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ANTIBACTERIALS

29 important questions on ANTIBACTERIALS

What symptoms did the 14-year-old male present with at the physician's office?

Thigh pain and fever since yesterday afternoon.
Minimal limp and no history of trauma.
T37.6°C, HR 90, RR 18, BP 110/70.
Alert and not toxic.
Tenderness in mid femur region.

What were the findings from the radiographs and bone scan?

Plain radiographs of femur and hip are normal.
CRP and ESR are high.
Bone scan shows a hot spot in mid-femur.

What is nitrofurantoin and what are its adverse effects?

Nitrofurantoin is orally administered, achieving antibacterial concentrations in urine. It's effective against urinary tract infections. Adverse effects include:

Gastrointestinal symptoms and rashes
Haemolytic anaemia in glucose-6-phosphate deficiency
Peripheral neuropathy and pulmonary fibrosis with prolonged use

What initial treatment was given for acute osteomyelitis?

Hospitalized for acute osteomyelitis.
Initially treated with IV vancomycin.
Orthopedic procedure to drain pus and obtain culture and biopsy.

What are the uses and major adverse effects of Metronidazole?

Used in protozoal infections (e.g., trichomoniasis, amoebiasis, giardiasis).
Effective against anaerobic bacteria, including B. fragilis and C. difficile.
Treats serious anaerobic infections, mild to moderate C. difficile-associated diarrhea.
Combined with gentamicin and amoxicillin for intra-abdominal sepsis.
Major adverse effects: peripheral neuropathy, seizures following high doses.

Describe the properties of Quinupristin-dalfopristin.

Quinupristin-dalfopristin is a streptogramin antibiotic with bacteriocidal and bacteriostatic properties. Bacterial synthesis is inhibited by binding to different sites on the 50s bacterial ribosomal subunit to form a stable complex.

What changes were made to the treatment on hospital day 3?

Clinical condition improved.
Cultures show Staph aureus sensitive to cephalosporins and methicillin.
Antibiotics changed to IV oxacillin.
Recommended treatment for 6 weeks with IV antibiotics.

What are the characteristics and uses of Macrolides?

Include Erythromycin, clarithromycin, azithromycin.
Antibacterial spectrum similar to penicillin.
Erythromycin: nausea, vomiting; less with clarithromycin, azithromycin.
Clarithromycin: drug of choice for Legionella pneumophila.
Azithromycin: long half-life, once-daily dosing.
Used for pelvic inflammatory disease, community-acquired pneumonia.

Describe the action and absorption of ciprofloxacin.

Ciprofloxacin is bactericidal, inhibiting DNA-gyrase activity. It interferes with DNA replication and supercoiling. It's well absorbed orally and distributed into body tissues, mostly eliminated by kidneys.

How is Quinupristin-dalfopristin administered and excreted?

Quinupristin-dalfopristin is not absorbed and used as an intravenous infusion. It is 10–20% protein-bound and is excreted in bile, achieving high intracellular concentrations.

What is the pharmacological rationale for giving vancomycin initially?

Vancomycin is used initially to cover potential resistant organisms until culture results are available.

What are some adverse effects of aminoglycosides?

Genetic predisposition to oto-vestibular toxicity.
Cross placenta, causing eighth nerve damage in fetus.
Neuromuscular blockade, marked in myasthenia gravis.
Drug interactions: Prolong neuromuscular blockade of curare-like drugs.

How do tetracyclines function and what is their absorption characteristic?

Tetracyclines are bacteriostatic, binding to the 30S ribosomal subunit.
Adequately absorbed following oral administration.
Tissue distribution is good, eliminated mainly unmetabolised by biliary excretion.
Doxycycline has a long half-life.

What are the specific uses of Azithromycin and Clarithromycin?

Azithromycin: travelers' diarrhea, mild enteric fever, chronic bronchiectasis.
Clarithromycin: inhibits CYP3A4, interacts with simvastatin, azole antifungals, anti-retroviral agents.
Clarithromycin: prolongs QT interval, risk of arrhythmia in at-risk patients.

What are the adverse effects of ciprofloxacin?

Adverse effects include:

Minor gastrointestinal upsets; severe reactions are rare
Insomnia, confusion, convulsions
Associated with C. difficile and MRSA outbreaks
Cartilage damage in young animals; contraindicated in children/adolescents
Drug interactions with aluminium, magnesium, theophylline, caffeine, warfarin

Why was oxacillin used instead of a cephalosporin or methicillin?

Oxacillin was used because the cultures showed Staph aureus sensitive to cephalosporins and methicillin.

What are carbapenems closely related to, and how are they administered?

Carbapenems are closely related to the penicillins.
All require intravenous administration.
Imipenem has a broad spectrum of activity.
Meropenem is preferred in patients with epilepsy.

What is the antibacterial spectrum of aminoglycosides?

Gentamicin: Active against most aerobic Gram-negative rods.
Most streptococci: Resistant.
Tobramycin: More active against Pseudomonas.
Amikacin: Resistant to enzymes that inactivate gentamicin.

What are the adverse effects of tetracyclines?

Bind to calcium in bones and teeth, leading to impaired growth and discoloration.
Cross the placenta, contraindicated in pregnancy.
Large doses may cause hepatic necrosis.
Contraindicated in renal failure.
SE: Nausea, reflux, diarrhoea, photosensitivity.

What are the indications and effects of Clindamycin?

Effective against penicillin-resistant staphylococci, many anaerobes.
Well absorbed orally, penetrates tissues.
Used in serious conditions: osteomyelitis, joint infections, tissue infections.
Treats life-threatening Group A beta-haemolytic streptococcal infections.
Associated with C. difficile-associated diarrhea.

What is the antibacterial spectrum of ciprofloxacin?

Ciprofloxacin is active against aerobic Gram-negative bacteria, including P. aeruginosa. Less effective against Gram-positive bacteria. Useful for Pseudomonas infections and effective in gastrointestinal infections from traveller’s diarrhoea to Salmonella.

What is the mechanism of action and elimination for aminoglycosides?

Bind to the 30S subunit of bacterial ribosomes.
Lead to misreading of mRNA codons.
Elimination is mainly by glomerular filtration.
Gentamicin is administered via intermittent infusion.

Describe the sulphonamide–trimethoprim combinations.

Co-trimoxazole: Contains sulphamethoxazole and trimethoprim (5:1).
Bacterial cells: Impermeable to folic acid.
Trimethoprim: Inhibits dihydrofolate reductase.
Co-trimoxazole: Well absorbed, renal excretion.

What is the antibacterial spectrum of tetracyclines?

Effective against a wide range of bacteria.
Useful in respiratory tract infections, including Pneumococcus, Haemophilus species.
Effective against Chlamydia, Mycoplasma, Coxiella burnetii, rickettsiae, Brucella cholera, Lyme Borrelia.
Adjuncts for acne treatment.

What are the adverse events associated with prolonged Linezolid use?

Prolonged linezolid use is associated with myelotoxicity, like anaemia and thrombocytopenia. Mitochondrial toxicity may occur with peripheral neuropathy, lactic acidosis, and rarely optic neuropathy.

What are the adverse effects of aminoglycosides related to?

Two major adverse reactions: nephrotoxicity and ototoxicity.
Renal lesion consists of tubular destruction.
Eighth nerve damage can be vestibular or auditory.
Oto- and vestibular-toxicity in short-term therapy.

What are the adverse effects of Co-trimoxazole?

Sulphonamide: Rashes, Stevens–Johnson syndrome.
Trimethoprim: Impaired haemopoiesis.
Use caution in acute kidney injury.
Displaces bilirubin in newborns.
Drug interactions: Hepatic enzyme competition.

Describe the antibacterial spectrum and uses of Linezolid.

Antibacterial spectrum: Broad Gram-positive spectrum of activity including vancomycin-resistant Enterococci and MRSA. Activity against Mycobacterium tuberculosis. Most commonly used in health-care associated Gram positive infections resistant to glycopeptides.

How does oral absorption and penetration of aminoglycosides occur?

Oral absorption is negligible.
Poor penetration into CSF.
Moderate penetration into bile.
Good entry to inflamed tissue.
Bacterial eradication enhanced with higher peak blood concentration.

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Phamarcology

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