food micro exam 3

name origin of clostridum perfringens

small spindles, per (through) frango (shatter or break into pieces)

characteristics of c. perfringens

• Gram-positive, rods

• Encapsulated, non-motile

• Aerotolerant anaerobic

(Compare with C. botulinum)

• Blood hemolysis

• Spore-former

i. Oval sub-terminal spores

ii. Sporulation: Sporadic, sometimes unpredictable

iii.Germination: Importance of heat-shock for spore germination

growth temp of c. perfringens

• Optimum: 40°C to 45°C

• Minimum: 20°C

mesophilic/thermophilic

generation time and prevalence of c. perfringens

Generation time

• Under optimum conditions: 8-10 min!!!

Prevalence

• Soil

• Intestine of humans and animals; healthy or otherwise

nutritional requirements

• amylase and lactase positive

• Complex needs = Rich foods

• CHO: Glucose, lactose, and starch

- Lactose → CO2 + H2 + Acid

- Stormy fermentation of milk

(only 4-6 hours!)

symptoms, onset and other diseases of clostridium perfringens gastroenteritis

• caused by clostridium perfringens enterotoxin

Symptoms

- Abdominal cramps

- abdominal distention (gas liberation)

- Profuse watery diarrhea

Onset/Incubation

6-24 hr. (short for infection mode!)

Subsides in 12-24 hrs

Other diseases of Clostridium perfringens

- Necrotic enteritis (Pig-Bel)

- Wound infections (e.g., during surgery!)

- Gas gangrene

Sequence of events leading to Clostridium perfringens gastroenteritis w picture

survival- oil (or rich foods) will protect spores from stomach

summary of Sequence of events leading toClostridium perfringens gastroenteritis

• Incidence of the spore-former in food

- Contaminated food (e.g., poultry, or meat)

- Ingredients (e.g., spices)

• Survival of the spores during food preparation/processing

- Sub-sporicidal heating (e.g., < 100°C)

• Growth in food to a large population (106-107 cells/g food)

- Slow cooling

- Other forms of temperature abuse (bar food)

• Ingestion of contaminated food by susceptible individuals

• Survival in the stomach

- Rise of stomach pH during consumption of a large meal

- Physical protection (e.g., food particle coated with lipids)

• Growth in the intestine, reaching stationary phase

• Sporulation in the large intestine and simultaneous release

of CPE toxin

what is the death of body tissue

necrotizingt

toxin types of clostridum perfringens

• Toxin types: More than 20 toxins produced

alpha, beta, gamma, epsilon, iota, etc.

• Species typing: Based on toxin(s) produced

(Type A, type B, type C, etc.)

• Clostridium perfringens enterotoxin (CPE)

- Produced mainly by Clostridium perfringens type A

- Causes C. perfringens gastroenteritis

- Unusual toxin production stage (Sporulation)

Laboratory diagnostics of

Clostridium perfringens gastroentiritis

• Detection of the microorganism and/or the toxin in food!

• Detection of the microorganism vs. toxin in feces!

control for clostridium perfringens

Dangerous Temperature range for holding food

• The “danger zone:” 40°F (4.4°C) to 140°F (60°C)

• Applies to many foods and most pathogens.

• “Hot food” should stay hot (> 60°C) and

• “cold food” should stay cold (< 4.4)

• Food reheating: 70°C to 100°C (not just warming it)

• Avoid slow-heating, cooling and defrosting

(Note: chicken carcass chiller and cooling rates)

Seasonality of C. perfringens gastroenteritis

• Almost 1 million people get the disease every year in the US.

• Many of the cases/outbreaks occur during the holidays (November and December)

Enterobacteriaceae Characteristics

• Gram-negative, rod-shaped

o 0.3-1.0 x 1.0-6.0 μm

• Motile by peritrichous flagella

• Mesophiles (optimum temp 22-35°C)

• Grow in the presence or absence of oxygen

(i.e., facultative anaerobes)

• Both respiratory and fermentative metabolism of carbohydrates

o Respiration (What is respiration?)

- Aerobic

- Anaerobic

o Fermentation

• Catalase-positive (most species)

• Oxidase negative (most species)

• Reduce nitrate to nitrite (most species)

• Why?- can use nitrate instead of oxygen

• Practical application in food safety?-fermented celery juice to still have nitrites

• How?

Oxidase Test

Determines whether a bacterium can oxidize certain aromatic amines(e.g., Tetramethylphenylendiamine; TMPD), which mimics a substrate for cell Cyt C oxidase, to form colored end products.

• This oxidation correlates with the “cytochrome c oxidase” activity of some bacteria. It is part of the respiratory electron transport chain

Ecology and host range of enterobacteriaceae

- Soil, water, and vegetation

- Human, animal and plant pathogens

- Common inhabitants of the intestinal tract

Latin origin of Salmonella

Daniel E. Salmon, an American veterinarian, who led the team that first isolated the bacterium from pigs in 1885

sources of salmonella

pork and poultry

biochemical characteristics of salmonella

Biochemical Characteristics

• Produce acid and gas from glucose

• Most strains do not ferment lactose (the genus could be considered- difference between this and pathogenic E. coli

lactose-negative)

• Reduce nitrates to nitrites

• Produce H2S on triple-sugar iron (TSI) agar

• Indole -, Methyl red +, Voges-Proskauer -, Citrate + (IMViC: -+-+).

Note that most Escherichia coli strains are (IMViC ++--)

• Catalase positive

• Oxidase negative

salmonella outbreak linked to fish vs backyard poultry name

Salmonella Litchfield

Salmonella infections with

serotypes Enteritidis, Hadar, Indiana, Infantis,Typhimurium, Mbandaka, and 1, 4,[5],12:i:-.

How many species and serovars does the genus Salmonella contain?

2 species (S. enterica and S. bongori) and about 2,500 serovars

What is a serovar?

A variant classified based on its antigenic characteristics (O, H, and Vi antigens).

What are the two Salmonella species?

Salmonella enterica and Salmonella bongori.

How many subspecies does Salmonella enterica have?

Six subspecies

What characteristics distinguish Salmonella subspecies?

Carbohydrate utilization, metabolic capabilities, phage susceptibility, and habitat

What are the three antigen types used in Salmonella classification?

O (somatic), H (flagellar), and Vi (capsular) antigens.

What does the O antigen represent?
What does the H antigen represent?
What does the Vi antigen represent?

The somatic (cell surface) antigen.

The flagellar antigen.

The capsular antigen

Which H antigen phases are used in serotyping?

Phase I and Phase II flagellar antigens.

What causes agglutination?

Antibody binding to a matching antigen.

Three major diseases caused by Salmonella?

Gastroenteritis (salmonellosis), enteric fever, septicemia

What serovar causes typhoid fever?

Salmonella enterica serovar Typhi

Key typhoid fever facts?

Human source, treated with antibiotics, lasts 1–8 weeks.

What is salmonellosis?

Non-typhoidal Salmonella gastroenteritis affecting the small intestine

Main symptoms of salmonellosis?

Diarrhea, fever, abdominal pain, vomiting, dehydration.

Major food sources of Salmonella?

Poultry, eggs, milk, produce, water, food handlers

Which serovar is multidrug-resistant?

Typhimurium DT104/DT204

Which serovar is heat-resistant?

Senftenberg.

biochemical characteristics of e. coli

can safely say indole and lactose positive

methyl red positive

vp negative- no acetoin from glucose

strains are IMViC ++ - -

Pathways for carbohydrate

metabolism by Enterobacteriaceae and what can e.coli do special

bio types of e. coli

classification based on biochemical characteristics)

Biotype 1: IMViC ++-- (95%). Biotype 2: IMViC -+-- (~5%)

serotypying of e. coli

• “O” antigen of lipopolysaccharide (LPS). ~170 known.

Defines serogroups

• “H” antigen of flagella. More than 50 known.

Defines serotypes

• Examples of serotypes (that happened to be pathogen):

“Escherichia coli O55:H6”, “E. coli O111:H8”, “E. coli O157:H7”

virotyping of e. coli

classification based on virulence; i.e., pathogenicity)

• Pathogenic

• Non-pathogenic (commensal)

diarrheagenic e. coli types

Enteropathogenic: EPEC

- Enterotoxigenic: ETEC

- Enteroinvasive: EIEC

- Enteroaggregative: EAEC

- Enterohemorrhagic EHEC

- Shiga toxin-producing

(Shigatoxigenic): STEC

Invade, cause tissue damage

Stack (like bricks) on intestine cells

Cause bloody diarrhea

Now combined

Attaching & effacing

Produce Shiga toxins

effacing- changing the landscape of the surfaces of microvilli

Naming that includes serotype and viroype

what are enterocytes

formation and attaching and effacing lesions in bacterial infection

ETEC interaction with the enterocytes e.coli

EIEC interaction with the enterocytes e.coli

EPEC interaction with the enterocytes e.coli

STEC interaction with the enterocytes e.coli

remove one nucleotide and whole ribosome is non working

famous serotypes of e. coli

- E. coli O104:H4

- E. coli O157:H7

Any biological relationship between serotype and Shiga toxin

production?

The "combo" matters:The worst food poisoning happens when a specific bacterial model (serotype) that is really good at sticking to your gut combines with the most dangerous version of the toxin weapon.

2 examples of STEC

In 1982, an E. coli (later found to be E. coli O157:H7) was initially identified as the cause of bloody diarrhea from eating undercooked or raw hamburger meat that was contaminated with the bacterium

In 2011, a Shigatoxin-producing Enteroaggregative E. coli O104:H4 strain (EAEC Stx2a+) caused a serious outbreak of acute gastroenteritis and hemolytic uremic syndrome (HUS) in Germany.*

—-Water, Sprouting for days, Fenugreek Seeds Sprouts

proposed scheme of new e. coli pathotype

AAF plasmid from EAEC and phage from eHEC combines to make that