UNASSIGNED: In this comparative case study, we discuss clinically relevant discrepancies of antimicrobial susceptibility testing (AST) interpretation for ceftriaxone against a non-typable, beta-lactamase negative, ampicillin-resistant (BLNAR) Haemophilus influenzae isolated from a blood culture.
UNASSIGNED: A 74-year-old man presented with a 3 day illness characterized by shortness of breath and dry cough, and was noted to be febrile and hypoxic on admission. A blood culture bottle flagged positive with Gram-negative coccobacilli, later identified as Haemophilus influenzae with the patient commenced on ceftriaxone. The isolate was beta-lactamase negative and antibiotic susceptibility testing (AST) using disc diffusion revealed the isolate resistant to ceftriaxone and ampicillin by EUCAST methodology, with the patient subsequently changed to amoxicillin/clavulanate. Further AST using the CLSI methodology in parallel demonstrated discrepant results between the two susceptibility methods. The patient recovered without complications.
UNASSIGNED: This discrepancy could lead to inconsistent reporting of susceptibilities between laboratories, and consequently antibiotic prescribing, especially for invasive isolates. As more laboratories adopt EUCAST methodologies for AST interpretation in Australia and globally, it is important for clinicians to consider the clinical implications of these methodological discrepancies.

流感嗜血杆菌（HI）感染是儿童常见的疾病，临床以菌血症、脑膜炎、肺炎、中耳炎、鼻窦炎和外阴阴道炎常见。目前引起感染的HI菌型以不定型菌株为主，侵袭性感染临床症状较严重。病原诊断包括各种标本的培养、核酸检测、抗原抗体检测。近年HI耐药日益严重，但对第三代头孢菌素敏感性较高。本建议在阐述HI病原学、疾病负担、细菌耐药性和临床表现的基础上，对本病的诊断、抗感染治疗策略提出建议，对疫苗预防提出新的思考。.

OBJECTIVE: EUCAST has recently authorized a new disc diffusion test for routine antimicrobial susceptibility testing of Haemophilus influenzae, calibrated to EUCAST MIC breakpoints. We investigated whether disc diffusion testing as recommended by EUCAST could discriminate strains of H. influenzae carrying the N526K substitution in penicillin-binding protein 3 from the wild-type population.
METHODS: A total of 170 recent clinical isolates, genetically characterized for the presence of acquired and mutational resistance mechanisms, were tested by disc diffusion of β-lactam antibiotics on supplemented Mueller-Hinton agar. Tentative epidemiological breakpoint values for the presence of the N526K substitution were suggested for various β-lactams, and the performances were calculated.
RESULTS: Epidemiological cut-off values of 19/20 mm for ampicillin (2 μg) and 11/12 mm for benzylpenicillin (1 U) accurately categorized 96% of the study strains, and outperformed cephalosporin-containing discs in the discrimination of mutational resistance in β-lactamase-non-producing isolates. Current EUCAST interpretative criteria for the categorization of clinical resistance showed concordance between resistance rates based on MIC and zone diameter breakpoints for both ampicillin and cefuroxime, but categorization of individual isolates was not consistent.
CONCLUSIONS: Disc diffusion testing of H. influenzae accurately identified β-lactamase-non-producing isolates with the N526K substitution by use of discs containing low amounts of penicillins. Cephalosporin-containing discs could detect mutational resistance in β-lactamase-producing isolates, but performed with reduced specificity.

An acute exacerbation of chronic bronchitis (AECB) is frequently caused by viral infection. Because of the impairment of mucociliary clearance, secondary bacterial infection is likely to ensue. Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis account for about 50% of all episodes of AECB. The best approach to antibiotic selection for bacterial exacerbations is stratification by exacerbation type, patient type, or antibiotic type.

暂无摘要。

暂无摘要。

An eight laboratory M23-A2 quality control (QC) study was performed for the re-evaluation of gatifloxacin, a new fluoroquinolone, using disk diffusion tests against Streptococcus pneumoniae ATCC 49619. The study also re-evaluated garenoxacin, a novel investigational des-F(6)-quinolone, using disk diffusion tests against S. pneumoniae ATCC 49619 and broth MIC for Hemophilus influenzae ATCC 49247. The gatifloxacin zone diameter results for S. pneumoniae did not indicate a need for QC range modification (26-34 mm; 98.3% of results); however, the garenoxacin zone diameters did demonstrate a need for a minor modification (1 mm; 26-34 mm; 96.3% of reported results). The broth MIC results for H. influenzae showed that 83.1% of the results were at the upper limit of the current range (0.008 microg/ml) published by the National Committee for Clinical Laboratory Standards (NCCLS). The proposed correction could either be 0.002-0.015 microg/mlor 0.004-0.015 microg/ml, each encompassing 100.0% of reported results (prior and current studies). All MIC results for control drugs, levofloxacin and moxifloxacin (disks) or gatifloxacin and clarithromycin (MIC), were within published NCCLS ranges.

We compared 75 nontypeable (NT) Haemophilus influenzae isolates by pulsed-field gel electrophoresis (PFGE), enterobacterial repetitive intergenic consensus (ERIC)-PCR, and automated ribotyping. PFGE was the most discriminatory of the techniques. ERIC-PCR provides a useful screen but should not replace other techniques as the sole method to group NT H. influenzae strains.

GAR-936, a new semisynthetic derivative of minocycline, has earlier shown promising activity against tetracycline-resistant pathogens, including Streptococcus pneumoniae. In this study, the activity of GAR-936 was tested against a total of 514 tetracycline-susceptible and -resistant strains of S. pneumoniae, beta-haemolytic streptococci, viridans group streptococci, Haemophilus influenzae and Neisseria gonorrhoeae. All strains of H. influenzae, were inhibited by < or =2 mg/l of GAR-936, with MIC(90)s for all streptococci and gonococci of < or =0.5 mg/l. Scattergrams of GAR-936 comparing MICs by broth microdilution testing and zone diameters using 30 microg disks, confirmed the proposed susceptibility criteria of < or 2 mg/l or > or =20 mm zone diameter. Clinical trial results should be correlated with these preliminary in vitro results to confirm and/or adjust these susceptibility interpretive criteria for GAR-936 when testing fastidious streptococci, H. influenzae and N. gonorrhoeae.

Antimicrobial resistance in bacterial respiratory tract pathogens is a rapidly evolving and increasingly disconcerting problem. Major factors that have contributed to resistance are inappropriate prescribing of antibiotics for viral infections and the use of antibiotics with poor activity. The treatment of respiratory tract infections is significantly affected by resistance in organisms such as Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis. Resistance to beta-lactams, sulfonamides, and macrolides continues to rise. Evidence-based guidelines, founded on clinical and bacteriological outcomes, are imperative to treat patients effectively, to limit the spread of these pathogens, and to minimize further development of resistance. Pharmacokinetic and pharmacodynamic parameters have recently been shown to correlate with clinical outcome, and offer a more rational approach to predicting antimicrobial efficacy and determining clinically relevant susceptibility breakpoints.