Treatment outcomes with benzylpenicillin and non-benzylpenicillin antibiotics, and the performance of the penicillin zone-edge test versus molecular detection of blaZ in penicillin-susceptible Staphylococcus aureus (PSSA) bacteraemia.

OBJECTIVES: The blaZ gene encodes penicillinase, which inactivates penicillin. As there were reports on suboptimal sensitivity for the penicillin zone-edge test, a phenotypic method for blaZ detection, we investigated treatment outcomes in patients with penicillin-susceptible Staphylococcus aureus (PSSA) bacteraemia (phenotypically negative for penicillinase), subjecting isolates to molecular testing for blaZ retrospectively. PATIENTS AND METHODS: A retrospective cohort study was conducted on 121 patients with a first episode of PSSA bacteraemia from 1 January 2012 to 31 October 2015 at Tan Tock Seng Hospital (TTSH), Singapore. Patients were grouped into IV benzylpenicillin and non-benzylpenicillin groups. The primary outcome was overall treatment failure, defined as either 30 day all-cause mortality and/or 90 day relapse. The penicillin (P10) zone-edge test was repeated on archived PSSA isolates, concurrently with penicillin MIC determination via gradient diffusion and PCR for blaZ. RESULTS: Among 121 patients, 57 patients (47.1%) received IV benzylpenicillin as the predominant antibiotic. There was no significant difference in overall treatment failure between treatment with the benzylpenicillin [7/57 (12.3%)] versus non-benzylpenicillin groups [12/64 (18.8%)] (P = 0.33) or cloxacillin/cefazolin [6/37 (16.2%)] (P = 0.59). For 112 PSSA isolates available for testing, repeat penicillin zone-edge testing was negative for penicillinase production, corroborating previous results. A single PSSA isolate with a negative penicillin zone-edge test was found to be positive for blaZ. CONCLUSIONS: We found no differences in overall treatment failure between patients with PSSA bacteraemia treated with benzylpenicillin, anti-staphylococcal ß-lactams cefazolin/cloxacillin and other antimicrobials, when using the penicillin zone-edge test as the phenotypic method for blaZ screening.

Instrumentation for quantitative analysis of volatile compounds emission at elevated temperatures. Part 1: Design and implementation.

A novel suite of instrumentation for the characterisation of materials held inside an air-tight tube furnace operated up to 250 °C has been developed. Real-time detection of released gases (volatile organic compounds (VOCs), CO2, NO, NO2, SO2, CO and O2) was achieved combining commercial off-the-shelf (COTS) gas sensors and sorbent tubes for further qualitative and semi-quantitative analysis by gas chromatography-mass spectrometry coupled to thermal desorption (TD-GC-MS). The test system was designed to provide a controlled flow (1000 cm3 min-1) of hydrocarbon free air through the furnace. The furnace temperature ramp was set at a rate of 5 °C min-1 with 10 min dwell points at 70 °C, 150 °C, 200 °C and 250 °C to allow time for stabilisation and further headspace sampling onto sorbent tubes. Experimental design of the instrumentation is described here and an example data set upon exposure to a gas sample is presented.

Instrumentation for quantitative analysis of volatile compounds emission at elevated temperatures. Part 2: Analysis of carbon fibre reinforced epoxy composite.

We have investigated the release of gases and volatile organic compounds (VOCs) from a carbon fibre reinforced epoxy composite matrix used in aircraft structural components. Analysis was performed at several temperatures both up to and above the recommended operating temperature (121 °C) for the material, to a maximum of 250 °C. Gas chromatography-mass spectrometry (GC-MS) combined with thermal desorption (TD-GC-MS) was used to identify and quantify VOCs, and in parallel real-time gas detection with commercial off-the-shelf (COTS) gas sensors. Under hydrocarbon free air, CO, SO2, NO, NO2 and VOCs (mainly aldehydes, ketones and a carboxylic acid) were detected as the gaseous products released during the thermal exposure of the material up to 250 °C, accompanied by increased relative humidity (4%). At temperatures up to 150 °C, gas and volatile emission was limited.

An Outbreak of Streptococcus pyogenes in a Mental Health Facility: Advantage of Well-Timed Whole-Genome Sequencing Over emm Typing.

OBJECTIVEWe report the utility of whole-genome sequencing (WGS) conducted in a clinically relevant time frame (ie, sufficient for guiding management decision), in managing a Streptococcus pyogenes outbreak, and present a comparison of its performance with emm typing.SETTINGA 2,000-bed tertiary-care psychiatric hospital.METHODSActive surveillance was conducted to identify new cases of S. pyogenes. WGS guided targeted epidemiological investigations, and infection control measures were implemented. Single-nucleotide polymorphism (SNP)-based genome phylogeny, emm typing, and multilocus sequence typing (MLST) were performed. We compared the ability of WGS and emm typing to correctly identify person-to-person transmission and to guide the management of the outbreak.RESULTSThe study included 204 patients and 152 staff. We identified 35 patients and 2 staff members with S. pyogenes. WGS revealed polyclonal S. pyogenes infections with 3 genetically distinct phylogenetic clusters (C1-C3). Cluster C1 isolates were all emm type 4, sequence type 915 and had pairwise SNP differences of 0-5, which suggested recent person-to-person transmissions. Epidemiological investigation revealed that cluster C1 was mediated by dermal colonization and transmission of S. pyogenes in a male residential ward. Clusters C2 and C3 were genomically diverse, with pairwise SNP differences of 21-45 and 26-58, and emm 11 and mostly emm120, respectively. Clusters C2 and C3, which may have been considered person-to-person transmissions by emm typing, were shown by WGS to be unlikely by integrating pairwise SNP differences with epidemiology.CONCLUSIONSWGS had higher resolution than emm typing in identifying clusters with recent and ongoing person-to-person transmissions, which allowed implementation of targeted intervention to control the outbreak.Infect Control Hosp Epidemiol 2018;852-860.

Postoperative Mycoplasma hominis brain abscess: keep it in mind!

A temporal lobe abscess was diagnosed in a 57-year-old man. A urethral catheter had been inserted 12 days earlier, just prior to clot evacuation of a subacute haematoma secondary to an arterio-venous malformation. Fever persisted despite debridement and treatment with meropenem and vancomycin. Gram stains of operative samples showed no bacteria. Extended cultures grew pinpoint colonies after 5 days. Meanwhile, sequencing of bacterial 16S rDNA from operative specimens had identified Mycoplasma hominis; the bacterial colonies were subsequently similarly identified. The patient responded promptly following addition of oral doxycycline 100 mg two times per day. There is a growing literature of similar cases. Transient bacteraemia, following urinary catheterisation, with seeding of existing sites of inflammation is the proposed explanation. Urethral carriage of M. hominis is 15% and catheterisation is a common procedure. Mycoplasma hominis maybe more common than appreciated, especially as the need for extended cultures makes a correct diagnosis less likely.

Intracranial abscess secondary to dental infection.

We report a case of Aggregatibacter actinomycetemcomitans (A. actinomycetemcomitans) bacteraemia and secondary brain abscess in a patient where periodontal disease was implicated as the probable source.

Symptomatic primary Cytomegalovirus infection in a HIV-positive pregnant woman.

We describe a case of symptomatic primary Cytomegalovirus infection in a HIV-positive pregnant woman on antiretroviral treatment with a CD4 count >200 × 10(6)/l requiring intravenous ganciclovir. No adverse consequences from ganciclovir or evidence of congenital Cytomegalovirus infection were found.