Antimicrobial Drugs and Therapy Principles

Antimicrobial Drugs

• Antimicrobial drugs destroy pathogens, including antibiotics and chemically synthesized drugs.
• Antibiotics are antimicrobial agents produced naturally by bacteria or fungi.
• Antimicrobial drugs have target specificity, harming the target organism without affecting the host.

Principles of Antimicrobial Therapy

• Appropriate indication for the drug.
• Correct dosage of the drug is important.
• Treatment period should be suitable (typically 7-10 days).
• Determining when to start treatment.
• Identifying the target of therapy (whether prophylaxis or treatment).
• The host's immune system should be intact.
• Pharmacokinetics and potential risk of the drug must be known.
• Combination therapy is used in specific situations.

Identification of the Organism

• Acutely ill patients (such as those with meningitis or neutropenic conditions).
• Identifying the site of infection and patient history are crucial factors.
• Community-acquired or hospital-acquired infection should be considered.
• Patient age is relevant.
• Antibiotic combinations may be used to cover various types of bacteria (Gram-positive, Gram-negative, and anaerobes).

Status of the Patient

• Immune system function.
• Renal function.
• Hepatic function.
• Pregnancy status.
• Lactation status.
• Patient age.

Bacteriostatic versus Bacteriocidal Drugs

• Bacteriostatic drugs halt bacterial growth and replication, relying on the body's immune system to eliminate the pathogen.
• Bacteriocidal drugs kill bacteria, reducing the total number of viable organisms.

Spectrum of Activity

• Broad-spectrum antibiotics affect a wide range of bacteria, potentially disrupting beneficial flora.
• These antibiotics are often used in cases of rapidly developing life-threatening infections due to the time constraints.
• Narrow-spectrum antibiotics have a limited range and require identification of the specific pathogen.

Goals of Antibiotics Use

• Prophylaxis: Preventing an initial infection or recurrence (examples: meningitis, use of ciprofloxacin or rifampicin, or ceftriaxone for pregnant contacts.)
• Empiric therapy: Initial treatment for infections where the pathogen isn't yet identified, using broad-spectrum antibiotics.
• Definitive therapy: Applying specific antibiotics to organisms once identified. This is typically following testing and identification.

Principles of Antibiotics Use

• Antibiotics cannot distinguish between beneficial and harmful bacteria. A healthy balance of bacteria in the body is essential.
• Antibiotics, especially broad spectrum, can disrupt the normal body's bacterial ecology rendering the host more susceptible to various infections.

Dosage and Antibiotics Effectiveness

• Shortened antibiotic courses can allow resistant bacteria to survive and develop resistance.
• Crucial to maintaining the prescribed dosage as inadequate doses facilitate resistance development.

Broad Spectrum Antibiotics and Immunity

• Broad-spectrum antibiotics can affect immune system development, as it has implications for the microbiome.
• Children exposed to broad-spectrum antibiotics before two years of age are more likely to develop asthma compared to those who did not receive such antibiotics.

Purposes for Use of Antibiotics

• Medical prophylaxis, such as exposure to high viral pathogens (e.g. HIV, N. meningitis).
• Pretreatment may prevent other conditions, like tuberculosis or meningitis, in individuals closely exposed to infected patients.
• Treating rheumatic heart disease, which requires long-term treatment.
• Surgical prophylaxis, such as preventative treatment before dental procedures involving implanted prosthetic devices.

Combinations of Antimicrobial Drugs

• Using combinations is indicated for severe infections of unknown origin.
• Using combinations is also useful in cases of mixed infections.
• Using combinations can delay the development of antibiotic resistance.
• When a single antibiotic isn't effective, combining them sometimes produces a synergistic effect.
• Some antibiotic combinations are used to reduce side effects.

Drug Resistance

• Bacteria are resistant to antibiotics if their growth isn't halted by the highest tolerated dose in a host.

Misuse of Antibiotics

• Treating untreatable infections.
• Treating fever of undetermined origin.
• Using improper dosages.
• Relying on antibiotics when surgical care is needed for conditions such as purulent exudates or necrotic tissue.
• Insufficient bacteriological information and diagnosis contribute to inappropriate antibiotic use.

Complications of Antibiotic Therapy

• Hypersensitivity reactions (ranging from urticaria to anaphylaxis).
• Direct toxicity (examples: aminoglycosides causing ototoxicity).
• Superinfections (due to antibiotic-induced alterations of normal flora, leading to overgrowth of opportunistic organisms).

Failure of Treatment

• Incorrect antibiotic indication.
• Ineffective choice of the antibiotic.
• Incorrect dosage.
• Inadequate duration of the treatment.
• Development of antibiotic resistance.
• Change in the causative pathogen (e.g., the infection changes to a new strain or resistant bacteria).

Classify Antibiotics

• Categorizing according to chemical structure.
• Spectrum of activity and effects (broad or narrow spectrum, bacteriostatic or bacteriocidal).
• Mechanism of action (what the antibiotic targets).

Main Targets of Antibiotics

• Cell wall synthesis, DNA replication and RNA synthesis
• Protein synthesis (ribosomal targets), and Antimetabolites.

Classification of Beta-Lactams

• Penicillins, Cephalosporins, Carbapenems and Monobactams

Penicillins

• Bacteriocidal.
• Primarily effective against Gram-positive bacteria.
• Examples include nafcillin and oxacillin.

Mechanism of Penicillin Action

• Entry into bacterial cells via cell wall.
• Binding to penicillin-binding proteins (PBPs), causing disruption to cell wall synthesis.
• Bacterial cell death resulting from cell lysis.

Explore the fundamentals of antimicrobial drugs, including their types, mechanisms, and therapeutic principles. This quiz covers the identification of pathogens and the critical aspects of drug administration, such as correct dosage and treatment duration. Test your knowledge on the principles of antimicrobial therapy and the specifics of patient treatment.