Β-lactam antibiotic reactions to any β-lactam antibiotic may occur in up to 10% of patients receiving that agent (a small fraction of which are truly IgE-mediated allergic reactions, see amoxicillin rash). Anaphylaxis will occur in approximately 0.01% of patients. There is perhaps a 5%-10% cross-sensitivity between penicillin-derivatives, cephalosporins, and carbapenems; but this figure has been challenged by various investigators. Nevertheless, the risk of cross-reactivity is sufficient to warrant the contraindication of all β-lactam antibiotics in patients with a history of severe allergic reactions (urticaria, anaphylaxis, interstitial nephritis) to any β-lactam antibiotic. A Jarisch–Herxheimer reaction may occur after initial treatment of a spirochetal
Quinolone antibiotic not be used as a first-line agent for community-acquired pneumonia, instead recommending macrolide or doxycycline as first-line agents. The Drug-Resistant "Streptococcus pneumoniae" Working Group recommends fluoroquinolones be used for the ambulatory treatment of community-acquired pneumonia only after other antibiotic classes have been tried and failed, or in cases with demonstrated drug-resistant "Streptococcus pneumoniae". Resistance to quinolones can evolve rapidly, even during a course of treatment. Numerous pathogens, including "Escherichia coli", commonly exhibit resistance. Widespread veterinary usage of quinolones, in particular in Europe, has been implicated. Fluoroquinolones had become the class of antibiotics most commonly prescribed to adults in 2002. Nearly