Ampicillin ; Side-effects For all PENICILLINS. See PENICILLINS. For AMPICILLIN. Frequency not known. Colitis haemorrhagic. Allergy and cross-sensitivity For all PENICILLINS. See PENICILLINS. Pregnancy. Not known to be harmful. Breast feeding. Trace amounts in milk, but appropriate to use. Renal impairment. With intravenous use. Accumulation of electrolytes contained in parenteral preparations. Ampicillin and gentamicin are preferred over ampicillin and a third-generation cephalosporin (eg, cefotaxime or … Bacterial meningitis in the neonate: Treatment and outcome …and discussed in detail separately Ampicillin is the agent of choice for neonatal meningitis resulting from ampicillin-susceptible strains of E. coli. Ampicillin-resistant E. coli and other gram-negative. Ampicillin is used for treating infections of the middle ear, sinuses, stomach and intestines, bladder, and kidney caused by susceptible bacteria.It also is used for treating uncomplicated gonorrhea, meningitis, endocarditis and other serious infections. Because of the increased use of antibiotics, many bacterial strains have become resistant to penicillins; bacteria causing serious infections. Ampicillin is used to treat a wide variety of bacterial infections.It is a penicillin-type antibiotic.It works by stopping the growth of bacteria.This antibiotic treats only bacterial infections.