Microbiology Antibiotics Quiz

Bacteria and Peptidoglycan

• Gram-positive bacteria primarily contain peptidoglycan in their cell walls.
• Gram-negative bacteria have a thinner layer of peptidoglycan, which is sandwiched between an outer membrane and an inner membrane.

Treatment of Gram-positive Cocci

• Natural penicillins are effective against Streptococcus pyogenes, a Gram-positive cocci responsible for Strep throat.

Antibiotics

• Dicloxacillin belongs to the penicillin class of antibiotics.
• Tetracycline is another common class of antibiotics used to treat infections, with specific precautions.

Bacterial Identification and Grouping

• Gram-negative rods are a category of bacterial morphology, and an example given is Escherichia coli.
• Actinomyces and Bacteroides are classified as anaerobic bacteria.

Antimicrobial Stewardship (AMS) Programs

• AMS programs aim to promote responsible use of antimicrobial agents, reducing antibiotic resistance and improving patient outcomes.
• They are required in Australian hospitals and healthcare settings.
• A key component of an AMS program is education for physicians and other healthcare workers.

Antimicrobial Therapy and its Types

• Empirical therapy uses antibiotics based on clinical suspicion and the most likely pathogens, before culture results are available.
• Directed therapy is antibiotic treatment tailored to confirmed or suspected pathogens based on laboratory identification.
• One goal of narrow-spectrum therapy is to minimize the risk of antibiotic resistance.

Key Considerations in Antimicrobial Stewardship

• In empirical therapy, the narrowest-spectrum agent should be used first to avoid unnecessary exposure to broad-spectrum antibiotics.
• Tetracyclines should be taken on an empty stomach for optimal absorption.
• Amoxicillin is a good choice for mild pneumonia that covers strep and some resistance, however, if the patient is not improving after 48 hours, further investigation and possibly different treatment is needed.
• Tetracyclines can cause photosensitivity, which means that the skin becomes more sensitive to sunlight.
• Tetracyclines should not be used in children under 18 weeks old due to tooth discoloration and other harmful developmental effects.

Clarithromycin

• Clarithromycin has a key distinction from other macrolides in that it has significant immunomodulatory and anti-inflammatory properties.
• Taking tetracycline with plenty of water and staying upright afterward can prevent esophageal problems.

Pneumonia Causes and Hypersensitivity

• Atypical bacteria are responsible for about 20% of pneumonia cases.
• Type I hypersensitivity reactions are the most frequent type of allergic reaction with beta-lactam allergies.

Macrolide Antibiotics

• Macrolides are a group of antibiotics with a broad antimicrobial spectrum and generally a favorable safety profile.
• There is an estimated 1-10% risk of developing anaphylaxis when receiving beta-lactam antibiotics.
• Clarithromycin has a relevant drug interaction: it inhibits the metabolism of certain medications, potentially leading to increased blood levels.

Cephalosporin Antibiotics

• Cefazolin is a first-generation cephalosporin and can be used in patients with a mild urticarial rash from a non-severe beta-lactam allergy.

Tetracyclines for Atypical Bacteria

• Doxycycline, a tetracycline, is commonly prescribed for atypical bacteria.
• Macrolides have a known side effect of gastrointestinal upset, such as nausea, vomiting, or diarrhea.

Carbapenems for Multidrug Resistant Bacteria

• Carbapenems like imipenem and meropenem are used for severe infections caused by multidrug-resistant organisms.

Aminoglycoside Antibiotics

• Aminoglycosides, such as gentamicin, are bactericidal antibiotics.
• They are used to treat severe infections caused by Gram-negative bacteria.
• Macrolides are effective against atypical respiratory pathogens like Mycoplasma pneumoniae.
• Clarithromycin and erythromycin inhibit the 50S ribosomal subunit of bacteria.

Considerations in Penicillin Allergies

• 10–20% of patients allergic to penicillin are likely to also be allergic to cephalosporins (older theory- newer research suggests it is less).
• Cefuroxime and ceftazidime should be avoided in patients with amoxicillin allergy.

Cefazolin

• Cefazolin is a first-generation cephalosporin that can be used in patients with a mild urticarial rash from a non-severe beta-lactam allergy. It's important to note that even mild urticaria can sometimes be associated with more severe allergic reactions in the future.

Important Note About Antibiotic Resistance

• It's crucial to avoid using unnecessary antibiotics to minimize the development of antibiotic resistance. The misuse of antibiotics can lead to the emergence of multidrug-resistant organisms, which are difficult to treat.

Monitoring Aminoglycosides

• Aminoglycosides require monitoring due to potential for toxicity if treatment exceeds 48 hours.

Ototoxicity

• Vestibular ototoxicity is a type of ototoxicity that affects balance and can cause nausea and vertigo.

Monitoring Aminoglycosides

• The preferred monitoring method for aminoglycosides is therapeutic drug monitoring (TDM).
• Aminoglycosides are clinically used to specifically target infections like Pseudomonas aeruginosa infections.
• Nephrotoxicity, renal damage, should be considered when treating patients with aminoglycosides for more than 7-10 days.
• Gram-negative bacilli should be covered when treating febrile neutropenia, which is a serious condition characterized by fever and low white blood count.
• Aminoglycosides can cause nephrotoxicity (damage to the kidneys). This risk is increased if peak levels are always high.