Case Study
Pathogenic Bacteriology
2009
Case #8
Case Summary
The patient was a 55-year-old male with a 2-month history of fevers, night sweats,
increased cough with sputum production, and a 25-lb weight loss.
Personal History:
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Denied intravenous drug use or homosexual activity
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had multiple sexual encounters
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“sipped” a pint of gin a day
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was in jail for 2 years
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Had gunshot and stab wounds in the past.
Physical Examination
 Temperature above normal (39.4 degree Celsius)
 Lymph nodes adenopathy (neck, armpit)
 Positive HIV serology
 Low absolute CD4+ lymphocyte count
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Acid-fast positive for stain of sputum
Organism was detected in bronchoalveolar lavage fluid from right middle lobe
Bronchoalveolar Lavage Fluid
Bronchoalveolar Lavage Fluid (BALF):
Body fluid obtained by washout of the
alveolar compartment of the lung.
 BAL is a medical procedure in which a
bronchoscope is passed through the
mouth and nose into the lungs. Fluid is
then squirted into a small part of the lung
and recollected for examination.
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Key Information Pointing to
Diagnosis
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Fevers
Cough with sputum production
Weight loss
Heavy drinker
Enlarged lymph nodes
HIV +
Low CD4+ lymphocyte counts
Acid fast +
Presence of BALF in right middle lobe
Organism of Infection
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Organisms that can be positive for acidfast are:
Mycobacterium
 Nocardia
 Corynebacterium
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Based on the medical history of the
patient, the most likely organism to be
causing the infection is Mycobacterium
tuberculosis.
Mycobacterium tuberculosis
Classifications:
 Family Mycobacteriaceae
 Obligate aerobe
 Acid-fast bacilli
 Slow growing
 Weakly G+ rods
 Nonmotile
 nonsporing
Mycobacterium tuberculosis

Colonies are
rough, dry,
granular, nonpigmented to buff
colored colonies
Disease and Pathogenesis of
M. tuberculosis
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Causative agent of tuberculosis
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Mode of transmission
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Latent tuberculosis: no symptoms and not contagious. Latent infection can become
active.
Active tuberculosis: developed various symptoms and are contagious.
Spread through droplets: when someone coughs, sneezes, or talks, tiny droplets of
saliva or mucus are expelled into the air, which can be inhaled by another person.
Once infectious particles reach the alveoli, macrophage engulfs the TB bacteria,
transmitting it to the lymphatic system and bloodstream, where it gets spread to other
organs.
The bacteria further multiply in organs that have high oxygen pressures (i.e upper
lobes of lungs, the kidneys, bone marrow, and meninges)
Virulence factors:
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cord factor – glycolipid, trehalose 6,6’ dimycolate; toxic to leukocytes; resistant to
chemical damage; interferes with mitochondrial function in mice; develops
granulomatous lesions.
Intracellular growth - sulfolipids prevent phagosome-lysosome fusion so that the
organisms are not exposed to lysosomal enzymes.
Iron capturing ability – required for survival inside phagocytes.
Diagnosis/Identification of M.
Tuberculosis
Diagnostic methods:
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Acid fast staining
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Tuberculin skin test (Mantoux skin test or PPD) - determines if someone has
developed an immune response to the bacterium that causes TB, indicated
by a hard, raised margins at the injection site.
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Lumbar puncture
Chest X-ray
Sputum or biopsy or body fluid culture
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Lowenstein-Jensen medium (slow growth: 18-24 days)
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Middlebrook medium (faster growth: 12-14 days)
Polymerase Chain Reaction (PCR)
Identification:
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Rate of growth
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Pigmentation and photoreactivity (nonphotochromogens-may produce pigment ranging
from white to yellow, but pigment does not intensify upon exposure to light.)
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Biochemical tests:
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Niacin +
Nitrate reduction + and Catalase – at 68 degree Celsius
Chest X-ray
Before treatment
After treatment
Chest X-ray
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1950medication
was not
available
Placed
paraffin sheet
on top of
cavity-like
lesion
Therapy and Prevention of Patient
Infected with M. tuberculosis
Some effective drugs:
 Isoniazid (INH)
 Rifampin
 Streptomycin
 Pyrazinamide
 Ethambutol
Prevention:
 BCG vaccine (could give TB skin test a false-positive)
 Those identified with latent tuberculosis are given INH every 6-12 months to
prevent M. tb from becoming active.
 Those identified with active tuberculosis are hospitalized and kept in a room
with controlled ventilation and airflow until they can no longer spread the tb
germs. Hospitals and clinics can take precautions to prevent the spread of
tb by using ultraviolet light to sterilize the air, special filters, and special
respirators and masks.
Tuberculosis Risk Factors in Adults
in King County, Washington
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Buskin SE, Gale JL, Weiss NS, Nolan CM. Tuberculosis risk factors
in adults in King County, Washington, 1988 through 1990. Am J
Public Health 1994;84:1750–1756.
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Purpose: to examine risk factors contributing to tuberculosis in
adults (over a course of 3 years)
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Risk factors include age, gender, race, place of birth, alcohol and
smoking status, and medical history.
Methods: In King County, Washington State (1988-1990), the
characteristics of patients with tuberculosis were compared with
census data, and a case-control study was conducted. Selfadministered questionnaires were completed by 151 patients with
active tb and 545 control subjects without active tb.
Results
Results (cont.)
Results (cont.)
Results (cont.)
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Results: Infection with the human
immunodeficiency virus, non-White
race/ethnicity, and foreign birthplace were each
associated with a sixfold or greater increase in
risk. Each of the following was associated with
at least a doubled risk: history of medical
conditions, low weight for height, low
socioeconomic status, and age 70 years and
older. Men had 1.9 times the risk of women,
smokers of 20 years or more duration had 2.6
times the risk of nonsmokers, and heavy alcohol
consumers has 2 times the risk of nondrinkers.
Conclusion: Targeting the identified groups may
be an effective way to reducing the incidence of
tuberculosis.
Take Home Message
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Mycobacterium Tuberculosis
Tuberculosis involves association between person to person.
Typical symptoms
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Fever
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night sweats
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progressive coughs
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chest pain
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weight loss
Diagnostics procedures
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acid-fast stain
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Tuberculin skin test
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Lumber puncture
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Sputum or biopsy or body fluid
Therapy is based on zzz (tuberculin skin test?)
Prognosis: Active tb can almost always be cured with combinations of antibotics over a course of 6-8 months of
daily treatments.
Prevention:
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BCG vaccine
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Preventive therapy of household members
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Minimize exposure to patients with active tuberculosis
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Reduce risk factors by not smoking, drinking, or undertake activities that contribute to poor health.
Transmission is through air droplets, by means of coughs, sneezes, talks.
Threat : consuming large amount of alcohol, smoking heavily, drug-abuse, harmful/unprotected activities, ect.
References
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Buskin SE, Gale JL, Weiss NS, Nolan CM. Tuberculosis risk factors
in adults in King County, Washington, 1988 through 1990. Am J
Public Health 1994;84:1750–1756.
Singh, V. Tuberculosis in developing countries: diagnosis and
treatment. Paediatric Respiratory Reviews 7 2006. 132-135.
DeRiemer K et al. Quantitative impact of human immunodeficiency
virus infection on tuberculosis dynamics. Am J Respir Crit Care Med
2007 Nov 1; 176:936.
Centers for Disease Control. The use of preventive therapy for
tuberculosis infection in the United States: recommendations of the
Advisory Committee for Elimination of Tuberculosis. MMAR. 1990;
Rieder HL, Cauthen GM, Kelly GD. Tuberculosis in the United
States. JAMA. 1989;262:385-389.
39(RR-8):9-12.McQueen, Nancy. Winter 2009. Mycobacteriaceae.
Point Spread
Case summary
5
Key Information pointing to Diagnosis
10
Diagnosis
5
Microbiology of Pathogen
10
Pathogenesis of the disease
10
Diagnostic tests
5
Therapy and Prognosis
5
Prevention
5
Epidemiology and threats
5
Primary research article (last 5 years)
20
Take home message
5
Are all questions addressed?
5
Appearance
5
Presentation skills (individual)
5
Total
100