Food Microbiology Flashcards
PH04-05
name the foodborne bacterial pathogen
most frequent cause of foodborne outbreaks; highest number of cases & hospitalisations
(eggs, egg products, mixed foods)
Salmonella
name the foodborne bacterial pathogen
most frequently reported zoonosis;
most commonly reported GI pathogen in UK
(meat from chickens and turkeys)
Campylobacter
name the foodborne bacterial pathogen
most deaths
(dairy, meat products, fish)
Listeria monocytogenes
name the foodborne bacterial pathogen
(pork products, unoasteurised milk)
Yersinia enterocolotica
name the foodborne bacterial pathogen
(minced meat, unpasteruised milk, leafy greens, bean sprouts, water)
Shiga toxin-producing E. coli
name the 5 most common foodborne bacterial pathogens in the EU
- Salmonella
- Campylobacter
- Listeria monocytogenes
- Yersinia enterocolitica
- Shiga toxin-producing E. coli
name the 3 important EU food safety legislations
- Regulation (EC) 852/2004 article 4
- Reguation (EC) 2073/2005
- Regulation (EU) 2017/625
name the safe food legislation
gives defined limits on presence or number of microbes or their metabolites in food;
ensures food is produced hygienically and is safe for the consumer BUT cannot guarantee food safety
Microbiological Criteria for Foodstuffs
Regulation (EC) 2073/2005
name the 2 types of criteria established in Regulation 2073/2005 (microbiological criteria for foodstuffs)
- process hygiene criteria
- food safety criteria
what happens when a food safety criterion is not met?
batch of food should be removed from and not placed on market
name the criteria established in Regulation 2073/2005
purpose for testing against this criteria is NOT to assess the fitness of individual carcases or processed meat for human consumption BUT to provide an indication of performance and control of the slaughter, dressing and production hygienic process at time of sampling;
applies to:
1. carcases
2. minced meat
3. meat preparations
4. mechanically separated met
process hygiene criteria
this is a measure of bacteria in the sample that can survive in the conditions on the surface of carcases or in processed meat;
includes bacteria arising both from animals and from the slaughterhouse or meat processing environment
(requirement of process hygiene criteria)
Aerobic Colony Count (ACC)
this is a grouping of bacteria that live in the intestines of animals and the environment
(includes E. coli and Salmonella)
Enterobacteriaceae
name the criteria established in Regulation 2073/2005
these have been set out for fresh poultry meat, minced meat, meat preparations, meat products and mechanically separated meat;
if criteria are exceeded, the batch tested is unsatisfactory and should be removed from the market (or not placed on the market)
Food safety criteria
demonstration of compliance with food safety criteria for meat and processed meat is required by the absence of Listeria monocytogenes in …
ALL ready-to-eat foods
demonstration of compliance with food safety criteria for meat and processed meat is required by the absence of Salmonella in …
carcases/meat
what is the only compulsory test for working surfaces when making ready-to-eat products under food safety criteria
for Listeria monocytogenes
what species of Campylobacter is responsible for 90% of human enteric illness
C. jejuni
name 5 conditions that Campylobacter is susceptible to
- low oxygen
- dessication
- freezing
- low pH
- high temperature
what is the biggest reservoir of Campylobacter causing human infections
poultry
name 4 ways to control Campylobacter on-farm
- improved biosecurity and hygiene
- simple modification of diet (add organic acids or probiotics)
- reduce slaughter age (33-35d)
- discontinue thinning
name 3 ways to control Campylobacter in the slaughter house
- cleanliness of birds
- good hygienic practices & HACCP throughout
- accurate evisceration
what is the most common species of Salmonella causing gastroenteritis
Salmonella enterica
name 3 serovars of Salmonella enterica that cause disease
- Typhimurium
- Enteritidis
- Newport
name the type of salmonellosis
nausea, vomiting, abdominal cramps, diarrhoea, fever, headache
enteric salmonellosis
name the type of salmonellosis
septicaemia;
endemic to Africa, Asia, Central and South America;
more a disease of poverty and poor hygiene conditions
Typhoidal salmonellosis
what is the most common source of enteric salmonellosis infection?
poultry
(both meat and eggs)
name 2 important aspects of control of Samonella
- vaccine
- Red Lion Code
this is a notorious strain of shiga toxin-producing E. coli (STEC);
causes mild diarrhoea to haemorrhagic colitis, haemolytic uraemic syndrome (HUS), thrombocytopaenia purpura
E. coli O157:H7
what is the main reservoir for STEC;
they are asymptomatic, super shedder individuals
cattle
name 5 clinical signs of listerosis in humans
- bacteraemia
- septicaemia
- meningitis, encephalitis
- miscarriage
- neonatal disease
name the zoonotic foodborne virus
(most foodborne viruses are not zoonotic)
Hepatitis E
name the foodborne virus
most common cause of infectious intestinal disease in the UK;
highly infectious and easily transmissible;
can be transmitted through food, BUT majority of cases NOT foodborne;
symptoms: vomiting, diarrhoea, headaches, abdominal pain, fever
norovirus
name the type of hepatitis virus
those that are parenterally transmitted
‘serum’ hepatitis
name the type of hepatitis virus
those transmitted through the faecal-oral route i.e. “enteric” hepatitis
“infectious” hepatitis
name the 2 types of hepatitis virus that cause “enteric” hepatitis
- Hepatitis A
- Hepatitis E
what animal is the biggest reservoir for Hepatitis E
pigs
name the method for bacterial food testing
methods based on detection, isolation, characterisation and identification of microbes
qualitative methods
name the method for bacterial food testing
methods based on the detection & enumeration of microbes (usually in liquid and/or agar material)
quantitative methods
name the 5 steps of qualitative lab culture methods
- sample collection
- culture of samples in enriched broth
- culture on selective media
- confirmatory tests
- examine identification tables
name the type of bacteriological agar
non-selective, non chromogenic;
most bacteria appear similar (white colonies)
Luria-Bertani Agar / Nutrient Agar
name the type of bacteriological agar
non-selective;
used for assessment of haemolysis (Clostridium perfringens);
can grow a large variety of other more fastidious organisms
blood agar (sheep, horse)
name the type of bacteriological agar
semi-selective;
used for Salmonella and Shigella isolation;
some Salmonella can metabolise thiosulphate - produces hydrogen sulphite and colonies turn black in the centre
xylose lysine deoxycholate (XLD) agar
name the type of bacteriological agar
selective for enterobacteriaceae (due to bile salts);
chromogenic: lactose fermenters appear pink/red (E. coli), non-fermenters appear white (Salmonella)
MacConkey agar
name the type of bacteriological agar
selective for Campylobacter;
have to be incubated in reduced oxygen (5%)
charcoal-cefoperazone-deoxycholate agar (CCDA)
name the rapid method of detection
used to separate & concentrate target organism;
10 min procedure;
specific Ab fixed on paramagnetic beads added to broth;
binding of pathogen to Ab, magnet used to immobilise pathogen, removal of remainder
immunomagnetic separaton (IMS)
name the rapid method of detection
firefly luciferin-luciferase;
two-step biochemical reaction takes place, which produces light;
most widely used for monitoring cleaned surfaces
ATP bioluminescence
name the rapid method of detection
widely used in food testing;
sensitivity varies;
can be specific for pathogen at species and subspecies/strain level;
can also detect toxins and allergens
ELISA
(Enzyme Linked Immunosorbent Assay)
name the rapid method of detection
can be very specific;
can identify pathogen strain;
multiple primers can be used at once to specifically ID more than one bacterial strain;
degenerate primers can be used to ID multiple strains of same species but additional confirmatory tests needed afterwards
Specific Nucleic Acid Amplification / Detection
(PCR)
name the rapid method of detection
serum from immunised animals provides fast (2 min) and specific detection;
bacterial cells cross link via surface antigens bound to antibodies in the sera;
easily used for Salmonella type identification
serum agglutination
