Tularemia

Plague is infection with the gram-negative coccobacillus Yersinia pestis, transmitted by rodent fleas, presenting as bubonic, septicemic, or pneumonic disease with sudden fever and, in the bubonic form, an intensely painful regional bubo. Diagnosis rests on Gram/Wright-Giemsa stain and culture of aspirate, blood, or sputum, and treatment is empiric streptomycin or gentamicin, or a fluoroquinolone, started without waiting for confirmation because untreated pneumonic plague is uniformly fatal.

Anthrax is caused by Bacillus anthracis spores acquired by inhalation, cutaneous inoculation, or ingestion, with cutaneous disease most common and inhalational disease most lethal. Systemic disease is treated with ciprofloxacin or doxycycline plus additional agents and antitoxin for 60 days, and any inhalational case is a bioterrorism sentinel event requiring immediate public health notification.

Bartonella henselae, acquired from cat scratches or bites, most often causes cat-scratch disease, a clinical diagnosis of an inoculation papule with tender regional lymphadenopathy that is usually self-limited but is treated with azithromycin to speed resolution, while disseminated, ocular, hepatosplenic, or immunocompromised disease needs doxycycline or azithromycin plus rifampin.

Sporotrichosis is a subacute fungal infection caused by direct cutaneous inoculation of the dimorphic fungus Sporothrix schenckii, classically from a rose thorn or plant matter, producing a nodular ulcer that spreads along lymphatic channels; diagnosis requires culture of the organism, and itraconazole is first-line treatment for cutaneous and lymphocutaneous disease.

Brucellosis is a zoonotic infection from unpasteurized dairy, undercooked meat, or animal contact causing undulant fever, hepatosplenomegaly, arthralgia, and depression, diagnosed by extended-incubation blood or marrow culture and serum agglutination titer, and treated with doxycycline plus rifampin or gentamicin for six weeks.

Q fever, caused by inhalation of Coxiella burnetii aerosols from infected livestock, most often produces a self-limited febrile illness with atypical pneumonia or hepatitis, but it is a major cause of culture-negative endocarditis when infection becomes chronic. Acute disease is treated with doxycycline for 2 weeks; endocarditis requires combination therapy for more than 18 months.

Lymphadenitis is infection or inflammation of a lymph node and lymphangitis is infection of the superficial lymphatic channels draining toward it, most often two presentations of the same acute bacterial process (usually Streptococcus pyogenes or Staphylococcus aureus) that also causes erysipelas and cellulitis. The disease is diagnosed clinically from a tender node with a linear streak tracking from a skin portal of entry, treated with an escalating antibiotic sequence tied to severity, and distinguished from cat-scratch disease, nontuberculous mycobacterial lymphadenitis, and other subacute mimics when the course is not acute and purulent.

Community-acquired pneumonia is a lower respiratory tract infection acquired outside the hospital that is diagnosed by a compatible clinical syndrome plus a new infiltrate on chest imaging, risk-stratified with CURB-65 or the Pneumonia Severity Index to guide site of care, and treated with empiric antibiotics chosen by site of care and comorbidity, escalating to cover MRSA or Pseudomonas aeruginosa when risk factors are present.