Ampicillin Resistance in Haemophilus influenzae as Determined by a Rapid Test for Beta-Lactamase Production

Abstract

A rapid capillary tube method was used to demonstrate beta-lactamase production by ampicillin-resistant strains of Haemophilus influenzae .

Evaluation of four methods for detecting the beta-lactamase activity in Neisseria gonorrhoeae isolated in Cuba

“…Four methods for determination of beta-lactamase were used: (1) inhibition method, according to the methodology of Palmer et al (2000), using chocolate agar plates containing 1 mg/l of ampicillin, and the Oxford strain of Staphylococcus aureus (NTCC 6571) as a biological indicator; (2) iodometric method in tube (Thornsberry 1980); (3) acidimetric method of Thornsberry and Kirven (1974), using paper disc impregnated with a solution of penicillin and phenol red as a pH indicator; (4) chromogenic cephalosporin method, employing a commercial reagent (Nitrocefin, Oxoid), prepared as liquid solution (Llanes et al 2000).…”

Isolation of an ampicillin-resistant, non-beta-lactamase-producing strain of Haemophilus influenzae

“…290, 1978) have presented preliminary data on an ampicillin-resistant, ,B-lactamasenegative strain of H. parainfluenzae suggesting the latter mechanism. Of note is the fact that the non-,8-lactamase-producing strains previously described have had MICs of 8 jig of ampicillin per ml (20,22), similar to the MIC of the strain described herein. As a rule, f8-lactamaseproducing strains of H. influenzae have MICs of 16 ,ug or more of ampicillin per ml.…”

“…Such isolates have been recognized infrequently. Thornsberry and Kirven reported that 2 of20 strains of ampicillinresistant H. influenzae gave negative results for fi-lactamase by the rapid acidometric capillary tube method (22). Neither of these strains was a type b organism.…”

“…Most of these strains elaborate a ,-lactamase (10) whose production is mediated by genes located on a plasmid (6, 19). Occasionally, ampicillin-resistant strains of H. influenzae have been isolated and found not to produce ,B-lactamase (11,20,22 Fig. …”

Haemophilus influenzae: antibiotic susceptibility

“…Although transformation is known to occur in Haemophilus spp., the efficiency of this mechanism of genetic exchange is very low in the absence of homologous plasmid DNA sequences (1). However, the conjugative resistance plasmids are not infrequently integrated into the chromosome (102 Non-beta-lactamase-producing strains of ampicillin-resistant H. influenzae are also known to occur (45,60,112 (122). However, the incidence of beta-lactamase-producing encapsulated strains had increased to 14% by 1981 in Great Britain (81).…”