In vitro activity of sulbactam/ampicillin against ampicillin-resistant, beta-lactamase-producing bacteria isolated in Italian hospitals.
A multicenter study aimed at assessing the in vitro activity of sulbactam/ampicillin against a wide range of bacterial pathogens was performed using 2,209 clinical strains, all recently collected from inpatients in seven Italian centers and preliminarily screened as being ampicillin-resistant and beta-lactamase producers. In comparative disk diffusion trials using 8 large-spectrum antimicrobials, the percentage of resistance to sulbactam/ampicillin in staphylococci was similar to the percentage of resistance to netilmicin and lower than to the other antibiotics; with gram-negative bacteria, only netilmicin, ofloxacin, and, less consistently, cefotetan showed lower incidences of resistance. The minimal inhibitory concentrations (MICs) of ampicillin alone and sulbactam/ampicillin together were determined using the agar dilution method. The Enterobacteriaceae strains which shifted to ampicillin susceptibility in the presence of sulbactam averaged 68%, but values significantly above or below average were observed in some genera of this family. The percentage of strains which the presence of sulbactam rendered ampicillin-susceptible in vitro reached 97% in Haemophilus strains and 100% in branhamellae and gonococci. High percentages were also recorded in staphylococci, with a peak of 100% in oxacillin-susceptible Staphylococcus aureus strains. In general, center-to-center differences were relatively limited.
Varaldo
P E
PE
Institutes of Microbiology, University of Ancona, Italy.
Ripa
S
S
Nicoletti
G
G
Covelli
I
I
Satta
G
G
Carlone
N
N
Fontana
R
R
D000667:Ampicillin / Q000494:pharmacology*; D000668:Ampicillin Resistance; D004352:Drug Resistance, Microbial; D004359:Drug Therapy, Combination / Q000494:pharmacology; D006801:Humans; D007558:Italy; D008826:Microbial Sensitivity Tests; D015337:Multicenter Studies as Topic; D010403:Penicillin Resistance; D013407:Sulbactam / Q000494:pharmacology*; D001618:beta-Lactamases / Q000096:biosynthesis
D000667:Ampicillin; D001618:beta-Lactamases; D013407:Sulbactam