Tuberculosis is a bacterial infection caused by Mycobacterium tuberculosis 

-M.tuberculosis is an obligate intracellular bacteria that is aerobic, acid fast, and nonencapsulated

-One-third of the world’s population is infected with TB

-TB usually affects the lung, but virtually all other organ systems may be involved

-Infection is transmitted by aerosolized respiratory droplet nuclei

Symptoms & Signs

Pulmonary tuberculosis: Fatigue, weight loss, fever, cough and night sweats; Primary tuberculosis may coalesce into a small granuloma in the upper lobe (Ghon complex) 

Spinal tuberculosis ( Pott disease):  Pain, deformity, the most common sites involved are the thoracic and lumbar vertebrae 

Lymph nodes(Scrofula): painless swelling of cervical and supraclavicular nodes

TB of the skin (Scrofuloderma): Skin ulcerations in the inguinal or cervical region with lymphadenopathy 

Urinary tract: urethral stricture, nephritis, hematuria, “sterile” pyuria 

Diagnosis 

Tuberculin skin test (TST)

Interferon gamma release assays (IGRAs): QuantiFERON, T-SPOT test

Culture of the sputum, urine, tissue, bone 

Biopsy: Granulomas with caseating necrosis 

Chest X-ray: Diagnostic test of choice; shows upper lobe infiltrates with cavitation and/or lymphadenopathy 

Treatment 

-Treatment is with standard multidrug regimens

-Antimicrobial therapy should be administered for 6–9 months

-Isoniazid, rifampin,Rifapentine, pyrazinamide,streptomycin and ethambutol 

-Pyridoxine should be given to patients taking isoniazid to reduce nervous system side effects 

-Test Visual acuity and red-green color vision before initiating ethambutol

-Perform audiometry before initiating streptomycin 

Prevention: BCG vaccine can prevent up to 50% of TB cases 

-Yersinia pestis is a nonmotile, non-spore forming, bipolar staining Gram-negative bacillus 

-Plague is a systemic zoonosis (infections in humans acquired by contact with animals) caused by Yersinia pestis, a gram-negative bacillus 

-It is a disease of rodents transmitted to humans by flea bites 

Symptoms & Signs 

Plague occurs in three common forms: 

Bubonic plague: sudden onset of fever, chills, prostration,headache, delirium,ulcer at the site of inoculation; regional lymphadenitis with suppuration of nodes (bubo) is the initial lesion

Pneumonic plague (Black Death): Cough, dyspnea, cyanosis, hemoptysis 

Septicemic plague: hemorrhage into skin and mucous membranes, shock

Diagnosis 

Aspirate from a bubo; culture of pus, sputum and blood; serologic testing 

Cultures show bipolar staining, Gram-negative coccobaccili (short rods with rounded ends with a ‘closed safety pin’ appearance) 

Treatment 

Doxycycline, ciprofloxacin,  levofloxacin, moxifloxacin, streptomycin, gentamicin, TMP-SMX

Salmonellosis Typhoid fever 

-Typhoid fever is caused by Salmonella typhi 

-Salmonella is a facultative gram-negative rod

-it is transmitted by the fecal-oral route and by contamination of food or water 

Symptoms & Signs

-Headache, nausea, vomiting, abdominal pain, abdominal distension, “pea soup” diarrhea, erythematous maculopapular lesions that blanch on pressure (Rose spots), slow rise of fever to maximum and then slow return to normal (stepladder fever), relative bradycardia, splenomegaly, temperature pulse dissociation (bradycardia relative to fever)

Diagnosis 

Labs: leukopenia 

Culture: Culture of bacteria from blood, stool, urine, and bone marrow 

Treatment 

Ciprofloxacin, levofloxacin, chloramphenicol, azithromycin

Prevention

-Oral and intramuscular vaccines are available for travelers to endemic areas

-Vaccine repeated after 5 years 

Q. What are the most serious complications of typhoid fever? gastrointestinal hemorrhage and perforation