Home style frying of steak and meat products: Survival of Escherichia coli related to dynamic temperature profiles.

Microbial survival of heating and cross-contamination are the two transmission routes during food preparation in the consumers' kitchen that are relevant for QMRA (Quantitative Microbial Risk Assessment). The aim of the present study was to extend the limited amount of data on microbial survival during real-life preparation of meat and meat products and to obtain accessory temperature data that allow for a more general (product unspecific) approach. Therefore survival data were combined with extensive measurements of time- and location dependent temperature using an infrared camera for the surface and buttons for the inside of the product, supplemented with interpolation modelling. We investigated the survival of heating of Escherichia coli O111:H2 in beefsteak, hamburgers (beef and 50% beef 50% pork (HH)), meatballs (beef and HH) and crumbs (HH). For beefsteak, survival as a whole is dominated by the sides, giving a log reduction of 1-2 (rare), 3-4 (medium) and 6-7 (done). Limited measurements indicated that done preparation gave 5-6 log reduction for crumbs and at least 8-9 log for the other products. Medium preparation gave a higher reduction in hamburgers (2-4 log) than in meatballs (1-2 log) and in beef (3-4) than in HH (2-3) hamburgers. In general, our 'done' results give larger inactivation than found in literature, whereas 'rare' and 'medium' results are similar. The experiments resulted in two types of curves of D70/z-values, dependent on product, doneness and for beefsteaks sides vs. top/bottom. One type of curve agrees reasonably with literature D70/z estimates from isothermal temperature experiments, which supports using these estimates for home style cooking QMRA calculations. In case of the other type of curve, which is mainly found for (near) surface contamination in close contact with the pan, these literature estimates cannot be applied. We also applied a simplified approach, assuming thermal inactivation is dominated by the highest temperatures reached. The time duration of this highest temperature gives accessory D-values which prove to fit with isothermal temperature literature data, thus suggesting application of such data for QMRA is possible by this approach also, which is less labor intensive both in terms of measurements and modelling. In real life, variability in product properties and preparation styles is large. Further studies are needed to analyze the effect on survival, preferably focusing on determining the essential variables. More variation in heating time will allow for estimating D70/z point estimates rather than curves representing possible sets of D70/z-values.

Genetic identification of the main opportunistic Mucorales by PCR-restriction fragment length polymorphism.

Mucormycosis is a rare and opportunistic infection caused by fungi belonging to the order Mucorales. Recent reports have demonstrated an increasing incidence of mucormycosis, which is frequently lethal, especially in patients suffering from severe underlying conditions such as immunodeficiency. In addition, even though conventional mycology and histopathology assays allow for the identification of Mucorales, they often fail in offering a species-specific diagnosis. Due to the lack of other laboratory tests, a precise identification of these molds is thus notoriously difficult. In this study we aimed to develop a molecular biology tool to identify the main Mucorales involved in human pathology. A PCR strategy selectively amplifies genomic DNA from molds belonging to the genera Absidia, Mucor, Rhizopus, and Rhizomucor, excluding human DNA and DNA from other filamentous fungi and yeasts. A subsequent digestion step identified the Mucorales at genus and species level. This technique was validated using both fungal cultures and retrospective analyses of clinical samples. By enabling a rapid and precise identification of Mucorales strains in infected patients, this PCR-restriction fragment length polymorphism-based method should help clinicians to decide on the appropriate treatment, consequently decreasing the mortality of mucormycosis.

Molecular taxonomy of the Trichophyton rubrum complex.

The validity of taxa around Trichophyton rubrum was evaluated by a combination of phenetic and molecular methods. Morphological and physiological features were compared to results of sequencing of the internal transcribed spacer region of the ribosomal operon, PCR fingerprinting, and amplified fragment length polymorphism analysis. The 15 species and varieties investigated (Trichophyton circonvolutum, Trichophyton fischeri, Trichophyton fluviomuniense, Trichophyton glabrum, Trichophyton gourvilii, Trichophyton kanei, Trichophyton kuryangei, Trichophyton megninii, Trichophyton pedis, Trichophyton raubitschekii, Trichophyton rodhaini, Trichophyton rubrum var. nigricans, Trichophyton soudanense, Trichophyton violaceum var. indicum, and Trichophyton yaoundei) were reclassified or synonymized as T. rubrum or T. violaceum.

Molecular and conventional taxonomy of the Microsporum canis complex.

The validity of taxa around Microsporum canis was evaluated by a combination of phenetic and molecular methods. Morphological and physiological features were compared with results of sequencing of the internal transcribed spacer (ITS) region of the ribosomal operon, polymerase chain reaction (PCR) fingerprinting and amplified fragment length polymorphism (AFLP) analysis. The seven species investigated seem to be infraspecific taxa and were reclassified or synonymized as M. canis (teleomorph: Arthroderma otae), M. ferrugineum, and M. audouinii.

Molecular taxonomy of Trichophyton mentagrophytes and T. tonsurans.

Most members of the anamorph genus Trichophyton are anthropophilic and have evolved with the human host. Classical parameters for the identification of dermatophytes include clinical features, cultural characteristics, conidial morphology and physiological test results. Phenotypic variability and pleomorphism due to culturing on artificial media is common among this group of organisms and has led to the description of numerous species. The validity of taxa around T. mentagrophytes and T. tonsurans was verified. Morphological and physiological features were compared to results of three different molecular techniques (sequencing of the internal transcribed spacer (ITS) region of the ribosomal operon, PCR fingerprinting and amplified fragment length polymorphism (AFLP) analysis). Twenty-four species or varieties investigated could be reduced to five taxa and were reclassified or synonymized as Trichophyton tonsurans, T. interdigitale, T. mentagrophytes, T. simii and T. erinacei.

Case report. A disseminated infection due to Chrysosporium queenslandicum in a garter snake (Thamnophis)

A male garter snake (Thamnophis) from a private terrarium was spontaneously and simultaneously infected with Chrysosporium queenslandicum and Geotrichum candidum. The autopsy revealed disseminated mycotic alterations in skin, lungs and liver. Chrysosporium queenslandicum grew well at 28 degrees C, the optimal temperature of the animal. This is the first description of a Chrysosporium queenslandicum infection in a garter snake.

Phylogeny and taxonomy of the family Arthrodermataceae (dermatophytes) using sequence analysis of the ribosomal ITS region.

The internal transcribed spacer (ITS) region, covering the ITS1, ITS2 and 5.8S ribosomal DNA was used to evaluate phylogenetic relationships within the fungal family Arthrodermataceae. Sequences of variable length, ranging between 522 and 684 base pairs were aligned. An unrooted consensus tree based on parsimony analysis showed Trichophyton to be polyphyletic, and Microsporum to be paraphyletic. Non-monophyly of these two genera is in conflict with traditional classification. But this relation is not strongly supported by bootstrap analysis. Phylogenetic analysis showed that the two known members of the genus Epidermophyton grouped widely apart from each other. Within Trichophyton, our results suggest a separation of human pathogenic species and primarily geophilic species. Bootstrap support for these two groups is fairly high and both groups are recognized by current taxonomy. Three lineages were revealed within the T. mentagrophytes species complex. Microsporum canis, M. audouinii and M. equinum were found to be closely related. The topology of the tree was robust to various methods of analysis (parsimony and distance) and a different weighting scheme. Weighting of transversions over transitions did not improve the status of poorly supported branches of the tree.

Human onychomycosis caused by Trichophyton equinum transmitted from a racehorse.

We report fingernail onychomycosis caused by Trichophyton equinum in a farmer who breeds racehorses. In addition to the thumbnail, T. equinum had infected one of the racehorses. Oral terbinafine cured the infection in the farmer.

[Fungi and yeasts isolated in mycological studies in skin and nail infections in The Netherlands, 1992-1993]. / Schimmels en gisten gevonden bij mycologisch onderzoek van huid- en nagelinfecties in Nederland, 1992-1993.

OBJECTIVE: To describe fungi and yeasts isolated from skin and nail infections in the Netherlands. DESIGN: Retrospective. SETTING: Centraalbureau voor Schimmelcultures (CBS), Baarn, the Netherlands. METHOD: Results of mycological investigation of skin and nail samples in the period 1992-1993 were analysed. After a clinical diagnosis of mycosis, performed by dermatologists and general practitioners, material was sent to the CBS for mycological research. RESULTS: The clinical diagnosis of onychomycosis was rather accurate, especially if made performed by dermatologists. Mycoses of the skin were sometimes confused with other skin diseases. When microscopical observation showed a positive result, 93% of the cultures were positive as well. The main agent of onychomycosis was Trichophyton rubrum; T. mentagrophytes was more frequently isolated from tinea manuum/pedis and T. tonsurans from tinea corporis/cruris. Epidermophyton floccosum was only isolated from skin lesions and Microsporum canis, T. soudanense and T. verrucosum only from tinea corporis/cruris. The most important yeasts isolated were Trichosporon mucoides, Candida guilliermondii, C. parapsilosis, C. famata and Malassezia furfur. Other fungi isolated were either pigmented (melanin, carotene), thermophilic or belonged to the order of the Onygenales. CONCLUSION: Mycological research to confirm the clinical diagnosis of a skin mycosis is advisable. Species isolated differed in their predilection for different parts of the human body. Yeasts were mainly isolated as double infections. Apart from the dermatophytes there is a special group of fungi which can cause mycoses.