This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: None, Subject name: Pharmacology
Not true about aztreonam ? 
Select and explain. 
A. f3-lactarn, B. Monobactarn, C. Active against pseudomonas, D. Shows cross reactivity with other penicillins
D: Shows cross reactivity with other penicillins
Answer: D: Shows cross reactivity with other penicillins 
Explanation: Ans. is 'd' i.e., Shows cross reactivity with other penicillins Aztreonam It belongs to monobactams group of 13-lactam antibiotics. It is active against gram negative organisms including pseudomonas, but has no activity against gram positive organisms or anaerobes fi-lactam antibiotic with aminoglycosides spectrum. It is the only fi-lactam antibiotic that lack cross-reactivity with other P-lactam antibiotics, permiting its used in patients allergic to penicillins or cephalosporins.