Medical MicrobiologyMedical Microbiology

Systemic BacteriologyG-ve BacilliG-ve Bacilli

EnterobacteriaceaeEnterobacteriaceae

Lecture-12Dr. Saleh M Y OTHDr. Saleh M Y OTH

PhDPhDMedical Molecular Biotechnology and Infectious DiseasesMedical Molecular Biotechnology and Infectious Diseases

12/11/201012/11/2010MBBS-Phase II-IMS - MSUMBBS-Phase II-IMS - MSU

Eschericchia Klebsiella EnterobacterCitrobacter

Salemonella Shigella ProteusYersinia

LF = Coliforms

Opportunistic

Non-LFPathogenic

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

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

Klebsiella speciesDiseases 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

Klebsiella speciesDiseases 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.

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

Diseases caused by

Enterobacter species

Causes urinary tract

infections and sepsis

Citrobacter species

- Citrobacter freundii associated with nosocomial infections (UTI, pneumonias, and intraabdominal abscesses)

- Ferments lactose and hydrolyzes urea slowly

- Resembles Salmonella sp.

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)

Salmonella (cont’d)

Salmonella on MacConkey

- 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

- 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)

- 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)

- 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)

- 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)

- 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)

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.

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)

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)

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)

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)

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 TestAbs appear in the srum of the patient during the second week of illness and reach maximum titre during the 4th week.

Salmonella (cont’d)

Diagnosis of Enteric Fever:

3- Serological Diagnosis: Widal TestAbs 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)