Antimicrobial Therapy Quiz

Antimicrobial Drugs

• Antimicrobial drugs are chemicals that destroy pathogens. This includes antibiotics and chemically synthesized drugs.
• Antibiotics are antimicrobial agents produced naturally from bacteria or fungi.
• Antimicrobial drugs have target specificity, meaning they injure the target organism without affecting the host.

Principles of Antimicrobial Therapy

• Therapy should have appropriate indication and dosage.
• Treatment duration usually ranges from 7-10 days.
• The host defense mechanisms should be intact.
• Understanding the pharmacokinetics and potential risks of the drug are crucial.
• Combining drugs is only necessary in certain conditions and a proper combination should be chosen.

Identification of the Organism

• Acute ill patients, like those with meningitis or neutropenia, require specific antibiotic selection.
• Selection should consider the infection site, patient history, whether the infection is community-acquired or hospital-acquired, and the patient's age.
• Antibiotic combinations may be required to cover different types of bacteria (Gram-positive, Gram-negative, and anaerobes).

Status of the Patient

• Factors such as immune system status, renal function, hepatic function, pregnancy, lactation, and age influence treatment.

Bacteriostatic vs. Bacteriocidal Drugs

• Bacteriostatic drugs arrest bacterial growth and replication, allowing the body's immune system to eliminate the pathogens.
• Bacteriocidal drugs kill bacteria, decreasing the total number of viable organisms.

Spectrum of Activity

• Broad-spectrum antibiotics affect a wide range of bacteria, potentially disrupting the normal body flora, particularly in cases of rapid-onset life-threatening infections where there is no time to culture the causative agent.
• Narrow-spectrum antibiotics have a limited range and require pathogen identification.

Goals of Antibiotics Use

• Prophylaxis: Preventing initial or recurrent infections, e.g., meningitis prophylaxis in children or pregnant contacts, tuberculosis prophylaxis.
• Empiric therapy: Treating infections when the causative organism is not yet identified, often using broad-spectrum drugs for a limited period (typically up to 72 hours).
• Definitive therapy: Treating infections after the causative organism(s) are identified and then tailored to a more specific, narrower-spectrum, antibiotic treatment.

Principles of Antibiotics Use

• Antibiotics cannot differentiate between 'good' and 'bad' bacteria.
• The body maintains a delicate balance of bacteria, with beneficial bacteria like bifidobacteria and acidophilus in the gut and skin.
• Continuously using broad-spectrum antibiotics significantly disrupts the normal bacterial balance, increasing susceptibility to infections.

Importance of Dosage in Antibiotic Use

• Inadequate dosage of antibiotics prevents effective treatment and promotes bacterial resistance.
• Taking less or stopping antibiotics before prescribed leads to the survival of more resistant strains.

Broad-Spectrum Antibiotics and Immune System Development

• Broad-spectrum antibiotics may interfere with the development of healthy immune systems.
• Children receiving broad-spectrum antibiotics under two years old have a threefold increased risk of asthma onset compared to children who are not given these antibiotics.

Purposes for Use of Antibiotics (Target of Therapy)

• Prophylaxis:
  • Medical: Preventing infection in individuals exposed to virulent pathogens (HIV, N. meningitis). Preventing streptococcal infections in patients with rheumatic heart disease.
  • Surgical: Preventing Endocarditis in patients undergoing dental extractions with prosthetic devices.
• Treatment: Treating existing infections caused by a certain type of pathogen.

Combinations of Antimicrobial Drugs

• Indications for drug combinations include the treatment of severe infections of unknown origin, mixed infections, and when a combination drug provides an effect not possible with one drug alone.

Drug Resistance

• Bacteria are resistant to an antibiotic if their growth is not halted by the maximum tolerated dose of the antibiotic.

Misuse of Antibiotics

• Causes of antibiotic misuse include treating untreatable infections, incorrect dosages, lack of appropriate bacteriological information, and relying on chemotherapy without appropriate surgical drainage.

Complications of Antibiotic Therapy

• Hypersensitivity reactions: ranging from urticaria (hives) to anaphylaxis (severe allergic reaction).
• Toxicity: Some drugs can be toxic at high levels, causing damage to organs like the kidneys (nephrotoxicity) or the ears (ototoxicity).
• Superinfections: Broad-spectrum antibiotics can lead to overgrowth of undesirable microorganisms, causing new infections.

Failure of Treatment

• Failure can result from inappropriate indication, ineffective antibiotic, incorrect dose, or inadequate treatment duration, alongside bacteria developing resistance or the causative pathogens changing.

Classify Antibiotics

• Classification can be based on chemical structure, spectrum of activity and effects, and mechanism of action.

Spectrum of Antibiotic Activity

• This refers to the range of bacteria that a specific antibiotic affects. It can be narrow or broad.

Effects of Antibiotics

• This includes whether the drug is bacteriostatic (inhibits growth) or bacteriocidal (kills).

Mechanism of Action (Site of Action)

• Identifying the specific cellular mechanisms a drug targets is important for understanding how it works.

Main Targets of Antibiotics

• Cell wall synthesis is targeted by beta-lactams, vancomycin, and others.
• DNA replication is targeted by quinolones and metronidazole.
• RNA synthesis is targeted by rifampin.
• Protein synthesis is targeted by macrolides, aminoglycosides, tetracyclines, and others.
• Antimetabolites have different target points of action.

Penicillins

• Penicillins are a group of beta-lactam antibiotics that often kill bacteria (bacteriocidal). They are frequently used against Gram-positive bacteria.
• Various penicillin types exist with different properties (oral vs parenteral, acid stability).
• Beta-lactamase inhibitors like clavulanate and sulbactam are frequently combined with penicillin to overcome bacterial resistance to penicillin.

Cephalosporins

• Cephalosporins are a group of beta-lactam antibiotics that have a broader spectrum of activity compared to penicillins. There are different generations of cephalosporins which differ in the types of bacteria they target.
• The effectiveness against Gram-negative bacteria typically increases with increasing generation number.

Glycopeptides

• Glycopeptides, like vancomycin, are typically used against Gram-positive bacteria, including many that are resistant to other antibiotics.

Bacitracin

• Bacitracin is a polypeptide antibiotic that is usually used topically to prevent superficial skin and eye infections.

Adverse Reactions

• Hypersensitivity reactions (ranging from rashes to severe allergic reactions), direct toxicity, and superinfections are common potential adverse reactions to these groups of antibiotics.

Clinical Uses of Antibiotics

• Various uses for antibiotics exist, including prophylaxis (preventing infections), treatment of infections and community-acquired and hospital-acquired infections.