antibiotics and their usages

Antibacterials

Classes and Clinical Uses

Serious nosocomial infections

Active against staphylococci and gram negative rods including Pseudomonas aeruginosa

Often used in combination with a beta-lactam antibiotic

Monitor serum levels to ensure effectiveness and avoid toxicity

Aminoglycosides

monobactams

Broad spectrum parenteral antibiotics

Ototoxicity and nephrotoxicity

Streptomycin

Anti-tuberculosis agent

Spectinomycin

Gonorrhoea

Amikacin,

gentamicin,

tobramycin

netilmicin

Gram-positive bacteria like staphylococcus, streptococcus

Gram negatives like Neisseria, Haemophilus, Bordetella, Moraxella and Campylobacter but NOT against Enterobacteriaceae or Pseudomonas

Legionella, Mycoplasma and Chlamydia

Treponema pallidum

Wide spread resistance is encountered

Macrolides

Erythromycin

Atypical pneumonias

Mild skin and soft tissue infections

Whooping cough

Syphilis (penicillin allergy)

Campylobacter infections

Azithromycin, Clarithromycin

As for erythromycin but preferred because of less adverse effects and more convenient dosing regimen

Very broad spectrum :

Gram positive, Gram negative and anaerobes

(ertapenem not active against Ps aeruginosa)

Stable to ESBLs

protein synthesis inhibitors

Clinical use : severe gram negative nosocomial infections

Imipenem,

meropenem,

ertapenem

doripenem

Lincosamides

Active against Gram-positive bacteria and anaerobic bacteria

Clindamycin

Anti-MRSA agent

Anaerobic infections

Oral administration

Associated with pseudomembranous colitis due to Clostridium difficile

carbapenems

Broad spectrum

Gram positive

Gram negative

Rickettsia, chlamydia, mycoplasma, legionella

Spirochaetes

Protozoa eg Plasmodium

Resistance is common but fortunately not in the pathogens where tetracyclines are the drug of choice

Tetracyclines

Tetracycline

Mild skin and soft tissue infections

Acne vulgaris

Doxycycline

Scrub typhus

Leptospirosis

Melioidosis (maintenance phase)

Malaria

Tigecycline

A glycylcycline, compound related to tetracycline

Active against many resistant nosocomial pathogens like MRSA, ESBL producing Klebsiella and resistant Acinetobacter baumanii

Used for serious nosocomial infections due to resistant organisms

4th Gen

Good gram-negative and gram-positive activity –

cefepime

For serious nosocomial infections eg febrile neutropaenics

Clinical uses

Serious Gram negative nosocomial infections

Moderate to serious community acquired pneumonia (ceftriaxone)

Biliary infections (cefoperazone)

Bacterial meningitis (cefotaxime and ceftriaxone)

Melioidosis (ceftazidime)

3rd Gen

Good gram-negative activity including Pseudomonas aeruginosa but less Gram positive action

Cefotaxime,

cefoperazone,

ceftazidime,

ceftriaxone

Much abuse of cephalosporins resulting in emergence of resistance

ESBL (extended spectrum betalactamase) is a major problem

No activity against Enterococcus and MRSA

the issue with cephalosporins

cephalosporins

2nd Gen

Gram-positive and Gram negative activity but no anti-pseudomonal action

eg Cefuroxime

Urinary infections

Respiratory infections

cell wall synthesis inhibiters

glycopeptides

1st Gen

primarily Gram positive activity with some Gram-negative activity

eg Cephalexin

(urinary tract infections)

Vancomycin, teicoplanin

Mainly Gram-positive activity

Clinical uses

Infections caused by MRSA (Methicillin-resistant Staphylococcus aureus) and methicillin-resistant coagulase-negative staphylococci

Clostridium difficile infection (oral administration)

Need to monitor levels to ensure clinical efficacy and to avoid toxicity

penicillins

Beta-lactum & betalactamase inhibitor combo

Augmentin (amoxycillin-clavulanate),

Unasyn (ampicillin-sulbactam),

Tazocin (Piperacillin-tazobactam)

Augmentin and Unasyn

Mild to moderate community acquired pneumonias

Urinary tract infections

Bacterial sinusitis and otitis media

Skin and soft tissue infections including diabetic foot

Tazocin

Serious gram-negative nosocomial infections

broad-spectrum penicillins

Ampicillin and amoxicillin

Active against Gram positives but also Gram negatives like E. coli, Salmonella, Shigella, Haemophilus

Destroyed by beta-lactamases

Clinical uses

Uncomplicated urinary tract infections

Acute exacerbations of COPD and mild community acquired pneumonias

Uncomplicated bacterial sinusitis and otitis media

Enteric fever

Helicobacter infection

Metronidazole

beta-lactamase stable penicillins

Cloxacillin, flucloxacillin

Treatment of beta-lactamase producing Staphylococcus aureus (MSSA or methicillin-sensitive Staphylococcus aureus)

Cloxacillin is MORE EFFECTIVE than vancomycin for MSSA infections

benzyl - penicillins

• Very effective antibiotic against staphylococci, streptococci, spirochaetes
• Destroyed by beta-lactamase
• Clinical Uses
• Streptococcal infections
• eg pharyngitis, skin infections
• Pneumococcal pneumonia
• Syphilis, leptospirosis

Inhibitors of Nucleic Acid Synthesis

Quinolones

Synthetic compounds with broad spectrum of activity

Ciprofloxacin

Active against Gram negatives including Ps aeruginosa

Active against Staph aureus (resistance emerge readily) but less activity against streptococci and enterococci

Wide range of clinical uses including urinary infections, gastrointestinal infections (including typhoid fever), hepatobiliary infections, gram negative blood stream infections and osteomyelitis

Not recommended for staphylococcal or streptococcal infections

Overuse has led to emergence of resistance

Levofloxacin, moxifloxacin, gatifloxacin

Enhanced activity against Streptococcus pneumoniae

Also be used in respiratory infections including pneumonia

Interact and break up cell’s DNA

Anti-anaerobic and anti-protozoal agent

Clinical uses

Anaerobic infections

Clostridium difficile infection

Amoebiasis

Trichomoniasis

Giardiasis

Inhibitors of DNA replication

Rifampicin

Inhibitors of RNA polymerase

Activity against Gram-positive organisms and Mycobacterium

Main clinical use in tuberculosis

Also used for MRSA infections but in combination with another anti-staphylococcal agent

Inhibitors of synthesis of precurosrs

Sulphonamides

Cotrimoxazole

Fixed ratio combination (1 : 5) of trimethoprim and sulphamethoxazole (a sulphonamide)

Broad spectrum of activity but resistance is now common

Main clinical uses

Urinary tract infections

Enteric fever

Pneumocystitis carinii

Stenotrophomonas maltophilia (ICU pathogen associated with overuse of carbapenems)

Trimethoprim

Polymyxins

Act on cell membrane of bacteria

High toxicity : neuro- and nephrotoxic

Active against Gram-negative bacteria including multi-resistant strains

Not uncommon to now encounter strains of Acinetobacter and Ps aeruginosa that are resistant to all antibiotics except the polymyxins

Used to treat multi-resistant gram negative infections mainly in ICUs