GIS Microbiology Practicals Flashcards
(33 cards)
Antibiotic for Campylobacter gastroenteritis
Macrolides (azithromycin / clarithromycin)
X quinolones (resistance)
Management of Campylobacter gastroenteritis
Fluid and electrolyte replacement
Antibiotics
Specimen for investigation of suspected Campylobacter gastroenteritis
Stool -> culture
List three culture media to investigate Campylobacterosis and describe the appearance of the organism
MacConkey agar: pink non-mucoid (lactose fermenters e.g. E. coli, Klebsiella)
XLD agar: yellow mucoid
Charcoal cefoperazone deoxycholate agar (CCDA) incubated in microaerophilic environment: grey-whitish mucoid (growth suppressed)
Appearance of Campylobacter under Gram stain
Gram-negative curved bacilli
Gas generator to create microaerophilic environment
Is water / catalyst / hydrogen needed?
CampyGen (pump gas into vacuum)
No
VS AnaeroGen (obligate anaerobes)
Campylobacter can be transmitted via … hence it is classified as …
Poultry
Zoonosis
Antibiotic for typhoid and paratyphoid fever
Third generation cephalosporins (ceftriaxone, cefotaxime)
Fluoroquinolones (ciprofloxacin, levofloxacin)
Azithromycin
Diagnostics for typhoid and paratyphoid fever
Culture: blood, stool, (rectal swab, urine, BM)
Serology: Widal’s test, Antigen detection tests (immunochromatographic)
A 24 years old lady returned to Hong Kong after visiting her friends in India. She
then developed fever for one week with headache and malaise, and the fever did
not respond to three days of oral cefuroxime prescribed by a general practitioner.
She had mild diarrhoea and abdominal discomfort lasting a few days initially.
Physical examination revealed an enlarged liver and spleen and faint, pink
macules over the trunk.
What possibilities should be considered?
Typhoid fever
Malaria (no skin rash)
A 24 years old lady returned to Hong Kong after visiting her friends in India. She
then developed fever for one week with headache and malaise, and the fever did
not respond to three days of oral cefuroxime prescribed by a general practitioner.
She had mild diarrhoea and abdominal discomfort lasting a few days initially.
Physical examination revealed an enlarged liver and spleen and faint, pink
macules over the trunk.
List the most important clinical manifestations.
Rose’s spots
Hepatosplenomegaly
Gram stain appearance and oxygen requirement of Salmonella typhi
GNB
Facultative anaerobe
Purpose of Widal’s test
Differentiate between Salmonella typhi & paratyphi A/B/C
Laboratory investigations for foodborne outbreaks e.g. C. jejuni gastroenteritis, sampling from which sources?
Patients, food handlers
Food, environment
Principle of Widal’s test
Each tube: same volume & amount of Salmonella antigen (TO / TH / AH / BH / CH)
-> serial dilution of patient’s serum
-> incubation
-> positive = visible agglutination / clumping (Ab-Ag)
-> antibody titre = highest serum dilution that gives visible agglutination
-> four-fold increase = diagnostic
Point-of-care testing for Salmonella enterica serotype Typhi
IgM/IgG detection
Route of transmission of typhoid / paratyphoid fever
Faecal-oral route / Foodborne (food handler) / Waterborne
A 58 years old lady was recently admitted to the hospital for antibiotic treatment
of acute exacerbation of chronic obstructive pulmonary disease. Sputum culture
grew Haemophilus influenzae. She was given amoxicillin-clavulanate with
symptomatic improvement. However, she developed a fever of 38.5°C three days
after discontinuation of the antibiotic, with lower abdominal pain and frequent,
bloody diarrhoea.
Gram stain of isolate from CHROMID C. difficile agar showed Gram-positive anaerobic spore-forming bacilli.
Colonoscopy showed bleeding at sigmoid colon, mucosal inflammation and diffuse yellowish pseudomembranous plaques.
What are the clinical and aetiological diagnosis?
Antibiotic-associated diarrhoea with pseudomembranous colitis
C. difficile produces toxins. What investigation?
Nucleic acid amplification test for toxin gene
Enzyme immunoassay (GDH antigen, Toxins A&B)
An 80 years old man was admitted for fever and right sided abdominal pain for 5
days. He had a history of poorly controlled diabetes mellitus, hypertension,
coronary artery disease, and chronic kidney disease. There was no known history
of biliary tract diseases. On examination, his body temperature was 38.6ºC, and
there was right upper quadrant tenderness. Blood results showed a WBC count of
18.6 × 109/L, and elevated alkaline phosphatase and alanine transaminase. Blood
culture was taken and a contrast CT scan of the abdomen was performed.
Contrast CT shows hypodense lesion in liver.
Blood culture shows non-haemolytic greyish white mucoid colonies.
MacConkey agar shows pink mucoid colonies.
What is the most likely clinical diagnosis?
Pyogenic liver abscess caused by Klebsiella pneumoniae
Disseminated infections
Failure of collection of stool sample for a patient with suspected typhoid fever due to constipation. Alternative sample?
Rectal swab
Components of viral transport medium
Antibacterial
Antifungal
pH indicator
Components of MacConkey agar
Lactose
Sodium deoxycholate
pH indicator
Both commensal and 0157:H7 E. coli form pink colonies on MacConkey agar. What agar to use to distinguish them?
Sorbitol MacConkey agar
Commensal E. coli: pink
O157:H7 E. coli: yellow
