Mezlocillin: Semisynthetic ampicillin-derived acylureido penicillin. It has been proposed for infections with certain anaerobes and may be useful in inner ear, bile, and CNS infections.Penicillins: A group of antibiotics that contain 6-aminopenicillanic acid with a side chain attached to the 6-amino group. The penicillin nucleus is the chief structural requirement for biological activity. The side-chain structure determines many of the antibacterial and pharmacological characteristics. (Goodman and Gilman's The Pharmacological Basis of Therapeutics, 8th ed, p1065)Ticarcillin: An antibiotic derived from penicillin similar to CARBENICILLIN in action.Azlocillin: A semisynthetic ampicillin-derived acylureido penicillin.Carbenicillin: Broad-spectrum semisynthetic penicillin derivative used parenterally. It is susceptible to gastric juice and penicillinase and may damage platelet function.Meningitis, Listeria: Inflammation of the meninges caused by LISTERIA MONOCYTOGENES infection, usually occurring in individuals under the age of 3 years or over the age of 50 years. It may occur at any age in individuals with IMMUNOLOGIC DEFICIENCY SYNDROMES. Clinical manifestations include FEVER, altered mentation, HEADACHE, meningeal signs, focal neurologic signs, and SEIZURES. (From Medicine 1998 Sep;77(5):313-36)Microbial Sensitivity Tests: Any tests that demonstrate the relative efficacy of different chemotherapeutic agents against specific microorganisms (i.e., bacteria, fungi, viruses).Penicillinase: A beta-lactamase preferentially cleaving penicillins. (Dorland, 28th ed) EC 3.5.2.-.Ampicillin: Semi-synthetic derivative of penicillin that functions as an orally active broad-spectrum antibiotic.Enterobacteriaceae: A family of gram-negative, facultatively anaerobic, rod-shaped bacteria that do not form endospores. Its organisms are distributed worldwide with some being saprophytes and others being plant and animal parasites. Many species are of considerable economic importance due to their pathogenic effects on agriculture and livestock.