Application of subtyping by combined allozyme, whole-cell protein and antibiotic resistance analysis in epidemiological investigations of food-borne infections.

Allozyme pattern, whole-cell protein pattern and antibiotic resistance were used as markers for epidemiological subtyping (below the species level) of food-relevant bacteria. The results of this study confirm the applicability of these patterns as epidemiological markers also for this special purpose. Electrotyping using also a reduced allozyme set seems to be the method with the highest discriminatory power of the three methods evaluated. Several examples demonstrate that complex typing of bacteria based on a combination of these three methods is useful for the analysis of food-borne infections and establishment of their causes but also for zoonotic studies. We see, beyond this, further applications of molecular subtyping methods in food microbiology and food hygiene such as safety checking in food industry or monitoring in biotechnological processes.

[Nosocomial colonization and infection by multiresistant Enterobacter cloacae strains on a pediatric oncological unit]. / Nosokomiale Kolonisation und Infektion durch multiresistente Enterobacter cloacae-Stämme auf einer onkologischen Kinderstation.

A multiresistant E. cloacae strain spread during a six month period in a paediatric oncology ward amongst nine children, who had different tumors and malformations. Three children who had shared a room were especially affected. E. cloacae was isolated 122 times from the children with tumors and five times from their environment. Specimens from which the bacteria were isolated, included blood cultures, catheter tips, wound swabs, drains, skin and mucous membranes from most parts of the body. The majority of the E. cloacae strains were resistant to ampicillin, mezlocillin, piperacillin, azlocillin, doxycycline and cephalosporins of the second and third generation and sensitive to imipenem, aminoglycosides and quinolones. The antimicrobial resistance patterns of the E. cloacae strains from the paediatric oncology ward were compared to those isolated from other wards in the hospital. E. cloacae isolates from the intensive care unit had a reduced sensitivity to beta-lactam antibiotics, whereas the isolates from the other wards were, with the exception of ampicillin, sensitive to beta-lactam antibiotics. The analysis of the E. cloacae strains from the paediatric oncology ward revealed the same antimicrobial resistance pattern, bacteriocin type, RFLP-type and an identical enzyme and whole cell profile. Isolates from other wards showed considerably deviating patterns. The systematic registration and isolation of patients, colonized or infected with multiresistant E. cloacae strains, together with infection control methods, lead to a significant reduction in infections.

Analysis of Legionella pneumophila strains associated with nosocomial pneumonia in a neonatal intensive care unit.

A premature child received continuous mechanical ventilation in a neonatal intensive care unit. On day 10 of his life he developed pneumonia due to Legionella pneumophila serogroup 1, monoclonal subtype Bellingham. The strain was cultured from a tracheal secretion taken on day 10 and detected by immunofluorescence using monoclonal antibodies on days 10, 12 and 17. Legionella pneumophila serogroups 1 and 6 (10(2)-4 x 10(4) cfu/l) were cultured from both central and peripheral hot water systems. Monoclonal antibody testing, macrorestriction analysis of the genomic DNA using pulse-field electrophoresis, and electrophoretic alloenzyme typing showed the isolate from the child to be identical to the serogroup 1 strains from the hot water system. Four unrelated Legionella strains of the same monoclonal subgroup Bellingham were studied for comparison. Legionellae were also isolated from two other incubators, but no clinical or microbiological indications of legionellosis were found in the neonates hospitalised there. Serogroup 1 strains isolated from the patient and from the hot water system and serogroup 6 isolates from the hot water supply were able to multiply in cultured Acanthamoeba castellanii cells and in guinea pigs. The serogroup 6 strain, although prevalent in the incubators, was not found in any of the clinical specimens by either culture of immunofluorescence.

Identification of infant food as a vehicle in a nosocomial outbreak of Citrobacter freundii: epidemiological subtyping by allozyme, whole-cell protein and antibiotic resistance.

A total of 38 Citrobacter freundii strains was isolated from patients and their environment at a neonatal intensive care unit of a large hospital where colonization and clinical diseases due to the agent had been observed. Epidemiological investigations were carried out by subtyping, for which a combination of allozyme, whole-cell protein and resistance pattern analysis was used. Infant formula was identified as a vehicle of nosocomial spread. This shows that the role of foods in the transmission of hospital infections should not be underestimated. The combination of methods applied, in particular a limited enzyme set, is recommended also for epidemiological investigations of food-borne infections and establishment of their causes.

Genetic diversity and clonal relationships of Acinetobacter baumannii strains isolated in a neonatal ward: epidemiological investigations by allozyme, whole-cell protein and antibiotic resistance analysis.

Sixty-five strains of Acinetobacter baumannii which had been isolated from patients and the indoor environment of a neonatal intensive care unit and, for comparative purposes, isolates from three other wards, were examined by means of electrotyping and analysis of whole-cell protein and antibiotic resistance patterns. Fourteen different electrotypes were determined. The predominant type, a multiply resistant acinetobacter clone, persisted in the neonatal ward over several months. The results underline the usefulness of electrophoretic subtyping, in particular by means of allozyme pattern and as a supplement to whole-cell protein pattern analysis, in epidemiological investigations into the routes of transmission of nosocomial A. baumannii infections.

[Epidemic occurrences of multiresistant Acinetobacter baumannii strains in a neonatal intensive care unit]. / Epidemisches Vorkommen multiresistenter Acinetobacter baumannii-Stämme auf einer neonatologischen Intensivstation.

In a period of nine months (May 1991 to January 1992), 39 infants were colonized with Acinetobacter baumannii in a paediatric intensive care unit. Colonization was observed mainly in premature infants, weighing between 680 g and 2,000 g, who were artificially ventilated. Shortly after birth, A. baumannii was isolated regularly from tracheal washings, and less frequently from other material, such as gastric juice, catheter tips, and umbilical swabs. In older children or adults, the bacteria were found only in very low frequency. In the intensive care unit, A. baumannii could be isolated from tap water, sinks, water traps of the ventilation devices, the inner wall of incubators, and from the hands of medical personnel. Patients strains of A. baumannii, and those isolated monitoring the intensive care unit had an identical biochemical profile and a similar pattern of antimicrobial resistance, as well as a similar reaction in other typing methods. Anti-infective measures are discussed.

[Determination and occurrence of aflatoxin M1 in milk and dried milk products]. / Bestimmung und Vorkommen von Aflatoxin M1 in Milch und Trockenmilchprodukten.

Basing on a review of the present situation of the contamination of milk and powdered milk products with aflatoxin M1 a further investigation is regarded as necessary to assess the hygienic toxicological situation. For this purpose the TLC detection method of Tuinstra and Bronsgeest is recommended, which was modified to be used with powdered milk and baby food. This method enables the detection of 0.04 micrograms M1/l milk and 0.5 micrograms/kg powdered milk respectively on practical conditions. Investigating 142 raw milk samples and 70 samples of powdered milk products only 2 positive powdered milk samples were detected. This relatively low contamination rate is explained by the use of feed that is predominantly produced in the GDR and that is vastly free from aflatoxins. According to these results it is possible to estimate the contamination of milk with aflatoxin M1 in the GDR as extremely low.

[Hygienic significance of sterigmatocystin in vegetable foods. 1. Analytical detection of sterigmatocystin]. / Zur hygienischen Bedeutung von Sterigmatocystin in pflanzlichen Lebensmitteln. 1. Mitt. Analytischer Nachweis von Sterigmatocystin.

The present paper gives a survey of the chemical, physical and biological properties of the mycotoxin sterigmatocystin. It must be regarded as toxic to warm-blooded animals and as cancerogenic. It is likely to occur in foods; therefore, its analytical detection is necessary. With reference to known confirmatory reactions, a method is described for the semi-quantitative determination of sterigmatocystin in fruit and vegetables. This method permits to detect 20 microgram/kg of food by means of thin-layer chromatography, after column-chromatographic purification on silica gel. The identity is confirmed by derivatization to the semi-acetal by treatment with trifluoro-acetic anhydride. The method is suited especially for the routine control of foods.

[Hygienic significance of sterigmatocystin in vegetable foods. 2. Production of sterigmatocystin by Aspergillus versicolor]. / Zur hygienischen Bedeutung von Sterigmatocystin in pflanzlichen Lebensmitteln. 2. Mitt. Zur Bildung von Sterigmatocystin durch Aspergillus versicolor.

To test the suitability of fruit as an appropriate substrate for the formation of the mycotoxin sterigmatocystin, various fruit products were inoculated with a suspension of spores of a toxicogenic strain of Aspergillus versicolor. After incubation at 22 degrees C for 14 days, the fruits and juices overgrown with mould were homogenized with ethyl acetate and subjected to thinlayer chromatography. Sterigmatocystin had been formed on most products, the largest amounts being found in gooseberry preserves (9.4 microgram/g) and in grapes (10 microgram/g). The experiments show that fruit is generally suited as a substrate for the formation of sterigmatocystin; consequently, the latter is likely to occur in the presence of Aspergillus versicolor.

[Hygienic significance of sterigmatocystin in vegetable foods. 3. Occurrence of sterigmatocystin]. / Zur hygienischen Bedeutung von Sterigmatocystin in pflanzlichen Lebensmitteln. 3. Mitt. Zum Vorkommen von Sterigmatocystin.

A total of 142 samples of vegetable foods was examined for the occurrence of sterigmatocystin. The samples examined were fruits and vegetables which had spontaneously gone mouldy or begun to rot under natural conditions on the one hand, and organoleptically impeccable fruit juices and maize specimens on the other hand. The samples were taken at the manufacturing plant or procured on the market in the framework of operative controls. Sterigmatocystin was detected in none of the samples under investigation. From this it may be concluded that the risk of its occurrence in vegetable foods is not very great in our country. Nevertheless, due to its cancerogenic and toxic properties, sterigmatocystin should remain included in the examination for mycotoxins in the framework of food control.

[Hygienic significance of patulin in foods. 1. Analytical detection of patulin]. / Zur hygienischen Bedeutung von Patulin in Lebensmitteln. 1. Mitt. Zum analytischen Nachweis von Patulin.

The authors describe a thin-layer chromatographic method for determining patulin in fruit and vegetable products which is suited for routine work in hygiene practice. The samples are extracted with ethyl acetate, and the extracts are purified on a Florisil column. Separation is performed by means of a one-dimensional technique, using toluene/ehtyl acetate/formic acid (5 + 4 + 1), or, in the presence of interfering contaminants, by means of a two-dimensional technique, using benzene/methanol/glacial acetic acid (90 + 5 + 5) for the first run, and toluene/ethyl acetate/formic acid (5 + 4 + 1) for the second run. Patulin is detected by spraying with a benzidine solution, after chlorination. The limits of detection are 5 microgram/l of juice and 5 microgram/kg of fruit or vegetable. Derivatization with acetic anhydride/pyridine is used for corroborating the results obtained. The significance of 5-hydroxymethylfurfural as an interfering substance in apple juices is discussed.

[Hygienic significance of patulin in food. 2. Occurrence of patulin in fruit and vegetables]. / Zur hygienischen Bedeutung von Patulin in Lebensmitteln. 2. Mitt. Zum Vorkommen von Patulin in Obst und Gemüse.

The analyses of more than 200 samples of various foods of plant origin showed that patulin was contained in 36% of the fresh and canned fruits infested with mould, and in 7% of the vegetables. Besides apples, pears, plums, peaches and tomatoes contained also patulin. In organoleptically impeccable fruit juices, the contamination rates were 40% (for apple juice) and 16% (for the other juices, such as sour cherry, currant, sea buckthorn juices). The patulin content varied from 20 to 200 microgram/l, the mean value being 80 microgram/l. It ranged from 0.1 to 5 microgram/g in apples and sterile apple preserves. The authors discuss the hygienic-toxicologic significance of these findings, and suggest to include patulin in the examination of foods for mycotoxins, stipulating a permissible value.

[Thin layer chromatographic detection of aflatoxins on ready-made silica gel plates]. / Zum dünnschichtchromatographischen Nachweis von Aflatoxinen auf Kieselgel-Fertigplatten

Silica gel instant plates with an aluminium reflection foil as the carrier material (Silufol) were tested for their suitability for the thin-layer chromatographic separation of aflatoxins in comparison with conventiol silica gel G coated glass plates. Besides the well-knwon merits of instant plates, the Silufol plates offer remarkable analytical advantages; increased sensibility and shorter time of development. For this reason, the Silufol plates may be recommended for routine examinations of foods for aflatoxins.