1) Klebsiella species are normal inhabitants of the intestines and respiratory tract. K. pneumoniae commonly causes pneumonia, wound infections, and UTIs through hospital-acquired transmission. 2) Salmonella species can cause typhoid fever through consumption of contaminated food/water as well as acute gastroenteritis. Diagnosis involves blood/stool/urine culture early in infection or serological tests like the Widal test later. 3) Enterobacter species normally inhabit the intestines and can cause wound infections, UTIs and sepsis through hospital-acquired transmission in debilitated patients.

1. Medical MicrobiologyMedical Microbiology
Systemic Bacteriology
G-ve BacilliG-ve Bacilli
EnterobacteriaceaeEnterobacteriaceae
Lecture-12
Dr. Saleh M Y OTHDr. Saleh M Y OTH
PhDPhD
Medical Molecular Biotechnology and Infectious DiseasesMedical Molecular Biotechnology and Infectious Diseases
12/11/201012/11/2010
MBBS-Phase II-IMS - MSUMBBS-Phase II-IMS - MSU

2. Eschericchia
Klebsiella
Enterobacter
Citrobacter
Salemonella
Shigella
Proteus
Yersinia
LF = Coliforms
Opportunistic
Non-LF
Pathogenic

3. Klebsiella, Enterobacter, Serratia
& Hafnia sp.
- Usually found in intestinal tract
- Wide variety of infections, primarily pneumonia, wound, and
UTI
- General characteristics:
- Some species are non-motile
- Simmons citrate positive
- H2S negative
- Phenylalanine deaminase negative
- Some weakly urease positive
- MR negative;
- VP positive
- Indole -ve

4. Klebsiella species
- Normaly are inhabitnts of the intistine and
respiratory tract.
- They saprophytes in the soil and water.
- Some couse diseases in Humans.
** K. pneumoniae is mostly commonly isolated species
* Possesses a polysaccharide capsule, which protects against
phagocytosis and antibiotics AND makes the colonies moist
and mucoid due to the production of abundant extracellular
slime.
* Has a distinctive “yeasty” odor
* Frequent cause of nosocomial pneumonia

5. Klebsiella species
Diseases caused by K. species
1- K. pneumoniae: (Freidlander’s bacillus)
* Cuases lobar pneumonia an can produce extensive
hemorrhagic necrotizing consolidation of the lung.
* It occasionally produces urinary tract infection and
bacteremia with focal lesions in debilitated patients.
* Cause hospitla-aquired infections.
* It is highly pathogenic to mice nad cuase their death
withen 24-48hs /when we inject the bacterial cells IP

6. Klebsiella species
Diseases caused by K. species
2- K. oxytoca:
* cause hospital-acquired infections
Two other klebsiellae are associated with
inflammatory conditions of the upper respiratory tract
3- K. ozaenae : progressive atrophy of mucous membranes of
the uper RT.
4- K. rhinoscleromatis : from rhinoscleroma, a destructive
granulomatous lessions in the nose and throat.

7. Enterobacter species
- Comprised of 12 species; E. cloacae and E.
aerogenes are most common
- Isolated from wounds, urine, blood and CSF
- Major characteristics
* Colonies resemble Klebsiella
* Motile
* MR negative; VP positive

8. Diseases caused by
Enterobacter species
Causes urinary tract
infections and sepsis

9. Citrobacter species
- Citrobacter freundii associated with
nosocomial infections (UTI, pneumonias, and
intraabdominal abscesses)
- Ferments lactose and hydrolyzes urea slowly
- Resembles Salmonella sp.

10. Salmonella
- Produce significant infections in humans and
certain animals
- On differential selective agar, produces clear,
colorless, non-LF pale-colonies with black
centers (if media contains indicator for
hydrogen sulfide)

11. Salmonella (cont’d)
Salmonella on MacConkey

12. - Lactose negative
- Negative for indole, VP, phenylalanine
deaminase, and urease
- Most produce H2S
- Do not grow in potassium cyanide
- Large and complex group of organisms;
grouped by O, H, and Vi (for virulence)
antigens
Salmonella (cont’d)
Biochemical activities

13. - There are more than 2200 serotypes
- Only 4 that can cause diseases:
- S. typhi, S. paratyphi A, B and C causes
enteric fever in Humans.
- S. typhimurium and S. enteritidis cause food
poisoning or enterocolitis
Salmonella (cont’d)

14. - Clinical Infections
* Acute gastroenteritis or food poisoning
+ Source = handling pets, insufficiently cooked eggs and chicken,
and contaminated cooking utensils
+ Occurs 8 to 36 hours after ingestion
+ Requires a high microbial load for infection
+ Self-limiting in health individuals (antibiotics and antidiarrheal
agents may prolong symptoms)
Salmonella (cont’d)

15. - Typhoid and Other Enteric Fevers
* Prolonged fever
* Bacteremia
* Involvement of the RE system, particularly
liver, spleen, intestines, and mesentery
* Dissemination to multiple organs
* Occurs more often in tropical and subtropical
countries
Salmonella (cont’d)

16. - Salmonella Bacteremia
- Carrier State
* Organisms shed in feces
* Gallbladder is the site of organisms (removal of
gallbladder may be the only solution to carrier state)
Salmonella (cont’d)

17. - Salmonella Serotypes
* Possess O and H antigens
* There is some sharing of the O Ag between S. typhi and
S. paratyphi A, B and C
* Some possess a surface Vi or virulence antigen wich
frequently interferes with agglutination of S. typhi by
anti-O antisera
* Certain salmonella serotypes can be subdivided into
phage-types or biotypes for epidemiologicall purposes.
Salmonella (cont’d)

18. Diseaes caued by Salmonella:
* Enteric fever (S. typhi and S. paratyphi A,B and C)
* Enterocolitis (food poisoning)
* Bacteraemia with focal lessions; osteomylitis, pnemonia
and meningitis
Salmonella (cont’d)
The source of infection is the stool or urine of cases or
carriers.
The organisms enter the body by oral route in
contaminated food or drinks e.g; raw vegetables, fruits,
raw shell fish and milk products.

19. After ingestion, the organisms multiply in Peyer’s
patches then it passes through the lymphatics to the
blood steam causing bacteraemia that prsists for one
week.
Then disseminate to the kidney and is excrted in urine.
It disseminated also to the liver and excerted in bile to
reach the intestine.
Salmonella (cont’d)

20. It may rarely reach the periosteum, lungs or meninges.
Manifestations:
The symptoms appear after an incubation period of 2 weeks in
the form of fever, malaise, headache, delirium, tender abdomen,
constipation with enlargement of the spleen.
Rose spots may appear on the abdomen.
Salmonella (cont’d)

21. The complications:
Complications of typhoid fever such as intistinal haemorrhage
and perforation nowadays reduced due to proper antibiotics.
Carriers:
After recovery, some individuals continue to harbour salmonella
in their tissues as convalescent or chronic carriers.
They carry the organisms in the gall bladder or UT that excerete
in the stools or urine. These individuals should not work as food
handlers.
Salmonella (cont’d)

22. Diagnosis of Enteric Fever:
Depends on the stage of the disease and can be accomplished by :
a- Isolation of the organisms from blood,
urine and stool.
b- Serologically by detecting of the
antibodies in the serum of the patient.
1- During the first week:
Isolation from blood because the organisms are found in the
blood during 1st
week.
It is to be noted that the organisms disappear from the blood shortly after
chloramphicol therapy.
Salmonella (cont’d)

23. Diagnosis of Enteric Fever:
2- During the second week and onward:
Isolation from the stool or urine, and repeated stool
exam should be attempted.
3- Serological Diagnosis: Widal Test
Abs appear in the srum of the patient during the second week of
illness and reach maximum titre during the 4th
week.
Salmonella (cont’d)

24. Diagnosis of Enteric Fever:
3- Serological Diagnosis: Widal Test
Abs appear in the srum of the patient during the second week of
illness and reach maximum titre during the 4th
week.
Serial dilutions of the patient’s serum (1/20, 1/40/, 1/80, 1/160
..etc) are made in five sets of test tubes
Prophylaxis
Treatment
Salmonella (cont’d)