Question 21-29 Flashcards
What is the D value, the Z value and the F value?
D-value
- Basic parameter to characterize the inactivation kinetics of microorganisms, defined for specific organisms
- Decimal reduction time/destruction value, how many minutes are needed at certain temperature to reduce initial count of particular MO under defined conditions for one decimal power?
- D90 = 2 min → at 90°C bacterial count is reduced by one decimal power in 2 min
F-value
- Sum of D-values for reduction of several decimal powers under constant conditions
F690 = 12 min → it takes 12 min to reduce initial bacterial count at 90°C by 6 decimal powers
Z-value
Names the change in temperature necessary to change D-/F-Value by factor 10, specific for each MO
Biotechnological processes- composting, biogas fermentation
→ Rise in temperature, natural die off effects, structural damages due to solved substances (b, f, v, p)
→ Competition for nutrients, natural antibiosis (b, f)
Composting(temperature, competition for nutrients)
- Thermophilic procedure, optimized structure and aeration, aerobic
- At least 55°C over 2 weeks, 60°C over 6 d or 65°C over 3 d within the whole rotting material
- Disinfection of raw material possible
Biogas fermentation (temperature, competition for nutrients)
- Thermophilic plant, maize silage, cattle and pig manure, marc, vegetables are mixed and stored under anaerobic conditions
- At 50-57°C and min 24h and min 20 days mechanic retention time disinfection possible, but kind of unstable, reduction of min 5 log10 steps necessary
Principles of the validation of biotechnological processes used for the disinfection of recycled biomass (process validation)
Direct validation
test organisms
+ basic information of efficacy of process, helps defining parameters, reproducible results
- cost and labor intensive, seldom supervisions, accidental disturbances are not detected
Quantitative detection of artificial test organisms in substrates (input-output-analysis)
+ direct assessment of process, sometimes no spiking necessary
- suitable test organisms?, limit in type of treatment, works only for bfv, have to determine shortest real exposure time with suitable tracer
- Selection: should have comparable chemo and heat resistance, survival patterns in aerobic or anaerobic treatment and comparable tenacity against environmental stress as key pathogens; easy handling in lab and pose no risk
- Salmonella Senftenberg W775, H2S-negative
+ high thermos resistance, often used (many data available), easy differentiation from native salmonellae, reliable enrichment and isolation, salmonella are epidemiologically important
- still pathogens, does not cover all relevant resistance patterns of viruses
- E. coli, parvovirus, oocysts of Cryptosporidium, endospores of Bacillus subtilis, prions
- Test bodies: carry test organisms, semipermeable membranes, are applied into biotechnological process, quantitative re-isolation
Indirect validation process parameters (temp., pH …)
+ easy, quick, continuous control possible, no expertise needed
- limited representativeness for whole process, only valuable in comb. with direct validation
Microbiological supervision of end products
+ easy, limited expertise required, cheap
- limited representativeness for whole process, only good in combination
Classification of fungi
General properties : Heterotrophic eukaryotes, osmotrophic (adsorptive) metabolism, mostly saprophytes in soil (digest dead organic substances)
Benefits: edible, food industry (yeast, cheese, bread …), pharma industry (antibiotics, painkillers, immunosuppresssants), destruction of xenobiotics, biological pesticides
Harm: toxic, biodeterioration of feed and food, diseases
By size:
- Macromycetes: mushroom, in part striking fruiting bodies
- Micromycetes: microscopic small fungi, most medically important fungi
By mode of reproduction:
- Sexual (fungi perfecti): gametes - fusion to diploid oocysts – meiotic and mitotic spores
- Asexual (vegetative, fungi imperfecti): mitotic production of spores used for distribution
By morphology:
- Yeasts: monocellular roundish micromycetes
- Filamentous fungi (hyphae): molds and dermatophytes
- Dimorphic fungi: can grow as yeasts as well as hyphae depending on the environment
By differentiation:
- Fruiting bodies → spores
- Fruiting bodies → conidia
Examples of important fungal disease
Dermatophytes: live parasitic on and in the skin, adapted to body temperature, they have exoenzymes like keratinase, wait in soil
- Dermatophytosis = skin disease, affects animals and humans, skin lesions, fungus only active at edge of lesions, difficult diagnosis
→ vaccines, sunlight, lotions
Candidiasis: acute, subacute, or sometimes chronic systemic mycosis caused by yeasts like C. albicans
- Usually limited to skin and mucosa, transmission by inhalation or oral
- Ongoing disease: thrush (upper digestive system), diarrhoea, pneumonal mycosis, urinary tract infections, abortion and mastitis, mycotic ulcers in various organs
- Easy diagnosis, hard to treat, good prophylaxis necessary
Cryptococcosis: lung, skin, mucosa, central nervous system, caused by Cryptococcus neoformans
- Mostly dogs, cats or humans with AIDS, sometimes lifestock
- Difficult therapy, good prophylaxis necessary
Aspergillosis: caused by Aspergillus fumigatus, respiratory system of birds, abortion in cattle
What are the main parasitic zoonotic diseases?
Zoonosis: disease/infection that is naturally transmissible between vertebrate animals and humans
Parasitic zoonoses: disease agents are parasites (protists, helminths, arthropods) or vectors are parasites (blood- or tissue feeding insects, ticks)
Trematodes (flukes, Plattwurm):
Liver flukes: lives in bile ducts, cysts in fresh water fish, bile duct carcinoma
- Heterophyes: small intestine, fresh water fish, intermediate salinity, long term inflammation of myocard
- Schistosomiasis: blood vessels of abdomen, penetrate human skin or ingestion with water, fibrosis
Cestodes (tapeworms, Bandwurm):
- Fish/beef/pork tapeworm
- Echinococcus (dog tapeworm from sheep)
Nematodes (threadworm, Fadenwurm)
Entamoeba histolytica: amoebiasis, leave intestine, ingest red blood cells, liver abscess, can enter CNS
Toxoplasma gondii: intracellular, dangerous for unborn babies, cerebral in AIDS-patients
Trypanosoma cruzi: bugs transfer infective stage via feces into human wound, also with fruit juice, can infect tissues like heart muscle
Giardia lamblia: attach to microvilli of intestine, take up nutrients, periodical diarrhea, constant irritation and damage of epithelium
Cryptosporidium: severe diarrhea, dangerous for YOPI, cling to epithelium of intestine, steal nutrients, form cysts, constant auto-reinfection
Direct and indirect effects of zoonosis
Zoonosis: Disease/infection that is naturally transmissible between vertebrate animals and humans
General aspects:
Human and animal health are closely related to each other by direct or indirect effects (one health)
Direct effects:
- Certain pathogens can cross the species barrier
- Transmitted via animal products or environment (e.g. water, farm yard-crops) from animals to humans
Indirect effects
- Availability of enough and high-quality animal proteins and fats for human nutrition
- Insufficient performance of kept livestock → losses due to epidemics are causing protein shortage and malnutrition in the related human populations
Reasons for the emerging of zoonotic diseases
Why diseases spread: Urbanization, conflict, slow response, natural disasters, air travel
Factors contributing to the occurrence of emerging zoonoses:
- Microbiological adaptation
- Environmental changes (climate variability, animal displacement)
- Globalization (food production and trade, ecotourism, immigration), urbanization
- Human behaviour (like ethnic food preferences), human-animal bonds
- Decline of public health systems and increasing poverty
- Rising number of susceptible persons (age, immunosuppression)
- Intentional release of agent, laboratory biosecurity
What is Food security, what food safety?
Food security: Refers to the availability of food and one’s access to it.
- “When all people at all times have access to sufficient, safe, nutritious food to maintain a healthy and active life” (according to World Food Summit 1996)
- Food availability = sufficient quantity on a consistent basis
- Food access = having sufficient resources to obtain appropriate foods for nutritious diet
- Food use = appropriate use based on knowledge of basic nutrition and care; adequate water and sanitation
Food safety: a scientific discipline describing handling, preparation, and storage of food in ways that prevent foodborne illness.
