Bacterial testing of platelets - has it prevented transfusion-transmitted bacterial infections in Australia?

BACKGROUND AND OBJECTIVES: Australia introduced bacterial contamination screening (BCS) for platelet components in April 2008. This study presents analysis performed to assess the efficacy of testing. MATERIALS AND METHODS: Seven-day aerobic and anaerobic culture is performed using the BacT/ALERT 3D system. Following an initial machine positive (IMP) flag, all associated components are recalled, and/or clinicians treating already transfused patients are notified. IMPs are categorized as 'machine false positive', 'confirmed positive' or 'indeterminate' depending on culture results of initial and repeat samples. RESULTS: Between 2010 and 2012, 1·1% of platelet donations tested IMP; since 2013, this rate has fallen to 0·6% through improved instrument management, reducing false-positive IMPs but maintaining sensitivity for cultures yielding bacterial growth. On average, 66% of confirmed positive and indeterminate platelet units had been transfused at the time of detection. The majority (95%) of these grew Propionibacterium sp., a slow-growing organism that rarely causes sepsis in the transfusion setting. The incidence of reported transfuion-transmitted bacterial infection (TTBI) has fallen since the introduction of BCS, with a 4·2-fold [0·5, 28·2] lower rate from platelets. CONCLUSION: BCS has been successful in detecting platelet units containing pathogenic bacteria. The incidence of TTBI from platelets has fallen since the introduction of BCS, but the risk has not been eliminated due to rare false-negative results. In the absence of a pathogen inactivation system for red blood cells, BCS provides 'surrogate' testing of red blood cells from which platelets have been manufactured.

Emergence and spread of predominantly community-onset Clostridium difficile PCR ribotype 244 infection in Australia, 2010 to 2012.

We describe an Australia-wide Clostridium difficile outbreak in 2011 and 2012 involving the previously uncommon ribotype 244. In Western Australia, 14 of 25 cases were community-associated, 11 were detected in patients younger than 65 years, 14 presented to emergency/outpatient departments, and 14 to non-tertiary/community hospitals. Using whole genome sequencing, we confirm ribotype 244 is from the same C. difficile clade as the epidemic ribotype 027. Like ribotype 027, it produces toxins A, B, and binary toxin, however it is fluoroquinolone-susceptible and thousands of single nucleotide variants distinct from ribotype 027. Fifteen outbreak isolates from across Australia were sequenced. Despite their geographic separation, all were genetically highly related without evidence of geographic clustering, consistent with a point source, for example affecting the national food chain. Comparison with reference laboratory strains revealed the outbreak clone shared a common ancestor with isolates from the United States and United Kingdom (UK). A strain obtained in the UK was phylogenetically related to our outbreak. Follow-up of that case revealed the patient had recently returned from Australia. Our data demonstrate new C. difficile strains are an on-going threat, with potential for rapid spread. Active surveillance is needed to identify and control emerging lineages.

Spinal-injured neuropathic bladder antisepsis (SINBA) trial.

OBJECTIVE: To determine whether Methenamine Hippurate (MH) or cranberry tablets prevent urinary tract infections (UTI) in people with neuropathic bladder following spinal cord injury (SCI). STUDY DESIGN: Double-blind factorial-design randomized controlled trial (RCT) with 2 year recruitment period from November 2000 and 6 month follow-up. SETTING: In total, 543 eligible predominantly community dwelling patients were invited to participate in the study, of whom 305 (56%) agreed. METHODS: Eligible participants were people with SCI with neurogenic bladder and stable bladder management. All regimens were indistinguishable in appearance and taste. The dose of MH used was 1 g twice-daily. The dose of cranberry used was 800 mg twice-daily. The main outcome measure was the time to occurrence of a symptomatic UTI. RESULTS: Multivariate analysis revealed that patients randomized to MH did not have a significantly longer UTI-free period compared to placebo (HR 0.96, 95% CI: 0.68-1.35, P=0.75). Patients randomized to cranberry likewise did not have significantly longer UTI-free period compared to placebo (HR 0.93, 95% CI: 0.67-1.31, P=0.70). CONCLUSION: There is no benefit in the prevention of UTI from the addition of MH or cranberry tablets to the usual regimen of patients with neuropathic bladder following SCI.

Choosing the right antibiotic.

BACKGROUND: With the increasing complexity of the antibiotic armamentarium and the increasing prevalence of resistance, the choice of an appropriate antibiotic is more difficult than ever before. There is also increasing concern that overuse of broad spectrum antibiotics may help reduce their effectiveness in the future. In attempting to make rational antibiotic choices, competing interests must be balanced in order to preserve one of our most powerful medical tools. OBJECTIVE: The aim of this paper is to discuss some of the factors that should be considered when selecting an antibiotic and to provide general principles for use in day to day decision making. DISCUSSION: A knowledge of the patient combined with a working knowledge of the likely target organism and its predicted susceptibility profile is the basis of antibiotic selection.

Mixed morphotype testing of Pseudomonas aeruginosa cultures from cystic fibrosis patients.

Bronchial secretions of patients with cystic fibrosis (CF) inevitably become colonised with Pseudomonas aeruginosa. This organism often exhibits multiple phenotypes with different antibiotic susceptibility profiles. Isolating each colonial morphotype and determining its antibiotic susceptibility profile is labour-intensive and time-consuming. Two disk diffusion methods for mixed morphotype susceptibility testing were examined; 134 morphotypes of P. aeruginosa from 50 respiratory specimens from CF patients were tested. Mixed cultures were prepared by (a) combining morphologically different colonies of P. aeruginosa directly from the sputum specimen primary culture plates from individual patients or (b) mixing colonies of individual morphotypes after isolation and subculture. Agreement with the results for testing morphotypes individually were 85.8% and 91.6%, respectively, for the two methods. These agreement rates rose to 95.6% and 99.4%, respectively, when minor errors (intermediate misclassified as susceptible or resistant or vice versa) were excluded. Mixed morphotype testing of P. aeruginosa directly from sputum specimen culture plates in chronically colonised CF patients is more efficient, reduces turn-around time and provides clinically meaningful information about antibiotic susceptibility.

Is hepatitis C serology reliable? Problems with clinical application.

OBJECTIVE: To describe some inherent difficulties in the interpretation of anti-hepatitis C virus (HCV) antibody testing. CLINICAL FEATURES: A 30-year-old carpark attendant sustained an accidental needlestick injury. The results of serological and biochemical investigations were suggestive of HCV infection but were not conclusive. INTERVENTION AND OUTCOME: Further testing was carried out on his stored sera in an attempt to establish a diagnosis. Two second generation enzyme-linked immunosorbent assay tests (Abbott and Ortho) gave differing results but were suggestive of seroconversion and subsequent seroreversion to HCV. Further testing with recombinant immunoblot assay and polymerase chain reaction did not resolve the issue. CONCLUSION: Our findings in this patient illustrate how the use of anti-HCV antibody tests in some clinical settings can result in confusion and misdiagnosis. These tests should be restricted to situations in which diagnostic usefulness has been established.