for undergraduate and post graduate students Pyrexia of unknown origin

1. Dr. Abhijeet Mane

2. Introduction and History
• Genus Brucella consists of very small, non
motile, aerobic, GNCB
• Zoonosis. Primarily affecting goats, sheep,
cattle, buffaloes, pigs
• Also known as Mediterranean fever, Malta
fever, undulant fever
• Named after British Doctor, David Bruce
• Species causing human infections – melitensis,
abortus, suis

3. David Bruce

4. Morphology
• Coccobacilli or short
rods, 0.5-0.7 x 0.6-
1.5um in size, arranged
singly or short chains
• Maybe mistaken for
cocci
• Non motile, non
capsulated, non sporing
• Gram negative and non
acid fast

5. Cultural characteristics
• Strict aerobes
• B.abortus is capnophilic, 5-10% CO2
• Optimum temp. – 37 deg C, pH – 6.6-7.4
• Simple media – growth is slow
• Serum dextrose agar, serum potato infusion
agar, trypticase soy agar, tryptose agar

6. • Selective – addition of bacitracin, polymyxin,
cycloheximide
• Liquid media – growth uniform
• Solid media – colonies small, moist,
translucent, glistening. Mucoid, smooth and
rough types of colonies appear
• Erythritol – stimulating effect

7. Biochemical reactions
• Carbohydrates not fermented
• Catalase positive, oxidase positive

8. Urease
positive

9. • Nitrates reduced to nitrites
• Citrate not utilized
• Indole not produced
• MR and VP negative

10. Resistance
• Killed by Pasteurization
• Remain viable in refrigerated milk for 10 days,
1 month – ice cream, 4 months – butter, many
weeks - meat

11. Antigenic structure
• Somatic antigen determinants – A and M
• Present in various amounts in 3 major species
• Antigenic cross reaction exist between
brucellae and vibrio cholerae

12. Classification
• Classified into different species based on CO2
requirement, H2S production, sensitivity to
dyes, agglutination by monospecific sera,
phage lysis
• B.melitensis
• B.abortus
• B.suis

14. Bacteriophage
• Tblisi (Tb) phage designated as reference
phage
• Routine test dilution lyses only B.abortus
• B.suis – lysed at 10000 RTD
• B.melitensis – not lysed at all

15. Pathogenicity
• All 3 major species of Brucellae are pathogenic
to human beings
• B.melitensis – most pathogenic
• Primarily intracellular pathogen affecting RE
system
• LPS component of cell wall - virulence factor
• Organisms from infected animal enter human
body (thru wound, conjunctiva, inhalation,
ingestion)

16. • Incubation Period :– 10 – 30 days
• Organisms spread from site of infection thru
lymphatic channels to local lymph glands
• Then spill over in blood stream
• Disseminated through out the body
• Predilection for placenta, due to erythritol,
stimulates brucellae
• Fever, sweats and extreme fatigue - in 2-4 weeks

17. • Human infection maybe of 3 types:
• Latent infection with serological but no clinical
evidence
• Acute or sub acute brucellosis
• Chronic brucellosis

18. • Acute brucellosis
• Mostly due to B.melitensis
• Known as undulant fever, maybe misleading
• Associated with prolonged bacteremia and
irregular fever
• Symptoms – muscular pains, asthamatic attacks,
nocturnal drenching sweats, exhaustion,
anorexia, constipation, nervous irritability, chills
• Complications – articular, osseous, visceral or
neurological

19. • Chronic Brucellosis
• Maybe non bacteremic, low grade infection
• Symptoms generally related to state of
hypersensitivity in the patient
• CF – sweating, lassitude, joint pain, with
minimal or no pyrexia
• Illness lasts for years

20. • Immunity
• Mainly CMI
• Activated macrophages can kill bacteria
• Th1 type T helper cell response and CMI required
• TNF alpha and gamma & IL 1 and 12 important
mediators of protective response
• Tissue reaction - granuloma formation with EC,
giant cells, lymphocytes and plasma cells
• Granulomas heal with fibrosis and sometimes
calcify

21. Epidemiology
• Human infection acquired
from animals
• Goats, sheep, cattle, buffalo
• Modes of infection: ingestion,
contact, inhalation or
accidental inoculation
• Most important vehicle: raw
milk
• Ingestion; Milk products, meat
and raw vegetables or water
supplies contaminated by
faeces or urine of infected
animals

22. • Contact infection: veterinarians, butchers,
animals handlers
• Inhalation: of dried material of animal origin
such as dust from wool
• Most human infections in various parts of
India due to B.melitensis

23. Laboratory diagnosis
• Blood culture:
• Most definitive method for diagnosis
• Blood inoculated into bottle of trypticase soy
broth or Brucella broth in a biphasic medium
• Castaneda method
• Cultures not be declared negative in less than 6-8
weeks
• Automated cultures become positive in 5-6 days

25. • Castaneda method:
– Minimizes materials and manipulation
– Reduces chances of contamination
– Reduces risk of infection to laboratory workers
• Blood cultures positive in only 30-50% cases
• Bone marrow yield higher
• remain positive long after
blood culture is negative

26. • Other samples:
• Lymph nodes, CSF, urine, abscesses
• Occasionally, sputum, breast milk, vaginal
discharges and seminal fluid

27. • Serological methods
• Standard agglutination test (SAT)
– Tube agglutination test
– Performed most often
– Significant titre: 160 or more
– Most patients with acute brucellosis develop titres
of 640 or more by 3-4 weeks

28. • Sources of error
• Presence of blocking or non agglutinating
antibodies
• Prozone phenomenon to high titres (Upto 1/640)
is very common in brucellosis
• Hence several serum dilutions need to be tested
• False positive: cholera, tularemia, Yersinia
infection
• Express agglutinin titres in IU

29. • Both IgM and IgG antibodies appear in 7-10
days
• Agglutination test mainly identifies IgM
• Rise in titre is diagnostic

30. • Complement fixation test
– More useful in chronic cases as it detects IgG also
• ELISA
– Sensitive and specific
– Can detect IgM and IgG separately
• Rapid methods: dipstick and rose Bengal card
test

32. • Delayed hypersensitivity-type skin tests
– With brucella antigens
• Detection in milk and infected animals:
– Microscopy of pathological specimens
• Immunofluorescence

33. • Rapid methods
• Milk ring test
• Whole milk + stained brucella antigen
• (a conc. Suspension of killed B.abortus stained
with hematoxylin)
• Incubated in water bath at 70 deg. C x 40-50 mins
• Positive: bacilli agglutinated, rise with cream to
form blue ring at top, milk unstained
• Rose Bengal card test and Rapid plate
agglutination tests – screening infected herds

35. Prophylaxis
• Majority infections by
ingestion of contaminated milk
• Checking dairy animals for brucellosis
• Pasteurization of milk
• B.abortus strain 19 vaccine protective in cattle
• No suitable vaccine for human use

36. Vaccination

37. Treatment
• Combination of Doxycycline for 45 days with
i.m. Streptomycin daily for 2 weeks
• For children, cotrimoxazole with Rifampicin or
Gentamycin