1. Brucella
Brucellosis
Dr Kamran Afzal
Asst Prof Microbiology

2. Background
 Brucella melitensis discovered by Bruce in 1887
 Members of this genus are pathogenic to animals from which
they are transmitted to man causing „brucellosis‟
(Undulant or Malta fever)

3. The genus includes
 Br. melitensis, causing infection in goats and sheep
 Br. abortus, causing abortion of cattle
 Br. suis, causing infection in pigs
 Br. ovis, causing infection in birds
 Br. canis, causing infection in dogs
Pathogenic types in humans:
 Br. melitensis, abortus, canis and suis
Zoonotic disease

4. Epidemiology

5. Morphology
 Gram negative short cocco-bacilli, non- motile, non-
sporing and non capsulated
 Aerobes, require enriched media for growth
 10-20% CO2 is required for primary growth of Br.
abortus but not for the others
 Br. abortus and Br. suis produce H2S
Antigenic structure:
Two Lp antigens, A and M are present in different
proportions in the four species
They can be differentiated by specific monoclonal
antibodies

6. Who is at Risk?
 Occupational Disease
 Cattle ranchers/ dairy farmers
 Veterinarians
 Abattoir workers
 Meat inspectors
 Lab workers
 Hunters
 Travelers
 Consumers of unpasteurized dairy products

7. Transmission
Three methods of transmission:
 Ingestion – unpasteurized milk or dairy products
Ingestion is most common method of transmission
 Inhalation – breathing in the aerosolized organism
Lab workers are at high risk

8.  Inoculation/Wound contamination – high risk
occupations include hunters, slaughterhouse workers, meat
packing plant workers and veterinarians

9. Transmission

11. Pathogenesis
 Incubation period 1-6weeks
 Can multiply and survive
within the neutrophils and
macrophages
 Reticuloendothelial system
 Liver spleen and bone marrow
(Septicemia)

12.  Cell mediated response of the host results in granuloma and
abscess formation in the bone or any organ

13. Brucellosis: Undulant fever
 An acute bacteraemic phase
 A chronic stage that may extend over many years
and may involve many tissues
 Intermittent fever, bouts of fever for 3-4 weeks,
alternating with afebrile period of a similar duration
 A prolonged course accompanied with weakness,
malaise, profuse sweating, headache, joint and
muscle pain
 Enlarged lymph nodes, liver, and spleen
 It may be complicated by osteomyelitis

14. Lab Diagnosis
 Specimens
 Blood, pleural/peritoneal fluids, CSF, Bone marrow (92%
sensitive), biopsy: liver, spleen and lymph node

15. Lab Diagnosis
I-Blood Culture: Isolation of the organism from the blood
by repeated blood cultures incubated in 10-20% CO2 for
4-6 weeks
 Subcultures are done on serum dextrose agar (SDA),
chocolate agar, Thayer-Martin medium
 Isolated organisms are serologically identified by specific
antisera

16. II-Serologic diagnosis: Detection of antibodies
 A tube agglutination test is done using dilutions of the serum
 A titer of at least 1/60 in convalescent serum is diagnostic
Coomb’s antiglobulin method : to detect the non-agglutinating
IgA antibodies that appear during the subacute stage of
infection, and tend to persist for years
They are called blocking or incomplete antibodies
Detection of IgG and IgM by ELISA

17. III-Direct detection in clinical material by PCR
IV- Brucellin test: It is similar to tuberculin test and is based on
delayed type hypersensitivity, it is unreliable and is rarely used

18. Treatment
 Prolonged treatment
 Chronicity of the disease
 Intracellular survival of the organism
 6 weeks course of a combination of antibiotics
 Doxycycline and rifampin or doxycyclin and streptomycin or
rifampin and trimethoprim-sulfamethoxazol are used

19. Prevention/Infection control
 Pasteurizing milk and dairy products
 Eradicating infection from herds and flocks
 Live attenuated vaccine is used for cattle
 No vaccine is available for humans
 Observing safety precautions for occupational
exposures including
 rubber boots
 wearing impermeable clothing
 gloves and face masks
 practicing good personal hygiene

20. Biological warfare
 In 1954, B. suis became the first agent weaponized by the US
 Brucella species survive well in aerosols and resist drying
 Brucella and all other remaining biological weapons in the U.S.
arsenal were destroyed in 1971–72 when the U.S. offensive
biological weapons (BW) program was discontinued
 The United States BW program focused on three agents of the
Brucella group:
 Porcine Brucellosis (Agent US)
 Bovine Brucellosis (Agent AB)
 Caprine Brucellosis (Agent AM)

21. Mycoplasma
Mycoplasmosis
Atypical pneumonia

22. Mycoplasmas
 Smallest free-living capable of autonomous growth
 Key genera: Mycoplasma, Spiroplasma
 Lack cell walls
 Key components of peptidoglycan are missing
 Muramic acid and diaminopimelic acid
 Mycoplasma cells are pleomorphic
 Cells may be cocci or filaments of various lengths

23. Taxonomy

24. Differentiation of species
 M. pneumoniae - glucose
 M. hominis - arginine
 U. urealyticum - urea
 M. genitalium - difficult to culture

25. Diseases
O rg a n is m D is e a s e
M . p n e u m o n ia e U p p e r re s p ira to ry tra c t d is e a s e ,
tra c h e o b ro n c h itis , a ty p ic a l
p n e u m o n ia , (c h ro n ic a s th m a ? ? )
M . h o m in is P y le o n e p h ritis , p e lv ic
in fla m m a to ry d is e a s e ,
p o s tp a rtu m fe v e r
M . g e n ita liu m N o n g o n o c o c c a l u re th ritis
U . u re a ly tic u m N o n g o n o c o c c a l u re th ritis ,
(p n e u m o n ia a n d c h ro n ic lu n g
d is e a s e in p re m a tu re in fa n ts ? ? )

27. Morphology
 Smallest free-living bacteria (0.2 - 0.8 µm)
 Small genome size
 Strict aerobe
 Lack a cell wall
 Grow slowly by binary fission
 “Fried egg” colonies

28. “Fried Egg” Colonies of Mycoplasma
M. pneumoniae colonies have a granular appearance

30. Can be part of normal flora
 They reside extracellularly in the respiratory and urogenital tracts
and rarely penetrate the sub-mucosa, except in the case of
immunosuppression or instrumentation, when they may invade
the bloodstream and disseminate to numerous organs and tissues

31. Mycoplasma are cell wall deficient
 Cross-section of Mycoplasma bacteria

32. Pathogenesis
 Adherence
 P1 pili
 Movement of cilia ceases
 Clearance mechanism stops
 Toxic metabolic products
 Peroxide and superoxide
 Immuno-pathogenesis
 Activate macrophages
 Stimulate cytokine production

33. Clinical manifestations
 Tracheo-bronchitis
 70-80% of infections
 Pneumonia
 Approximately 10% of all atypical pneumonias
 “Primary atypical pneumonia”
 Mild disease but long duration

34.  Incubation 2-3 weeks  Radiological signs
 Persistent non-productive cough precede symptoms
 Slow resolution
 Rarely fatal

35. Laboratory Diagnosis
 Microscopy
 Difficult to stain
 Immunochromatography (ICT)
 Immunofluorescence (IF)
 Culture (definitive diagnosis)
 Sputum (usually scant) or throat washings
 May take 2-3 weeks
 Molecular diagnosis
 PCR-based tests, rapid, sensitive and specific

36.  Serology  Cold agglutinins (40C)
 ELISA  1/3 - 2/3 of patients
 Complement fixation  Appear earlier
 May take 4-6 weeks  Non-specific
 Fourfold rise in titer  Presumptive diagnosis

37. Culturing Mycoplasma
 Mycoplasma can be cultured on liquid or solid media
 Broth enriched with 20% horse or human serum
 Grows optimally at 35 - 370 C up to 3 weeks
 The colonies appear as fried egg

39. Treatment and Prevention
 Treatment
 Tetracycline or erythromycin
 Newer fluoroquinolones
 They are relatively resistant to pencillins and cephalosporins
 Prevention
 Avoid close contact
 No vaccine