Antibiotic resistance pattern of foodborne Salmonella isolates in Addis Ababa (Ethiopia).

A total of 39 Salmonella cultures isolated from raw minced beef and chicken (gizzard, liver, and heart) samples in Addis Ababa were examined for susceptibility to a group of 10 selected antimicrobials. 34 isolates (87.2%) were resistant to one or more antibiotics. The antibiotics to which isolated Salmonella strains were most often fully resistant included nitrofurantoin (48.7%), furazolidone (48.7%) and streptomycin (46.2%). Only 4 antimicrobials (gentamycin, kanamycin, rifampicin and sulphamethoxazole-trimethoprim) were effective against all Salmonella isolates with the exception of 2 which were intermediate in resistance to kanamycin (1) and sulphamethoxazole-trimethoprim (1). 77.8% of the S. Enteritidis strains showed multiple resistance to up to four antibiotics followed by S. Typhimurium (60.0%) and S. Dublin (33.3%). The high level of antibiotic resistance of foodborne Salmonella isolates in the study area is an indication of indiscriminate and continuous use of subtherapeutic doses of antibiotics in animals.

[The epidemiology of helicobacteriosis in humans; studies of the survival capacity of the microbe in food]. / Zur Epidemiologie der Helicobacteriose des Menschen; Untersuchungen zur Uberlebensfähigkeit des Erregers in Lebensmitteln.

In man suffering from diseases of the stomach and the duodenum (gastritis, ulcus, enteritis, neoplasms), Helicobacter pylori (H..pylori) is frequently detected in the mucous membrane of the stomach. Up to now the spread of this agent is not quite clear. Since the direct transmission in humans can be taken for granted, the following study was to find out whether and for how long the agent mentioned above is able to survive in selected food and whether an infection of the consumer by these contaminated food is possible. 376 samples of secretions from the udder of healthy cows and those with mastitis where tested for the presence of H. pylori along with 100 stomachs of chicken from different flocks. In no case H. pylori could be detected. H. pylori was inoculated in high concentrations into milk and some milk-products. From cooled milk samples the agent could still be reisolated after six days in a density up to 10(3) CFU/ml of milk. At room-temperature or 37 degrees C resp. the pathogen could be detected in milk for three to four days only. In yoghurt the agent kept viable for three hours only, whereas in kefir for 24 hours. Mean survival time of then hours was found in pH-neutral curd cheese. The incubation of H.pylori in sterile drip from chicken and in physiologic saline resulted in maximal survival time of at least 48 hours at room temperature. But in H.pylori-broth the number of microorganisms had dropped below the limit of detectability only after 72 hours. At refrigerator-temperature (7 degrees C) H. pylori could still be detected within these three media after 72 hours in high concentrations. In drip from chicken kept at-20 degrees C before thawing H. pylori showed a considerable survival time. After four weeks its number had only dropped by one to two log cycles, whereas in saline and in broth the agent could not be detected anymore after one week at the most. Experiments concerning tenacity showed: On culture-media with different pH-values the growth-optimum of H. pylori was between pH 6.1 and 7.3 H. pylori was suspended in melting water from chicken and brought in thin layers onto wooden board, plastic and ceramic tiles. The bacterium could be recultured from these surfaces only as long as these were moist. At room-temperature the bacterium could not be detected anymore on wood after 30 minutes, on plastic or ceramic tiles after 90 minutes. At refrigerator-temperature the administered suspensions dried more slowly, so that H. pylori survived longer, but it still could not be isolated anymore on wood after 240 minutes, on plastic or ceramic tiles after 300 minutes. The decimal reduction-time for H. pylori suspensions in broth were. 72 sec. at +50 degrees C 43 sec. at +52 degrees C 20 sec. at +55 degrees C 10 sec. at +57 degrees C 4 sec. at +60 degrees C from which data z = 7.9 +/- 0.01 degrees C can be calculated. From these experiments on can conclude, that in all probability fresh milk and chicken do not contain H. pylori and thus do not represent a source of infection for man. After contamination of slaughtered chicken within the abattoir or from milk and milk-products within dairy industry by insufficient hygiene-management of infected personnel it can not be excluded, that H. pylori gets into households by these foods. An infection of the consumer by this route is not very likely, but can not be excluded with complete certainly.

Control of food-borne infections and intoxications.

Most food-borne diseases are caused by microorganisms that initially contaminate the living plant or animal or recontaminate the food during handling or processing. Control measures are intended to (1) prevent microorganisms from contaminating food and involve all hygienic production measures (raw material, premises, equipment, cleaning and disinfection, personnel); (2) prevent microorganisms both from growing or forming toxins, e.g. through chilling, freezing or other processes that do not destroy microbes, such as reduction of aw or pH; (3) eliminate microorganisms, e.g. through thermal processing. Integrated systems for control of the microbiology and hygiene of foods aim at a gradual or stepwise reduction of health hazards at all stages of production and processing until final operations. As a further development of HACCP (Hazard Analysis Critical Control Point), other systems such as the LISA (Longitudinally Integrated Safety Assurance) concept, include also the primary stages of harvesting. With respect to food animals, this clearly involves veterinary control of the livestock as an initial stage of food production. As with salmonellosis, the implementation of control systems is helpful in reducing risks at particular critical points. However, isolated measures do not solve the problem as a whole and cannot meet the demands of consumer protection. At least in the case of salmonellosis a global strategy of control is needed which requires political decisions from the relevant public health bodies.

Estimation of most probable number of Salmonella in retail samples of minced pork.

The number of salmonellae in 174 samples of minced pork was determined by the Most Probable Number (MPN) method in two separate laboratories. The material examined was taken from a collection of samples which were Salmonella positive in an earlier study. The MPN estimation was carried out using portions of original samples which had been divided (2 x 100 g) before the initial examination and which had been deep frozen and stored for 1 to 14 weeks at -18 degrees C until re-examination. Of the 174 samples initially positive for Salmonella, 131 (75.3%) were positive on re-examination using pre-enrichment in buffered peptone water (BPW) and selective enrichment in Rappaport-Vassiliadis medium (RV) and in tetrathionate medium according to Muller-Kauffmann (MK). The majority of the samples gave Salmonella counts below 1000/100 g (96.7% at lab. A and 97.3% at lab. B). Comparison of the results from both laboratories showed good agreement in the distribution pattern of the frequencies within the MPN classes, but agreement between the same sample pair was poor (r = 0.23). RV medium proved to be superior to the MK medium.

[Effect of high frequency treatment on several microorganisms important to food health]. / Untersuchungen zum Einfluss der Hochfrequenzbehandlung auf einige lebensmittelhygienisch bedeutsame Mikroorganismen.

There is an increasing consumer interest in the microwave oven as a more convenient and quicker means of meal preparation. This study investigated whether growth or inactivation of microorganisms in the microwave field follows the same dynamics as conventional heat processing. Product safety during microwave treatment of food products is of special interest. As parameters D-values of Escherichia coli, Salmonella typhimurium and Staphylococcus aureus were calculated after microwave exposure and conventional heat treatment at +55 degrees C and +60 degrees C respectively. The irradiation frequency was 2450 MHz; the microwave power ranged from 0 to 1037 W. Furthermore an assessment was made on the growth rates of E. coli at +37 degrees C and on the influence of microwaves on lyophilized E. coli-cells. With a special temperature measurement system (Luxtron 1000 A) which used nonmetallic and microwave transparent fiber optic probes, the temperature was recorded during each experiment. At certain temperatures some of the strains showed slight although significant differences depending on which of the abovementioned techniques had been applied. However there was no particular trend evident from the results. D-values of E. coli at +55 degrees C and S. typhimurium at +55 degrees C and +60 degrees C obtained from both heat sources were coincided. Microwave reduction of S. aureus at +55 degrees C was more rapid than conventional heat inactivation; on the other hand a slower inactivation rate of S. aureus and E. coli at +60 degrees C was observed. Growth of E. coli was slightly delayed during microwave incubation. There are no effects concerning microwave-treated E. coli-cells. The hypothesis positing the existence of so called "athermal effects" was neither proved nor rejected on the basis of the experiments. In terms of product safety, it must be taken into account that microwave heat processing in general use may result in a markedly uneven distribution of temperature within the product. Adequate means should be provided for heat conduction so as to allow temperatures of "hot" and "cold" spots to be sufficiently equilibrated.

[The hygiene of refrigerated and frozen foods]. / Hygiene von gekühlten und tiefgekühlten Lebensmitteln.

Health and spoilage hazards arising from refrigerated and deep frozen foods may be due to - raw materials, e.g. pathogenic microorganisms which come from infected living animals or contaminate raw foods during handling. Psychrotrophic organisms have particular significance as pathogens or spoilage organisms as they can multiply also during refrigeration; - improper processing. Temperature abuse and incorrect time/temperature relations are main causes for microorganisms being not destroyed at the expected rate or even getting a chance of multiplying. Proper handling after refrigeration or frozen storage of foods ("hygiene of thawing") deserves also particular attention. - contamination, i.e. initial contamination of raw products which are ready for consumption without further processing (fruits, raw salads). Recontamination which follows a heat process is much more important and occurs before, during and after application of cold. In those cases, again, one has to distinguish between products which (a) are ready for consumption without a process (bakery and confectionary goods, ice cream, drinking milk) and (b) have to pass a process which reduces the bacterial load before consuming the food (ready to eat dishes or other foods ready for reheating in the home). Sites of increased hygienic hazard are a) lack of partitioning "clean" and "unclean" areas and processes, b) defects of sanitation and hygiene of personnel, c) defects of packaging, d) leakage during aseptic filling. Hazards are controlled through product and plant specific analysis of the process flow followed by continuous monitoring the "Critical Control Points". As an example, a report is given on a study on random samples taken from 180.000 prepackaged deep frozen menus which had been produced for a mass meeting. Microbiological monitoring of the process revealed time/temperature relations as critical control points of primary importance. Particular problems arose from any stoppage at the production line. Reliable means to assure food safety and protect consumer's health are HACCP concept based in plant control programs rather than sporadic microbiological monitoring of end products.

[The influence of thermal load on the immunochemical detection of dried blood plasma supplements in meat mixtures]. / Einfluss der thermischen Belastung auf den immunchemischen Nachweis von Trockenblutplasma-Zusätzen in Fleischgemengen.

Addition of blood plasma to meat products is not permitted in the FRG unless these products are heat processed using an internal temperature of 80 degrees C (German regulation of meat and meat products: "Verordnung für Fleisch und Fleischerzeugnisse"). Such heat process may have an unfavourable effect on the detectability of blood plasma. Since blood plasma or dried plasma may originate from different animal species (porcine or bovine) two different anti dried blood plasma-sera (porcine and bovine) are required for immunochemical analysis. The varying quality of these sera has to be considered when interpreting the results. Seven M urea extract turned out to be suitable for detection of dried plasma additives and proved to be highly effective particularly when examining heated samples. Both the gel-diffusion and the electro immuno assay proved useful for the detection of dried blood plasma, provided the examined extracts had been adequately diluted. Immunochemical reactivity was hampered by the heat process which was given to the sample. Accordingly, the concentration of the plasma in a particular sample cannot be determined unless the time/temperature data of the process applied to the sample were given and model samples were tested for comparison.

[Food-borne infections and poisonings]. / Lebensmittelinfektionen und -intoxikationen.

A survey of the most common food borne infections (salmonellosis, tuberculosis, brucellosis, campylobacteriosis) is followed by a description of the most common food borne intoxications (botulism, staphylococcal intoxications, biogenic amines, toxic algae in mussels, i.e. "Paralytic Shellfish Poisoning").

Microflora of Edible Offal with Particular Reference to Salmonella.

Feeding of raw offal has been suspected to be a major source of Salmonella infections among pets, particularly among dogs, in the city of Berlin (West). The present study revealed that 231 (56.6%) of 408 samples of edible offal (liver, lungs, heart, bovine rumen, porcine esophagus) contained 24 types of Salmonella . Salmonella typhimurium prevailed (145 samples = 62.8% of the positive samples = 35.5% of the total), including 8 strains of S. typhimurium var. copenhagen . Three types had an incomplete seroformula. The investigation covered a period of 26 months. The percentage of positive findings did not significantly differ during various seasons. Positive findings were most frequent with porcine esophagus (40/49) and least frequent with imported swine liver (17/58) and bovine rumen (13/45). Presence of salmonellae was not correlated with other microbiological criteria, in particular aerobic plate count and number of Enterobacteriaceae . All samples were sold at West-Berlin's central wholesale meat market and originated from slaughter animals judged as "fit for consumption", which means that they were also intended for human consumption and not only as animal feed. Repeated isolation of the same Salmonella type from different samples taken on the same day indicated rapid spreading during transport and storage. This contamination did not persist for a longer period but was replaced by other strains which subsequently appeared. Since raw offal for retail sale represents a considerable health hazard, it is recommended that this material should not be offered for retail sale unless in hermetically sealed packages. Packages should have labels with directions for proper handling of the contents in the home. Warning should also be given that viscera should neither be eaten raw nor fed to pets unless the material is adequately heated.

[Staphylococcus aureus in poultry--biochemical characteristics, antibiotic resistance and phage pattern (author's transl)]. / Staphylococcus aureus beim Schlachtgeflügel--biochemische Eigenschaften, Antibiotikaresistenz und Lysisspektrum.

In a poultry processing plant in northern Germany 1412 swabs were taken from poultry carcasses together with 608 swabs from the personnel. The broilers came from 22 different chicken farms. The swabs taken from the poultry and those taken from the personnel proved to be 35% and 48% Staph. aureus positive respectively. The swabs taken from the feathers and from the skin were staphylococcal positive at a higher level (47%) than the swabs taken from the cloaca (19%) and the throat (23%). Between 8% and 63% of the animals from the various chicken farms were Staph. aureus positive. The frequency of staphylococcal contamination increased during the course of slaughter. 57% of the swabs taken from the gloves and the hands and 42% from the aprons of the personnel were Staph. aureus positive. Some biochemical properties, the phage patterns, and the antibiotic resistance against oleandomycin, erythromycin, bacitracin, streptomycin, tetracyclin, penicillin, chloramphenicol, virginiamycin and flavomycin were determined from 445 poultry and 345 personnel Staph. aureus isolates. Only small differences could be established between both sources in this way. Only 20% of the personnel and 34% of the chicken strains were resistant to antibiotics. In the strains collected from personnel, penicillin-resistance predominated while the poultry isolates showed predominantly tetracyclin-resistance. Of all antibiotics applied nutritively in the chicken fattening, there was a higher resistance only against oleandomycin (11% of the poultry strains). Between the chicken farms there was a different frequency of resistance (0--68%). The source of the staphylococci could be determined for only some of the strains. Only 2.5% of the chicken isolates showed characteristics described in the literature to be "poultry-specific", whereas 37% of the personnel and 24% of the poultry isolates were shown to be "human-specific" strains. It seems that the vast majority of the staphylococci originated from the slaughterhouse personnel. The rest of the strains differed in varying combinations of their properties from the given species characteristics. Although Staph. aureus was brought into the slaughterhouse by the poultry, the contaminations of the final product seemed to originate mainly from human beings.

[Problems in obtaining antiserum to staphylococcal enterotoxin D]. / Problemi pri poluchavaneto na stafilokokov enterotoksin-D--antiserum

Experimentally were demonstrated the difficulties overcome and the possibilities of producing a Staphylococcus-enterotoxin D antiserum of a 1:80 titer. The product was shown to be suitable for work as well as for further studies. Given are the schemes of immunizing a rabbit serving as a serum producer and those for purifying the antiserum (eliminating heterologous antibodies), its titration with a microimmunodiffusion test, etc. In this connection some problems are referred to concerning the production of the amounts necessary of enterotoxin D, its purification and toxicity for test animals, etc., that are successfully solved by the authors.

[Official inquiry into the presence of salmonella in frozen slaughtered poultry on the German market (author's transl)]. / Erhebungen über das Vorkommen von Salmonellen bei gefrorenem Schlachtgeflügel auf dem deutschen Markt

Between the period of August 1973 and May 1974, 553 roasting chickens, soup chickens, ducks, and geese from seven different countries were examined for the presence of Salmonella. In 284 (= 51,4%) specimens 23 various Salmonella serotypes were discovered. Out of 475 Salmonella isolates 244 (= 51,4%) were resistant to streptomycin, the sulfonamide complex or their combination whereas 195 (= 41,0%) were sensitive to all eight tested antibiotics. Of greater importance for nutritive and therapeutic application of antibiotics is, however, the resistance of 36 (= 7,6%) Salmonella strains to tetracyclines, ampicillin and kanamycin, 28 (= 5,9%) of the salmonellae showing resistance exclusively to tetracyclines. The water tested from 10 thawed specimens 2 of which contained diphosphates, produced dubious results with the general inhibitor test. Regarding the bacterial yield, both the selenite and tetrathionate enrichments were of equal value. Nevertheless with each individual enrichment the isolated partial amount of the entire collection of positive samples was not identical so that the highest yield of Salmonella was obtained from a combination of both methods. Incubation of the selenite enrichment at a maximum of 43 degrees C definitely produced a higher percentage than at 37 degrees C. A selenite enrichment proved to be superior to that of tetrathionate for the isolation of Salmonella serotypes which rarely occur in fowl. The excellent selectivity of the Brilliant-green Phenol-red Lactose Sucrose Agar, as repeatedly described in the literature, is also confirmed by these tests.