics
macrolides
tetracyclines
fluoroquinolones
chloramphenicol
rifampin
tigecycline
β-lactams
glycopeptides
aminoglycosides
colistin
daptomycin
● Free diffuse through cytoplasmic
membranes
● Active vs intracellulare pathogens
● Eliminated by hepatic metabolism
● Unable to diffuse through cytoplasmic
membranes
● Inactive vs intracellulare pathogens
● Eliminated renally as unchanged drugs
Thank you for your attention