Prolonged outbreak of meticillin-resistant Staphylococcus aureus in a cardiac surgery unit linked to a single colonized healthcare worker

BACKGROUND

In low- as well as in high-prevalence settings, healthcare workers (HCWs) may be a substantial, under-recognized, reservoir of meticillin-resistant Staphylococcus aureus (MRSA) and an important potential source of transmission to patients.

AIM

To report an outbreak of MRSA in a cardiac surgery unit in England over a 10-month period.

METHODS

Cases were defined as patients and staff on the cardiac surgery unit from whom the outbreak strain was newly isolated between 20 May 2011 and 16 March 2012. Representative isolates from all cases were characterized by spa-typing, pulsed-field gel electrophoresis and multi-locus variable-number tandem-repeat analysis (MLVA).

FINDINGS

Four patients appeared to acquire MRSA during their inpatient stay on the cardiac surgery unit. All four patients and one HCW were found to be carrying an identical epidemic (E)MRSA-15 strain (spa t032, pulsotype A, MLVA profile 16-6-3-1-1-17-1-4). No other members of staff were found to be colonized with MRSA. The colonized HCW was thought to be the source of the outbreak and was decolonized using a combination of nasal mupirocin, chlorhexidine body wash and oral rifampicin and doxycycline.

CONCLUSIONS

This report highlights recent changes in the epidemiology of MRSA in England and suggests an important role for colonized HCWs in the transmission of MRSA to patients. Screening HCWs may provide an increasingly valuable strategy in managing linked hospital acquisitions and well-defined outbreaks where initial investigation does not reveal a source.

Abstract P3-07-05: Bisphosphonate use after primary breast cancer and risk of contralateral breast cancer using pharmacy data

Background: It is not clear if bisphosphonates (BP) are associated with improved breast cancer prognosis in women with early breast cancer. Clinical trials have reported mixed results, yet BPs may be most beneficial in patients with low estrogen levels. However, BPs and risk of second (contralateral) breast cancer has been minimally studied. We examined the association of oral BP use (ever/never and duration) on risk of contralateral breast cancer (CBC) in 17,224 women with early stage breast cancer treated with tamoxifen.

Materials and Methods: A cohort was assembled of women diagnosed with their first primary breast cancer (Stage 0, I, II) from 1996 to 2007 on tamoxifen and followed through 31 December 2009 at Kaiser Permanente Northern and Southern California. Demographic, tumor, pharmacy, and cancer treatment information was extracted from electronic medical records and SEER-affiliated cancer registries at each site. Second (contralateral) tumors were identified from the cancer registries. Detailed information on oral BP use (before and after initial breast cancer diagnosis) was obtained from pharmacy databases. A record of >90 days supply was considered the minimum exposure. Initiation and duration of post-diagnosis use was categorized as 1) non-use (≤90 days supply) and use (>90 days supply) and 2) non-use (≤90 days supply), 91 days–<1 year supply, 1-<2 years supply, and ≥2 years supply. Delayed entry Cox regression models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) with BP use modeled as a time-varying covariate. Women were followed through CBC, health plan disenrollment, death, or end of study, whichever occurred first. We adjusted for age, stage and year of diagnosis; race/ethnicity; income; comorbidity; tumor factors; primary and adjuvant cancer treatments; previous BP use, and study site.

Results: Over a mean (SD) follow-up of 6.4 (6.3) years, 586 women (3.4%) were diagnosed with CBC after their initial breast cancer diagnosis. Around 19.2% (n = 3303) of the cohort used a BP post-initial breast cancer diagnosis (>93% alendronate). To minimize confounding by indication, all models were adjusted for prior use of BPs before breast cancer diagnosis (n = 1047, 6.1%) and excluded women with prior 5-year history of osteopenia, osteoporosis, and fractures (n = 1808, 10.5%). Compared to non-users, ever use (>90 days supply) was associated with a modestly lower CBC risk (HR = 0.80; 95% CI: 0.61, 1.16). However, stratified analyses by age at breast cancer diagnosis (<50 years vs. ≥50 years) suggested lower risk among older women (HR = 0.80; 95% CI: 0.57, 1.12) compared with younger women (HR = 1.00; 95% CI: 0.39, 2.52). Increasing duration of use was not associated with CBC risk compared to non-use and possibly reflective of some residual confounding by indication: <1 year (HR = 0.56; 95% CI: 0.30, 1.02), 1-<2 years (HR = 0.99; 95% CI: 0.56, 1.72), ≥2 years (HR = 0.91; 95% CI: 0.58, 1.42).

Discussion: While we found modestly lower CBC risk with BP use after diagnosis of primary breast cancer, the protective effects were perhaps confined to older women compared with younger women. Next steps include adding BMD to further explore confounding by indication and examining BP use and breast cancer recurrence and mortality.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P3-07-05.

Mitochondrial DNA analyses of the saltwater crocodile (Crocodylus porosus) from the Northern Territory of Australia

The saltwater crocodile is distributed throughout south-east Asia and Australia. In Australia, it is most abundant in the Northern Territory and Queensland, where it is sustainably farmed for its skins and meat. The aim of this study was to elucidate the relationships and genetic structure among saltwater crocodiles from the Northern Territory of Australia using mitochondrial control region sequences from 61 individuals, representing nine river basins and six of unknown origin, as well as published sequences from other regions. Eight mitochondrial control region haplotypes were identified among both published and novel sequences. Three of the haplotypes appear to be restricted to specimens from northern Australia, with a single haplotype being the most widely dispersed across all river basins. Although Analysis of Molecular Variance provides some support for differentiation among river basins, the frequency of shared haplotypes among these geographical units and median-joining network analysis do not support a clear genetic structure or phylogeographic pattern for saltwater crocodiles in the Northern Territory. The results of this study will assist in furthering our understanding of the genetic diversity of wild saltwater crocodile populations used for ranching in the Northern Territory, as well as providing a framework for assessing the origin of unknown specimens in the future.

Mycotic aneurysm of the aorta as a complication of Bacillus Calmette-Guérin instillation

Bacillus Calmette-Guérin (BCG) is a live attenuated strain of Mycobacterium bovis that has been widely used for the treatment of superficial transitional cell carcinoma of the bladder. We describe a rare case of supra-renal mycotic aortic aneurysm secondary to BCG instillation in a 75-year-old male. Patients presenting with systemic symptoms post-instillation, possibly with an aneurysm, should raise suspicion of BCG dissemination, which requires early instigation of anti-mycobacterial drugs.

Mapping Rph20: a gene conferring adult plant resistance to Puccinia hordei in barley

A doubled haploid (DH) barley (Hordeum vulgare L.) population of 334 lines (ND24260 × Flagship) genotyped with DArT markers was used to map genes for adult plant resistance (APR) to leaf rust (Puccinia hordei Otth) under field conditions in Australia and Uruguay. The Australian barley cultivar Flagship carries an APR gene (qRphFlag) derived from the cultivar Vada. Association analysis and composite interval mapping identified two genes conferring APR in this DH population. qRphFlag was mapped to the short arm of chromosome 5H (5HS), accounting for 64-85% of the phenotypic variation across four field environments and 56% under controlled environmental conditions (CEC). A second quantitative trait locus (QTL) from ND24260 (qRphND) with smaller effect was mapped to chromosome 6HL. In the absence of qRphFlag, qRphND conferred only a low level of resistance. DH lines displaying the highest level of APR carried both genes. Sequence information for the critical DArT marker bPb-0837 (positioned at 21.2 cM on chromosome 5HS) was used to develop bPb-0837-PCR, a simple PCR-based marker for qRphFlag. The 245 bp fragment for bPb-0837-PCR was detected in a range of barley cultivars known to possess APR, which was consistent with previous tests of allelism, demonstrating that the qRphFlag resistant allele is common in leaf rust resistant cultivars derived from Vada and Emir. qRphFlag has been designated Rph20, the first gene conferring APR to P. hordei to be characterised in barley. The PCR marker will likely be effective in marker-assisted selection for Rph20.