Antimicrobials

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Penicillin G/V activity

S. aureus: -
S. pnemo: +
Enterococcus: +
E. coli: -
Klebsiella spp: -
H. flu: -
Pseudomonas: -
B. fragilis: -

Cloxacillin activity

S. aureus: +
S. pnemo: +
Enterococcus: -
E. coli: -
Klebsiella spp: -
H. flu: -
Pseudomonas: -
B. fragilis: -

Amoxicillin activity

S. aureus: -
S. pnemo: +
Enterococcus: +
E. coli: -/+
Klebsiella spp: -
H. flu: -/+
Pseudomonas: -
B. fragilis: -

Amox/clav activity

S. aureus: +
S. pnemo: +
Enterococcus: +
E. coli: +
Klebsiella spp: +
H. flu: +
Pseudomonas: -
B. fragilis: +

Pip/Tazo

S. aureus: +
S. pnemo: +
Enterococcus: +
E. coli: +
Klebsiella spp: +
H. flu: +
Pseudomonas: +
B. fragilis: +

beta-lactams

Penicillins, cephalosporins, monobactams and carbapenems. All are bactericidal. Combine and inactivate penicillin-binding proteins responsible for transpeptidation that cross-links peptidoglycan, therefore weakening cell wall and causing cell lysis

Vancomycin

Glycopeptide that prevents proper cell wall cross-linking through stearic hindrance and results in cell lysis

Extended spectrum penicillins

possess all the activity of penicillin but have a broader spectrum against many strains of certain species of gram-negative bacteria

Clavulanic acid (Clav) and tazobactam (Tazo)

Inhibits beta-lactamases

Broad specturm penicillins

all the activity of ampicillin but increased activity against many Enterobacteriaceae (eg. Klebsiella pneumoniae), most Pseudomonas aeruginosa strains and many anaerobes (including Bacteroides fragilis). It is mostly used to treat polymicrobial infections and hospital-acquired gram-negative bacterial infections.

Cephalosporins

resistant to penicillinases but susceptible to
cephalosporinase

First generation cephalosporins

Cefazolin/cephalexin
are very active against staphylococci and all streptococci (except E. faecalis). In addition, they are active against gram-negative bacilli.
Used as alternatives to penicillins in patients with a history of type III (delayed) hypersensitivity. Commonly used as pre-operative prophylaxis to prevent post-surgical infections.

Second generation cephalosporins

Cefuroxime and its oral form cefuroxime axetil. Cefoxitin.
active against all streptococci (except E. faecalis) and slightly less active against staphylococci than first generation.

Third generation cephalosporins

Ceftriaxone Ceftazidime
offer excellent anti-streptococcal activity, but anti-staphylococcal activity is relatively poor. They are very active against gram-negative bacilli including Enterobacter spp., Serratia spp., etc. In addition, these agents are very active against Neisseria gonorrhoeae and some spirochetes such as Treponema pallidum and Borrelia burgdorferi. Ceftazidime possesses excellent activity against P.aeruginosa. These agents are primarily used to treat serious hospital-acquired infections due to gram-negative bacilli.

Cefazolin activity

S. aureus: +
S. pnemo: +
Enterococcus: -
E. coli: +
Klebsiella spp: +
H. flu: -/+
Pseudomonas: -
B. fragilis: -

Cefuroxime activity

S. aureus: +
S. pnemo: +
Enterococcus: -
E. coli: +
Klebsiella spp: +
H. flu: +
Pseudomonas: -
B. fragilis: -

Cefoxitin activity

S. aureus: +
S. pnemo: +
Enterococcus: -
E. coli: +
Klebsiella spp: +
H. flu: +
Pseudomonas: -
B. fragilis: +

Ceftriaxone activity

S. aureus: -/+
S. pnemo: +
Enterococcus: -
E. coli: +
Klebsiella spp: +
H. flu: +
Pseudomonas: -
B. fragilis: -

Ceftazidime activity

S. aureus: -/+
S. pnemo: +
Enterococcus: -
E. coli: +
Klebsiella spp: +
H. flu: +
Pseudomonas: +
B. fragilis: -

Imipenem activity

S. aureus: +
S. pnemo: +
Enterococcus: +
E. coli: +
Klebsiella spp: +
H. flu: +
Pseudomonas: +
B. fragilis: +

Vancomycin

S. aureus: +
S. pnemo: +
Enterococcus: +
E. coli: -
Klebsiella spp: -
H. flu: -
Pseudomonas: -
B. fragilis: -

B-lactam hypersensitivity reactions

Type I, II and III

Type I and II

If your patients have these reactions to penicillin, never give them another b-lactam!!

Increasing penicillin and cephalosporin generation

As generation increases, gram positive activity decreases and gram negative activity increases

Protein Synthesis Inhibitors

act by binding to the procaryotic ribosome at the 30s site or the 50s site which leads to inhibition of protein synthesis.
Except aminoglycosides, are considered bacteriostatic

Aminoglycosides

Gentamicin, netilmicin, tobramycin and amikacin kill most aerobic and facultative gram-negative bacilli.
used to treat serious infections involving gram-negative bacilli.
synergism with beta-lactams also makes them useful to treat serious Staphylococcal and Streptococcal infections.

Nephrotoxicity and ototoxicity

Adverse side effects of aminoglycosides

Chloramphenicol

very broad spectrum with activity against gram-positive and -negative, aerobes, anaerobes, spirochetes), rickettsia, chlamydophila and mycoplasma. Clinically, its major use is for treatment of anaerobic infections, multi-drug resistant meningitis, and severe salmonella infections (eg. typhoid fever).

Aplastic anaemia

Insufficient production of RBCs
Adverse effect of chloramphenicol

Clindamycin

active against gram-positive cocci (Staphylococci and Streptococci, except Enterococci) and anaerobes (including B.fragilis). Main use is treatment of mixed Staphylococcal/ Streptococcal and anaerobic infections

Clindamycin adverse effects

Most frequently associated with CDAD!!
Gastrointestinal intolerance (nausea, vomiting) is common with diarrhea occurring in up to 20% of patients.

Macrolides

erythromycin, clarithromycin and azithromycin are macrocyclic lactone rings attached to 2 sugar moieties

Adverse fx of macrolides

one of the safest antibiotics. However, gastrointestinal problems are very common (less common with clarithromycin, azithromycin and telithromycin). Cholestatic hepatitis is rare and reversible (almost always the estolate form). Hepatotoxicity has been reported with telithromycin.

Tetracyclines

derivatives of the polycyclic naphthacenecarboxamide. Tetracycline is considered a short-acting agent while minocycline and doxycycline are long acting agents.

Adverse effects of tetracyclines

contraindicated in pregnancy and in children up to the age of 8 years because they depress bone growth and cause tooth discoloration. These agents should not be used in patients with hepatic or renal impairment. In patients with renal failure use of tetracyclines (except doxycycline) may worsen renal function.

Linezolid

-Methicillin-resistant S.aureus (MRSA),
-Methicillin-resistant S.epidermidis (MRSE),
-vancomycin-resistant Enterococcus (VRE),
-penicillin-resistant S.pneumoniae (PRSP).

This agent which is available orally (100% bioavailable) and IV, is indicated for bacteremia, complicated skin/soft tissue infections and nosocomial pneumonia caused by resistant gram-positive cocci.

Safest antibiotics in pregnancy

Beta-lactams,
Clindamycin, Erythromycins other than estolate, Methenamine,
Ethambutol,
Nystatin and
Amphotericin B

Worst antibiotics for pregnancy

Aminoglycosides, Chloramphenicol
Erythromycin Estolate
Fluoroquinolones
Sulfonamides
Tetracyclines

Fluoroquinolones

Their main use is for treatment of serious gram-negative bacillary infections (these are the only agents that can be used orally for this purpose).

Sulfonamides

-drug of choice for Pneumocystis carinii pneumonia
-gram-positive cocci,
-gram-negative bacilli,
-Nocardia asteroides,
-Chlamydophila trachomatis,
Almost all anaerobes are resistant. Commonly used for urinary tract, gastrointestinal and respiratory infections.
TMP/SMX

used as prophylaxis in neutropenic patients as an alternative to fluoroquinolones

Metronidazole

-very active against anaerobes,
-Gardnerella vaginalis
-Trichomonas vaginalis
and is the drug of choice for mild-moderate pseudomembranous-colitis (PMC) [except in severe cases when vancomycin is used].

a nitroimidazole that works by being reduced inside the cell to short-lived intermediate compounds or free radicals that produce a bactericidal action by interacting with DNA and other macromolecules.

Resistance is not common.

Rifampin

-gram-positive cocci,
-some gram-negative cocci and bacilli.
-Mycobacterium tuberculosis,
-Legionella pneumophila
-C. trachomatis.

inhibition of DNA-dependent RNA-polymerase which prevents transcription
resistance develops within a matter of days if the agent is used alone. Thus, it is used only in combination to provide synergy except for short-term use for meningitis prophylaxis

Topical antibiotics

bacitracin, polymyxin, gramicidin, neomycin and mupirocin.

Bacitracin

-Staphylococci and Streptococci,
-Clostridium spp.
-NOT gram-negative bacilli.

It is used locally for the treatment of furuncles, carbuncles and abscesses. It is also used orally for treatment of pseudomembranous-colitis.

Gramicidin

-Staphylococci and Streptococci,
-gram-negative bacilli being resistant.

It is used for similar infections as bacitracin and demonstrates virtually no toxicity when used topically.

Neomycin, Framycetin, Paromomycin

- gram-positive cocci
- gram-negative bacilli

aminoglycosides that are too toxic to be used systemically.

Polymyxins

active against gram-negative bacilli
NOT for gram-positive bacteria

bactericidal by interfering with the structure and function of the outer and cytoplasmic (inner) membranes.
Topically, they are rarely used alone and are
usually combined with bacitracin or gramicidin or neomycin which possess activity against
gram-positive bacteria.

Mupirocin

It is active against Staphylococci (including MRSA) and Streptococci (except Enterococcus).

inhibits protein synthesis by binding to bacterial isoleucyl
-tRNA synthetase, leading to a bactericidal action (due to high concentrations achieved
topically). It is used for impetigo, folliculitis and other skin infections caused by
Staphylococci and/or Streptococci. It is used to eliminate nasal carriage of MRSA.

Fusidic Acid

-Staphylococci
-Streptococci.
Used to treat Staphylococcal and/or Streptococcal skin
Infections.

Erythromycin

-gram-positive cocci
-fastidious gram-negative cocci and bacilli (Legionella, Campylobacter, Moraxella, Neisseria, Haemophilus),
-Mycoplasma pneumoniae
-Chlamydophila trachomatis.

Clarithromycin and azithromycin

More activity than Erythromycin for
-gram-positive cocci
-fastidious gram-negative cocci and bacilli (Legionella, Campylobacter, Moraxella, Neisseria, Haemophilus),
-Mycoplasma pneumoniae
-Chlamydophila trachomatis
-M avium intracellulare complex
-H. pylori

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