Chapter 12: GI GramNegative Rods

1
Chapter 12 GI Gram-Negative Rods

• Enteric Gram-negative rods
• All found w/in GIT
• Alternative inhabitants of soil H2O
• Sensitive to drying
• Facultative anaerobes grow well in O2 presence
• Contain LPS endotoxin, antigenic
• Fecal contamination transmission
• Person-to-person, fecal-oral via contaminated
  food/H2O
• Representative microorganisms
• Escherichia spp. 5. Vibrios spp.
• Salmonella spp. 6. Yersinia
• Campylobacter spp. 7. Helicobacter
• Shigella 8. Micellaneous
  Enterobacteriaceae

2
Escherichia

• Family Enterobacteriacea
• Genus Escherichia
• Species Escherichia coli (E. coli)
  Escherichia hermani (E. hermani)
• General Genus Characteristics
• Gram-negative bacillus
• Escherichia-Shigella DNA homology 70-90
• Aerobe/Facultative anaerobe
• 2 clinically important species isolated form
  humans
• E. coli
• E. hermani

3
Escherichia

• General Genus Characteristics
• E. coli is the
• Most predominant facultative organism in human LI
• Part of normal flora pathogenic BOTH w/in and
  outside GIT
• Most frequently isolated enteric bacillus in
  clinical laboratory
• Subject of more experimental research than any
  other organism

4
Escherichia

• Biochemical Cultural Characteristics
• Culture grows well on most media
• Typically ferment sugars
• E. coli ferments lactose (Lac)
• E. coli produces both acid gas during CHO
  fermentation
• Distinguishing Reactions (IMViC)
• Indol Methyl Red Voges-Proskauer Citrate
• - -
• Structure Physiology of E. coli
• Fimbriae/pili adherence to host mucosal
  surfaces
• Some strains motile (w/ flagella), others
  non-motile (no flagella)
• Motile w/ peritrichous flagella (distributed all
  over the surface)
• All strains are true facultative anaerobes

5
Escherichia

• Structure Physiology of E. coli
• All strains can ferment Glucose
• All strains are oxidase negative (lack enzyme
  cytochrome oxidase)
• Typing based of differences in 3 antigens O, H
  and K
• O Ag (somatic or cell wall Ag) part of
  polysaccharide portion of LPS are heat-stable
• H Ag associated w/ flagella only seen w/ motile
  strains (flagellated)
• K Ag associated w/ the capsule or, less often,
  w/ fimbriae
• Ex. E. coli O157H7 causes a severe hemorrhagic
  colitis

6
Escherichia

• Pathogenesis
• 6 groups of E. coli strains intestinal
  pathogens.
• Each group w/ distinct characteristics, but share
  the following
• Virulence factors found on plasmids
• Interaction w/ intestinal mucosa
• Production of enterotoxins (EXCEPT EPEC)
• Classified w/in specific OH serotypes

7
Escherichia

• Clinical Significance Intestinal Disease
• Transmission m/c person-to-person fecal-oral
  route via contaminated food H2O sources
• 6 different types of E. coli Intestinal
  Infections
• Enterotoxigenic E. coli (ETEC)
• Enteroinvasive E. coli (EIEC)
• Enteropathogenic E. coli (EPEC)
• Enterohemorrhagic E. coli (EHEC)
• Enteroaggregative E. coli (EAggEC)
• Enteroadherent E. coli (EAEC)

8
Escherichia

• Enterotoxigenic E. coli
• infection of developing countries (rare in US)
  Travelers diarrhea/Infant diarrhea
• Transmission thru food H2O contaminated w/
  human waste and person-to-person
• Colonization of SI via pili
• Vibrio cholera like toxin (choleragen-like
  toxin) enterotoxin causes watery diarrhea,
  abdominal cramps, low-grade fever.
• Prolonged hypersecretion of Cl- and H2O by
  intestinal mucosal cells inhibition of Na
  reabsorption
• Result gut is full of H2O and watery diarrhea
  ensues over several days.
• Enterotoxin w/ heat-stable (ST) component and
  heat-labile (LT) component (Fig 12.4 p. 113)
  LT ? AC ? ? cAMP
• 
  ST ? GC ? ? cGMP

9
Escherichia

• Enteroinvasive E. coli (EIEC)
• Endemic in less developed countries
• Inflammatory disease w/in LI
• Penetrates or invades epithelial lining of LI
• Very much like Shigella able to invade
  intestinal mucosa, causing dysentery-like illness
  (bloody stools mucous, severe abdominal cramps,
  fever)
• Shiga-like toxin is produced bloody diarrhea
• Def. Dysentery a term applied to various
  intestinal disorders, esp. of the colon, marked
  by inflammation of the mucous membrane
  characterized by abdominal pain, tenesmus, and
  diarrhea w/ passage of mucous or blood
• Def. Tenesmus spasmodic contraction of anal
  sphincter w/ pain and persistent desire to empty
  the bowel, w/ involuntary ineffectual straining
  efforts)

10
Escherichia

• Enteropathogenic E. coli (EPEC)
• Poorly defined
• Infant diarrhea in developing countries w/ poor
  sanitation
• Newborn gets infected during birth, or in utero
• Destruction of microvilli of intestinal tract
• Attachment to mucosal cells
• Characteristic lesions produced
• NO tissue invasion NO toxin produced
• Watery diarrhea, fever, vomiting
• Diarrhea can become chronic on rare occasions

11
Escherichia

• Enterohemorrhagic E. coli (EHEC)
• m/c strain E. coli O157H7
• Important epidemic problem in NA, SA, Europe
• Has been associated w/ increasing out-breaks in
  U.S. over past 15 -20 yrs.
• Transmission to humans from animals via
  contaminated raw milk or undercooked meat
• NORMAL INHABITANTS OF CATTLE (primary reservoir)
  INTESTINES BUT INTESTINES CAN SPLIT OPEN IN
  SLAUGHTER-HOUSES, ALLOWING FECAL CONTAMINATION OF
  THE MEAT (GETS GROUND IN)
• Must thoroughly cook hamburger/ground beef at
  160F to kill E.coli pasteurization of milk
  kills E. coli

12
Escherichia

• Enterohemorrhagic E. coli (EHEC)
• Bind to cells in LI produce exotoxin (Verotoxin
  or Shiga-like toxin)
• Attachment to intestinal mucosa (fimbriae)
• NO mucosal invasion of inflammation
• Clinical Disease
• Starts a watery diarrhea w/ abdominal pain (4
  days post-exposure) develops into BLOODY
  diarrhea (Hemorrhagic Colitis) 1-2 days later.
• Recovery complete w/in 10 days
• 10 children lt5 yoa dis. develops into
  Hemolytic-Uremic Syndrome (HUS)
• Toxin causes direct kidney damage is life
  threatening

13
Escherichia

• Enteroaggressive E. coli (EAggEC)
• Infant diarrhea in developing countries
• SA, CA, India
• Aggregate appearance in Hep-2 cells
• Enteroadherent E. Coli (EAEC)
• Cause a dysentery-like syndrome w/ fever and
  bloody stools
• Persistent watery diarrhea in children HIV pts

14
Escherichia

• Clinical Significance Extraintestinal Disease
• Source of infection is often patients own flora
  individuals own E. coli is non-pathogenic in the
  intestines. But, it can cause disease.
• Urinary Tract Infections (UTIs)
• E. coli m/c cause of UTI, including cystitis
  pyelonephritis
• females at particular risk
• Uncomplicated cystitis (m/c UTI) d/t
  uropathogenic strains of E. coli
• Complicated UTI (pyelonephritis) obstructed
  urinary flow d/t non-uropathogenic strains.
• Neonatal Meningitis
• E. coli m/c cause w/in the 1st month
• Nosocomial infections
• Sepsis/bacteremia, endotoxic shock, pneumonia

15
Escherichia

• Laboratory Indentification/Dx
• Isolation identification
• Lactose fermenter
• Antigenic structure O, K, H antigens
• EIEC may be detected on MacConkey Agar
• EHEC may be detected on MacConkey Sorbitol Agar
• NOTE Lactose-fermenting, Gram-negative rods
  (i.e., the Enterobacteriasceae) produce pink
  colonies on MacConkey Agar.
• - production of acids decrease the pH of agar
  acidity causes pH indicator in the agar to turn
  pink (fig. 4.8 p. 24)
• - inhibits the growth of Gram-positive organisms
  and some fastidious Gram-negative bacteria (i.e.,
  Neisseria Haemophilus spp.)

16
Escherichia

• Treatment
• Antibiotics NOT recommended for intestinal
  disease. Why? to prevent resistant strains
• BEST Tx management of fluids electrolyte
  balance prevention of dehydration
• Let it run its course will eventually get
  better
• Resistance see with prior hx of antimicrobial
  treatment
• Prophylaxis recommended for travelers diarrhea
• Active/passive immunization not recommended

17
Salmonella

• Family Enterobacteriaceae
• Genus Salmonella
• Species Salmonella typhi (typhoid fever)
  Salmonella enteritidis (GI)
• Microscopic Morphological Appearance
• Gram-negative bacilli
• Non-spore formers
• Motile/non-motile
• Growth Conditions
• Non-selective media not fastidious
• Selective media additive bile salts (enterics
  survive in gut bile salts)
• Facultative anaerobe (survival w/ or w/o O2)
• Mesophile
• Most strains Lac-, and produce acid gas during
  fermentation of glucose
• Production of H2S

18
Salmonella

• Epidemiology
• Widely distributed in nature
• S. typhi human pathogen only other strains
  associated w/ animals food (esp. eggs
  poultry)
• Mode of transmission fecal-oral
• HIGH RISK GROUPS young children elderly
• Pathogenesis
• Invasion of epithelial cells of SI
• Diseases remain localized or become systemic
  (systemic foci)

19
Salmonella

• Clinical Disease (Salmonella infection
  Salmonellosis)
• Enteric Fever Typhoid Fever
• Disease of reticuloendothelial (lymphatic) system
• Causative agent S. typhi
• Transmission fecal-oral route
• Contaminated water or food
• Carrier food or beverage handler HIGHEST RATE
  OF TRANSMISSION
• Note carrier can be asymptomatic and shed the
  bacteria in the stool bacteria can also hide in
  GB

20
Salmonella

• Clinical Disease (Salmonella infection
  Salmonellosis)
• Enteric fever Typhoid Fever
• Mode of Infection
• Ingestion Acid Tolerance Response (ATR) gene
• ensures bacterial survival in acid pH of stomach
• Adherence/Penetration epithelial lining of SI
  Peyers Patches (Lymphoid tiss)
• Phagocytosis by Macrophages
• Multiplication Colonization w/in macrophages
  (not killed by hydroytic enzymes) ? Primary
  Virulence Factor!
• ATR gene
• Catalase and superoxide dismutase
• Engulfment by macrophages ? carried to
  mesenteric lymph nodes ? fixed macrophages
  (liver, spleen and bone marrow)
• Transfer from lymphatic system to bloodstream

21
Salmonella

• Clinical Disease (Salmonella infection
  Salmonellosis)
• Enteric fever Typhoid Fever
• Mode of Infection
• Lysis release of endotoxins cause of initial
  sxs
• Infectivity organs tissues d/t systemic
  bacteremia
• Initial Symptoms d/t release of Endotoxin
• Fever, malaise, lethargy, HA, aches and pains
• Later Symptoms continual invasion cyclical
  pattern as bacilli enter the bloodstream
• Fever - 104F
• Abdominal tenderness and distention
• rose spots maculopapular rash on trunk
  chronic bacteremia stage
• Diarrhea or constipation
• Vomiting
• Risk Groups Infants Elderly

22
Salmonella

• Clinical Disease (Salmonella infection
  Salmonellosis)
• Enteric fever Typhoid Fever
• Diagnosis Identification
• Isolation of S. typhi blood, feces, urine, left
  over foods
• Convalescence/Immunity
• Permanent
• Treatment
• 3rd generation Antibiotic Tx to decrease
  febrile illness period
• Carriers
• Antibiotic of choice ampicillin
• Administration period 3 months (b/c bacilli in
  the macrophages)
• Surgical removal of GB (harboring place for the
  bacilli)?
• Prevention/Control
• Pasteurization of milk
• Pure water supply
• Efficient disposal of sewage
• Sanitary control of food eating places
• Detection isolation of carriers

23
Salmonella

• Clinical Disease (Salmonella infection
  Salmonellosis)
• Gastroenteritis (enterocolitis)
• Causative agent S. enteritidis
• Transmission Fecal-oral route
• Contaminated food or water
• Carrier food/beverage handler
• Pets chicks/chicken or turtles
• Mode of infection Human infection limited to
  lumen of intestine
• Ingestion
• Multiplication Colonization lumen of SI
• Inflammation intestinal mucosa
• Cellular endotoxins released when bacteria
  autolyse
• Cytotoxin inhibits protein synthesis in
  intestinal epithelial cells

24
Salmonella

• Clinical Disease (Salmonella infection
  Salmonellosis)
• Gastroenteritis (enterocolitis)
• Sudden Onset of Symptoms
• HA, chills, abdominal pain
• Later Symptoms
• Nausea, vomiting, watery diarrhea, low-grade
  fever
• Risk Groups
• Infants and elderly
• Occupational risk slaughter houses
• Diagnosis
• Isolation ID of bacteria from intestinal tract
  in stool
• Treatment
• Oral rehydration maintain fluid electrolyte
  balance (supportive tx)
• Antibiotic Tx not recommended, except in extreme
  cases
• Control/Prevention
• Maintenance of food and water supplies
• Proper refrigeration cooking
• Carrier detection
• Sanitary procedures in slaughter house

25
Shigella

• Family Enterobacteriaceae
• Genus Shigella
• Species Shigella dysenteriae
  Shigella flexneri Shigella boydii
  Shigella sonnei
• NOTE All spp. are primarily pathogens of humans
  all cause dysentery in humans
• Recall Dysentery serious diarrhea accompanied
  by mucus and blood in the stool along w/ severe
  abdominal cramping.

26
Shigella

• Microscopic Morphological Appearance
• Gram-negative bacilli
• Non-spore former
• unencapsulated
• Non-motile Shigella has no flagella
• Growth Conditions
• Selective Media thiosulfate citrate bile agar
• Mesophile
• Facultative anaerobe
• NOT fastidious
• Shigella Infection (Shigellosis) sick gut
• Limited to GIT

27
Shigella

• Epidemiology
• Transmission person-to-person contact via
  contaminated stools (major) fecal-oral route
  flies and contaminated food water
• Person-to-person via fecal-oral route by the 4
  Fs
• Fingers, food, feces, flies
• Shigellosis w/ low infectious dose
• lt200 viable organisms sufficient to cause disease
• S. sonnei causative agent of bacillary
  dysentery (HIGHEST )
• S. dysenteriae cause most severe type of
  dysentery lowest in US

28
Shigella

• Mode of Infection
• Ingestion (only low 200)
• PERISTALTIC action transfers bacteria from SI ?
  LI
• Attachment endothelial cells (M cells) that
  line intestines attachment stimulates M cells to
  phagocytize bacteria
• Phagocytosis by macrophages Shigella lyses
  macrophages
• Multiplication colonization
• Shallow ulcers cell death/necrosis of
  epithelial calls
• Pseudomembrane formation mixture of cellular
  debris, necrotic mucous membrane, bacteria,
  fibrin clot formation
• Scar Tissue consequence of healing

29
Shigella

• Pathogenesis Toxin production
• Enterotoxin early stages of infection
• Toxic lipopolysaccharide
• Released during autolysis
• Effect irritation of bowel watery diarrhea,
  abdominal cramps fever
• Exotoxin or Shiga Toxin later stages of
  infection
• Cytotoxic activity inhibits protein synthesis
  get cell death
• Effect inflammation of gut wall, local erosion
  ulceration degeneration of intestinal villi

30
Shigella

• Early Symptoms (d/t enterotoxin)
• Abdominal cramps, fever, watery diarrhea
• Later symptoms (d/t Shiga toxin)
• Lower abdominal cramps, abundant pus blood in
  stool
• Recall EHEC produces Shiga-like toxin!
• Risk Groups
• Travelers travelers diarrhea
• Infants pediatric disease (1-10yoa)
• Institutional pts.
• Homosexuals gay bowel syndrome

31
Shigella

• Convalescence/Immunity
• Self-limiting infection recovery in 3-7 days
• Limited immunity
• Diagnosis Identification
• bacterial isolation from feces or intestinal
  tract
• Treatment for High Risk Groups
• Antibiotic therapy
• Fluid electrolyte replacement/balance
• Prevention/Control
• Sanitary control
• Isolation of pts disinfection of excreta
• Determination of subclinical cases food
  handlers
• No satisfactory vaccine

32
Shigella Salmonella Summary
33
Campylobacter

• Family Campylobacteriacae
• Genus Campylobacter
• Species Campylobacter jejuni
• Note Camplyobacter is the leading cause of
  food-borne disease in US
• Microscopic Morphological Appearance
• Gram-negative bacilli
• Curved, spiral, S-shaped or gull-winged pairs
• Motile darting mobility or corkscrew (short
  jumping motion)
• Microaerophilic require O2, but at lower
  than atm
• Transmission
• Fecal-oral via contaminated food (esp. poultry)
  water supplies

34
Campylobacter

• Epidemiology
• Widely distributed in nature
• Reservoirs mammals and fowl, both wild
  domestic
• Gastroenteritis (Campylobacteriosis)
• Causative agent C. jejuni
• Infection of intestines causes ulcerative,
  inflammatory lesions in jejunum, ileum or colon
  bacteremia may occur
• Mode of Infection
• Ingestion
• Adherence Multiplication intestinal mucosa of
  SI
• Enterotoxin or C. jejuni toxin (C.J.T.)
  production
• Exotoxin raises intracellular levels of cAMP and
  stimulates secretory diarrhea
• Same mechanism as w/ V. cholerae

35
Campylobacter

• Symptoms
• Malaise
• Fever
• Abdominal pain, painful abdominal cramping
• Watery and bloody diarrhea
• Risk groups
• Most severe in very young elderly malnourished
• Occupational risk - slaughterhouses
• Convalescence/Immunity
• Self-limiting infection in uncompromised pt (1
  week)
• Therapy recommended to reduce length and severity
  of disease

36
Campylobacter

• Diagnosis Identification
• Isolation of bacteria in fecal samples
• Direct examination of fresh feces by dark field
  or phase contrast microscopy look for
  darting/corkscrew motility (characteristic)
• Culture on selective Hektoen agar
• Treatment
• Rehydration electrolyte balance therapy
• Antibiotic therapy
• No vaccines
• Prevention/Control
• Sanitary control of water and milk supplies
• Careful hygiene, esp. avoiding transmission from
  animals to food and H2O
• Hygienic handling of raw meats

37
Vibrios

• Family Vibrionacea
• Genus Vibrio
• Species Vibrio cholerae Vibrio
  parahaemolyticus Vibrio vulnificus
• Microscopic Morphological Appearance
• Gram-negative bacilli
• Short, curved, rod-shaped
• Motile vibrating motion single polar flagellum
• Facultative anaerobes that utilize glucose as
  source of E

38
Vibrios

• Growth Conditions
• Mesophile b/c infections in humans
• Non-selective media
• Selective media
• V. cholerae alkaline media containing bile (pH
  9.0-9.5) thiosulfate citrate bile salts sucrose
  (T.C.B.S.) yellow colonies
• V. parahaemolyticus V. vulnificus Halophilic
  bacteria (marine bacteria pathogens of sea
  water found in association w/ seafood) media
  supplemented w/ 2-7 NaCl

39
Vibrios

• Epidemiology/Transmission
• Fecal-oral route via contaminated water or food
• No known animal reservoirs
• N. Am. transmission of microbe by food or water
  contaminated by carriers
• Clinical Disease
• Cholera or Asiatic Cholera
• Acute enterotoxin-mediated infection
• Causative agent V. Cholerae 01 serotype

40
Vibrios

• Clinical Disease
• Cholera
• Mode of infection
• Ingestion large s (104)
• Adherence and Colonization of intestinal mucosa
  of LI and SI ONLY organisms attach and
  proliferate, but do NOT invade NO penetration
  into tissues
• Exotoxin Production Virulence of V. cholerae
• Exotoxin Choleragen Primary Virulence Factor!
• Produced by bacteria colonizing the intestinal
  tract
• Produces heat-labile enterotoxin, composed of 2
  protein subunits (AB).
• Toxin is bound to intestinal cell receptors by
  Subunit B Subunit A then enters the cell and
  activates AC

41
Vibrios

• Clinical Disease
• Cholera
• Exotoxin Production
• Choleragen stimulates activity of Adenyl
  Cyclase (AC), which converts ATP into cAMP,
  increasing of cAMP
• ATP ? cAMP enz AC
• Increased cAMP stimulates secretion of chloride
  (Cl-) and bicarbonate (HCO3-) ions
• Shedding of electrolytes into the intestine is
  followed by severe H2O loss from epithelial
  cells watery stool
• Acidosis d/t loss of HCO3-
• Dehydration d/t loss of fluids
• Increase in blood viscosity d/t fluid loss
• Shock
• Death d/t rapid dehydration and electrolyte
  imbalance

42
Vibrios

• Clinical Disease
• Cholera
• Symptoms
• Vomiting
• Large amounts of watery diarrhea or secretory
  diarrhea
• rice water stools colorless and odorless,
  flecks of mucus, epithelial cells and large of
  bacteria
• Fluid loss 1 L/hr. !!!
• Secondary Symptoms
• Extreme fluid loss, muscle cramps, severe thirst,
  sunken eyes, apathy and circulatory involvement
  (d/t loss of H20)
• Overall Symptom
• Severe dehydration loss of 50 of body wt.
• Risk groups
• Children, weakened/debilitated (elderly)

43
Vibrios

• Clinical Disease
• Cholera
• Convalescence/Immunity
• Unknown
• Repeat attacks w/ different serotypes possible
• Diagnosis
• Usu. dxed by clinical observation look for
  bacteria in stools
• Stool sample recovery of organisms and growth
  on selective alkaline media
• Direct fluorescent Ab test on stool
• Treatment
• Prompt replacement of water/fluid and electrolyes
• Antibiotics decrease of bacteria present ?
  ?toxin production lessen duration volume of
  diarrhea
• Prevention/Control sewage treatment and H2O
  purification

44
Vibrios

• Clinical Disease
• Gastroenteritis
• Causative agent V. parahaemolyticus pathogen
  carried by seafood highest rate of transmission
  d/t undercooked seafood common in costal sea
  waters (10 NaCl)
• Causative agent V. cholerae (non 01 serotype)
• Mode of Infection
• Ingestion of raw, partially cooked or
  unrefrigerated seafood
• Symptoms
• HA, low-grade fever, watery diarrhea, nausea,
  vomiting, abdominal cramps
• Convalescence/Immunity self-limiting infection
• Prevention/Control cook seafood well proper
  refrigeration during transport storage
• Outbreaks m/c cause of gastroenteritis in Japan

45
Vibrios

• Clinical Diseases
• Cutaneous Infection
• Causative agent V. parahaemolyticus
  V. vulnificus
• Both are marine bacteria Halophilic
• Mode of Infection
• Trauma to body site wound or burn
• Symptoms
• Swelling around wound, localized tiss.
  involvement
• Risk groups
• Occupational risk dock/ship workers, fishermen
• Convalescence/Immunity
• Self-limiting infection
• Treatment
• Antibiotics, possible debridement

46
Yersinia

• Family Enterobacteriaceae
• Genus Yersinia
• Species Yersinia enterolotica enterocolitis
  Yersenia pseudotuberculosis
  Yersenia pestis (etiological agent of bubonic
  plague)
• M/c disease in humans infection w/ Y.
  enterolitica enterocolitis or gastroenteritis
• Bacterium is associated w/ domestic animals
• Transmission to humans via contaminated
  foodstuffs or directly from dogs or swine
• Often transmitted in milk affect on large s of
  people
• Typically found in contaminated H2O food,
  unpasteurized milk

47
Yersinia

• Microscopic Morphological Appearance
• Gram-negative bacilli
• Motile
• No capsule
• Pathogenesis Clinical Significance
• Infection from ingestion of food contaminated
  thru contact w/ domestic animals, or raw meat
  (esp. pork)
• Result ulcerative lesions in ileum of SI,
  necrotic lesions in Peyers patches, and
  enlargement of mesenteric lymph nodes (mesenteric
  adenitis)
• Enterocolitis (Y. enterolitica)
• Characterized by fever, abdominal pain, diarrhea
  (sometimes bloody) and HA resolution 1-3 weeks.
• When accompanied by LRQ pain/tenderness
  leukocytosis clinically indistinguishable from
  appendicitis, leading to unnecessary removal of
  appendices.

48
Yersinia

• Laboratory Identification
• Bacterium obtained from stool sample
• Isolation by selective media
• MacConkey agar
• Cefsulodin-irgasan-novobiocin
• Identification
• Based on biochemical screening there are gt50
  serotypes
• Serological testing anti-Yersinia Abs
• Treatment/Prevention
• Measures to limit contamination of meat proper
  handling preparation
• Antibiotic Therapy to tx systemic involvement
  (Septicemia) ONLY

49
Helicobacter

• Family Enterobacteriaceae
• Genus Helicobacter
• Species Helicobacter pylori causes acute
  gastritis AND peptic ulcers (duodenal gastric)
  unusual ability to colonize the stomach.
• Microscopic Morphological Appearance
• Gram-negative bacilli
• Curved or spiral rods
• Multiple polar flagella rapid corkscrew mobility
• Urease positive production of enzyme urease
• microearophilic

50
Helicobacter

• Epidemiology
• Infections are common w/ worldwide distribution
• Transmission thought to be person-to-person b/c
  there has been no isolation from food or water
• Untreated infections can become
  chronic/life-long
• Pathogenesis (fig. 12.16 p. 125)
• Colonization of gastric mucosal (epithelial)
  cells in stomach also metaplastic gastric
  epithelium of duodenum or esophagus
• Survival in mucous layer that coats epithelium
  causes chronic inflammation attracted to
  chemotactic substances hemin and urea
• Recruitment activation of inflammatory cells
• Release of Urease cleaves Urea (NH2CONH2),
  producing Ammonia (NH3) ions that NUETRALIZE
  stomach acid around the microbe.
• Ammonia and the H. pylori cytotoxin cause
  destruction of mucous-producing gastric cells
  (Goblet cells), exposing the underlying CT to
  stomach acid ? leads to ucleration (ulcer
  formation)

51
Helicobacter

• Clinical
• Initially, acute gastritis w/ possibly diarrhea
  lasts 1 week
• Infection usu. becomes chronic w/ diffuse,
  superficial gastritis epigastric discomfort
• Doudenal Gastric Ulcers linked to infection
  w/ H. pylori
• Complications infection risk factor for
  gastric carcinoma gastric B-cell lymphoma
  (mucosa-associated lymphoid tumor or MALT)

52
Helicobacter

• Laboratory Identification/Dx
• Serologic tests (ELISA for serum antibodies to H.
  pylori) For ELISA discussion, see pp 28-9.
• Breath tests for urease
• Pt takes in radioactively labeled urea by mouth.
  If microbe present, urease will split the urea to
  CO2 (radioactively-labeled and detected upon pt.
  exhalation)
• NH2CONH2 H2O ? 2NH3 CO2
• Gastric biopsy (endoscopy)
• H. pylori detection from gastric specimens
  histological analysis, cultural analysis, test
  for urease
• Treatment/Prevention
• Combination antibiotic therapy (2 or more Rxs)

53
Opportunistic Enteric Bacilli

• All organisms of Family Enterobacteriaceae
• Organisms collectively of low virulence, but are
  opportunistic often nosocomial pathogens
• Often present as normal transient inhabitants of
  intestinal tract of animals humans, primarily
  Large intestine
• Some found in water, sewage and soil
• Representative species belong to genera
  Enterobacter Klebsiella Serratia and Proteus,
  Providencia and Morganella

54
Opportunistic Enteric Bacilli

• Enterobacter spp.
• Motile and Lac
• Cause human disease frequently colonize
  hospitalized pts, esp. in association w/
  antibiotic tx, indwelling catheters, invasive
  procedures.
• Can infect burns, wounds, and RT (causes
  pneumonia) and UT (UTIs)
• 5 clinically important species
• E. cloacae most commonly encountered
• Most frequently isolated form UTIs
• Produces enterotoxins (like E. coli)
• E. aerogenes UTIs
• E. agglomerans
• E. gergoviae
• E. sakazakii neonatal meningitis

55
Opportunistic Enteric Bacilli

• Klebsiealla spp.
• Large, non-motile bacilli, Lac
• Large, mucoid polysaccharide capsule
• Prevents phagocytosis
• Aids in colonization of Respiratory Tract
• Endotoxin Enterotoxin both identified
• 4 clinically important species
• K. pneumoniae m/c member of the genus Primary
  Pneumonia
• K. oxytoca
• K.ozaenae
• K. rhinoscleromatis
• K. pneumoniae K. oxytoca cause necrotizing
  lobar pneumonia in individuals compromised by
  alcoholism, diabetes or COPD.
• K. pneumoniae also causes UTIs and bacteremia
  meningitis

56
Opportunistic Enteric Bacilli

• Serratia spp.
• Motile
• slowly ferment lactose
• Most frequently encountered S. marcescens
• may cause pneumonia, cystitis, UTIs, lower RT
  infections
• Most clinical infections are of urinary tract or
  burns

57
Opportunistic Enteric Bacilli

• Proteus, Providencia and Morganella
• Gram-negative bacilli
• Aerobe/faculatative anaerobe
• closely related members of normal bacterial flora
  of bowel (Commensals of LI)
• Ubiquitous distribution found in water, soil,
  sewage, and intestinal tracts of animals and
  humans
• 2 clinically important species
• P. mirabilis majority of Proteus infections, gt
  90
• P. vulgaris
• In urinary tract causes formation of calculi
  (renal stones), UTI
• Alkalization of urine damages renal epithelium
• Urease production correlates w/ the severity of
  disease
• UTIs both nosocomial and community acquired
• Proteus gt only bacteria the characteristically
  swarms growth of bacteria takes up entire plate