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Objectives: Implementation of EUCAST susceptibility testing in an Australian hospital laboratory demonstrated higher rates of aminopenicillin and amoxicillin/clavulanate resistance in Haemophilus influenzae than previously recognized. This study aimed to better define the variability in the detection of β-lactam resistance based on EUCAST and CLSI disc diffusion (DD) methodology, by comparison with the recommended reference method, broth microdilution (BMD), and by concordance with genomic analysis.Methods: A total of 100 random H. influenzae isolates were assessed for ampicillin and amoxicillin/clavulanate susceptibility by EUCAST and CLSI DD and BMD. WGS was used to analyse the ftsI gene of a subset of isolates with β-lactam resistance, other than that due to isolated β-lactamase production.Results: Of the 100 isolates, 32 were categorized as either β-lactamase negative, ampicillin resistant (BLNAR) (n = 18) or β-lactamase positive, amoxicillin/clavulanate resistant (BLPACR) (n = 14) by EUCAST DD. All 18 EUCAST BLNAR isolates were genotypically confirmed by WGS. Five of 18 BLNAR isolates were concordant by CLSI DD, 12 by EUCAST BMD and 4 by CLSI BMD. Nine of 14 EUCAST BLPACR isolates were confirmed by WGS; the remaining 5 were 1 mm below the EUCAST DD breakpoint. Only one isolate was detected as BLPACR by CLSI DD. Group III mutations associated with high-level ampicillin resistance were identified in 10/32 isolates.Conclusions: The EUCAST DD susceptibility method is more reliable than either CLSI or BMD for the detection of genotypically defined BLNAR resistance. However, accurate categorization of amoxicillin/clavulanate resistance remains problematic. Continuous and reproducible surveillance of resistance is needed; for this to be possible, robust susceptibility methods are required. [ABSTRACT FROM AUTHOR]

Plasmid-mediated class C β-lactamases are reported from Escherichia coli and Klebsiella pneumoniae with increasing frequency. No screening and confirmatory tests have been uniformly established for these strains. We investigated for the presence of plasmid-mediated AmpC production in 51 clinical isolates of Enterobacteriaceae, comparing two different boronic acid formulations, phenylboronic acid (PB) and 3-(N-Boc-amino)phenylboronic acid (APB), using polymerase chain reaction (PCR). PB performed better than APB. [ABSTRACT FROM AUTHOR]

This article focuses on a study which examined the use of ORSAB (Oxacillin Resistance Screening Agar Base) for isolation and detection of MRSA (methicillin-resistant Staphylococcus aureus) in a routine clinical laboratory. The study was divided into two parts: part 1 examined the effectiveness of ORSAB as compared with LSM agar after 24 h and 48 h incubation and part 2 compared the ability and accuracy of four media (ORSAB agar, LSM agar, MSA and DNase agar) to differentiate and identify MSSA and MRSA clinical isolates. Both ORSAB and LSM agar achieved a high level of sensitivity and specificity for detection of positive MRSA swabs. In part 2 of the study, no difference was found between ORSAB agar, LSM agar, MSA and DNase agar.

Cites a study on the rapid detection of non-multidrug-resistant and multidrug-resistant methicillin-resistant staphylococcus aureus (MRSA) using cycling probe technology for the mecA gene. Evaluation of Velogene-Cycling Probe Technology (CPT), a new DNA probe assay; Reliability of the Velogene-CPT for the detection of methicillin and oxacillin resistance; Use of the test as a valuable detection tool against MRSA.

The article presents a case study in which laboratory findings from 27 different cases of pneumococcal bacteraemia occurring in patients attending the Concord Repatriation General Hospital, Concord, Australia, were analysed within a 1-year period. Blood culture bottles were inoculated by medical officers as recommended by the manufacturer. Susceptibility testing was performed using the disc diffusion methods described by the National Committee for Clinical Laboratory Standards. Results indicate that the interpretation of blood culture smears for diagnosis of pneumococcal bacteraemia can be problematic. This is largely due to the morphological changes that arise from production of autolysins.