Danilla Grando

Coagulase-negative staphylococci in very-low-birth-weight infants: inability of genetic markers to distinguish invasive strains from blood culture contaminants

Selected coagulase-negative staphylococci from the blood of very-low-birth-weight infants in the Neonatal Intensive Care Unit at the Royal Women’s Hospital, Melbourne, collected over a 5-year period were examined. Isolates were classified as invasive or contaminants, speciated, typed by pulsed-field gel electrophoresis, and examined for biofilm genes (icaA, icaC, and icaD), adhesion genes (atlE, fbe), and the number of copies of IS256. Of the 24 isolates studied, there were 13 contaminants and 11 invasive isolates. The collection included 15 Staphylococcus epidermidis, eight Staphylococcus capitis, and one each of Staphylococcus warneri and Staphylococcus haemolyticus. Two small clusters of S. epidermidis that belonged to the same molecular type were identified. All S. capitis isolates belonged to the same molecular type or subtype, suggesting that a particular clone was circulating in the unit. There was no significant difference in the species found, the presence of icaA, icaC, icaD, atlE, or fbe, or the number of copies of IS256 between invasive isolates and contaminants. A series of nasal isolates from nonhospitalized adults differed from hospital isolates in the absence of IS256 and the low prevalence of icaC. There was no evidence of IS256-mediated insertion into ica genes as a mechanism of phase variation. These findings suggest that contaminants and invasive isolates derived from the same pool of hospital strains capable of causing sepsis in compromised hosts and that other mechanisms of phase variation exist, apart from IS256 insertion into ica genes.

Bartonella henselae Associated with Parinaud's Oculoglandular Syndrome

Bartonella henselae was recovered from the conjunctival scraping of a 38-year-old woman who presented with a 2-week history of tender preauricular lymphadenopathy and a 1-day history of a red left eye. Dry adherent colonies were observed on agar plates at 21 days of incubation, and the isolate was identified through conventional and molecular tests. Polymerase chain reaction (PCR) amplification of a specific region of the 16S rRNA gene and confirmation by a separate PCR reaction with hybridization of the product with a B. henselae-specific probe confirmed the isolate as B. henselae. This is the first reported isolation of the causative agent of cat scratch disease from ocular tissue in a patient with Parinauds oculoglandular syndrome.

A novel method for simultaneous Enterococcus species identification/typing and van genotyping by high resolution melt analysis ☆

In order to develop a typing and identification method for van gene containing Enterococcus faecium, two multiplex PCR reactions were developed for use in HRM-PCR (High Resolution Melt-PCR): (i) vanA, vanB, vanC, vanC23 to detect van genes from different Enterococcus species; (ii) ISR (intergenic spacer region between the 16S and 23S rRNA genes) to detect all Enterococcus species and obtain species and isolate specific HRM curves. To test and validate the method three groups of isolates were tested: (i) 1672 Enterococcus species isolates from January 2009 to December 2009; (ii) 71 isolates previously identified and typed by PFGE (pulsed-field gel electrophoresis) and MLST (multi-locus sequence typing); and (iii) 18 of the isolates from (i) for which ISR sequencing was done. As well as successfully identifying 2 common genotypes by HRM from the Austin Hospital clinical isolates, this study analysed the sequences of all the vanB genes deposited in GenBank and developed a numerical classification scheme for the standardised naming of these vanB genotypes. The identification of Enterococcus faecalis from E. faecium was reliable and stable using ISR PCR. The typing of E. faecium by ISR PCR: (i) detected two variable peaks corresponding to different copy numbers of insertion sequences I and II corresponding to peak I and II respectively; (ii) produced 7 melt profiles for E. faecium with variable copy numbers of sequences I and II; (iii) demonstrated stability and instability of peak heights with equal frequency within the patient sample (36.4±4.5 days and 38.6±5.8 days respectively for 192 patients); (iv) detected ISR-HRM types with as much discrimination as PFGE and more than MLST; and (v) detected ISR-HRM types that differentiated some isolates that were identical by PFGE and MLST. In conjunction with the rapid and accurate van genotyping method described here, this ISR-HRM typing and identification method can be used as a stable identification and typing method with predictable instability based on recombination and concerted evolution of the rrn operon that will complement existing typing methods.

New opportunities for improved ribotyping of C. difficile clinical isolates by exploring their genomes.

Clostridium difficile causes outbreaks of infectious diarrhoea, most commonly occurring in healthcare institutions. Recently, concern has been raised with reports of C. difficile disease in those traditionally thought to be at low risk i.e. community acquired rather than healthcare acquired. This has increased awareness for the need to track outbreaks and PCR-ribotyping has found widespread use to elucidate epidemiologically linked isolates. PCR-ribotyping uses conserved regions of the 16S rRNA gene and 23S rRNA gene as primer binding sites to produce varying PCR products due to the intergenic spacer (ITS1) regions of the multiple operons. With the explosion of whole genome sequence data it became possible to analyse the start of the 23S rRNA gene for a more accurate selection of regions closer to the end of the ITS1. However the following questions must still be asked: (i) Does the chromosomal organisation of the rrn operon vary between C. difficile strains? and (ii) just how conserved are the primer binding regions? Eight published C. difficile genomes have been aligned to produce a detailed database of indels of the ITS1s from the rrn operon sets. An iPad Filemaker Go App has been constructed and named RiboTyping (RT). It contains detail such as sequences, ribotypes, strain numbers, GenBank numbers and genome position numbers. Access to various levels of the database is provided so that details can be printed. There are three main regions of the rrn operon that have been analysed by the database and related to each other by strain, ribotype and operon: (1) 16S gene (2) ITS1 indels (3) 23S gene. This has enabled direct intra- and inter-genomic comparisons at the strain, ribotype and operon (allele) levels in each of the three genomic regions. This is the first time that such an analysis has been done. By using the RT App with search criteria it will be possible to select probe combinations for specific strains/ribotypes/rrn operons for experiments to do with diagnostics, typing and recombination of operons. Many more incomplete C. difficile whole genome sequencing projects are recorded in GenBank as underway and the rrn operon information from these can also be added to the RT App when available. The RT App will help simplify probe selection because of the complexity of the ITS1 in C. difficile even in a single genome and because other allele-specific regions (16S and 23S genes) of variability can be relationally compared to design extra probes to increase sensitivity.

Anti-Amyloidogenic Properties of Some Phenolic Compounds

A family of 21 polyphenolic compounds consisting of those found naturally in danshen and their analogues were synthesized and subsequently screened for their anti-amyloidogenic activity against the amyloid beta peptide (Aβ42) of Alzheimer’s disease. After 24 h incubation with Aβ42, five compounds reduced thioflavin T (ThT) fluorescence, indicative of their anti-amyloidogenic propensity (p < 0.001). TEM and immunoblotting analysis also showed that selected compounds were capable of hindering fibril formation even after prolonged incubations. These compounds were also capable of rescuing the yeast cells from toxic changes induced by the chemically synthesized Aβ42. In a second assay, a Saccharomyces cerevisiae AHP1 deletant strain transformed with GFP fused to Aβ42 was treated with these compounds and analyzed by flow cytometry. There was a significant reduction in the green fluorescence intensity associated with 14 compounds. We interpret this result to mean that the compounds had an anti-amyloid-aggregation propensity in the yeast and GFP-Aβ42 was removed by proteolysis. The position and not the number of hydroxyl groups on the aromatic ring was found to be the most important determinant for the anti-amyloidogenic properties.

A simple and inexpensive device for biofilm analysis

The Calgary Biofilm Device (CBD) has been described as a technology for the rapid and reproducible assay of biofilm susceptibilities to antibiotics. In this study a simple and inexpensive alternative to the CBD was developed from polypropylene (PP) microcentrifuge tubes and pipette tip boxes. The utility of the device was demonstrated using Candida glabrata, a yeast that can develop antimicrobial-resistant biofilm communities. Biofilms of C. glabrata were formed on the outside surface of microcentrifuge tubes and examined by quantitative analysis and scanning electron microscopy. Growth of three C. glabrata strains, including a clinical isolate, demonstrated that biofilms could be formed on the microcentrifuge tubes. After 24 h incubation the three C. glabrata strains produced biofilms that were recovered into cell suspension and quantified. The method was found to produce uniform and reproducible results with no significant differences between biofilms formed on PP tubes incubated in various compartments of the device. In addition, the difference between maximum and minimum counts for each strain was comparable to those which have been reported for the CBD device.

Associations with asymptomatic colonization with candida in women reporting past vaginal candidiasis: an observational study

OBJECTIVE Asymptomatic vaginal colonization with Candida species is a known risk factor for vulvovaginal candidiasis (VVC). Taking known risk factors for symptomatic VVC, the authors sought to identify factors associated with asymptomatic colonization. STUDY DESIGN As part of a randomized controlled trial which compared vaginal candidal colony counts in women taking garlic tablets or placebo, 192 asymptomatic women collected a baseline screening swab for Candida species. Eligibility for this study included at least one self-reported episode of VVC in the previous 12 months and age 18-50 years. Known risk factors for VVC were compared in women colonized with candida and those without colonization. RESULTS 37% of asymptomatic women who self-reported VVC in the previous 12 months were colonized with vaginal Candida species. Using multivariate analysis, two factors were associated with asymptomatic colonization: a current sexual partner (P=0.02) and being born outside of Australia (P=0.05). Use of oral contraceptives was not statistically significant (P=0.27). CONCLUSIONS Clinical relevance of asymptomatic colonization with vaginal yeast and its link to episodes of VVC warrants further investigation.

High resolution melt analysis to track infections due to ribotype 027 Clostridium difficile

The increased prevalence of hypervirulent ribotype 027 Clostridium difficile requires rapid identification of isolates in order to implement timely infection control strategies. High resolution melt (HRM) analysis of PCR products can identify strain variation amongst genera of bacteria. The intergenic (16S-23S rDNA) spacer region contains sequence regions conserved within genera and other sequence region variables between species within genera. We wished to investigate whether HRM analysis of PCR ribotyping products could identify ribotype 027 C. difficile. Ribotyping was performed on 93 clinical isolates and five control strains and band patterns were analysed using GelCompar II (Applied Maths, USA). Real-time PCR using ribotyping primers was performed and normalised melt curves were generated. The HRM data was then imported into ScreenClust software (QIAGEN) to generate principal component analysis graphs depicting clustered relationships of strains. Ribotyping produced clear PCR bands for 88/98 isolates tested. Dendrograms generated by GelCompar showed a diversity of ribotype patterns amongst these 88 isolates with 18 groups identified with 70% homology. One clinical isolate showed 100% homology with the control 027 strains. ScreenClust analysis of the same 88 HRM results showed clustering of isolates, with 027 strains identifiable as a unique cluster. HRM analysis correctly identified the control 027 stains and the clinical isolate shown to be 027. HRM combined with ScreenClust analysis of real-time PCR products of the 16S-23S rDNA spacer region successfully identified ribotype 027 strains. For infection control purposes this was achieved within 2-3 h of colony isolation.

Respiratory tract infections among children younger than 5 years: Current management in Australian general practice

Objective: To explore the current management in Australian general practice of common respiratory tract infections (RTIs) in children younger than 5 years.

Management of respiratory tract infections in young children—A qualitative study of primary care providers’ perspectives

Respiratory tract infections in young children are the most common cause of general practice visits in Australia. Despite the availability of clinical practice guidelines, the treatment and management of respiratory tract infections in young children is inconsistent. The aim of the study was to explore the management of respiratory tract infections in young children from a multi-disciplinary perspective using across-sectional qualitative research design based on the theoretical domains framework and the Capability, Opportunity and Motivation-B model. In-depth interviews were conducted with 30 primary care providers to explore their knowledge, views and management of respiratory tract infections in young children. Interviews focused on symptomatic management, over-the-counter medications and antibiotic use, and data were thematically analysed. Our findings showed that factors such as primary care providers’ time constraints, parental anxiety, general practitioners’ perception of what parents want, perceived parental pressure, and fear of losing patients were some of the reasons why primary care providers did not always adhere to guideline recommendations. Primary care providers also provided conflicting advice to parents concerning over-the-counter medications and when children should resume normal activities. Overall, this study showed that complex interactions involving emotional and psychological factors influenced the decision making process of primary care providers’ management of respiratory tract infections in young children. A team care approach with consistent advice, and improved communication between primary care providers and parents is vital to overcome some of these barriers and improve guideline adherence. The findings of this research will inform the development of interventions to better manage respiratory tract infections in young children.Respiratory tract infections: Clinicians swayed by parental anxiety and pressureThe emotions and psychology of both parents and clinicians influence how respiratory tract infections (RTIs) are managed in young children. Researchers in Australia, led by Ruby Biezen from Monash University, interviewed 30 primary care clinicians about their views on how to care for children with RTIs, such as the common cold. The interviews focused on symptomatic management, over-the-counter medications and antibiotic use. Despite the availability of best-practice guidelines, clinicians did not always follow the recommendations owing to factors such as time constraints, parental anxiety, perceived parental pressure, and fear of losing patients. These are some of the reasons why clinicians sometimes advise or prescribe unnecessary medications. The authors suggest that a team approach involving multiple healthcare professionals who deliver consistent advice could improve guideline adherence.