Rhodococcus hoagii

Background

Facultative intracellular, non-spore-forming, Gram-positive, weakly acid-fast coccobacillus
- More coccoid when grown on solid media, and more bacillary with varying lengths (often beaded) when grown in liquid media
Within the family Nocardiaceae and order Actinomycetes
Obligate aerobic and facultatively intracellular
Found in dry and dusty soil
Makes red pigment, hence the name

Infects domesticated animals: Horses (and in foals it causes pneumonia), Goats, Pigs, Sheep, and Cattle
Most commonly infects people with cell-mediated immunodeficiency, particularly HIV, with or without a notable infectious exposure

Necrotizing pneumonia is usual presentation, as well as nodules, cavitation, pleural effusion, and lung abscess
- Typically subacute onset with fever, cough, and fatigue, as well as pleuritic chest pain
Specifically in immunocompromised patients, it can cause a cavitary lung disease and is on the differential with mycobacteria and nocardiosis
Extrapulmonary disease can occur with or without pulmonary involvement
- In conjunction with other infections, can have abscesses in liver, spleen, thyroid, kidney, psoas, bone, prostate, intraabdominal cavity, and paraspinous tissue
Extrapulmonary disease without pulmonary involvement has three main presentations:
- Localized infection following traumatic inoculation, causing wound infection, traumatic septic arthritis, or endophthalmitis
- Isolated bacteremia with fever, typically recently after chemotherapy causing neutropenia
- Gastrointestional inoculation followed by lymphatic dissemination, causing peritonitis, pelvic masses, and mesenteric adenitis
- Others include otitis media with mastoiditis, colonic polyp infection, and osteomyelitis

May be misidentified as Corynebacterium in blood culture or Kocuria on Vitek