title: [Characterization of Haemophilus influenzae's resistance to ampicillin].
abstract: BACKGROUND
  The resistance of Haemophilus influenzae to ampicillin is nearly always dependent on plasmid-mediated betalactamase production. The betalactamase type most frequently identified was TEM-1; type ROB has occasionally been identified. The presence of plasmid-mediated betalactamase has been studied in H. influenzae strains moderately susceptible or resistant to ampicillin.
  
  
  METHODS
  The test used in the detection of the presence of betalactamase was nitrocefin hydrolysis; the enzyme type was identified by analytic isoelectric focusing; the codifying gene of this betalactamase was identified by hybridisation with a TEM-1 probe labeled with digoxigenine. Strains studied were 110, obtained during the period 1987 to 1989 and isolated from four Hospitals of the Vallés area of Barcelona.
  
  
  RESULTS
  Enzyme production was detected in 105 of 110 strains studied; TEM-1 type betalactamase was identified in 108 and positive hybridisation was obtained in these strains with the TEM-1 probe.
  
  
  CONCLUSIONS
  Nitrocefin hydrolysis is a reliable test for the detection of betalactamase production, although it may be unable to detect it (falses negatives) when the production is low. The only betalactamase type identified was TEM-1. The frequency of the strains with non-enzymatic resistance was 1.8%.
authors.affiliation: Microbiología-Medicina, Universidad Autónoma de Barcelona.
authors.forename: R
authors.initials: R
authors.lastname: Reig
authors.forename: M
authors.initials: M
authors.lastname: Hermida
authors.forename: D
authors.initials: D
authors.lastname: Fontanals
authors.forename: J
authors.initials: J
authors.lastname: Lite
authors.forename: C
authors.initials: C
authors.lastname: Martí
authors.forename: M A
authors.initials: MA
authors.lastname: Morera
authors.forename: C
authors.initials: C
authors.lastname: Roy
mesh_terms: D000328:Adult; D000668:Ampicillin Resistance / Q000502:physiology*; D002648:Child; D006193:Haemophilus influenzae / Q000201:enzymology*; D006801:Humans; D001618:beta-Lactamases / Q000096:biosynthesis*
chemical_list: D001618:beta-Lactamases; C034413:beta-lactamase TEM-1
vernacular_title: Caracterización de la resistencia de Haemophilus influenzae a la ampicilina.