Antibiotics

Signs that the body is responding to an invader

Fever

Lethargy

Slow-wave sleep induction

Classic signs of inflammation (redness, swelling, heat, and pain)

Classifications of Bacteria

Gram - positive, the cell wall retains a stain or resists decolourization with alcohol

Gram - negative, the cell wall loses a stain or is decolorized by alcohol

Aerobic, depend on oxygen for survival

Anaerobic, do not use oxygen

Definition - Chemicals that inhibit specific bacteria

Introduction

Direct microscopy or organisms

Culture and Sensitivity Resistance

Spectrum of activity

Types

Bacteriostatic antimicrobials: inhibit bacterial cell growth but do not destroy cells.

Bacteriocidal antimicrobials: directly kill bacteria.

Practical aspects

Compliance Timing of doses

Completing the course Observation of effectiveness

Site of infection - penetration of agent Lowest risk of toxicity

Route of administration Client’s drug history e.g. allergy

Record nature of allergic reactions as some patients are poor historians

Complicating factors e.g. pregnancy, contraceptive pill, renal / hepatic function.

Side effects

Penicillins

First antibiotics introduced for clinical use.

Inhibit cell wall synthesis – inhibit peptidoglycan transpeptidase so prevent formation of peptidoglycn cross bridges. Resulting in bacterial cell lysis. Bactericidal, active against Gram positive cocci.

Useful for treating infections caused by streptococci, pneumococci, meningococci, gonococci.

Ampicillin and amoxicillin are broad-spectrum, as well as killing Gram positive cocci; they are also effective against some Gram negatives such as Heamophilus, E.coli and Proteus.

Useful for middle ear and sinus infections, exacerbations of chronic bronchitis and UTIs.

Side effects

Allergy - metabolites combine with host proteins to form antigens.

Skin rashes, urticaria, oedema and fever may indicate hypersensitivity.

Alterations to gut flora and subsequent suprainfection with resistant organism.

Diarrhoea, vomiting, nausea.

Beta-lactamase sensitivity

Staphylococcus produce beta-lactamase.

Beta-lactamase hydrolyse many penicillins.

Many penicillins are beta-lactamase sensitive, e.g. penicillin G, amoxicillin.

This means beta-lactamase sensitive antibiotics will not be effective against staphylococcal organisms.

Some penicillins are beta-lactamase resistant so are not hydrolysed by beta-lactamase, e.g. flucloxacillin, these will be effective against Staph.

Classification of penicillins; Penicillinase - resistant or Penicillinase - sensitive penicillins.

Staph usually cause skin and soft tissue infections.

Spectrum of activity of beta-lactamase sensitive antibiotics may be extended by including a beta-lactamase inhibitor such as clavulanic acid or tazobactam, e.g. Augmentin.

Other preparations combine a penicillinase - resistant with a penicillinase – sensitive antibiotic, e.g. ampicillin with cloxacillin.

Classifications / types of antibiotics

B-lactam antimicrobials

All work by inhibiting peptidoglycan synthesis. Include penicillins, cephalosporins, cephamycins, carbapenems and monobactams.

Cephalosporins

Similar to penicillin in structure and activity

Widely distributed in body tissues and may pass blood brain barrier, into pleura, pericardium and joints. Widely used in clinical practice. e.g. cephradine, cefuroxime.

Tetracyclines

Broad spectrum, bacterostatic. Work by inhibition of protein synthesis to prevent cell replication e.g. oxytetracycline.

Useful when penicillin is contraindicated

Sulphonamides

Introduced in 1930s. Inhibit enzyme necessary for folic acid synthesis

e.g. Sulfadiazine and sulphamethoxazole. May be given in combination with trimethoprim, another foliate inhibitor.

Aminoglycosides

A group of powerful antibiotics used to treat serious infections caused by gram-negative aerobic bacilli.

Alter functioning of ribosomes, causing irreversible inhibition of protein synthesis. e.g. Gentamicin, streptomycin.

Ototoxicity and nephrotoxicity are dose related effects.

Macrolides

Actions: Binds to cell membranes causing a change in protein function and cell death; can be bacteriostatic or bactericidal e.g. Erythromycin, clarithromycin.

Indications: Treatment of respiratory, dermatological, urinary tract, and GI infections caused by susceptible strains of bacteria

Chloramphenicol

Wide spectrum, but may disrupt bone marrow function.

Fluoroquinolones

Relatively new class of antibiotics with a broad spectrum of activity, eg ciprofloxacin

Metronidazole

Active against protozoa and bacteroides.

Antiviral agents

Prevention of viral entry e.g. Amantadine

Inhibition of reverse transcriptase e.g. AZT

Inhibition of nucleic acid synthesis e.g. acyclovir

Viral protein inhibitors e.g. Indinavir

Prevention of viral budding e.g. Interferons

Aciclovir - herpes simplex

Adefovir – chronic hepatitis B

Penciclovir – herpes labialis

Idoxuridine – topical for herpes zoster and simplex

Oseltamivir and zanamivir – influenza A and B if used within first 48 hours.

Ribavrin – chronic hepatitis C in combination with interferon