Interlaboratory evaluation of Mucorales PCR assays for testing serum specimens: A study by the fungal PCR Initiative and the Modimucor study group

Interlaboratory evaluations of Mucorales qPCR assays were developed to assess the reproducibility and performance of methods currently used. The participants comprised 12 laboratories from French university hospitals (nine of them participating in the Modimucor study) and 11 laboratories participating in the Fungal PCR Initiative. For panel 1, three sera were each spiked with DNA from three different species (Rhizomucor pusillus, Lichtheimia corymbifera, Rhizopus oryzae). For panel 2, six sera with three concentrations of R. pusillus and L. corymbifera (1, 10, and 100 genomes/ml) were prepared. Each panel included a blind negative-control serum. A form was distributed with each panel to collect results and required technical information, including DNA extraction method, sample volume used, DNA elution volume, qPCR method, qPCR template input volume, qPCR total reaction volume, qPCR platform, and qPCR reagents used. For panel 1, assessing 18 different protocols, qualitative results (positive or negative) were correct in 97% of cases (70/72). A very low interlaboratory variability in Cq values (SD = 1.89 cycles) were observed. For panel 2 assessing 26 different protocols, the detection rates were high (77-100%) for 5/6 of spiked serum. There was a significant association between the qPCR platform and performance. However, certain technical steps and optimal combinations of factors may also impact performance. The good reproducibility and performance demonstrated in this study support the use of Mucorales qPCR as part of the diagnostic strategy for mucormycosis.

Invasive rhino-orbital-cerebral aspergillosis in an immunocompetent patient

INTRODUCTION

Rhino-orbital-aspergillosis (ROA) is a rare but serious disease in immunocompetent patients. Diagnosis is often delayed due to the absence of specific clinical symptoms. We describe the case of a patient who presented initially with ROA which spread progressively to the right ethmoid-sphenoid sinuses and then to the brain.

OBSERVATION

A 61-year-old patient with a history of well-controlled diabetes presented with a sudden severe decrease in right visual acuity. Cerebral MRI showed the presence of an infiltrate in the right orbital apex extending to the homolateral cavernous sinus without any cerebral involvement. A diagnosis of right orbital myositis was made and corticosteroid therapy was started. His symptoms worsened progressively leading to quasi-blindness. A new MRI showed the development of right sphenoid-ethmoid osteolytic lesions. A fungal aetiology was suspected and tests for fungal biomarkers found a β-(1-3)-D-glucan level of 99pg/ml but negative galactomannan. An ethmoid biopsy was performed for histological and mycological investigations, including the detection of Aspergillus DNA by qPCR. qPCR was positive and culture resulted in the isolation of multi-sensitive Aspergillus fumigatus. Treatment was initiated with voriconazole. Due to persistence of blindness and the appearance of a lesion extending to the right frontal lobe, surgical excision was performed followed by antifungal treatment for a total duration of 1year. The patient is currently stable, but has persistence of blindness in the right eye.

CONCLUSION

Invasive ROA is a rare but serious disease in immunocompetent patients which should be evoked in the differential diagnosis of a tumour or vasculitis. Early diagnosis is essential for optimal management.

[Regionalisation of perinatal care in Basse-Normandie, France: evolution over 5 years]

OBJECTIVES

To compare evolution and characteristics of in utero transfers (IUT) in Basse-Normandie area, France, between 2004 and 2008, and to describe characteristics of IUT in 2008.

MATERIALS AND METHODS

Analysis of data from the IUT registry, collected prospectively since 2004.

RESULTS

An average of five IUT per week was observed. The rate of IUT regularly increased (P=0.003) and reached 16.2 per 1000 pregnancies in 2008. Extra network IUT decreased steadily (P=0.04). For level 3 units, the proportion of IUT from level 2 units increased (P<10(-3)). Before 32 weeks of gestational age, all IUT were done towards a level 3 unit. Median time between IUT and delivery and caesarean section rates were variable according to IUT indication (for threats of premature delivery, respectively 5 days and 23.3%). The rate of retransfer towards initial unit of towards a birth site of relevant level was 5.3%.

CONCLUSION

The IUT registry gives useful information on evolution and characteristics of IUT in our area. An increased regionalisation and more frequent adequate IUT were observed. The registry must now serve as a basis for practices assessment.

Towards an Integrated Approach in Supporting Microbiological Food Safety Decisions

Decisions on food safety involve consideration of a wide range of concerns including the public health impact of foodborne illness, the economic importance of the agricultural sector and the food industry, and the effectiveness and efficiency of interventions. To support such decisions, we propose an integrated scientific approach combining veterinary and medical epidemiology, risk assessment for the farm-to-fork food chain as well as agricultural and health economy. Scientific advice is relevant in all stages of the policy cycle: to assess the magnitude of the food safety problem, to define the priorities for action, to establish the causes for the problem, to choose between different control options, to define targets along the food chain and to measure success.

Prevalence and growth of Listeria monocytogenes in naturally contaminated cold-smoked salmon

AIM

To investigate Listeria monocytogenes contamination and behaviour in naturally contaminated French cold-smoked salmon (CSS).

METHOD AND RESULTS

Between 2001 and 2004, L. monocytogenes was detected in 104 of 1010 CSS packs, produced by nine French plants, with different prevalence (from 0% to 41%). The initial contamination, measured with a sensitive filtration method, was low (92% of contaminated products below 1 CFU g(-1)) and growth was limited.

CONCLUSION

Growth was consistent with results of a predictive model including microbial competition.

SIGNIFICANCE AND IMPACT OF THE STUDY

To be included in a quantitative risk assessment.

Effect of temperature, water-phase salt and phenolic contents on Listeria monocytogenes growth rates on cold-smoked salmon and evaluation of secondary models

Salting and smoking are ancient processes for fish preservation. The effects of salt and phenolic smoke compounds on the growth rate of L. monocytogenes in cold-smoked salmon were investigated through physico-chemical analyses, challenge tests on surface of cold-smoked salmon at 4 degrees C and 8 degrees C, and a survey of the literature. Estimated growth rates were compared to predictions of existing secondary models, taking into account the effects of temperature, water phase salt content, phenolic content, and additional factors (e.g. pH, lactate, dissolved CO2). The secondary model proposed by Devlieghere et al. [Devlieghere, F., Geeraerd, A.H., Versyck, K.J., Vandewaetere, B., van Impe, J., Debevere, J., 2001. Growth of Listeria monocytogenes in modified atmosphere packed cooked meat products: a predictive model. Food Microbiology 18, 53-66.] and modified by Giménez and Dalgaard [Giménez, B., Dalgaard, P., 2004. Modelling and predicting the simultaneous growth of Listeria monocytogenes and spoilage micro-organisms in cold-smoked salmon. Journal of Applied Microbiology 96, 96-109.] appears appropriate. However, further research is needed to understand all effects affecting growth of L. monocytogenes in cold-smoked salmon and to obtain fully validated predictive models for use in quantitative risk assessment.

Growth rate and growth probability of Listeria monocytogenes in dairy, meat and seafood products in suboptimal conditions

AIMS

To evaluate the performances of models predicting the growth rate or the growth probability of Listeria monocytogenes in food.

METHODS AND RESULTS

Cardinal and square root type models including or not interactions between environmental factors and probability models were evaluated for their ability to describe the behaviour of L. monocytogenes in liquid dairy products, cheese, meat and seafood products. Models excluding interactions seemed sufficient to predict the growth rate of L. monocytogenes. However, the accurate prediction of growth/no-growth limits needed to take interactions into account. A complete and a simplified form (preservatives deducted) of a new cardinal model including interactions and parameter values were suggested to predict confidence limits for the growth rate of L. monocytogenes in food. This model could also be used for the growth probability prediction.

CONCLUSIONS

The new cardinal model including interactions was efficient to predict confidence limits for the growth rate of L. monocytogenes and its growth probability in liquid dairy products, meat and seafood products. In cheese, the model was efficient to predict the absence of growth of the pathogen.

SIGNIFICANCE AND IMPACT OF THE STUDY

The suggested model can be used for risk assessment and risk management concerning L. monocytogenes in dairy, meat and seafood products.

Use of Bayesian modelling in risk assessment: application to growth of Listeria monocytogenes and food flora in cold-smoked salmon

An attempt to use a Bayesian approach to model variability and uncertainty separately in microbial growth in a risk assessment is presented. It was conducted within the framework of a French project aiming at assessing the exposure to Listeria monocytogenes in cold-smoked salmon. The chosen model describes the effect of time and temperature on bacterial growth. A Bayesian approach close to the one proposed by Pouillot et al. [Int. J. Food Microbiol. 81 (2003) 87] is used to estimate the variability and uncertainty of growth parameters from both literature data and data experimentally acquired during the project. Variability between strains and between products is taken into account. The growth of the food flora of cold-smoked salmon is also modelled by the same method. The results obtained for both models are used to predict the simultaneous growth of L. monocytogenes and food flora in cold-smoked salmon with a competitive model, expressing variability and uncertainty through a second-order Monte Carlo simulation.

Reflections on the use of robust and least-squares non-linear regression to model challenge tests conducted in/on food products

In this research, we question the straight-forward use of the classical sum of squared error criterion for identifying the typical parameters of a primary model (like growth rate mumax and lag time lambda) when applied to growth curves obtained in and on food products. Firstly, we base our reflections on 62 Listeria monocytogenes laboratory challenge tests collected in various environments (broth, crushed cold-smoked salmon, and surface of cold-smoked salmon slices). Whereas growth data in broth resulted in residual values consistent with a Gaussian distribution, growth data in the crushed product and even more on the surface of slices appeared different. Secondly, we propose the use of an alternative so-called robust non-linear regression method suitable when experimental error is non-normally distributed, which seems, according to this research, typical for microbial challenge tests in/on food products, and which lead to apparent outliers or leverage points in the experimental data. Properties of the robust regression procedure are illustrated on simulated data first, whereafter its use on the considered challenge tests is illustrated. To conclude, reflections on the assumptions and related realism underlying challenge tests and recommendations for fitting growth curves obtained in and on food products are presented.

Modelling the effect of a temperature shift on the lag phase duration of Listeria monocytogenes

The aim of this work is to study and model the effect of a temperature shift on h(0), the product of the growth rate by the lag phase duration (mulambda). Our work is based on the data of Whiting and Bagi [Int. J. Food Microbiol. 73 (2002) 291], who studied the influence of both the pre-incubation temperature (T(prior)) and the growth temperature (T(growth)) on lambda values of Listeria monocytogenes. We introduce a new model to describe the evolution of the parameter h(0) as a function of T(prior) and T(growth), and compare it to Whiting and Bagi's published polynomial model that describes the influence of T(prior) and T(growth) on lambda independently of mu. For exponential as well as stationary phase cells, h(0) increases almost linearly with the magnitude of the temperature shift. A simple linear model of h(0) turns out to be more suitable to predict lambda values than a polynomial model of lambda.

Physiological significance of the cytometric distribution of fluorescent yeasts after viability staining

This article describes a new method for the early detection of alcoholic fermentation arrest. This methodology is based on the flow cytometric assessment of Saccharomyces cerevisiae yeasts stained with a carboxyfluorescein diacetate fluorescent viability probe. Multicomponent analysis of viable cell distribution constitutes a promising new tool to describe physiological and dynamic changes to heterogeneous viable populations during alcoholic fermentation, through its ability to discriminate between successful processes and those ending prematurely. This framework, which is based on the comparison of cytometric histogram descriptors' combinations that can be related to simple physiological significance comparison, quickly and simply, allows testing yeasts for their fermentation ability and can be used to detect any kind of viability loss so that fermentation arrest can be avoided.

[Suprahepatic vein catheterization in 4 cases of severe septic shock]

Splanchnic hypoperfusion, with pathogenic implications for multiple organ failure, can occur during septic shock. We report four patients with septic shock in whom regional hepatosplenic splanchnic perfusion was monitored through suprahepatic vein catheterization and gastric tonometry. Suprahepatic lactate and oxygen saturation showed splanchnic hypoperfusion in all patients. These parameters improved only in the patient that survived. Gastric tonometry was more inconsistent. We conclude that suprahepatic vein catheterization could have a role in the management of septic shock.

Fitness and competitive growth advantage of new gentamicin-susceptible MRSA clones spreading in French hospitals

Since 1991, new epidemic methicillin-resistant Staphylococcus aureus (MRSA) strains characterized by the unexpected reappearance of heterogeneous phenotypic expression of resistance to methicillin and by susceptibility to gentamicin and various other antibiotics (GS-MRSA) have been reported in France. GS-MRSA strains have progressively replaced MRSA clones expressing homogeneous resistance to methicillin and resistance to gentamicin (GR-MRSA). In this study, we investigated the physiological characteristics of these new clones. In particular, we evaluated and compared the maximal growth rate and the deduced generation times (related to fitness of strains) of the major French epidemic MRSA clones. The population studied consisted of 79 isolates including (i) GR-MRSA that comprised six different types on the basis of PFGE; (ii) GS-MRSA the majority of which clustered into two PFGE types, A1 (usually resistant to erythromycin) and B (usually susceptible to erythromycin); (iii) methicillin-susceptible S. aureus (MSSA). GS-MRSA-A1 and MSSA strains were shown to have a significant fitness benefit (about 20%) with shorter generation times (theta = 23.7 +/- 0.1 and 22.9 +/- 0.05 min, respectively) than GR-MRSA and GS-MRSA-B strains (theta = 30.3 +/- 0.2 and 32.5 +/- 0.5 min, respectively). These data suggest that a link exists between genetic patterns, resistance profiles and physiological properties. In vitro competitive experiments indicated that GS-MRSA- A1 strains were able to rapidly outgrow GR-MRSA strains. The growth advantage observed should be taken into account in understanding the spread of some new clones of MRSA.

Characterization of unexpected growth of Escherichia coli O157:H7 by modeling

Modeling of batch kinetics in minimal synthetic medium was used to characterize Escherichia coli O157:H7 growth, which appeared to be different from the exponential growth expected in minimal synthetic medium and observed for E. coli K-12. The turbidimetric kinetics of 14 of the 15 O157:H7 strains tested (93%) were nonexponential, whereas 25 of the 36 other E. coli strains tested (70%) exhibited exponential kinetics. Moreover, the anomaly was almost corrected when the minimal medium was supplemented with methionine. These observations were confirmed with two reference strains by using plate count monitoring. In mixed cultures, E. coli K-12 had a positive effect on E. coli O157:H7 and corrected its growth anomaly. This demonstrated that commensalism occurred, as the growth curve for E. coli K-12 was not affected. The interaction could be explained by an exchange of methionine, as the effect of E. coli K-12 on E. coli O157:H7 appeared to be similar to the effect of methionine.

[Epidemiological aspects of malaria in 2 villages of the Manyemen forest region (Cameroon, southwest province)]

In terms of parasitaemia in blood, the prevalence was 18.7% for Plasmodium falciparum, 10.5% for P. ovale and 1% for P. malariae in the villages of Mungo Ndor and Kokobuma. The plasmodial index of children from 2 to 9 years of age was 38.2% and the spleen index 26.6%, with a mean HACKETT score of 1.56. Malaria is thus meso-endemic in the region. The immunofluorescent test performed with a P. falciparum antigen was positive in 66% of the children in the same age group. Parasites were seen in 15% of new-born children. The malaria infection indices were higher in Mungo Ndor, which is located on the main road in the vicinity of the Manyemen hospital, than in Kokobuma. Morbidity and mortality due to malaria remain major problems in this part of the South-West Province, in spite of improving primary health care facilities and free chloroquine distribution. Anopheles gambiae is the main vector of malaria in the area, and transmission is interrupted only during the short dry season.

[Epidemiologic and parasitologic survey concerning the Hassan Addakhil dam and branches to the Tafilalet province (Morocco, May-June 1975)]

In conclusion we know human and animal gathering is usually required for the development of water invertebrate populations, and particularly Bulinus contortus or Culicidae larvae, in a water system polluted with excrements or sewage. Such conditions are not those of Hassan Addakhil lake and the latter is not to-day, on its surface, a source of contamination. As we report p. 486, the study of an eventual increase of malaria and bilharzia endemia due to new aval more or less distant irrigations, belongs to the control of the Hygiene Institute of Morocco and collaborators of physicians of the Tafilalet province. This item will be discussed later on.