Food Microbiology Exam 3 Gram Negatives

Enterobacteriaceae

gram negative, facultative anaerobic rods

can be motile or non-motile

many have fimbriae that aid in adhesion

Coliforms

non-spore formers

gram negative rods

ferment lactose at 35-37 degrees celcius

associate with GI tracts of warm-blooded animals

indicator organisms for fecal contamination

E. coli

most are commensal and non-pathogenic

not heat resistant, some acid and antibiotic resistance

categorized by antigens, virulence, pathogenicity, clinical symptoms, and flagella

higher hospitalization rates

Diffuse anchoring E. coli (DAEC)

pathogenic

infant/child diarrhea (can be bloody, typically mild)

01, 02, 021, 075

adheres to HEp-2 and HeLa cell lines

non-invasive

no heat stable enterotoxin

Enteroaggregative E. coli (EAEC)

pathogenic

persistent diarrhea in infants/children

03, 015, 044, 077, 086, 0104, 0111, 0127

aggregative adherence to HEp-2 cells (stacked bricks)

second most common form of traveler's diarrhea

Enteropathogenic E. coli (EPEC)

assoc with developing countries

O55, O86, 011ab, O119, O126, O127, O128ab, O143

human reservoir

watery diarrhea

light invasion of epithelial cells (Hep2 cell lines)

localized colonization/adherence

Enteroinvasive E. coli (EIEC)

non-bloody diarrhea, dysentery

O28, O29, 0112, O124, O134, O143, 0144, O152, O164, O167

invasion by ingestion

invades epithelial cells and escapes phagosome

abdominal cramps, diarrhea, vomiting, fever/chills, malaise

localization in colon.

larger than normal plasmid, outer membrane proteins

Enterotoxigenic E. coli (ETEC)

diarrhea in infants and travelers diarrhea

not common outside U.S.

O: 6, 8, 15, 20, 25, 27, 63, 78, 85, 115, 128ac, 148, 159, 167

colonizes small intestine using fimbriae

not usually serious

water diarrhea, abdominal pain, cramps, low fever, nausea

produces enterotoxin: heat stable, accumulation of fluid

toxicoinfection similar to vibrio cholera

Enterohemmorrhagic E. coli (EHEC)

important worldwide

167 O antigens, 53 H antigens, 74 K antigens

primary: O157 : H7

Big 6: O: 26, 103, 111, 121, 145

shigatoxin

low infectious dose

O157 & non-O157 STEC

hemmorrhagic colitis

self-limiting

severe cramps, watery then bloody diarrhea, some vomiting, low grade fever

sometimes hemolytic uremic syndrome or thrombotic thrombocytopenic purpura

Animal reservoirs: especially cattle

Sources: produce, ground beef, unpasteurized milk/cheese, water, petting zoo, childcare

O157

acid-resistance

antibiotic resistance

negative for sorbitol fermentation

non-invasive

aggregative adherence and intimate attachment

immune response to attachment causes diarrhea

toxins result in cell death (bloody diarrhea)

Salmonella enterica

invasive infection

leading cause of bacterial food illness

resilient to temp and pH changes

survival at low aw

Source: meat and poultry, fish, produce, low moisture

GI tract: can spread to spleen, liver, lymph nodes, bile

Diseases: typhoid fever, gastroenteritis, systemic infection

Shigella

no lactose fermentation

low infectious does

human reservoir

fecal-oral route

shell-fish, vegetables, salads, daycares

Shigellosis: bloody diarrhea, abdominal/rectal pain, cramps, fever

S. dysenteriae produces Shigatoxin (Stx1 and 2)

invasive or non-invasive depending on temp

invasive uses T3SS

Yersinia spp.

small gram negative rods

Y. pestis= cause of plague

Y. entercolitica= primary food pathogen

Psychotrophic

inadequate heat and post processing

raw milk, ice cream, pork isolated from pigs

fever, abdominal pain, diarrhea, pseudo appendicular syndrome

invasin and Yop proteins to avoid phagocytosis

Campylobacter spp.

spirilli rods, motile

microaerophilic

fastidious

animal/shellfish reservoir

veggies, water, raw milk

seasonal outbreaks

onset: 2-5 days duration: 1 week

self-limiting

fever, abdominal cramps, sometimes bloody diarrhea

invasive GI tract infection

cholera-like enterotoxin that activates adenylate cyclase

Guillain-Barre syndrome

Vibrio spp.

short motile curved rods

tolerant of high salt

developing countries

serogroup 1: contaminated water/seafood

profuse watery diarrhea- dehydration and shock

death within hours without treatment

Non-01: shellfish in warm waters, fever, diarrhea, abdominal cramps, no outbreaks only sporadic cases

V. parahaemolyticus

gastroenteritis: nausea, fever, chills, vomiting, cramps, headache

onset: 4-96 hours duration: 2-5 days

contaminated seasonal shellfish

most common type in U.S.

V. vulnificus

flesh-eating bacteria

most common vibrio death in U.S.

infects through wounds (oceans)

gastroenteritis

septicema: 50% mortality, liver disease

Brucella

abortus (cattle)

melitensis (sheep/goats)

suis (pigs)

invasive

incubation (3 weeks)

persistent fever, sweats, muscle pain fatigue, headaches, arthritis, endocarditis

undercooked meats, unpasteurized dairy

biological warfare agent: aerosolized

Gram positive

some form spores and produce toxins

higher infectious dose

non-pathogenic: LAB, many strains of Listeria, Clostridium, and Bacillus

Staphylococcus aureus

clusters of cocci, mesophile, facultative anaerobe

resistant to low aw, and high salt

bind to mucousal barriers assoc with human and cattle

quick onset (1-6 hours) duration: 24-48 hours

vomiting, nausea, cramps, diarrhea, headache,

produce toxin in stationary phase

heat stable enterotoxin

toxic shock syndrome

temp abuse and handling, protein rich foods

Bacillus cereus

aerobic/facultative anerobic

hydrophobic-spore-forming rods

non-fastidious mesophilic

motile and non-motile

environmental contamination source

emetic toxin: cereulide

onset: 0.5 - 5 hours duration: 6-24 hours(severe)

diarrheal enterotoxin: onset 8-16 hours duration: 12-25 hours

self-limiting

starchy foods (rice pasta), dairy foods, cross contamination of meats, soups, puddings, sauces, milk

Clostridium botulinum

anaerobic, spore-forming (stationary)

produce toxin at end of log phase

water, sediment, soil are contamination source

Group 1: A, proteolytic B and F

greater heat resistance, high neurotoxin production

Group 2: E, non-proteolytic B, and F

less heat resistance, no growth less than 3 degrees

vacuum packaged foods

_________________

most natural lethal toxin known

heavy and light chain

not heat resistant toxin

onset: 12-36 hours

nausea, vomiting, dry mouth and throat, neurological, fatigue, dizziness, headaches, loss of muscle function and vision

fermented foods, canned foods, honey

Prevention: nitriles, competition, hurdle, high thermal inactivation

Clostridium perfringens

anaerobic, spore forming

quick doubling time

environmental contaminant

fastidious

toxicoinfection: CPE enterotoxin produced by vegetative cells

sporulating and lysing cells release toxin in small intestine by binding to epithelial cells

onset: 8-16 hours duration: 12-24 hours

self-limiting

EXPLOSIVE diarrhea, abdominal cramps,

temp abused foods, undercooked meats, high protein foods, gravies, stews

Prevention: freezing, cook thoroughly, sanitizing

Listeria spp.

psychotroph, facultative anaerobe, non-spore former

peritrichous flagella, tumbling motility

form biofilms

natural resistance and adaptation

Listeria monocytogenes

enters and invades host cells,

invasive infection that uses actin polymerization

avoids antibodies and requires cellular mediated immune response

blood transports cells within macrophage to lymph nodes

can cross blood-brain and placental barriers if it passes thru liver and spleen

Listeriosis

onset: up to 5 weeks

flu-like fever, GI distress: vomiting, diarrhea, nausea

high mortality

septicemia, meningitis, encephalitis, intrauterine cervical infections

RTE high risk foods: deli, soft cheese, ice cream, frozen foods

zero tolerance policy

Exosporium

proteins, lipids, carbs

some protection

surface interactions

Spore coat

proteins, resistant to enzymes

Cortex

peptidoglycan and dipicolinic acid (DPA), dehydrated core

responsible for resistance

Core of Spore

DNA, ribosomes, SASP, low water content

Two goals of spore

replicate/metabolism and survive

Yeast spores

ascospores

multiple spores per yeast

Aflatoxins

primary mycotoxin concern in U.S.

from Aspergillus flavus and parasiticus

targets liver

chronic immune suppression

Infection

colonization of cells that causes symptoms

can be invasive or not

Toxicoinfection

both colonization of cells and intoxication

Intoxication

true-food poisoning

toxin responsible for disease

Non-invasive infections

ingested bacteria colonize intestinal lining

most diarrheagenic E. coli

attach but do not invade

Type 3 secretion system

ex: norovirus

Invasive infection

shigella, salmonella, EIEC, Listeria monocytogenes

adherence and invasive factors: adhesions and T3SS

invades cells with actin polymerization

Intoxication

S. aureus, C. botulinum, B. cereus, C. perfringens

usually associated with a quick onset (hours)

Toxicoinfections

vibrio cholerae, EHEC, ETEC, C. botulinum (infant)

C. perfringens and B. cereus