Polymorphism of gene in and emergence of cefotaxime resistance in two Tunisian hospitals.

The decreased affinity to β-lactams is usually caused by specific alterations in penicillin-binding protein 3 due to varieties of substitutions in gene. This study aimed to characterize the polymorphism of gene in 19 strains, isolated between 2014 and 2016 (different resistance phenotypes to β-lactams ( = 9) and susceptible strains ( = 10) used for comparative purposes). All strains were characterized for capsular type by PCR and agglutination tests and for β-lactam resistance by amplification and sequencing of . Biotyping and clonality were performed by API-NH and pulsed-field gel electrophoresis, respectively. Four strains were β-lactamase-negative ampicillin-resistant and five were β-lactamase-positive clavulanic-acid-resistant. One strain from each group was resistant to cefotaxime. Our isolates belonged mainly to biotype IV and I and were non-typeable and genetically unrelated. According to mutation profiles of their , strains were classified as group I ( = 3), group II ( = 4), group-III-like ( = 1) and group III ( = 1). All group II strains were further classified as subgroup IIb, except for one strain, which harboured a new mutation (N422I). Ampicillin MICs of β-lactamase-negative ampicillin-resistant strains were 6 to 12 times the MICs of susceptible strains. Only was detected in β-lactamase-positive clavulanic-acid-resistant strains, and was responsible for high MICs for ampicillin (>256 mg/L), whatever the mutational resistance group. The emergence of cefotaxime-resistant isolates in our country is a matter of concern and requires strict surveillance and rationalization of antibiotic use to preserve these molecules.