Characterization of a Laboratory-Derived, High-Level Ampicillin-Resistant Salmonella enterica Serovar Typhimurium Strain That Caused Meningitis in an Infant

A Salmonella enterica serovar Typhimurium strain that harbored a plasmid carrying a TEM-1-type β-lactamase gene was isolated from the blood and cerebrospinal fluid of an infant with meningitis. This 3.2-kb plasmid was further characterized to be a nonconjugative pGEM series cloning vector containing a foreign insert. The strain was likely laboratory derived and contaminated the environment before it caused the infection.