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Monobactams & Carbapenems

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Monobactams are beta-lactam antibiotics that target aerobic gram-negative rods like pseudomonas, while carbapenems are broad-spectrum beta-lactam antibiotics that are effective against anaerobes, gram-positives, and gram-negative rods.

The spectrum of activity for monobactams, like aztreonam, is limited to aerobic gram-negative rods (like pseudomonas), with no activity against gram-positive bacteria or anaerobes. Aztreonam effectively treats severe infections like pneumonia and sepsis caused by susceptible gram-negative pathogens, and it is an alternative antibiotic for patients with penicillin allergies as monobactams have no immunologic cross-reactivity.

Carbapenems, which include doripenem, ertapenem, imipenem, and meropenem, are broad spectrum beta-lactam antibiotics that have coverage against anaerobes, gram-positives, and gram-negative rods like pseudomonas. Additionally, carbapenems can penetrate body tissues and fluids well, like CSF, making them valuable in combatting serious infections such as hospital-acquired pneumonia or sepsis. Adverse effects, particularly those associated with imipenem, include skin rash, gastrointestinal symptoms, and a lowered seizure threshold, especially in patients with renal dysfunction. Both monobactams and carbapenems are resistant to beta-lactamases, rendering them effective against extended spectrum beta-lactamase-producing gram-negatives like E. coli and Klebsiella.

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What are the key features of monobactams, such as aztreonam?

Monobactams, like aztreonam, are a type of beta-lactam antibiotic. They have the ability to bind to penicillin-binding proteins and stop peptidoglycan wall synthesis. Monobactams display effectiveness against aerobic gram-negative rods, making them a suitable treatment choice for serious systemic infections, such as meningitis, sepsis, and pneumonia caused by these pathogens. An additional feature is that beta-lactamases, which generally lead to antibiotic resistance, are ineffective against them.

How are monobactams and carbapenems used for treating pseudomonas infections?

Both monobactams and most carbapenems, with the exception of ertapenem, are potent against pseudomonas infections. Pseudomonas is a gram-negative bacterium known for its resistance against many antibiotics, making the use of these strong antibiotics an important treatment strategy.

What features differentiate carbapenems like imipenem from other antibiotics?

Carbapenems such as imipenem are broad-spectrum beta-lactam antibiotics. They are especially useful in the treatment of anaerobic infections that can cause pneumonia and intraabdominal infections. Another key feature is they remain effective against bacteria resistant to other treatments, including bacterial strains capable of producing extended-spectrum beta-lactamases. However, imipenem use may lead to certain side effects such as gastrointestinal disturbances (like nausea, vomiting, diarrhea) or a skin rash. Note that imipenem can lower the seizure threshold, especially in patients with renal dysfunction.

What is the role of cilastin in administering imipenem?

Cilastin is often administered alongside imipenem, a carbapenem. Its primary role is to inhibit dehydropeptidase in renal tubules in order to prevent the degradation of imipenem, thereby increasing its effectiveness as an antibiotic.

Can carbapenems be used to treat bacterial meningitis?

Yes, carbapenems such as imipenem can be used to treat bacterial meningitis. These broad-spectrum antibiotics are often used for severe infections when other antibiotics may be less effective, particularly in situations where resistant bacteria are suspected.