Cost-analysis of PCR-guided pre-emptive antibiotic treatment of Staphylococcus aureus infections: an analytic decision model

The aim of this study is to examine whether rapid polymerase chain reaction (PCR)-based screening is a cost-efficient tool to optimize pre-emptive antibiotic therapy of methicillin-resistant and methicillin-sensitive Staphylococcus aureus (MRSA and MSSA, respectively) infections. A decision analytic cost model was developed, based on data from the peer-reviewed literature. Sensitivity analyses were undertaken to investigate the impact of variation in the MRSA rate, cost ratio of the cost of inappropriate antibiotic therapy to the cost of appropriate antibiotic therapy, PCR test cost, and total hospital costs per case. At a current MRSA rate of 24.5 % in Germany, PCR-guided treatment regimens are cost-efficient compared to empirical strategies. The costs of alternative treatment strategies differ, on average, up to 1,780 <euro> per case. An empirical MRSA treatment strategy is least costly when the cost ratio is less than 1.06. When the total hospital cost per MRSA case is increased, pre-emptive MSSA treatment with PCR tests achieves the lowest average cost. Early verification and adaptation of an initial pre-emptive antibiotic treatment of S. aureus infections using PCR-based tests are advantageous in Germany and other European countries. PCR tests, accordingly, should be considered as elements in antimicrobial stewardship programs.

Transmission rates, screening methods and costs of MRSA--a systematic literature review related to the prevalence in Germany

Methicillin-resistant Staphylococcus aureus (MRSA) infections represent a serious challenge for health care institutions, which is inherent in the combination of prevalence, transmission rates and costs. Furthermore, performing an MRSA screening requires information on the complex system of effectiveness, accuracy and costs of different screening methods. The purpose of this study was to give an overview of parameters with decisive significance for the burden of MRSA and the selection of a specific MRSA screening strategy. A systematic literature search for peer-reviewed health economic studies associated with MRSA was performed (from 1995 to the present). Eighty-seven different studies met all inclusion and exclusion criteria. Primary outcomes included the prevalence of MRSA, MRSA transmission rates, performance characteristics of MRSA screening methods, costs for pre-emptive isolation precautions and costs per MRSA case. The prevalence rates reported for all inpatients (1.2-5.3 %) as well as for inpatients with risk factors or patients in risk areas (3.85-20.6 %) vary greatly. The range of cross-transmission rates per day reported for patients with MRSA in isolation is 0.00081-0.009 and for carriers not in isolation is 0.00137-0.140, respectively. For polymerase chain reaction (PCR) methods, the mean sensitivity and specificity were 91.09 and 95.79 %, respectively. Culture methods show an average sensitivity of 89.01 % and an average specificity of 93.21 %. The turn-around time for PCR methods averages 15 h, while for the culture method, it can only be estimated as 48-72 h. This review filtered important parameters and cost drivers, and covered them with literature-based averages. These findings serve as an ideal evidence base for further health economic considerations of the cost-effectiveness of different MRSA screening methods.

Dentition of eight species of Mediterranean Sea Gobiidae: do dentition characters of gobies reflect phylogenetic relationships?

Oral and pharyngeal dentition was analysed in eight Mediterranean species of five different genera using scanning electron microscopy (SEM). Number, position, shape and size of teeth in the jaws and the pharyngeal tooth plates were used as a basis for comparison among taxa. Three different groups could be established based on the dental morphology among the species investigated and homoplasy due to feeding ecology cannot be considered the reason for similarity among them. The established groups are suggested to reflect phylogenetic relationships and correspond with the scarce published data on the topic.

Can the Hazard Assessment and Critical Control Points (HACCP) system be used to design process-based hygiene concepts?

Recently, the HACCP (Hazard Analysis and Critical Control Points) concept was proposed as possible way to implement process-based hygiene concepts in clinical practice, but the extent to which this food safety concept can be transferred into the health care setting is unclear. We therefore discuss possible ways for a translation of the principles of the HACCP for health care settings. While a direct implementation of food processing concepts into health care is not very likely to be feasible and will probably not readily yield the intended results, the underlying principles of process-orientation, in-process safety control and hazard analysis based counter measures are transferable to clinical settings. In model projects the proposed concepts should be implemented, monitored, and evaluated under real world conditions.

Antimicrobial efficacy of the silver wound dressing Biatain Ag in a disc carrier test simulating wound secretion

AIM

The efficacy of antimicrobial compounds included in wound dressings has been determined using the quantitative suspension test according to EN 13727 before. However, as suspension tests are not an accurate reflection of the conditions under which wound antiseptics are used, it was investigated if a disc carrier test would yield results simulating practical conditions on wound surfaces. A silver-leaching foam wound dressing was used for evaluation of the disc carrier test method.

METHOD

The disc carriers consisted of circular stainless-steel discs measuring 2 cm in diameter and 1.5 mm in thickness, complying with the requirements of EN 10088-2. Carriers were contaminated with Staphylococcus aureus, methicillin-resistant S. aureus or Pseudomonas aeruginosa, respectively, together with an artificial wound secretion and left to dry at room temperature for 30 min. The wound dressings being tested were placed on the discs for the length of the exposure time, and after neutralization by thioglycolate in phosphate-buffered saline the number of surviving test organisms was then counted. The logarithmic reduction factor was calculated from the difference between the initial inoculum and the number of recovered test organisms.

RESULTS

The disc carrier test allowed determination of an antimicrobial efficacy in a realistic setting. It also imposed more stringent requirements on efficacy over time than the quantitative suspension test. The silver foam wound dressing showed a time-dependent antimicrobial efficacy. After 24-hour application time, the reduction factors against S. aureus, P. aeruginosa and the methicillin-resistant S. aureus were 1.9 ± 0.15, 2.1 ± 0.14 and 3.1 ± 0.18, respectively.

CONCLUSION

The disc carrier test was a useful method for testing the antimicrobial efficacy of a foam silver dressing. The antimicrobial dressing exhibited an antimicrobial effect after 3 h and achieved a reduction >2 log against the tested bacterial strains in the presence of a simulated wound secretion after 24 h.

Determination of antiseptic efficacy of rubs on the forearm and consequences for surgical hand disinfection

While hands are acknowledged to be the most important source of pathogens from the skin of the surgical team, the transmission of pathogens from the forearms may also be relevant. Preoperative hand disinfection is recommended, but evidence-based standards for the forearms are lacking. As neither the European standard EN 12791 nor the American guidelines ASTM 1115 are applicable to the forearms, a new test method based on the European standard EN 12791 and the German Society for Hygiene and Microbiology (DGHM) method for testing for the efficacy of skin antiseptics was developed to address the forearms. The antiseptic efficacy of a commercially available alcohol-based hand rub [76.7% (w/w) ethanol] was assessed on the upper arm after 15s, 2.5 min, and 30 min, and on the lower arm after 2.5 min, 30 min, and 3 h. On the upper arm, application of the product followed the DGHM standard procedure. On the forearm, the product was applied by the participants themselves with the right hand over the left forearm and vice versa as performed during preoperative hand disinfection. Sampling and culture were performed according to the DGHM method for skin antisepsis on the upper arm. Twenty-two volunteers were investigated. The efficacy of the antiseptic treatment on the forearm was not significantly lower than on the upper arm for any of the areas tested (P > 0.05). Reduction factors for all tested areas and times were quite similar, with confidence intervals ranging between 1.43 and 2.31 log₁₀. We suggest that an application time of 10s may be sufficient for the treatment of the forearm as part of preoperative hand disinfection, provided that an appropriate product is used.

Skin disinfection by plasma-tissue interaction: comparison of the effectivity of tissue-tolerable plasma and a standard antiseptic

Wound healing disorders frequently occur due to biofilm formation on wound surfaces requiring conscientious wound hygiene. Often, the application of conventional liquid antiseptics is not sufficient and sustainable as (1) the borders and the surrounding of chronic wounds frequently consist of sclerotic skin, impeding an effectual penetration of these products, and (2) the hair follicles representing the reservoir for bacterial recolonization of skin surfaces are not affected. Recently, it has been reported that tissue-tolerable plasma (TTP), which is used at a temperature range between 35 and 45°C, likewise has disinfecting properties. In the present study, the effectivity of TTP and a standard liquid antiseptic was compared in vitro on porcine skin. The results revealed that TTP was able to reduce the bacterial load by 94%, although the application of the liquid antiseptic remained superior as it reduced the bacteria by almost 99%. For in vivo application, however, TTP offers several advantages. On the one hand, TTP enables the treatment of sclerotic skin as well, and on the other hand, a sustainable disinfection can be realized as, obviously, also the follicular reservoir is affected by TTP.

Classification of wounds at risk and their antimicrobial treatment with polihexanide: a practice-oriented expert recommendation

Currently, there are no generally accepted definitions for wounds at risk of infection. In clinical practice, too many chronic wounds are regarded as being at risk of infection, and therefore many topical antimicrobials - in terms of frequency and duration of use - are applied to wounds. Based on expert discussion and current knowledge, a clinical assessment score was developed. The objective of this wounds at risk (W.A.R.) score is to allow decision-making on the indication for the use of antiseptics on the basis of polihexanide. The proposed clinical classification of W.A.R. shall facilitate the decision for wound antisepsis and allow an appropriate general treatment regimen with the focus on the prevention of wound infection. The W.A.R. score is based on a clinically oriented risk assessment using concrete patient circumstances. The indication for the use of antiseptics results from the addition of differently weighted risk causes, for which points are assigned. Antimicrobial treatment is justified in the case of 3 or more points.

Senescence rates in patients with end-stage renal disease: a critical appraisal of the Gompertz model

The most frequently used model to describe the exponential increase in mortality rate over age is the Gompertz equation. Logarithmically transformed, the equation conforms to a straight line, of which the slope has been interpreted as the rate of senescence. Earlier, we proposed the derivative function of the Gompertz equation as a superior descriptor of senescence rate. Here, we tested both measures of the rate of senescence in a population of patients with end-stage renal disease. It is clinical dogma that patients on dialysis experience accelerated senescence, whereas those with a functional kidney transplant have mortality rates comparable to the general population. Therefore, we calculated the age-specific mortality rates for European patients on dialysis (n=274 221; follow-up=594 767 person-years), for European patients with a functioning kidney transplant (n=61 286; follow-up=345 024 person-years), and for the general European population. We found higher mortality rates, but a smaller slope of logarithmic mortality curve for patients on dialysis compared with both patients with a functioning kidney transplant and the general population (P<0.001). A classical interpretation of the Gompertz model would imply that the rate of senescence in patients on dialysis is lower than in patients with a functioning transplant and lower than in the general population. In contrast, the derivative function of the Gompertz equation yielded the highest senescence rates for patients on dialysis, whereas the rate was similar in patients with a functioning transplant and the general population. We conclude that the rate of senescence is better described by the derivative function of the Gompertz equation.