Rapid intravenous desensitization to colistin

Lipopolysaccharide as an antibiotic target

Gram-negative bacteria, including Escherichia coli, Pseudomonas aeruginosa and Acinetobacter baumannii are amongst the highest priority drug-resistant pathogens, for which new antibiotics are urgently needed. Whilst antibiotic drug development is inherently challenging, this is particularly true for Gram-negative bacteria due to the presence of the outer membrane, a highly selective permeability barrier that prevents the ingress of several classes of antibiotic. This selectivity is largely due to an outer leaflet composed of the glycolipid lipopolysaccharide (LPS), which is essential for the viability of almost all Gram-negative bacteria. This essentiality, coupled with the conservation of the synthetic pathway across species and recent breakthroughs in our understanding of transport and membrane homeostasis has made LPS an attractive target for novel antibiotic drug development. Several different targets have been explored and small molecules developed that show promising activity in vitro. However, these endeavours have met limited success in clinical testing and the polymyxins, discovered more than 70 years ago, remain the only LPS-targeting drugs to enter the clinic thus far. In this review, we will discuss efforts to develop therapeutic inhibitors of LPS synthesis and transport and the reasons for limited success, and explore new developments in understanding polymyxin mode of action and the identification of new analogues with reduced toxicity and enhanced activity.

Approach to the evaluation of adverse antibiotic reactions in patients with cystic fibrosis

BACKGROUND

Adverse drug reactions (ADRs) to antibiotics in patients with cystic fibrosis (CF) are common and often mislabeled as allergies. The labeling of an antibiotic reaction as an allergy can lead to the use of antibiotics that are less efficacious, are more expensive, or have a greater risk of adverse effects.

OBJECTIVE

To establish a safe approach for the evaluation of ADRs to antibiotics in patients with CF to help clarify future use of these medications.

METHODS

Patients with CF whose antibiotic allergies were causing difficulty in their medical management were referred for an allergy evaluation that consisted of a thorough drug allergy history and antibiotic testing if appropriate. If the history was not consistent with a true hypersensitivity reaction (HSR) and test results were negative, the patient underwent a challenge to the offending agent(s) to rule out an HSR. Challenges were only performed if the medication was indicated for future use.

RESULTS

A total of 17 patients (mean age, 32.4 years) underwent a thorough allergy evaluation. A total of 17 antibiotic challenges were performed in 11 patients without a reaction consistent with an HSR or severe delayed reaction. Only 2 medications had a history consist with an HSR, and it was recommended that they undergo a desensitization procedure if the drug was required.

CONCLUSION

If treatment with appropriate antibiotics becomes difficult in patients with CF because of drug allergies, then referral to an allergist can help safely identify treatment options. Our findings suggest that a thorough evaluation by an allergy specialist can lead to more appropriate treatment options in patients with CF.