A microbiological evaluation of hospital cleaning methods

Hospital hygiene may be associated with hospital-acquired infection. This study evaluated four hospital cleaning methods: 'mop and vacuum', 'spray clean' and 'wet scrub' for floors, and one steam cleaning method for curtains. A standardised microbiological screening method was used to sample the environment before and after cleaning in order to quantify total viable counts as well as identify specific organisms. The results showed that all floor cleaning methods reduced the overall microbial load, although high counts and bacterial pathogens occasionally persisted despite cleaning. Spray cleaning gave marginally better results than traditional mopping and vacuuming. Wet scrubbing significantly reduced levels of coagulase-positive staphylococci (p = 0.03), which, in combination with routine methods, produced an effect that persisted for at least a week. Steam cleaning of curtains also reduced microbial counts (p = 0.08), but had little effect on Staphylococcus aureus and other potential pathogens. These results might help managers assess the costs of different cleaning methods against potential infection control benefits in a hospital.     

How antibiotics can make us sick: the less obvious adverse effects of antimicrobial chemotherapy

Antimicrobial agents are associated with side-effects, which are usually tolerated because the benefits of treatment outweigh the toxic effects. Clinicians know about these side-effects but are less likely to understand additional adverse events, such as the overgrowth of resistant microorganisms. Overgrowth can itself precipitate a secondary infection, which can be more difficult to treat. Resistant organisms then spread to other patients and the environment, and contribute to increasing antimicrobial resistance worldwide. Organisms exposed to antibiotics undergo molecular changes that might enhance virulence. Enhanced pathogenicity would affect patients, particularly if the organism is also multiply resistant. Clinicians have a responsibility to select the correct antibiotic as soon as they have diagnosed infection, but an absence of microbiological understanding and ignorance of the potential environmental effects have contributed to inappropriate prescribing. The less obvious results of antimicrobial consumption probably go unrecognised in routine clinical care.     

Hospital cleaning in the 21st century

More evidence is emerging on the importance of the clinical environment in encouraging hospital infection. This review considers the role of cleaning as an effective means to control infection. It describes the location of pathogen reservoirs and methods for evaluating hospitals’ cleanliness. Novel biocides, antimicrobial coatings and equipment are available, many of which have not been assessed against patient outcome. Cleaning practices should be tailored to clinical risk, given the wide-ranging surfaces, equipment and building design. There is confusion between nursing and domestic personnel over the allocation of cleaning responsibilities and neither may receive sufficient training and/or time to complete their duties. Since less labourious practices for dirt removal are always attractive, there is a danger that traditional cleaning methods are forgotten or ignored. Few studies have examined detergent-based regimens or modelled these against infection risk for different patient categories. Fear of infection encourages the use of powerful disinfectants for the elimination of real or imagined pathogens in hospitals. Not only do these agents offer false assurance against contamination, their disinfection potential cannot be achieved without the prior removal of organic soil. Detergent-based cleaning is cheaper than using disinfectants and much less toxic. Hospital cleaning in the 21st century deserves further investigation for routine and outbreak practices.     

Infant mortality and child nutrition in Bangladesh

The excess female infant mortality observed in South Asia has typically been attributed to gender discrimination in the intra-household allocation of food and medical care. However, studies on child nutrition find no evidence of gender differences. A natural explanation could be that in environments of high infant mortality of females, the surviving children are healthier, so that child nutrition cannot be studied independently of mortality. In this paper, we use data from the 2004 Bangladesh Demographic Health Survey to investigate if there are any gender differences in survival probabilities and whether this leads to differences in child nutrition. We argue the importance of establishing whether or not there exists a dependence relationship between the two random variables--infant mortality and child nutrition--and in order to detect this we employ a copula approach to model specification. The results suggest, for example, that while male children have a significantly lower likelihood of surviving their first year relative to female children, should they survive they have significantly better height-for-age Z-scores. From a policy perspective, household wealth and public health interventions such as vaccinations are found to be important predictors of better nutritional outcomes.     

How do we assess hospital cleaning? A proposal for microbiological standards for surface hygiene in hospitals

Increasing numbers of hospital-acquired infections have generated much attention over the last decade. The public has linked the so-called 'superbugs' with their experience of dirty hospitals, but the precise role of cleaning in the control of these organisms in unknown. Hence the importance of a clean environment is likely to remain speculative unless it becomes an evidence-based science. This proposal is a call for bacteriological standards with which to assess clinical surface hygiene in hospitals, based on those used by the food industry. The first standard concerns any finding of a specific 'indicator' organism, the presence of which suggests a requirement for increased cleaning. Indicators would include Staphylococcus aureus, including methicillin-resistant S. aureus, Clostridium difficile, vancomycin-resistant enterococci and various Gram-negative bacilli. The second standard concerns a quantitative aerobic colony count of <5 cfu/cm(2) on frequent hand touch surfaces in hospitals. The principle relates to modern risk management systems such as HACCP, and reflects the fact that pathogens of concern are widespread. Further work is required to evaluate and refine these standards and define the infection risk from the hospital environment.     

Direct evidence of cubic difference tone propagation by intracochlear acoustic pressure measurements in the guinea‐pig

The fine tuning mechanisms involved in the normal processing of sound in the cochlea are non-linear, hence combination tones are generated inside the cochlea when a pair of low-level pure tones with neighbouring frequencies f₁ and f₂ is used as a stimulus. Their detection as sounds in the ear canal proves that they undergo backward propagation in the cochlea and through the middle ear, and the non-invasive measurement of the combination tone at 2f₁–f₂, called the cubic difference tone (CDT), has become a routine method of monitoring cochlear function. In order to gain information on the hypothetical places where CDTs are generated, on their intracochlear levels and propagation velocities, direct measurements of CDT pressure waves were carried out in scala vestibuli and tympani of the first and second turn of the guinea-pig cochlea. Cubic difference tones at 2f₁–f₂ varied from 0.75 to 9 kHz and were measured with a miniature piezoresistive transducer. Its high sensitivity allowed the detection of CDTs whenever their levels exceeded 5 dB SPL in the ear canal, i.e. 40 dB SPL (re: 20 μPa) inside the cochlea. The levels of CDTs were similar in scala vestibuli of the first and second turn. Phase comparisons between measurements at 2f₁–f₂ in the first and second turn allowed determination of the place where the CDT phase was minimum. It provided an estimation of the generation site of the CDT, which appeared to be close to the place tuned to f₂ for stimulus levels lower than 70 dB SPL. Forward and backward travel times from one turn to the other were assessed at several frequencies, and both values were shorter than 0.2 ms. In contrast, the overall ‘round-trip’ delay of CDTs, measured in the ear canal, was about five times larger, suggesting that local filtering processes rather than propagation delays account for the overall CDT delay.