Differentiation of β-lactamase-negative ampicillin-resistant Haemophilus influenzae from other H. influenzae strains by a disc method

K. Ubukata, N. Chiba, K. Hasegawa, Y. Shibasaki, K. Sunakawa, M. Nonoyama, S. Iwata, M. Konno

Research output: Contribution to journalArticle

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Abstract

We established breakpoints for differentiating ampicillin (ABPC)-susceptible strains from resistant strains among Haemophilus influenzae isolates according to susceptibility to various β-lactam antibiotics, using a disc method. Susceptibility testing of isolates for 13 β-lactam agents was followed by analysis of the resistance genes, using a polymerase chain reaction (PCR) to identify the TEM-1 β-lactamase gene (bla) and the ftsI gene encoding penicillin-binding protein (PBP) 3, which affects β-lactam minimum inhibitory concentrations (MICs). A total of 228 H. influenzae isolates were classified into 114 β-lactamase-negative, ABPC-susceptible (BLNAS) strains; 29 β-lactamase-negative, ABPC-resistant (BLNAR) strains; 53 low-BLNAR strains with a low degree of ABPC resistance; 27 TEM-1-producing strains (BLPAR); and 5 strains with ftsI gene mutations in addition to TEM-1 production (BLPACR) according to the PCR results. To identify resistant strains by disc-method susceptibility testing, the zone of inhibition was measured for ABPC (10 μg/disc), cefaclor (30 μg/disc), cefpodoxime (10 μg/disc), and cefdinir (5 μg/ disc) discs. Strains were identified as BLNAS without resistant genes when the diameter was ≥27 mm for the ABPC disc and ≥21 mm for the cefaclor disc. Other strains were identified as BLNAR when the diameter was ≤22 mm for the cefpodoxime disc and ≤17 mm for the cefdinir disc. Remaining strains were identified as low-BLNAR. These criteria differentiated resistance types with high accuracy. A discrepancy was noted between genetic results and disc-testing breakpoints for differentiating resistant from susceptible H. influenzae. A disc-testing breakpoint for cefditoren (5 μg/disc) was proposed, with the susceptibility statistically defined as a diameter of ≥24 mm, which corresponds to the breakpoint (1 μg/ml) of the microdilution method recommended by the Japanese Society of Chemotherapy.

Original languageEnglish
Pages (from-to)50-58
Number of pages9
JournalJournal of Infection and Chemotherapy
Volume8
Issue number1
Publication statusPublished - 2002
Externally publishedYes

Fingerprint

Haemophilus influenzae
Ampicillin
cefdinir
cefpodoxime
Lactams
Cefaclor
Genes
Penicillin-Binding Proteins
Polymerase Chain Reaction
Microbial Sensitivity Tests
Anti-Bacterial Agents
Drug Therapy
Mutation

ASJC Scopus subject areas

  • Microbiology (medical)

Cite this

Ubukata, K., Chiba, N., Hasegawa, K., Shibasaki, Y., Sunakawa, K., Nonoyama, M., ... Konno, M. (2002). Differentiation of β-lactamase-negative ampicillin-resistant Haemophilus influenzae from other H. influenzae strains by a disc method. Journal of Infection and Chemotherapy, 8(1), 50-58.

Differentiation of β-lactamase-negative ampicillin-resistant Haemophilus influenzae from other H. influenzae strains by a disc method. / Ubukata, K.; Chiba, N.; Hasegawa, K.; Shibasaki, Y.; Sunakawa, K.; Nonoyama, M.; Iwata, S.; Konno, M.

In: Journal of Infection and Chemotherapy, Vol. 8, No. 1, 2002, p. 50-58.

Research output: Contribution to journalArticle

Ubukata, K, Chiba, N, Hasegawa, K, Shibasaki, Y, Sunakawa, K, Nonoyama, M, Iwata, S & Konno, M 2002, 'Differentiation of β-lactamase-negative ampicillin-resistant Haemophilus influenzae from other H. influenzae strains by a disc method', Journal of Infection and Chemotherapy, vol. 8, no. 1, pp. 50-58.
Ubukata, K. ; Chiba, N. ; Hasegawa, K. ; Shibasaki, Y. ; Sunakawa, K. ; Nonoyama, M. ; Iwata, S. ; Konno, M. / Differentiation of β-lactamase-negative ampicillin-resistant Haemophilus influenzae from other H. influenzae strains by a disc method. In: Journal of Infection and Chemotherapy. 2002 ; Vol. 8, No. 1. pp. 50-58.
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AU - Hasegawa, K.

AU - Shibasaki, Y.

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AU - Nonoyama, M.

AU - Iwata, S.

AU - Konno, M.

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