Considering the introduction of universal MRSA screening

More and more hospitals are introducing universal screening for meticillin-resistant Staphylococcus aureus (MRSA). As with many other interventions imposed in the name of infection control, the evidence for benefit remains controversial. Despite this, screening has aroused political interest and has now become mandatory in some countries. This Leader examines the implications of introducing universal screening for MRSA. In addition to resource requirements, there are practical difficulties and consequences that may not have been fully considered. These include: staff recruitment and working time arrangements in the laboratory; specificity and sensitivity of selected screening sites and laboratory methods; lack of isolation facilities on the wards; timely and continuing management of MRSA-infected and/or -colonised patients; and ethical issues raised by screening patients without considering the role of colonised staff. Furthermore, the focus on MRSA promotes undue emphasis of its importance, which could facilitate legal interest. We should remember that it is the precipitant actions from finding a new MRSA patient that aids control, not the simple act of screening by itself. There is no doubt that universal screening should be explored as a mechanism for controlling MRSA, but more evidence is required before it becomes routine.     

Monitoring environmental cleanliness on two surgical wards

Ten hand-touch sites were screened weekly on two surgical wards over two consecutive six-month periods. The results were analysed using hygiene standards, which specify (i) an aerobic colony count (ACC) > 2.5 cfu/cm(2), and (ii) presence of coagulase-positive staphylococci, as hygiene failures. Sites most often failing the standards were beds and hoist (64%: 33 of 52 weeks), bedside lockers (62%: 32 of 52) and overbed tables (44%: 23 of 52). Methicillin-susceptible/resistant Staphylococcus aureus (MSSA/MRSA) were more often recovered from lockers, overbed tables and beds. Recovery of MSSA/MRSA at any site was significantly associated with an ACC > 2.5 cfu/cm(2) from that site (p = 0.001; OR: 3.35 [95% CI 1.79, 6.28]). In addition, total ACC's > 2.5 cfu/cm(2) each week were significantly associated with weekly bed occupancies > 95% (p = 0.0004; OR: 2.94 [95% CI 1.44, 6.02]). Higher microbial growth levels from hand-touch sites reflect weekly bed occupancies and indicate a risk for both resistant and susceptible S. aureus. These organisms are more likely to be recovered from near-patient sites on the ward.     

Probabilistic microsimulation to examine the cost-effectiveness of hospital admission screening strategies for carbapenemase-producing enterobacteriaceae (CPE) in the United Kingdom

Background

Antimicrobial resistance has been recognised as a global threat with carbapenemase- producing-Enterobacteriaceae (CPE) as a prime example. CPE has similarities to COVID-19 where asymptomatic patients may be colonised representing a source for onward transmission. There are limited treatment options for CPE infection leading to poor outcomes and increased costs. Admission screening can prevent cross-transmission by pre-emptively isolating colonised patients.

Objective

We assess the relative cost-effectiveness of screening programmes compared with no- screening.

Methods

A microsimulation parameterised with NHS Scotland date was used to model scenarios of the prevalence of CPE colonised patients on admission. Screening strategies were (a) two-step screening involving a clinical risk assessment (CRA) checklist followed by microbiological testing of high-risk patients; and (b) universal screening. Strategies were considered with either culture or polymerase chain reaction (PCR) tests. All costs were reported in 2019 UK pounds with a healthcare system perspective.

Results

In the low prevalence scenario, no screening had the highest probability of cost-effectiveness. Among screening strategies, the two CRA screening options were the most likely to be cost-effective. Screening was more likely to be cost-effective than no screening in the prevalence of 1 CPE colonised in 500 admitted patients or more. There was substantial uncertainty with the probabilities rarely exceeding 40% and similar results between strategies. Screening reduced non-isolated bed-days and CPE colonisation. The cost of screening was low in relation to total costs.

Conclusion

The specificity of the CRA checklist was the parameter with the highest impact on the cost-effectiveness. Further primary data collection is needed to build models with less uncertainty in the parameters.

     

Experimental look at cochlear mechanics.

The mechanisms by which the organ of Corti is stimulated by acoustic stimuli are discussed on the basis of experimental observations. This discussion refers to the resonance theory as well as to the traveling wave (TW) theory. The measurement of the basilar membrane displacements, of the cochlear microphonic (CM) responses to pure tones and impulses, and the recording of the intracochlear acoustic pressure seem to indicate that, at least in the basal part of the cochlea and for frequencies up to the characteristic frequency of a given location, the cochlear responses do not exhibit large phase lags and long delays which characterize the one-dimensional long-wave models (in which a TW transports the energy along the cochlear partition). These experimental observations suggest that the cochlear partition is excited simultaneously as a whole, more or less like a bank of resonators, as proposed a long time ago by Helmholtz.     

Polymerase chain reaction diagnosis in culture-negative prosthetic valve methicillin-resistant Staphylococcus aureus endocarditis in a patient with chronic liver disease

We report the use of polymerase chain reaction for the diagnosis of prosthetic valve methicillin-resistant Staphylococcus aureus endocarditis in a patient with chronic liver disease where conventional laboratory testing failed. This case highlights the diagnostic and therapeutic potential of molecular techniques in the management of culture-negative endocarditis.     

Tactile motion activates the human middle temporal/V5 (MT/V5) complex

The human middle temporal/V5 complex (hMT/V5) plays a central role in the perception of visual motion. This region is considered a unimodal visual area with little direct involvement of other sensory modalities. The current study uses H215O PET to test whether tactile motion influences the activity of hMT/V5. Regional cerebral blood flow (rCBF) within hMT/V5 was estimated in eight subjects in separate tactile motion and visual motion conditions, each contrasted with a resting, control. The tactile motion condition involved a brush stroked proximal-to-distal along the volar forearm and palm, while the subject attended to the stimulus with closed eyes. The visual motion condition consisted of low contrast, grey-scale rings radiating at 15 degrees /s from a central point, upon which the subject was instructed to fixate. The location of hMT/V5 was defined for each subject separately as the local maximum of rCBF change during the visual motion condition (vs. control). The average change in rCBF within spherical regions of interest at each peak revealed significant bilateral activation of hMT/V5 in the tactile motion condition contrasted with a second, independent set of control scans. Additionally, a single subject received a sufficient number of scans to perform a pixel-wise, within-subject analysis. His functional images were coregistered to his anatomical MRI. In this subject, tactile motion produced a significant increase in rCBF that directly overlapped a region activated by visual motion at the posterior continuance of the inferior temporal sulcus, consistent with the known location of hMT/V5. These results suggest involvement of the hMT/V5 complex in tactile motion processing.