Star Team

Blog 2

MMIC: Case 2
Name: Kwan Siew Yan
Sex: Female
I/C No: S000123X
HRN: OPD001
Age:29 years
Ward/Clinic: Clinic X

Clinical Diagnosis
Complaints: Diarrhea
Diagnosis: Enterocolitis
Antibotic Treatment (if any): Nil

Enterocolitis
Enterocolitis is the inflammation of the large and small intestines. The most common symptom of enterocolitis is diarrhea.

Causative Agents

The most common way a person can get enterocolitis is by infection. Infection includes Bacteria, Virus and Parasites. Below are the identified causative agents that can cause enterocolitis.

Bacteria

Campylobacter jejuni
Salmonella species
Shigella species
Escherichia coli
Vibrio cholerae
Vibrio parahaemolyticus
Clostridium perfringens
Clostridium difficile

Virus

Rotavirus
Norovirus

Parasites

Giardia lamblia/ Giardia intestinalis

Biochemical Tests

Since this PBL is on bacterial pathology I’ll only be discussing the biochemical properties of the microorganisms from the bacteria group.



Campylobacter jejuni
Domestic animals such as cattle, chickens and dogs serve as a source of the organisms for humans. Food and water contamination with infected animal feces is the major source of human infection.
· Laboratory Diagnosis
o Gram Negative Rod
o Motile
o Non-lactose fermenter
o Microaerophilic
o Incubation at 42°c
o Oxidase positive
o Catalase positive
o Hippurate positive
o TSI shows no H2S production
o Urease negative
o Culture on Charcoal based selective medium
o Methylene blue stain of a fecal sample
· Antibiotic Treatment
o Erythromycin
o Ciprofloxacin

Salmonella species
Humans and animals serve as reservoirs for the bacteria.
The ingestion of food and water contaminated by human and animal waste is the main mode of transmission.
· Laboratory Diagnosis
o Gram Negative Rods
o Non-Lactose Fermenting colonies on MacConkey’s agar or EMB agar
o Motile
o Facultative Anaerobe
o TSI shows alkaline slunt but acid butt with both gas and H2S produced
o Catalase positive
o Oxidase negative
o Urease negative
o Indole test negative
o Methyl Red Positive
o Voges-proskauer negative
o Citrate positive
o Lysine decarboxylase positive
o Ornithine decarboxylase positive
o Slide agglutination Test
o Commonly grown on Xylose Lysine Deoxycholate (XLD) agar
o Serological test such as widal test can be used
o Methylene Blue stain of fecal sample


· Antibiotic Treatment
o Antibiotic treatment is usually not prescribed, as salmonella is a self limiting disease that resolves without treatment
http://www.bact.wisc.edu> the microbial world> salmonella

www.yahoo.com> escherichia coli on blood agar> http://www.visualsunlimited.com/browse/vu303/vu303820.html

www.yahoo.com> escherichia coli on MacConkey's agar> http://www.visualsunlimited.com/browse/vu416/vu416843.html

Vibrio cholerae
Vibrio Cholerae is transmitted by fecal contamination of water and food, primarily from human sources.
· Laboratory Diagnosis
o Gram Negative Rod
o Motile
o Non lactose fermenting colonies form on MacConkey’s agar
o Facultative anaerobe
o Urease negative
o Oxidase Positive
o Lysine decarboxylase positive
o Ornithine decarboxylase positive
o Methyl Red positive/negative (depending on strain)
o Voges-proskauer positive/negative (depending on strain)
o TSI shows acid slant and acid butt without gas or H2S
o A retrospective diagnosis can be made serologically by detecting a rise in antibody titer in acute and convalescent-phase sera.
· Antibiotic Treatment
o Antibiotics are not necessary, as treatment usually consists of replacement of water and electrolytes.
o Antibiotics such as tetracyclines shorten the duration of symptoms and reduce the time of excretion of the organisms.

Vibrio parahaemolyticus
· Laboratory Diagnosis
o Gram Negative Rod
o Motile
o Beta-hemolysis colonies observed when cultured on blood agar plates
o Non-lactose fermenting colonies form on MacConkey’s agar
o Facultative anaerobe
o Urease negative
o Oxidase Positive
o Lysine decarboxylase positive
o Ornithine decarboxylase positive
o Methyl red negative
o Voges-proskauer negative
o TSI shows acid slant and acid butt without gas or H2S
o A retrospective diagnosis can be made serologically by detecting a rise in antibody titer in acute and convalescent-phase sera.
o Differentiated from V.Cholerae on the basis of growth in Sodium Chloride V.Parahaemolyticus grows in 8% sodium chloride while V.Cholerae does not
· Antibiotic Treatment
o Antibiotics are not necessary, as treatment usually consists of replacement of water and electrolytes.
o Antibiotics such as tetracyclines shorten the duration of symptoms and reduce the time of excretion of the organisms.

Clostridium perfringens
Spores located in soil can contaminate food. The heat resistant spores survive cooking and germinate. The organisms grow to large numbers in reheated food, especially meat dishes.
· Laboratory Diagnosis
o Gram Positive Rod
o Endospore-forming
o Anaerobic
o Spore staining positive ( Bartholomew and Mittwer)
o Nagler test
· Antibiotic Treatment
o Self-limiting disease
o Symptomatic treatment is given, no antimicrobial drugs are administered

Clostridim difficile
Normal flora in the intestines, that can become opportunistic pathogens in patients treated with broad-spectrum antibiotics such as penicillin and cephalosporin. The most common nosocomial cause of diarrhea.
· Laboratory Diagnosis
o Gram positive Rod
o Motile
o Anaerobic
o Endospore forming
o Spore staining positive (Bartholomew and Mittwer’s)
o ELISA testing
o Cytotoxicity testing
· Antibiotic Treatment
o Causative antibiotic should be withdrawn
o Metronidazole
o Vancomycin




Identification of Microorganism

Culture on Blood agar in anaerobic conditions

Microorganisms that grow in anaerobic conditions: Salmonella species, Shigella species, , Escherichia coli, Vibrio cholerae, Vibrio parahaemolyticus, Clostridium perfringens, Clostridium difficile

Microorganisms that do not grow in anaerobic conditions: Campylobacter jejuni,(microaerophilic)

Anaerobic Microorganisms

Perform Gram stain and observe under microscope: to differentiate gram positive and gram negative bacteria

Gram Negative Microorganisms: Salmonella species, Shigella species, Escherichia coli, Vibrio cholerae, Vibrio parahaemolyticus

Gram Positive Microorganisms: Clostridium perfringens, Clostridium difficile

Gram Negative Microorganism

Perform Wet mount: To differentiate motile and non-motile organisms

Motile: Salmonella species, Escherichia coli, Vibrio cholerae
Vibrio parahaemolyticus

Non-Motile: Shigella species


Motile Microrganisms

Culture on MacConkey's/ Eosin-Methylene Blue (EMB) agar:
To differentiate between lactose and non-lactose fermenting microorganisms

Lactose Fermenters: Escherichia coli

Non-Lactose Fermenters: Salmonella species, Vibrio cholerae
Vibrio parahaemolyticus

Non-Lactose Fermenting Microorganisms

Perform Oxidase Test: To differentiate between microorganisms containing the enzyme cytochrome oxidase and microorganisms that do not contain the enzyme.

Oxidase Positive: Vibrio cholerae, Vibrio parahaemolyticus

Oxidase Negative: Salmonella species

To differentiate between Vibrio cholerae and Vibrio parahaemolyticus, culture the microorganism into a 8% sodium choloride broth. Vibrio Parahaemolyticus can grow in 8% sodium chloride but Vibrio Cholerae cannot.

Gram Positive Microorganisms
Since the patient is not on any antibiotic treatment, we can rule out Clostridium difficile, as it is a nosocomial cause of diarrhea. Therefore if the microorganism is observed to be gram positive, a spore stain can be done to confirm that it is Clostridium perfringen

# posted by Star team @ 4:34 PM