Enteric rods pdf - ...

True bacteria – Rods - Gram Negative Rods

Enteric Rods

Enterobacteriacease,Vibrio, Campylobacter,Helicobacter

Enterobacteriacease

General characters of Enterobacteriacease

(1) Numerous interrelated bacteria flora of intestine (GIT), some of them as normal

flora in the vagina (Klebsiella, Proteus)

(2) G

rods, non spore forming.

(3) Motile with peritrichate flagella, or non motile.
(4) Non acid fast.
(5) Ferment glucose with or without formation of gas.
(6) Nitrates + .
(7) Catalase + .
(8) Oxidase - .
(9) Facultative anaerobes, aerobes.

Classification of Enterobacteriacease

A- Based on action on lactose:- It’s an old method, practical value in diagnostic
bacteriology.

1- Lactose fermenter



e.g. Escherichia coli, Klebsiella,Citrobacter,Enterobacter

2- Late Lactose fermenter



e.g. Shigella sonnei, Serratia

3- Non Lactose fermentation



e.g. Proteus,Salmonella, Shigella , Hafnia

B- Modern taxonomical concept:-classified into tribes, genera and species by their
cultural and biochemical characters. The species are further classified into types,
biotypes, serotypes, bacteriophage type and colicin types. At present there are 5 tribes :

Tribe I: Escherichia

Tribe II:

Klebsielleae

Tribe III: Proteuae

Genus

Klebsiella



Genus

Escherichia



Enterobacter



Proteus



Edwardsiella

Hafina



Citrobacter



Serratia



Salmonella



Shigella



Tribe VI:

Erwinieae

Tribe V: Yersinae

Genus

Yersinia



Erwinia

Escherichia coli

It lives only in human or animal intestine so detection of this genus in drinking

water is taken as evidence of recent pollution with human or animal excretation .

Antigenic structure

There are 4 types of antigens:
1- Somatic antigen (O antigen) = they are heat – stable, divided into 164 groups
designated as 1, 2, 3 ----
2- Surface antigen (K antigen) = they are heat-labile, divided into 3 types:

a. L antigen is destroyed by heating at 100



C for 1hs, and it’s capacity to combine

with antibodies is lost.

b. A antigen is capsular antigen and is heat-stable and is associated with well-

marked capsule.

c. B antigen is destroyed by heating at 100



C for 1hr, and it’s capacity to combine

with antibodies is present.

3-  Flagellar  antigen  (H  antigen)  =  they  are  heat  –  labile,  about  75  types  have  been
described.
4-  Fimbrial  antigen  (F  antigen)  =  they  are  heat  –  labile  and  have  no  significance  in
antigenic classification E. coli.

Toxins

E. coli produces endotoxin, and produces 2 types of exotoxins which are:
a) Enterotoxin which is heat labile and the mode of action is by raising level of cAMP
in the cells, causing excretion of fluid and electrolytes in the lumen of intestine.
The 2 types of E. coli enterotoxin have been:
1- Heat labile toxin LT: is of large molecular weight (80, 000) protein, which gets
inactivated by heating at 60



C for 10 mins and their action through mediaton of cAMP.

2- Heat stable toxin ST: is of low molecular weight (8000 – 8500) protein, which is not
destroyed by heating and their action through mediaton of cGMP (cyclic guanosine
monophosphate).
b) Hemolysin which may be

1- Heat labile and lethal for animals.

Associated with bacterial cell .

Pathogenesis

A-  Gastroenteritis  :  Summer  diarrhea  occurs  in  children  during  second  and  third
summer  of  life  in  non  epidemic  form.  Lactic  acid  produced  from  lactose  fermentation
may cause irritation of the colon result in violent nausea, vomiting and diarrhea. There
are 5 groups of E. coli, which causes diarrhea disease (Figure 2):

1- Enterotoxigenic E. coli also called ETEC: They produce heat labile and heat stable

enterotoxin and thus producing watery diarrhea in children and traveler’s diarrhea.
They posses surface properties called colonization factors which promote their
virulence, and this factors may be pilli or special types of protein K Ag. caused:



Mild or moderately sever childhood diarrhea in developing countries.



Cholera – life syndrome in adults living in areas where cholera is epidemic.



Traveler’s diarrhea in persons from developed country that visits developing
countries.



Outbreaks of diarrhea in newborn nurseries in developed countries.



Outbreaks of diarrhea due to fecal contamination of food and water in developing

countries.

2-Enteropathogenic E. coli also called EPEC: They are carrying B type of surface
(K Ag), caused watery diarrhea in babies less than 18 months old.The  mechanism of
EPEC  is  there  tight  adherence  to  enterocytes  resulting  in  the  loss  of  microvilli  and
cupping of enterocytes membrane to bacteria.

3- Enterohemorrhagic E. coli also called EHEC: there is no fever but haemorrhage is
marked(bloody diarrhea). EHEC produces a cytotoxin, it’s called verotoxin because it’s
effects on Vero cells in tissue culture.
4-Enteroinvasive E. coli also called EIEC: They invade intestinal epithelium like other
dysentery  bacilli  (bloody  diarrhea),and  it  may  be  late  Lac+  or  Lac-  and  may  be
anaerobic. They invasion of Hela cells in tissue culture .
5- Enteroadherent  E. coli also called EAEC: cause watery diarrhea in children and in
patients infected with  HIV.

B- Urinary tract infection (UTI)  Infection may be precipitated by urinary obstruction
due  to  prostatic  enlargement  calculi  and  pregnancy.  Strains  carrying  K  Ag  are
responsible for pyelonephritis while strains form cystitis lack K Ag. UTI causing by  E.
coli  binding  to  epithelial  cells  receptors  by  means  of  adhesion,  such  as  uroepithial
adhesion assay has become one of the important parameters.

C-  Pyogenic  infection:  e.g.  wound  infection,  abscess,  peritonitis,  cholecystitis  and
meningitis. It may cause septicemia.

D-  Neonatal  Meningitis:  is  a  major  cause  of  this  disease  occurring  within  the  first
month  of  life.  The  K

Ag(capsular type, A type) is particularly associated with such

infections.

E. Nosocomial (hospital – acquired) infections: include sepsis, bacteremia, endotoxic
schock and pneumonia.
(The most common causes of neonatal meningitis



Group B Strep. + E. coli + Listeria.

The  most  common  causes  of  neonatal  sepsis  with  or  without  meningitis  →  Group  B
Strep. + E. coli).
F-  Septicemia:  It’s  one  of  the  commonest  causes  of  septicemia,  causes  fever,
hypotension, disseminated intravascular coagulation (endotoxin).Mortality is  high.

Laboratory diagnosis

Haematological investigation: Total leukocytes count → within normal limits ,

but

tissue

invasion=

moderate

leukocytosis.

Differential

leukocyte

count → polymorphonuclear cells in tissue invasion.

Bacteriological investigation: Specimen → in UTI mid steam urine is collected

under aseptic condition examined for pus cell, RBC and bacteria. The count of the
organism should be more than 100000/ml in UTI, it’s called significant bacteriuria.

In acute diarrhea a sample of faces or a rectal swab is collected, pus may be

collected on sterile condition.

Microscopic examination : shows moderate to large numbers of pus cells and G

bacilli, motile and noncapsulated.
   Macroscopic examination : culture in liquid broth → shows uniform turbidity . On
nutrient agar → colonies are circular 1-3 mm in diameter smooth, colourless, entire edge
with butyrous consistency and emulsified easily after 12 hs incubation. On MacConkey
agar  (selective  and  differential  media  for  all  Enterobacteriaceae  )→  colonies  are  pink
due  to  lactose  fermentation.  .  EIEC  strains  often  Lac-  and  may  be  detected  on
MacConkey media ,while EHEC, unlike other strains of E coli, ferment sorbitol slowly
if at all, and may be detected on MacConkey sorbitol agar. On blood agar, some strains
may show



-hemolysis.

Biochemical tests: ferments Lactose, glucose, sucrose, maltose and mannitol

forming acid and gas. IMVC show + + - -, urease - , H

S – and nitrates +.

Serological tests → ELISA, Precipitin test, radioimmunoassay are other useful

tests  to  identity  EPEC  strains.  Treatment  of  faecal  matter  with  fluorescent  –  labeled  O
group antisera is useful for early diagnosis of diarrhea.
           DNA probes for different EPEC forms are quite reliable and useful.
   It  can  survive  for  months  in  soil  and  water,  it  killed  at  60



C in 20 minutes and

chloride(0.5 -1 part/million).

Treatment and Prevention

Treatment by:
(1)maintenance of fluid and electrolyte balance .
(2)antibiotics sensitivity testing is necessary to determine the appropriate choice

of drugs (Figure 1). It’s sensitive to sulfonamides, trimethoprim, tetracyclines,
chloramphenicol and aminoglycosides.

(3) Nitrofurantoin + nalidixic acid may be useful for treating UTI.
(4) In septicemia or serious infection is required to be started treated immediately

without waiting for drug sensitivity tests as gentamicin.

(5)Preparation of vaccine against E.coli colonization factor Ag (CFA) is being

considered( CFAII, IV and I).

Prevention by care in selection, preparation and consumption of food and water.

Klebsiella

It’s found in the mucosa of upper respiratory tract, intestine, and genitourinary tract.

Its G- rod short, thick, large ,non motile , capsulated. It’s growing on ordinary media
forming large mucoid colonies of varying degree of stickiness. They are Lac

MacConkey  agar.  Ferment  carbohydrate  forming  acid  and  gas↑.  IMVC  are  -  -  +  +,
Urease  +.    Most  spps  are  pathogenic  and  classification  depends  on  biochemical
reactions which vary depends on capsular type, like spps below:
Klebsiella pneumonia

It causes labor pneumonia, sinusitis, otitis media, meningitis, and urinary tract

infections and bacteremia particularly in hospitalized patients.

K. pneumoniae and K. oxytoca cause necrotizing labor pneumonia in

individuals compromised by alcoholism, diabetes, or chronic obstructive pulmonary
disease.

Klebsiella ozaenae

It causes foul smelling nasal discharge (ozaena).Other strains cause

granulomatous lesion of nose in Mediterranean countries.
Klebsiella rhinosclermatis

Cause rhinoscleroma disease.

K. erogenes

Usually present in human intestine and isolated from faeces in small number than

E coli, so many survive longer out of intestine.
K. cloasa
It differs from other spps above in motility +, not always capsulated, liquefied
gelatin.

Citrobacter

It occurs as intestinal commensal in man. G-rods, motile, noncapsulated. Lac+,

citrate +, H

S+ . It has been isolated from enteric fever cases, and it cause UTI, gall

bladder infection and meningitis.

Enterobacter

It is G- rods, motile, noncapsulated. Lac+, IMVC are - - + +, gelatin+. It found
in human and animal faces and in soil. They rarely cause disease in humans, but
frequently colonize hospitalized patients especially in association with antibiotic
treatment in dwelling catheters, or invasive procedures. It may infect burns,wounds
and the respiratory tract (causing pneumonia) or urinary tracts.

Serratia

It is G-rods, motile, noncapsulated. Late Lac+. It can cause extraintestinal

infections such as those of the lower respiratory and urinary tracts especially among
hospitalized patients, its opportunistic pathogen. It has been isolated from cases of
meningitis, endocarditis, septicemia and respiratory infection.

Proteus

Antigenic structure

A number of O and H antigen are produced in P. vulgaris .

Pathogenecity

UTI, pyogenic lesions like abscess, wound infection, respiratory tract infections,

diarrhea by P. morgani. P. spps common causes of uncomplicated as well as nosocomial
UTIs. Other extraintestinal infections such as wound infection, pneumonias, and
septicemias are associated with comporomised patients .

Laboratory diagnosis

Hematological investigation → leukocytosis with increase in PMN cells .
Specimens  → urine, pus, sputum … etc
Microscopic  examination  :  G

rods showing great variation in size, actively

motile , non capsulated.

Macroscopic examination : In broth media → shows uniform and moderate

turbidity, powdery deposit and ammonical odor after 18-24 hs.

On MacConkey agar → shows Lac

with fishing or bad odor. On nutrient agar

→ shows swarming motility best seen at 20



C, while P. vulgaris and P. mirabilis

swarm on solid media at 37



C after 12-18hs incubation. Swarming may be due to

progressive surface growth spreading from the edge of parent colony. This phenomena
does not occur on MacConkey agar.

Biochemical reactions of P. spps are:

Glucose

Lactose

Urease

I M V C

P. vulgaris



+ + - +d

P. mirabilis



- + -



P. reltegri



+ + - +

P. morgani



+ + - -

    It  forms  acid  and  gas  from  glucose  (except  P.  reltegri).  Deaminates
phenylalanine  to  phenyl  pyruvic  acid.    urease    +  in  few  minutes.  All  of  the  them
nitrate +, Lactose –, MV are + - , H

S + only in P. vulgaris and P. mirabilis, Indole +

(except
P. mirabilis), Citrate + (except P. morgani),see the table above.

Salmonella

It’s found in intestine (man, animal , bird) and in contaminated food (egg and

meat) .Currently, all strains are grouped in a single spp: S. enterica which including the
clinically significant serotypes S. typhimurium and S. typhi.

Antigentic structure

1- Somatic antigen (O – Ag)



It’s phospholipid protein – polysaccharides complex,

stable by boiling ,alcohol and acid treatment. O - agglutination take place more
slowly, it’s less immunogenic, titer of O antibodies after infection or immunization
is lower than H – Ag.

2- Flagellar antigen (H- Ag)



is heat labile protein, destroyed by boiling, alcohol but

not by formaldehyde, it’s strongly immunogenic. H-Ag occurring in 2 phases:
phase I is specific designated as a, b, c, z, z

…etc

phase II is no specific designated as 1, 2, 3 or complex of e, n and x.

On the basis of somatic antigen (O-Ag), S. can be divided into 65 serogroups, each
group is designated as A, B, C and D .Species among each subgroup are recognized by
specific H-Ag (phases I and II).
3- Surface antigen(Vi antigen)



It’s labile antigen in agglutinable with O antiserum

because agglutinable after boiling or heating at 60



C for 1 h. It’s virulent to mice and

Vi Ab may provide protection, the resistance of Vi Ab indicates carrier state. It’s
present in S.typhi, S.paratyphi and S.dublin, and Citrobacter.

Epidemiology

S. typhi is human pathogen, whereas other strains are associated with animals and

foods  (egg  and  poultry).  Fecal/oral  transmission  occurs  and  may  involve  chronic
carriers. Young children ,elderly and individuals  in crowded institutions are particularly
susceptible to S. infection .

Pathogenesis and clinical significance

Disease may be remain localized or become

systemic  or  disseminated.  S.  invade  epithelial  cells  of  the
small intestine , survive in phagocytic cell (Figure 1) .  S.
infection  can  cause  both  intestinal  and  extraintestinal
disease  (typoidal  Salmonella).  So  it  may  produce  3  types
of  lesion :
1-  Enteric  fever:  it’s  caused  by  S.typi  85%  in  India
S.paratyphi A (15-21%) and S.paratyphi B.
   Infection  is  through  ingestion,  the  bacilli  may  enter
the  body  through  lymphoid  of  pharynx.  In  the  gut,  S.
attached  with  epithelial  cells  of  intestinal  villi  and
penetrate  lamina  proprira  and  submucosa,  they  are
phagocytes  by  PMN  or  macrophages  enter  mesenteric
lymph  nodes  to  multiply  there



enter thoracic duct and



blood stream



bacteremia and S. are seeded in liver,

gall  bladder,  spleen  bone  marrow,  lymph  node,  lung  and
kidneys. In these organs further multiplication occur, there
are bacteremia and shows clinical symptoms.
  Also  S.  invade  tissue  e.g.  Payer’s  patches  and
lymphoid  follicles  of  small  intestine,  the  intestinal  lesion
ulcerates and hemorrhage may occur.

S. produces endotoxin which produces toxic

symptoms  like  headache,  anorexia,  continuous  fever  and
congestion  of  mucus  membrane.  Incubation  period  is  10-
14  days  the  typical  features  are  step  ladder  pyrexia,
palpable  spleen  and  rose  spots  that  fadeon  pressure  and
they appear in 2

– 3

weeks of infection, S.paratyphi A +

S. paratyphi B cause paratyphoid fever resembling enteric
fever.

2- Septicemia



It’s caused by S. cholera suis. It produce chills and spiked fever, local

lesions occur in various parts of the body producing osteomyelitis, pneumonia,
pulmonary abscess and meningitis … etc. The bowel is not invaded and fecal culture
is –ve.
3- Food poising



It by ingestion of contaminated food (e.g. meat and egg), caused by

S. typhimaurium, S. enteritides, S. newports etc … lncubation period is 12-48 hs. There
is fever, vomiting, diarrhea (mucous and blood in stool) there may be ulceration of
intestinal mucosa. There is no bacteremia.

Laboratory diagnosis

Specimens

For diarrhea = stools. For enteric fever = blood, bone marrow, urine,

stool, and tissue from typical rose spots, some cases from CSF.

Hematological investigation : Total leukocytes count in typhoid fever = leucopenia.
Differential leukocytes count = lymphocytosis and monocytosis.

Microscopic examination : G

rod, motile (except S.gallinarum and S.pullorm),

non capsulated, may have fimbriae (Figure 2).

Macroscopic examination : In broth media



shows uniform turbidity ,no

pellicle formation. Selenite F and tetrathionate



these broths are commonly used as

enrichment transport media.

On MacConkey agar (M.A.) and Deoxycholate citrate agar(D.C.A.)



Lac

colourless colonies (Figure 2). On Salmonella Shigella Agar (S.S.A)



colonies with

black center(while Shigella colonies without black center). Bismuth Sulphite
Agar(B.S.A.)



black colonies with metallic sheen dye ( H

S formation may appear in

colonies) S. paratypi A produce green colonies. On Blood agar



large colonies,

circular low convex, translucent, smooth and non – hemolytic (



- hemolytic).

Biochemical reactions: ferments glucose (acid + gas), Lac-, ferments mannitol +

maltose (acid + gas)(except S. typhi, which produce only acid no gas) I M V C



-+ - +

, urease - , H

S+

It’s can survive in ice, snow and water for months together, and resistante to

brilliant green ,malachite green ,bile salts , tetrathionate and selenium salt. It may be
killed by heating at 60



C for 15-20 min, pasteurization, boiling and chlorination.

Macroscopic examination steps :

1- Blood culture



Its + (5-10 ml blood of patient is collected and is transferred into

100 ml brain heart broth bottle then subculture to blood agar and MacConkey agar).

2- Clot culture



Its + (blood clot is cultured in 15 ml bile broth bottle (0.5% bile salt)).

3- Fecal culture



It’s + throughout, repeated cultures are required . It’s more useful in

cases that are on chloramphenicol. Plated on M.A. , D.C.A. and B.S.A.

4- Urine culture



It’s useful than blood and feces culture, it’s + ve in 2

-3

weeks.

Urine is used after centrifuged and sediments are inoculated into enriched and selective
media.

5-  Other  material  =culture  is  +  as  bone  marrow  ,  rose  sposts,  pus  from  lesions,  CSF,
sputum  .  Autopsy  culture  may  be  obtained  from  gall  bladder,  liver,  spleen,  mesenteric
lymph nodes.
6- Bile culture



It’s important for the detection of carriers and later stages of disease,

bile aspirated by duodenal tube is processed like fecal specimen.

Serological  test  :  S.  Abs  appear  at  the  end  of  first  week,  widal  test  is  used  to
measure  H  and  O  Abs  in  the  sera  of  patients.    Typhoid  carrier  may  be  detected  as
follows:

1.  Widal test may show raised Abs titer. 1 / 160 , 1 / 320 , 1 / 640 .
2.  Vi agglutination test is + in a titer of 1/10 or more.
3.  Several stool cultures may help .
4.  Bile culture ,S. may be cultured from bile obtained after duodenal incubation.

Treatment and prevention

Antibiotics like chloramphenicol, flurazolidone, ampicillin trimethoprim

sulfamethoxazole, amoxicillin, cephalosporins, ceftriaxone, fluoroquinolones and
ciprofloxacin are used for enteric fever.

For gastroenteritis in uncompromised hosts, antibiotics therapy is not needed, and

may prolong the convalescent carrier state, which used cholecystectomy as treatment.
Prevention by proper sewage disposal, correct handling of food and good personal
hygiene.

Shigella

Causes shigellosis (basillary dysentery) – a human intestinal disease that occurs

commonly among young children.

Epidemiology

It typically spread from 1 person to person with contaminated stools, serving as a

major source of organism. 2 Flies and contamined food or water . 3 crowding conditions
or poor sanitation ( due to  low infectious dose fewer than 200 viable organisms  ). The
forty  serotypes  of  Shigella  are  organized  into  4  groups    (A,  B,  C,  D)  based  on  their
polysaccharide  O-Ag.  Group  D  (S.  sonnei)  is  the  serogroup  found  most  commonly  in
U.S.

Pathogenesis and clinical significance

It’s invade and destroy the mucosa of the large intestine. Infection rarely

penetrates to deeper layers of the intestine, and does not lead to bacteremia (Figure 1).

An exotoxin with enterotoxic and cytotoxic properties has been isolated from

these organisms, and it’s toxicity may play a secondary role in development of intestinal
lesions.

It’s cause classic dysentery, characterized by bloody diarrhea , mucus and

painful abdominal cramping. The disease is most severe in the very young and elderly
individuals,in whom shigellosis may lead to severe dehydration and some time death.

Laboratory identification

Microscopic examination : G- rod, non motile , noncapsulated(Figure 2) .
Macroscopic examination : Cultured from stools using differential selective media

like  Hektoen  agar  ,  or  media  specific  for  intestinal  pathogens    such  as  MacConkey’s
agar or  Deoxycholate citrate agar ( DCA) on which they form colorless colonies due to
Lac - , only S. sonnei give pale pink colonies which ferment lactose late( Late Lac+)
on both media . On Salmonella Shigella Agar,colorless colonies without black center.
    Biochemical reactions → glucose + acid only , nitrate +, Lac

(except S. sonnei),

I M VC are + + - - (like E coli), H

S -,uerase-, Catalase +, mannitol +.

Treatment and prevention

Antibiotics (ciprofloxacin, azithromycin) can used.

Prevention by

protection of the water and food supply and personal hygiene are

important (Figure 2) .

Hafina

It is also intestinal commensal. G-rods, motile, noncapsulated. Lac- . IMVC are

- - + +.

Note:

Klebsiella , Enterobacter, Proteus , Serratia are opportunistic pathogen,so

sensitivity test necessary to determine the appropriate antibiotics.

VIBRIOS

They are closely related to the family Enterobacteriaceae.

Antigentic structure

O and H Ags are both present, but only O Ags are useful in distinguishing

epidemic cholera. Pathogenic Vibrios include :

(1) V. cholerae, serogroup O1 strains that are associated with epidemic cholera.
(2) non-O

V.cholerae and related strains that cause sporadic cases of cholera-like and

other illness, is resemble to V. cholera in morphologically and biochemically, not
agglutinable with O antiserum of V. cholera .
(3) V. parahaemolyticus and other halophilic vibrios, which cause gasteroenteritis and
extraintestinal infections, also causes food poisoning .

Epidemiology

   V.  choleraeis  transmitted  by  contaminated  water  and  food.  There  are  2  biotypes
(subdivisions) of  V. cholerae spps : classic and El Tor. The El Tor strain, in contrast to
classic  strains,  is  distinguished  by  the  production  of  hemolysin,  higher  carriage  rates,
and the ability to survive in water for long periods.  (see the table below) .

Hemolysis

Chick

erythrocyte

agglutination

Polymyxin

B-sensitivity

Group IV

phage

susceptibility

Classical

cholera

El Tor

Vibro El Tor was the cause of epidemics of V. in south east Asian, and is related to
people with blood group O. Outbreak of both strains have been associated with raw
or undercooked seafood harvested from contaminated waters.

Pathogenesis

Following ingestion, V. cholera infects the small

intestine. Adhesion  factor(s)  are  important  for  colonization
and  virulence.  V.  are  noninvasive  and  causes  disease
through  the  action of  an  enterotoxin  (Figure  3), which  is  a
multimeric protein composed of an A and a B subunit. The
B subunit (consisting of 5 identical monomers) binds to the
receptor  of  cells  lining  the  intestine.  The  A  subunit  has  2
components:  A

, which facilitates penetration of the cell

membrane, and A

, which actives adenylate cyclase

produces elevated levels of cAMP, causes secretion of ions
and water to the lumen of the intestine.

Clinical significance

Cholera is characterized by massive loss of fluid and

electrolytes  from  the  body.  After  an  incubation  period
ranging from hours-few days, show watery diarrhea (rice-
water  stools)  beings.      Untreated,  death  from  severe
dehydration causing hypovolemic shock may occur in hours
to days, and the death rate may exceed 50%.

Non-O1 V. cholera and other non-halophilic Vibrios

causes sporadic cases of cholera indistinguishable from that
caused by V. cholera serotype O1. They also cause milder
illness comparable to that caused by enterotoxigenic E coli
(ETEC).

Laboratory identification

Hematological investigation

It’s not diagnostically significant in early stages.

However, there may be increase in, packed cell volume PCV and Hb.
Specimens  :  stools  is  may  be  collected    immediately  or  if  delay  transport  special
media used  (Venkat Raman  medium, VR)  ,in  this  medium  V. remain viable  for  weeks
but  do  not multiply. In case of rectal swab, trypticase taurocholate tellurite broth (pH
9.2) or alkaline peptone water broth is used.

Microscopic examination : G - rod thin, short, curved comma –shaped , occur

singly or as S-shape semicircular pairs, rapidly motile by a single polar flagellum (this
contrasts with the peritrichous flagella of the motile Enterobacteriacea) noncapsulated .

Macroscopic examination : The growth of many Vibrio strains either requires

or stimulated by NaCl (halophilic bacteria) . On B.A





- hemolytic



then



hemolytic later. Specimen is inoculated in Mansur’s media. Thiosulfate- Citrate-Bile
salts- Sucrose (TCBS) medium can enhance isolation.

Biochemical reactions : Lac - Oxidase +, nitrate +, glucose, sucrose, mannose,

arabinose + acid only . Indole +, gelatin +, Urease - .

Cholera red reaction



+ (adding H

to culture of V. cholera in peptone

water broth



red pink colour due to formation of nitrosoindole) .

Serological investigation : it’s little useful as slide agglutination with O group .

Treatment and prevention:

  1    Patients  with  suspected  cholera  need  to  be  treated  prior  to  laboratory
confirmation because death can occur within hours.
   2 Replacement of fluids and electrolytes  in preventing shock.
   3 Antibiotics as doxycycline, tetracycline (figure 4).

Prevention needs good personal hygiene + good cooking of foods + Vaccine E1

Tor type vaccine offers protection about 90-100% lasts for 3 years.

Campylobacter

It is a zoonosis disease (animal→human) ,was known by Vibrio fetus discussed

with Vibrios ,but recently differently (its Guanin≡Cytocin ratio lower than Vibro) led to

new group named Campylobacter (GC ratio 30-35% while Vibro 40-53%). Many strains

like C. jejuni, C.fetus, C.coli.

Epidemiology

C. is as commensals of many different vertebrate spps, including mammals and

fowl, both wild and domestic, serve as reservoirs of infection. C. is transmitted to

humans by:1-The fecal/oral route through direct contact.

2-Exposure to contaminated meat (poultry).

3-Contaminated water supplies.

Pathogenesis and clinical significance

Its infect the intestine and can cause ulcerative,

inflammatory lesions in the jejunum, ileum or colon

produce heat-labile exotoxin .So may cause both

intestinal and extraintestinal disease. C.jejuni cause:

1.Acute enteritis following 1-7 days incubation

(figure 1), lasts days to several weeks and generally is

self-limiting. Symptoms may be both systemic (fever,

headache, myalgia) + intestinal (abdominal cramping,

diarrhea may or may not be bloody).

2.Travelers diarrhea.

3. Pseudoappendicitis (appendicitis without

inflammation).

Fig 1 Forms of f bacterial food poisoning.

4.Bacterima in infants and the elderly (in host compromise). Complication include:

septic abortion, reactive arthritis, Guillain-Barre syndrome.

C. fetus cause endovascular infection and C. N. S. infection.

Laboratory identification

Specimens : feces using selective media and microaerophilic conditions. Because

of their small size, they are not retained by bacteriologic filters that hold back other

bacteria, so filtration of the fecal suspension may enhance recovery rate.

Microscopic examination : G- rod, curved spiral or S-shaped organisms

resemble vibrios, but it does not requires NACL in their growth . Its motile with a

single polar flagellum provides the organism with its characteristic darting motility.

Macroscopic examination : microaerophilic (require lower concentrations of

), use a respiratory pathway and do not ferment carbohydrates they require 3-6%

, 10% Co

hydrogen and nitrogen, need differential media like blood agar containing

antibiotics to inhibit growth of other fecal flora (like vancomycin, trimethoprim,

cycloheximde, polymyxin B) → γ-hemolysis.

Biochemical tests : H2S +, DNA hydrolysis to differentiate spps, hypopiruate

hydrolysis, oxidase +, catalase±, nitrate+, urease-.

Serological tests : Somatic, flagellar and capsular antigens all contribute to the

numerous serotype. Serotyping with O Ag by Indirect hemagglutination test , Cell wall

composition and Phage typing (bacteriocin typing).

Treatment and prevention

Using electrolyte and fluid replacement for diarrhea. For severe symptoms (high

fever, bloody diarrhea) antibiotics should be administered (figure 2). For C.jejuni

ciprofloxacin or erythromycin is used. For C.fetus ampicillin or third generation

cephalosporin for 4 weeks in C.N.S infection and for endovascular infection requires 4

weeks treatment with gentamycin.

Prevention by cooking of contaminated foods (poultry) + pasteurization of milk

and milk products is essential + surfaces used to prepare raw meat or poultry should be

disinfected before using them for uncooked foods, such as salads.

Helicobacter

Previously known by Campylobacter pylori ,recently it has been excluded from

C.geneus and has been renamed H.pyloridis because of these characters:

1- Bears multiple unipolar flagella,as corkscrew motion.

2- Produce large quantity of urease.

3- Has smooth cell surface.

4- Cell wall fatty acid composition

5- rRNA sequencing and DNA base composition is differ

Figure 2 Summary of Campylobacter disease.

Toxins and enzymes production

Toxins and enzymes produced by H. may account for mucosal injury in absence

of actual bacterial invasion, are:

1- Protease with endopeptiase causing degradation of gastric mucin.

2- Cytotoxin factor causing intracellular vaculation.

3- Urease production responsible for metabolism of urea to ammonia and CO

,causing gastric mucosal damage. This ammonia produced may →:

A. Directly toxic to epithelial cells (see figure 4).

B. Indirectly cause tissue injury by allowing hydrogen ion back diffusion.

Pathogenesis

H. spps are unusual in their ability to colonize the stomach where low ph

normally protects against bacterial infection.

Transmission of H. pylori is thought to be from person to person, the H. has not

been isolated from food or water. Untreated infections tend to be chronic, even

lifelong.

Figure 3

Summary of Helicobacter disease.

It colonize gastric mucosal (epithelial) cells in the stomach and metaplastic gastric

epithelium in the duodenum or esophagus but does not colonize the rest of the intestinal

epithelium. It survives in the mucosa layer causes chronic inflammation of the mucosa

(figure 4), its noninvasive, recruits and actives inflammatory cells. Urease released by

H. pylori→ NH3 that

(1)

neutralize stomach acid in the vicinity of H.→ Multiplication

of H.

(2)

both cause injury and potentiate the effects of a cytotoxic produced by H.→

destruction of mucous-producing cells, exposing underlying connective tissue to

stomach acid→ ulceration.

Clinical significance

Initial infection with H. pylori causes acute gastric, sometime with diarrhea lasts

about 1 week, then become chronic, with diffuse, superficial gastritis associated with

epigastric discomfort. Both duodenal ulcers and gastric ulcers are closely correlated

with infection by H. pylori (in 95% of duodenal ulcer + in all patients with gastric

ulcers, who do not use aspirin or other nonsteroidal antiflammatory drugs,both a risk

factors for gastric ulcers). H. pylori infection appears to be a risk factor for development

of gastric carcinoma and gastric bacteria-cell lymphoma [mucosa-associated

lymphoid tumors (MALTmas)].

Figure 4 Helicobacter pylori infection, resulting in ulceration of the stomach

Laboratory Identification

A-Noninvasive diagnostic tests include :

1- Serologic tests→ ELISA for serum Abs to H. pylori.

2- Breath tests for urease→ administering radioactively label urea by mouth, if H.

present in patients stomach the urease produced split the urea→

+Co

↑(radioactively labeled and exhaled).

B-Invasive diagnostic tests include:

Gastric biopsy specimens by endoscopy, also to detect H. histologically.

bacteriologically. Microscopic examination : G- curved or spiral rods (figure 3),

corkscrew motility resulting from multiple polar flagella.

Macroscopic examination : microaerophilic (10% Co

), need addition of blood

or other animal fluids to better growth. On blood agar → 36hr incubation show fine

colonies reaching maximum size in 2-4 days, colonies circular, cloudy, glistening with

entirc edge, butyrous consistency, slightly bluish greytinge. Selective media → Brewer’s

sodium thioglycolate, Skirrow’s medium, Butzler medium, and Smibert medium.

Biochemical tests →urease+, alkaline phosphates+, catalase+.

Treatment and prevention

Combination therapy with 2 or more antibiotics such as amoxicillin +

clarithromycin + omeprazole (a proton pump inhibitor) (figure 3).