Exam 2 Flashcards
what family is salmonella a part of?
enterobacteriaceae
stain shape and respiration of salmonella
gram-negative, motile, rod-shaped, facultative anaerobe, uses respiratory and fermentative pathways
what antigens does salmonella have?
O (surface) and H (flagellar)
what are the two primary species of salmonella?
S. bongori & S. enterica
S. bongori has 1 subspecies which is subspecies V
S. enterica has 6 subspecies w/most human pathogens being in subspecies 1
nontyphoidal vs typhoidal salmonella (enterica 1)
typhoidal: humans, typhoid fever, paratyphoid fever, usually where people congregate
nontyphoidal: humans and animals, gastroenteritis and extraintestinal
salmonella history
associated with poor sanitation/hygiene, typhoid mary carrier and chronic shedder cooked for multiple households in 1900s
typhoidal salmonella
s enteria, causes typhoid and paratyphoid fever, restricted growth in humans
nontyphoidal salmonella
causes disease in animals and humans, transmission from animal to person or food
how does salmonella create an infection
adheres and invades (unlike ecoli) intestinal epithelial cells in terminal portion of small intestine bacterial cells internalize and multiply cause inflammatory response,
pathogenicity island 1 aids in invasion then type 3 secretion system delivers virulence factors, pathogenicity island 2 allows bacteria to multiply
produce toxins which cause an immune response in host
salmonella pathogenicity island 1 (SPI-1)
aids with entry into intestinl epithelium, enables pathogen to exploit host intestinal environment
salmonella pathogenicity island 2 (SPI-2)
intracellular replication and initiation of systematic infection
type III secretion system (TTSS)
main way salmonella delivers virulence factors to host, needle structure extended by protein base forms a channel to host
salmonella containing vesicle & purpose
after ingestion salmonella enters a SCV through bacteria-mediated endocytosis, salmonella lives and multiplies in SCV = a method to avoid host immune response
what is salmonella main virulence factor and its effect
SopB, an enterotoxin associated with SPI-1 TTSS, induces an increase in concentration of inositol polyphosphate
water follows to balance osmolarity which will cause diarrhea = first virulence factor, will then lead to dehydration
where does salmonella come from
widely found in GI tracts of domestic and wild animals
livestock species, pets (turtles), pests, birds (harder to find in cattle and pig)
salmonella can cause illness in some livestock species unlike ecoli
how does salmonella get into meat
contamination occurs via the same mechanisms as ecoli contamination
cross contamination during processing/hide removal or within raw products, poor sanitation during processing
have samonella cases decreased throughout the years
no there has even been a slight increase, 2000 - 2011 have seen a 17% increase
salmonella serovar (types) in US
there are many strains that can be found across livestock species and we are even finding new ones that have not been identified previously
1/4 of all outbreaks we can’t identify
salmonellosis (dosage, incubation, symptoms, duration)
generally requires large infection dose (unlike ecoli) incubation period of 8 to 48 hrs, causes diarrhea, nausea, abdominal cramps, fever
duration of 3 - 7 days
self-limiting and usually resolve themselves
salmonella foodborne illness
most common bacterial foodborne illness ~34% illness in US, associated with multiple foods 20% poultry, 14% beef & pork, 57% produce eggs etc
>1 million illness & 450 deaths annually (prob more because people don’t report)
prevalence of salmonella in poultry
less in young chicken (4.2%) vs ground chicken (28%)
salmonella mitigation
control on the farm through pest control, biosecurity, environmental control (sanitizing barns water air)
process controll salmonella mitigation
sanitary processing, eliminating cross contamination
pre & post-harvest interventions
pranic acids, vaccines, direct-fed microbials, process interventions
what are challenges of salmonella control
salmonella is evading current surface interventions, it is an internalized bacteria and in pultry parts w/ bones and lymph nodes, antimicrobial resistance
monitoring Salmonella, who and how
FSIS, monitors pathogen reduction/HACCP systems, sets performance standards, only manage what you measure
Listeria genus and species
Listeria genus includes 10 species with only L.monocytogenes being human pathogen
listeria environmental pathogen and natural resivors
soil, water, GI tract, human carriers, pests, silage is vector
why is listeria unique?
is intracellular and passes from cell to cell, can penetrate brain and placenta
pathology of listeria (steps of infection)
L.mono enters through GI, interacts with GI (internalin-A & E-cadherin), cross epithelial layer via vacuole, resides in vacuole until lysed by listeriolysin, LLO toxin creates pores in host cell membranes, listeria multiplies, forms tail
exposure vs infection
exposure to L.mono is common, listeriosis is rare, less than 1% foodborne illness but 30% foodborne deaths
most in high risk groups: pregnant, newborns, immunocompromised
listeriosis incubation period and difficulty
incubation period ranges from 2-3days to 3-5 weeks making it hard to track, also first symptoms are flu-like then progress making it hard to catch
why is listeria problematic in food industry
can persist and grow in many environments and isn’t effected by same interventions that are used to kill ecoli etc in meat processing
tolerance to cold temps, moisture, salt concentrations
introduction of listeria in food
can be from contaminated animals, contaminated equipment, cross-contamination by employees (interventions in processing will work but after employee can still introduce)
listeria and RTE foods
zero tolerance policy for L.mono in RTE foods
contamination can occur post-processing, survive in product environment
Listeria monocytogenes biofilms
listeria grows and matures in biofilm before dispersing, they tend to grow in hard-to-reach areas within plant and are less susceptible to cleaning
controlling listeria in RTE meats
must comply with one of the following:
1. use post-lethality treatment AND antimicrobial agent
2. use post-lethality treatment OR antimicrobial agent
3. use sanitation measures only
campylobcateer basics
gram negative, s-shaped, non spore forming, obtain energy from amino acids, highly motile with flagella on one or both ends
campylobacter basic environment
microaerophilic (3-5% O2, 2-10% CO2) makes culturing difficult, prefer water activity (high moisture food w/ little salt), 37 and 42C (incapable of growth 30C) commonly carried in animal GI tract
campylobacter species
numerous species implicated in human illness, campylobacter jejuni & campylobacter coli are most common
campylobacter fetus - spontaneous abortion in cattle and sheep)
campylobacter pathology
little is known of pathology, flagella aid in colonization of SI, once colonized releases cytotoxins DCT, survive by chemotaxis since acidic gut environment not conductive,
campylobacteriosis
onset of disease range from 1-10days, symptoms for 3-6 days, death extended illness is rare
campylobacter epidemiology
14/100,000 people affected each year, 1/3 associated with poultry, rising number from raw milk
campylobacter & poultry
birds are natural reservoirs and asymptomatic carriers, greater risk with greater volume
prevalence varies by productive system flocks range from 2-100%, organic and free range have higher prevalence, once positive difficult to eliminate without depopulation b/c vertical integration
controlling campylobacter
begins at farm, sanitation, biosecurity, probiotics, feed acidifcation
at plant, segregation of positive flocks, regular monitoring to reduce cross-contamination
