PerspectivePerspective Growth, and Death Growth, and Death Of MicroorganismsOf Microorganisms

Professor Thomas J. Montville

Respecting our AncestorsRespecting our Ancestors

Earth formed 6 billion years agoEarth formed 6 billion years ago

BacteriaBacteria appear 3.5 billion years.

Dinosaurs go extinct 250 million years ago.

Humans arrive 3 million years ago.

Take home message:________________

Take home message:________________

Bacteria ‘R UsBacteria ‘R UsBacteria are the most predominant life

form, by number and mass.

(Take home: _______)

You are as many bacterial cells as human cells.

You are an open ecosystems.

““We do not live in a sterile world.”We do not live in a sterile world.”

“There’s nothing we can do to keep a bird from pooping on that field.”

Dr. Tom Montville, News Channel 4

Food Safety - Old ModelFood Safety - Old Model

Pinpoint Problem

Provide Solution

Promulgate Regulation

Punish

Food Safety -RealityFood Safety -Reality

Place Event ResultFarm Lettuce near pig pen 60 E.coli O157:H7

Truck Pasteurized after raw 30,000 salmonellosis Factory Pasteurize half of input-100 listeriosis

Outlet Undercook product E.coli O157:H7 outbreak

Home Wrong storage Temp. Botulism

Who is responsible for food safety? _______________

Food Safety Farm to ForkFood Safety Farm to Fork

**

Tauxe, 2005. (2005 data in MMWR of April 14, 2006 are similar. )

*

Questions and Answers:Questions and Answers:

Modes of Microbial GrowthModes of Microbial Growth

Bacteria:

Yeast:

Molds:

The bacterial growth cycle has four phases:The bacterial growth cycle has four phases:

time

log

cfu/

ml

4

8

12

lag

logarithmic or exponential

stationary

death

The Miracle (or curse) of Exponential GrowthThe Miracle (or curse) of Exponential Growth

N = NN = Nooeektkt

N = Number of bacteria at any time, t

No= Initial number of bacteria

k= Rate constant, influenced strongly by temperature, also influenced

by environmental conditions

In plain English, bacteria grow by doubling:In plain English, bacteria grow by doubling:

1 -> 2 -> 4 -> 8 -> 16 -> 32 -> 64 -> 128 -> 256 => 500 -> 1000 ->

One bacterium can grow to one million bacteria

in ___ doublings!

Handwashing reduces NHandwashing reduces Noo((http://users.aol.com/comcontrol/comply.htm)http://users.aol.com/comcontrol/comply.htm)

(http://www.asmusa.org/pcsrc/ochsur.htm) (http://www.asmusa.org/pcsrc/ochsur.htm)

Study of handwashing in restaurants, foodservice, healthcare settings show <2 washings per day.

FDA estimates poor handwashing contributes to 80 million cases in U.S.

94 % say they wash their hands after using public toilets.

68% observed wash their hands after using public toilets.

Bacteriological Survey ofBacteriological Survey of Sponges and Dishcloths Sponges and Dishcloths

(Enriquez, et al., 1997. Dairy Food Environ Sanitarian 17:20-24)(Enriquez, et al., 1997. Dairy Food Environ Sanitarian 17:20-24)

Organism Sponge Cloth

Total Coliforms 1 x 105 1 x 105

Fecal Coliforms 4 x 102 2 x 103

Salmonella 15% 20%Staphylococcus 20% 19%

Restaurants, Bars, and HomesRestaurants, Bars, and HomesYepiz-Gomez, et al. J. Food Protect. Trends. 26:786-Yepiz-Gomez, et al. J. Food Protect. Trends. 26:786-

792, 2006792, 2006

The ultimate comparison, Restaurants vs Homes!

““Reasonable” Microbiological Reasonable” Microbiological Criteria for Ready to Eat FoodsCriteria for Ready to Eat Foods

Salmonella 0/25 g

Listeria monocytogenes 0/25g

E. coli <10 cfu/g

O157:H7 “none”

Staphylococcus aureus <100 cfu/g

Clostridium perfringens <100 cfu/g

“Total” plate count <500,000 cfu/g

Influence of temperatureInfluence of temperature

0

1200

1000

800600

400

200

Dou

blin

g tim

e, m

in.

10 20 30 40

Temperature, °C

330

155

20

Temperature effect on growth- chickenTemperature effect on growth- chicken

time, days

log

cfu/

cm2

4

8

12

slime

odor

10° C 4.4° C 0° C

2 4 8 16

THE "40-140" RULETHE "40-140" RULE

FOODS SHOULD BE HELD:

BELOW 40° F

OR

ABOVE 140°F

COROLLARY:COROLLARY: WHEN HEATING OR COOLING, BRING FOODS THROUGH THE 40-140°F REGION AS RAPIDLY

AS POSSIBLE

Microbial death curve, Microbial death curve, IdealIdeal

time

log

cfu/

ml

4

8

12

0

IMPLICATIONS OF LOGARITHMIC DEATH:IMPLICATIONS OF LOGARITHMIC DEATH:

1) Sterility is theoretically impossible.

2) The effectiveness of a given heat treatment is dependent on the initial microbial load, i.e. a 6D process that "works" when the initial number is 104

cfu/ml will 'fail' when the initial number is 108 cfu/ml.

3) The significance of 'fractional survivors.' In a 6D process, if you start with 1 spore per unit, one in 106 units will contain a viable spore after processing.

““The perp walk”The perp walk”

Sporulation and GerminationSporulation and Germination

vegetative cell

sporulation

dormancy

activation

germination

outgrowth

Botulism and Temperature Abused Pot Pie Botulism and Temperature Abused Pot Pie (Morbidity and Mortality Weekly Report, Vol. 32, # 3, January 1983).

Patient: 56 year old diabetic woman

Symptoms: diplopia, weakness, difficulty breathing, chest pain, respiratory arrest.

Scenario: Son prepared pot pie for mother. Father brought home take-out hamburgers. Mother left pot pie out on shelf (in California, in August), and ate it two and one-half days later without reheating.

Illness: next day. Type A botulinum toxin was isolated from the left-over food and patient's serum.

Bacillus cereus Bacillus cereus - food poisoning- food poisoning

Diarrheal typeDiarrheal typeOnset: > 6 hr

Range = 6 - 14 hr

Average = 9 hr

Symptoms: Diarrhea

Nausea, Cramps

Rectal tenesmus

Fever generally absent

Recovery: 20 - 36 HR

Emetic typeEmetic typeOnset: < 6 hr

Range = 0.5 - 6 Hr

Average = 2 hr

Symptoms: Vomiting,

Nausea, Cramps

Diarrhea (+)

Fever generally absent

Recovery: 8 - 10 Hr

Foods associated with Foods associated with Bacillus cereus Bacillus cereus outbreaksoutbreaks

Meats and Gravies

Sauces and Puddings

Miscellaneous Vegetable Dishes

Fried Rice and Other Rice Products

Many Many Bacillus thuringiensisBacillus thuringiensis isolates isolates produce "produce "Bacillus cereusBacillus cereus" "

diarrheal toxin.diarrheal toxin.

S.G. Jackson, et al., 1995. Letters Appl. Microbiol. 21:103-105.P.H. Damgaard, et al., 1996. Letters Appl. Microbiol. 23:146-150.

Staphylococcus aureusStaphylococcus aureusFOOD POISONING SYNDROME

onset: 0.5 to 6 hours

recovery: 24 to 72 hrs

major symptoms: vomiting, diarrhea

other symptoms: nausea, salivation,

cramps, retching,

prostration

Staphylococcus aureus Staphylococcus aureus Case StudyCase StudyFlight from Tokyo to Copenhagen via Anchorage

196 of 343 passengers, 1 of 20 crew

food eaten:

1 h post Anchorage, snack, served to all

5.5 h post Anchorage, steak dinner, crew

5.6 h post Anchorage, cheese omelet w/ ham

passengers only

onset: 0.5 to 5.5 h after breakfast, average 2.5 h

symptoms:

diarrhea (88%), vomiting (82%)

cramps (74%), nausea (68%)

Staphylococcus aureus Staphylococcus aureus InvestigationInvestigation

Isolated SED-producing S. aureus from fecal swabs of 5 patients and from left over omelet and ham.

Isolated SED from omelet and ham. Breakfast prepared day before flight, held at room

temperature for 6 h during preparation Held 14.5 h at 10°C prior to the flight. Held at room temperature during the flight, then heated. Isolated SED-producing S. aureus from inflamed lesion

on the hand of the cook who had made the breakfast.

1989- STAPHYLOCOCCAL FOOD POISONING1989- STAPHYLOCOCCAL FOOD POISONING

Staphylococcal Enterotoxin Found

In Canned Mushrooms From

Peoples Republic of China

4 Outbreaks, > 100 Cases

English, et al., Dec. 1990, Food Technol. p. 74

centralized agriculture:

local farm plant export

2 to 4 hours

free market agriculture:

local farm brokers plant export

weeks in PVC bags

S. aureus is poor competitor with aerobic

spoilage organisms, but competes well under

anaerobic conditions.

O2 respiratory demand = 3,160 cc/kg/h

PVC permeability = 21 cc/h

centralized agriculture:

local farm plant export

2 to 4 hours

free market agriculture:

local farm brokers plant export

weeks in PVC bags

S. aureus is poor competitor with aerobic

spoilage organisms, but competes well under

anaerobic conditions.

O2 respiratory demand = 3,160 cc/kg/h

PVC permeability = 21 cc/h

Why do "new" pathogens emerge?Why do "new" pathogens emerge?(Lynton Cox, Food Technol. 43(12)52-59, 1989)

1. CHANGES IN EATING HABITS, fresh, organic2. CHANGES IN AWARENESS , computer databases3. CHANGES IN DEMOGRAPHICS larger sensitive populations4. CHANGES IN PRIMARY FOOD PRODUCTION scale of operation, global production5. CHANGES IN FOOD PROCESSING

TECHNOLOGY. MA, chill, vacuum packaging6. CHANGES IN HANDLING AND PREPARATION home refrigeration, microwave7. CHANGES IN THE MICROORGANISMS, plasmids

Bad News on RefrigerationBad News on Refrigeration

Hutton, et al., 1991, J Food Safety 11:255-267

15 CITY - 100 SUPERMARKET STUDY OF REFRIGERATOR CASES

90% OVER 40°F

20% OVER 50°F

Woodburn, J. Am. Diet. Assoc. 87:322-326

21% OF HOME REFRIGERATORS OVER 50°F

Listeria monocytogenes-Listeria monocytogenes-disease syndromes

1. Low grade "flu-like" infection - not serious, except in pregnant woman (who abort).

Up to 16% women carry L. monocytogenes without illness. (Larmont and Postlethwaite, 1986, J. Infection 13:187-193.)

2. Listeric meningitis- headache, drowsiness, coma. 50%

fatality rate. If very young and old are excluded, this drops to 30%.

3. Perinatal infection - 0.15% to 2.0% of all perinatal mortality.

4. Encephalitis

5. Psychosis

6. Infectious mononucleosis

7. Septicemia

Los Angeles Mexican Soft Cheese Los Angeles Mexican Soft Cheese - 93 Perinatal cases:

19 Still births

10 Postnatal deaths

- 49 Adult cases:

18 Deaths

- Linked with Mexican soft cheese

- Same phage type isolated from cases

and processing plant

- Plant's milk throughput

exceeded capacity of pasteurizer

- Cheese was alkaline phosphate positive

Sporadic ListeriosisSporadic ListeriosisSchwartz, et al., 1988, Lancet 779-782Schwartz, et al., 1988, Lancet 779-782

• CDC population study of 34 million people yields 154 cases with 28%fatality.

• 82 cases matched with 239 controls reveals statistical link to uncooked hot dogs, undercooked chicken.

• Home refrigerator study

Risk for ListeriosisRisk for ListeriosisSouthwick & Purich, New Eng. J. Med. 334:770, 1996Southwick & Purich, New Eng. J. Med. 334:770, 1996

•General Population•Over 70 years old•Pregnant•H.I.V. positive

0.7 cases /100,000

3 times higher

17 times higher

100 - 300 times higher

There is a zero tolerance for L. There is a zero tolerance for L. monocytogenes in r-t-e foods, monocytogenes in r-t-e foods,

but no 100% accurate for but no 100% accurate for detecting it.detecting it.

1998/99 “Sara Lee” Outbreak1998/99 “Sara Lee” Outbreak(Bil Mar, Ball Park franks)

79 illnesses in 17 states12 deaths, three miscarages35 million pounds of product recalledRecall costs (to Sara Lee) $50-70 million Stock price falls from $55 to $25Oscar Mayer (Unit of Philip Morris) also has January recall of deli

meats due to illness report

These are the “big boys,”

what of the “mom & pops”?

SalmonellaSalmonella

SalmonellaSalmonella spp. spp.

Increasing antimicrobial resistance.

Large and dispersed outbreaks.

Habitat intestinal tract of animals.

49% of animal feed contaminated.

15-25% of poultry contaminated.

S. enteritidisS. enteritidis

Colonizes ovaries.

Internal contamination of egg.

May penetrate egg shell during cooling.

Capable of multiplication at 10-15 C in egg yolk or albumen.

Generally low numbers recovered.

Low % contaminated samples.

S. enteritidisS. enteritidisOutbreak 1994, 224,000 persons in U.S.

develop S. enteritidis gastroenteritis after they ate ice cream.

Contamination was linked to transport of pasteurized ice cream premix in tanker trailers that had previously carried nonpasteurized liquid eggs.

SOP violations:British Airways Outbreak

Casino case

CONTROLCONTROL

Cook eggs thoroughly (Pass a Law)

Avoid cross-contamination

Employ proper refrigeration

Regulate employees CONTROL ON THE FARM

CampylobacterCampylobacter

Campylobacteriosis more common than salmonellosis.

Higher morbidity, lower mortality.

Infective dose can be small.

30-70% of all chickens infected.

E. coliE. coli O157:H7 O157:H7

E. coliE. coli O157:H7 O157:H7

DiseaseOnset 5 to 7d following ingestion

Hemorrhagic colitisBlood in stools

Severe abdominal pain

Some vomiting

No fever

E. coli O157:H7• Disease

– Hemolytic uremic syndrome (HUS)• Blood clots block tubules in kidney resulting in

accumulation of waste products• Renal failure in children

– Thrombotic thrombocytopenic Purpura (TTP)• Decrease number of platelets• Spontaneous hemorrhages beneath the skin• Blood clotting in brain

At least hamburgers get cooked!

FACTORS CONTRIBUTING TO OUTBREAKS, U.S.FACTORS CONTRIBUTING TO OUTBREAKS, U.S.(Snyder, J. Food Service Systems 6:107-139, 1991)(Snyder, J. Food Service Systems 6:107-139, 1991)

Contributory factor Percent1. Improper cooling 43.72. <12 between preparing and eating 22.63. Colonized person handling implicated food 18.14. Incorporating raw food/ingredient into foods that received no further cooking 15.85. Inadequate cooking/canning/heat processing 15.56. Improper hot handling 13.37. Inadequate reheating 10.68. Obtaining food from unsafe source 10.09. Cross contamination 5.410. Improper cleaning of equipment/utensils 5.4

Questions?Questions?Answers?Answers?

Comments?Comments?