Disk diffusion interpretive criteria for extended-spectrum cephalosporins with Haemophilus influenzae

Jorgensen, James H.; Maher, Louise; Redding, J S

doi:10.1128/jcm.26.9.1887-1889.1988

J Clin Microbiol

1988

DOI: 10.1128/jcm.26.9.1887-1889.1988

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Disk diffusion interpretive criteria for extended-spectrum cephalosporins with Haemophilus influenzae

James H. Jorgensen

Louise Maher

J S Redding

Abstract: Disk diffusion interpretive zone size criteria for use with Haemophilus test medium are proposed for five extended-spectrum cephalosporins. With cefuroxime, zones 224 mm ni diameter indicated susceptibility, while zones s20 mm implied resistance. With cefotaxime, ceftazidime, ceftizoxime, and ceftriaxone, a single susceptible-zone size,-26 mm, is proposed.

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Cited by 9 publications

(3 citation statements)

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“…The broth version of HTM consisted of cation-adjusted MH broth, 0.2 IU of thymidine phosphorylase per ml, and the same supplements used in HTM agar. In preliminary studies with 15 antimicrobial agents, laboratory-prepared agar and broth versions of HTM were stable and appeared to support the growth of fresh clinical isolates of H. influenzae (16,17). Other presumed advantages of HTM were its transparent nature, its ability to support disk diffusion tests with TMP-SMX, its lack of expense, and its chemical composition, which was more defined than that of MH-choc; in addition, HTM permitted the use of the same basal medium in both disk diffusion and broth dilution tests, and the broth version of the medium could be manufactured commercially.…”

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confidence: 99%

In vitro susceptibility testing of Haemophilus influenzae: review of new National Committee for Clinical Laboratory Standards recommendations

Doern

1992

J Clin Microbiol

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confidence: 99%

In vitro susceptibility testing of Haemophilus influenzae: review of new National Committee for Clinical Laboratory Standards recommendations

Doern

1992

J Clin Microbiol

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“…For testing the susceptibility ofHaemophilus influenzae to antimicrobial agents, supplemented Mueller-Hinton medium has been recommended (2)(3)(4)6). However, Mendelman et al (5) have described unsatisfactory results with the agar version of Haemophilus test medium (HTM).…”

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Haemophilus influenzae ATCC 49766, an alternative quality control strain for monitoring broth microdilution susceptibility tests with selected beta-lactams

Barry¹,

Jorgensen²,

Hardy³

et al. 1992

J Clin Microbiol

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A P-lactamase-negative, ampicillin-resistant strain of Haemophilus influenzae is currently used for quality control of broth microdilution tests performed with Haemophilus test medium (HTM). Studies with eight lots of HTM broth documented the fact that MIC limits for some antimicrobial agents are unrealistically stringent; i.e., only three of eight lots of HTM broth were satisfactory for testing cefaclor. An alternative, ampicillinsusceptible strain of H. influenzae (ATCC 49766) was found to provide much more reproducible results with five problematic drugs (cefaclor, cefuroxime, cefamandole, loracarbef, and cefonicid). Multilaboratory studies defined MIC control limits for both control strains tested against 12 antimicrobial agents.For testing the susceptibility ofHaemophilus influenzae to antimicrobial agents, supplemented Mueller-Hinton medium has been recommended (2-4, 6). However, Mendelman et al. (5) have described unsatisfactory results with the agar version of Haemophilus test medium (HTM). A P-lactamasenegative, ampicillin-resistant strain of H. influenzae (ATCC 49247) was selected for quality control of susceptibility tests that use HTM agar or broth (1, 6). It was selected because its relative resistance to ampicillin and other P-lactam compounds maximized the number of drugs with MIC endpoints that are likely to be within the range of concentrations normally tested in microdilution trays. However, in vitro tests with some cephalosporins are extremely inoculum dependent and are also influenced by a wide range of other technical variables that make it very difficult to obtain reproducible results with the control strain of H. influenzae (ATCC 49247). Doern et al. (1) proposed MIC limits for broth microdilution tests with 18 antimicrobial agents. They were unable to obtain useful control limits with cefaclor and also noted marked variability in cefuroxime and cefamandole control test results. The current report extends those observations by documenting the amount of variability with eight lots of HTM broth. Such variability emphasized the need for an alternative control strain that provides more reproducible results with cefaclor, cefuroxime, and related f-lactams.After careful evaluation of several clinical isolates that might serve that function, H. influenzae ATCC 49766 was selected by one of us (J.H.J.). A five-laboratory collaborative effort was subsequently initiated to define MIC control limits for 12 antimicrobial agents tested against two strains of H. influenzae (ATCC 49247 and ATCC 49766). The results of those studies are described in this report. * Corresponding author. MATERIALS AND METHODSInitial screening tests. Two lots of Mueller-Hinton broth were purchased from each of the following manufacturers: Difco Laboratories, Detroit, Mich.; Becton Dickinson Microbiology Systems, Cockeysville, Md.; Acumedia, Baltimore, Md.; and Unipath Oxoid, Ogdensburg, N.Y. Twofold dilutions of each antimicrobial agent were prepared in each of the eight broth media and dispensed into wells in microdilution tr...

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“…Interpretive inhibition zone size criteria were proposed for HTM agar used to test H. influenzae isolates against 10 different antimicrobial agents (5). The validity of disk tests with HTM agar has been confirmed, and extended studies developed interpretive criteria for additional antimicrobial agents (2,4). However, Mendelman et al (8) reported difficulties with ampicillin disk tests and HTM agar.…”

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Performance of Haemophilus Test Media prepared with 12 different lots of Mueller-Hinton agar from four manufacturers

Barry¹,

Packer²

1992

J Clin Microbiol

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Haemophilus Test Media (HTM) were prepared from 12 different lots of Mueller-Hinton agar. When tested with Haemophilus influenzae ATCC 49247, most lots were initially rejected because of small zones of inhibition for cefaclor, cefuroxime, and cefamandole disks, whereas five other drugs performed satisfactorily on the 11 lots that supported growth of the control strain. At the same time, tests of Escherichia coli ATCC 25922 and Staphylococcus aureus ATCC 25923 documented the acceptability of these agar media, with or without HTM supplements. The current control limits for cefaclor, cefuroxime, and cefamandole appear to be unrealistic. Because the 13-lactamase-negative, ampicillin-resistant control strain of H. influenzae (ATCC 49247) has altered penicillin-binding proteins, it is resistant to ampicillin and is probably also resistant to cefaclor, cefuroxime, and cefamandole. Consequently, media that produce no or very small zones of inhibition with those three drugs might be clinically correct and should not be rejected. One manufacturer provided three lots of Mueller-Hinton agar that gave unusually large zones of inhibition with all 13-lactams. The three other manufacturers provided eight Mueller-Hinton agars that were satisfactory for the preparation of HTM agar, provided that small zones of inhibition with cefaclor, cefuroxime, and cefamandole disks are accepted as the preferred result.

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Disk diffusion interpretive criteria for extended-spectrum cephalosporins with Haemophilus influenzae

Cited by 9 publications

References 14 publications

In vitro susceptibility testing of Haemophilus influenzae: review of new National Committee for Clinical Laboratory Standards recommendations

In vitro susceptibility testing of Haemophilus influenzae: review of new National Committee for Clinical Laboratory Standards recommendations

Haemophilus influenzae ATCC 49766, an alternative quality control strain for monitoring broth microdilution susceptibility tests with selected beta-lactams

Performance of Haemophilus Test Media prepared with 12 different lots of Mueller-Hinton agar from four manufacturers

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