Early onset Morganella morganii sepsis in a newborn infant with emergence of cephalosporin resistance caused by depression of AMPC beta-lactamase production.

A preterm infant with early onset Morganella morganii sepsis was treated with cefotaxime and gentamicin after confirmation of antimicrobial susceptibility. The infant developed persistent ventriculitis caused by the emergence of a cefotaxime-resistant Morganella variant with derepression of its AmpC beta-lactamase. When choosing antibiotic therapy, the risk of development of resistance to cephalosporins should be considered in infections caused by M. morganii and other Gram-negative organisms with inducible AmpC beta-lactamases.