Antibiotics Flashcards
Definition of infection?
Infection means the entry of a microorganism into the body, where it multiplies & causes disease
What are the 2 prerequisites for infection?
1, The host must be susceptible
2. The organism must be pathogenic (disease causing)
Definition of Pathogenic bacteria
These are disease causing bacteria as opposed to commensals (e.g. flora in the gastro-intestinal tract) that do not cause disease, but instead serve a useful purpose in preventing overgrowth of pathogenic bacteria
Opportunistic infections?
Under certain circumstances like in immunodeficiency or when broad spectrum antibiotics are overused, normally non-pathogenic organisms cause disease & these infections are called opportunistic infections
Nosocomial infections?
Infections obtained in the hospital environment
Super infection?
Infection occurring after or on top of an earlier infection, especially following Rx with broad-spectrum antibiotics
Selective toxicity?
A compound must exhibit selective toxicity, i.e. interfere with the growth of the infectious agent while having little or no deleterious(causing harm or damage) effect on host cells
Resistance?
Resistance to an antibiotic has occurred when an organism is no longer affected by a drug that previously killed it
What are the causes of drug resistance?
- Unnecessary use of antibiotics
- Inappropriate choice of antibiotics
- Using lower than effective doses.
- Using inappropriately long dosing intervals.
- Inappropriate use of broad spectrum agents.
- Inappropriate use of antibiotic combinations.
- Using bacteriostatic agents in immunodeficiency states.
- Continuing an antibiotic in the presence of resistance.
Drug Sensitivity?
The organism is sensitive to the drug if it is killed by it, or if the organism’s growth is inhibited by it
Broad spectrum & narrow spectrum antibiotics?
- Broad spectrum antibiotics kill / inhibit the growth of bacteria belonging to two / more different groups
- Narrow spectrum antibiotics only kill / inhibit a single / limited group of bacteria
Bactericidal antibiotics?
Antibiotics that kill bacteria.
Bacteriostatic antibiotics?
- Antibiotics that INHIBIT (stop) the growth of the bacterium & allow the body’s defense mechanisms to destroy the organism
- Some bacteriostatic drugs are bactericidal in high doses
Structure of bacteria?
- Bacteria are unicellular, living organisms with a cell wall, cytoplasm & a nucleus containing one chromosome
- They function like independent living cells
Description according to oxygen needs?
AEROBIC and ANAEROBIC
- Aerobic
These bacteria rely on oxygen from the environment to live; therefore they need an oxygenated environment to survive. - Anaerobic
These bacteria produce their own oxygen from other chemical compounds; therefore they do not need an oxygenated environment to survive
Description according to Gram staining. Gram-Positive
- Take up the crystal violet stain used in the test, & then appear to be purple-coloured when seen through a microscope
- This is because the thick peptidoglycan layer in the bacterial cell wall retains the stain after it is washed away from the rest of the sample, in the decolorization stage of the test
Description according to Gram staining. Gram-Negative
Cannot retain the violet stain after the decolorization step
•Their peptidoglycan layer is much thinner & sandwiched between an inner cell membrane & a bacterial outer membrane, causing them to take up the counterstain (safranin or fuchsine) & appear red or pink
Cell wall inhibitors
Beta-lactam antibiotics:
- Penicillin’s
- Cephalosporins
- Carbapenems
- Monobactams
- Penicillin’s
- Narrow spectrum: Penicillin G; Penicillin V; Benzathine penicillin; Procaine penicillin
- Penicillinase resistant: Flucloxacillin, Cloxacillin
- Broad spectrum: Ampicillin; Amoxycillin; Amoxycillin/clavulanic acid combination
- Antipseudomonal penicillins: Piperacillin
Mechanism of action for Penicillin’s; Cephalosporins; Carbapenemes; Vancomycin ?
- Inhibit bacterial cell wall synthesis (then cell lysis occur)
- Bactericidal
Mechanism of action for Clavulanic acid?
Clavulanic acid acts as a beta-lactamase inhibitor (the enzyme that is formed by bacteria to inactivate the drug)
Penicillin Indications Narrow spectrum?
•Gram-positive cocci:
→Staphylococcus,
→ Streptococcus
•Syphilis
- Streptococcal infections e.g. pneumonia
- Meningitis: good BBB penetration during infection
•Cloxacillin / Flucloxacillin:
→staphylococcal
infections of the
skin.
- Gonorrhoea (at present considered resistant)
- Cellulitis or systemic sepsis
Penicillin Indications Broad spectrum?
•Gram-negative organisms
→ Haemophilus
influenzae –
pneumonia.
→Salmonella –
typhoid fever.
→Shigella –diarrhoea
E. coli- urine tract infections.
→Gonococcus- gonorrhoea (resistance common).
•Gram-positive organisms
→ Streptococcus e.g.
pneumonia.
•Piperacillin
→Pseudomonas
infections.
Pharmacokinetics penicillin?
- Ampicillin is given IV because of the low oral bioavailability
- Amoxicillin has good oral bioavailability & the absorption is not influenced by food.
- Procaine penicillin & benzathine penicillin are in suspension & are only given IM.
- Food reduces the absorption of oral penicillin’s – give 1 hour before or 2 hours after meals
Penicillin Side effects?
- Nausea, vomiting, diarrhoea
- Allergic reactions (in less than 1% of patients)
- Overgrowth of fungi & resistant organisms - superinfections
Penicillin Contraindications?
Hypersensitivity to penicillins or cephalosporins
Cephalosporins generations?
- First generation: Cephalexin; Cephazolin, Cephalotin
- Second generation: Cefuroxime, Cefachlor
- Third generation: Ceftriaxone, Cefotaxime
- Fourth generation: Cefepime
Indications of 1st-generation of Cephalosporins?
- Mainly Gram-positive bacteria, •Proteus,
- E coli,
- Klebsiella
Indications of 2nd-generation of Cephalosporins?
- Mainly Gram-negative bacteria: Haemophilis; Also Bacteroides
- Less active against Gram-positive bacteria
Indications of 3rd-generation of Cephalosporins?
Mainly Gram-negative bacteria
Indications of 4th-generation of Cephalosporins?
Gram-negative- and Gram-positive bacteria, including Pseudomonas
Ceph side effects
•Allergic reactions (5-16% cross reaction with penicillin),
•Nausea, vomiting, diarrhoea.
•Nephrotoxic (in very ill patients).
•Super infections
•High doses neurotoxic.
•Disulfiram reaction with cefuroxime & cefamandole.
Bleeding tendency with cefamandole
Carbapenemes Indication Imipenem?
- Activity against many Gram-positive & Gram-negative aerobic & anaerobic bacteria, also some Pseudomonas.
- Use generally limited to severe nosocomial infections: septicemia, endocarditis, respiratory tract-, genitourinary-, intra-abdominal-, bone & joint-, skin & soft tissue infections.
- Formulated with cilastatin: a specific enzyme inhibitor that blocks renal metabolism of imipenem & enhances its urinary concentration.
Carbapenems side effects?
- Hypersensitivity
- Gastro-intestinal
- Haematological
- CNS
- Seizures
Carbapenemes Indication Meropenem?
- Similar spectrum of activity as imipenem
2. In addition penetrates well into CSF – alternative for bacterial meningitis
Vancomycin indications?
- Pseudomembranous enterocolitis – oral
- Resistant staphylococcal & enterococcal infections, methicillin-resistant
Staphylococcus aureus - Endocarditis in penicillin allergy
Vancomycin pharmacokinetics?
Must be given parenteral because oral absorption is negligible
Vancomycin Side effects?
- Nephrotoxic
- Ototoxic
- Red man syndrome due to histamine release (not true allergy)
- Monitor blood levels
Protein synthesis inhibitors?
- Tetracyclines
- Glycylcyclines
- Aminoglycosides
- Macrolides/Ketolides
- Clindamycin
Tetracyclines
- Doxycycline
2. Minocycline
Aminoglycosides
- Streptomycin
- Gentamycin
- Amikacin
- Tobramycin
Macrolides/ ketolides
•New generation: Azithromycin &
Clarithromycin : longer half-life
•Erythromycin
Tetracyclines, Aminoglycosides, Macrolides, Chloramphenicol, Clindamycin, Mechanism of action?
- Inhibit bacterial protein synthesis. Effective against atypical organisms
- Bacteriostatic
Tetracyclines indications?
- Severe acne
- Tick bite fever: Rickettsiae
- Malaria prophylaxis: doxycycline
- Atypical organisms: Chlamydia, Mycoplasma, Legionella
- Sexual transmitted illnesses
- Brucellosis, Chronic bronchitis
- Cholera, Typhoid fever (resistance common)
Tetracycline side effects?
- Phototoxic reactions
- Nausea, vomiting, diarrhoea
- Teeth discolouration & inhibition of bone growth in children due to binding with calcium
- Super infections e.g. Candida
Tetracycline Contraindications
- Children <12 years
2. Pregnancy & lactation
Tetracycline Drug interactions
•Food & cations like Ca, Mg, Al, Fe decreases oral absorption
Aminoglycosides
- Gram-negative bacteria: Pseudomonas, Klebsiella, E coli
- Tuberculosis
- Topical in the eye
- Brucellosis
Aminoglycosides
- Very polar & highly water soluble.
- Not absorbed orally – must be given IM or IV.
- Used in combination with penicillins because it can not cross cell membranes well
Aminoglycosides Side effects
- Ototoxic (related to high blood level & duration)
- Nephrotoxic
- Neuromuscular paralysis: act as a blocking agent at neuromuscular junction.
- Monitor blood levels - TDM
Aminoglycosides Contraindications
- Renal disease
- Pregnancy & lactation
- Myasthenia gravis
Which medications can cause yellow sclera,& clay colored stools?
- Erythromycin
- Phenazopyridine
The thing is Liver Toxicity, key term JAUNDICE.
A patient in sepsis is prescribed several antibiotics during their hospital stay. What patient teaching should be included?
- Levo_floxacin
& Doxy_cycline; both no Sun exposure and not baby safe. - Vanco_mycin & Azithro_mycin; they kill the kidney
SO Creatinine>1.3 means bad kidney and Urine output=<30ml means kidney is in distress
3 Azithro_mycin: Throws QT intervals and liver out of work.
Therefore:
- Avoid direct sun exposure.
- Oral birth control ineffective
- Take until finished
- Monitor QT intervals
- Monitor creatinine and BUN
Patient education when prescribing antibiotics?
- Finish Med: To prevent super infection.
Key words
•Take until all meds are finished
•DO NOT stop when feeling better.
- Accidental pregnancy
•C-Child Care
•C-“Cillins”: Penicillin, Amoxicillin
•C-“Cycline”: Doxycycline, Tetracyline.
key words:
•Oral contraceptives are ineffective
•Use additional contraceptives like IUD
- NO Alcohol
4. NO FOOD MTF "Move The Food" M- Macrolides: Azy_thromycin T-Tetra_cycline: Doxycycline F-Fluoroquinolones: Levo_floxacin
key words
•Take on an empy stomach
•With a FULL glass of water
5. NO Sun AVOID " Fun The Sun" F-Fluoroquinolones: Levo_floxacin T-Teracycline: Doxycycline S-Sulfa drugs= Sun Burn •Trimethoprim-sulfa methox azole (Brand: Bactrim).
- SUPER Toxic (Kidney + Ears)
Vencomycin, Gentamycin, Neomycin
