Infections in People Who Inject Drugs
Finding the hidden infection and treating the whole patient
Approach to fever
Assume bacteremia. Fever in a person who injects drugs (PWID) is bacteremia or endocarditis until proven otherwise, even when the patient attributes it to a viral illness or withdrawal. Draw at least two blood culture sets before antibiotics, start empiric vancomycin to cover MRSA, and obtain echocardiography when cultures are positive or endocarditis is suspected. Examine every injection site, listen for new murmurs, palpate the spine and the sternoclavicular and sacroiliac joints, and perform a dilated eye examination when vision changes or fungemia is possible.
Organisms. S. aureus, often MRSA, carried from the skin causes most infections. Injection practices explain the exceptions:
| Practice | Organisms | Typical infections |
|---|---|---|
| Unclean skin | S. aureus (incl. MRSA), β-hemolytic streptococci | Abscess, cellulitis, bacteremia, endocarditis |
| Needle licking | Viridans streptococci, Eikenella corrodens, oral anaerobes | Endocarditis, soft-tissue infection |
| Lemon juice to dissolve brown heroin | Candida | Endophthalmitis, endocarditis |
| Nonsterile water, shared equipment | Pseudomonas and other gram-negative rods | Endocarditis, vertebral and sternoclavicular infection |
| Black tar heroin, skin popping | Clostridia | Wound botulism, tetanus, gas gangrene |
Endocarditis and vascular infections
Right-sided endocarditis. Injected particulates and bacteria reach the tricuspid valve first, making S. aureus tricuspid endocarditis the classic PWID pattern. Vegetations embolize to the lungs: fever, cough, pleuritic chest pain, and hemoptysis with multiple peripheral nodules that often cavitate on CT, sometimes mistaken for pneumonia or tuberculosis. Peripheral stigmata are sparse, and the holosystolic murmur of tricuspid regurgitation at the left lower sternal border may be soft or absent early; it grows louder with inspiration (Carvallo sign).
Left-sided endocarditis. Aortic or mitral involvement carries a worse prognosis, produces systemic emboli (stroke, splenic and renal infarcts, limb ischemia) and classic peripheral signs, and has a broader organism list: S. aureus, streptococci, enterococci, Candida, and gram-negative rods. Details of diagnosis and valve surgery are covered with endocarditis.
Septic thrombophlebitis. An infected thrombus in an injected vein keeps blood cultures positive despite appropriate antibiotics and seeds the lungs with septic emboli. A tender, indurated venous cord or a thrombus on ultrasound or CT confirms it. Treatment is prolonged IV antibiotics, with excision of the vein or drainage when bacteremia persists; anticoagulation is individualized.
A tender, pulsatile groin mass with a bruit at a femoral injection site is an infected pseudoaneurysm until proven otherwise. Incision and drainage can cause exsanguinating hemorrhage; obtain duplex ultrasound or CT angiography first, start IV antibiotics, and involve vascular surgery.
Spine, joints, eyes, and soft tissue
Spinal epidural abscess and vertebral osteomyelitis. Hematogenous seeding, usually by S. aureus, causes focal back pain and fever that progress to radicular pain, then weakness, sensory loss, and bladder or bowel dysfunction, and finally paralysis. The full triad of back pain, fever, and deficits is often absent, and ESR and CRP are usually high.
- SuspectBack pain with fever, elevated ESR/CRP, or bacteremia in a PWID
- Urgent MRI with gadolinium of the entire spineSkip lesions are common; plain films are insensitive and lumbar puncture is not indicated
- Blood cultures, then empiric antibioticsVancomycin plus ceftriaxone, or cefepime when Pseudomonas is a concern
- Neurologic deficit or cord compressionEmergent surgical decompression and drainage
- DurationAbout 6 weeks for vertebral osteomyelitis, guided by clinical and inflammatory-marker response
When the patient is neurologically intact and stable and blood cultures are negative, image-guided biopsy before antibiotics identifies the organism.
Unusual joints. Bacteremia seeds fibrocartilaginous joints that are rarely infected otherwise: sternoclavicular, sacroiliac, and pubic symphysis. Pseudomonas is a classic cause alongside S. aureus. Confirm with CT or MRI and aspiration, give IV antibiotics, and drain abscesses; sternoclavicular infection can extend into the chest wall and mediastinum.
Candida endophthalmitis. Brown heroin dissolved in lemon juice can carry Candida, which seeds the eye: floaters, blurred vision, and pain with fluffy white chorioretinal lesions extending into the vitreous. Management is urgent ophthalmology, systemic fluconazole or voriconazole, and intravitreal antifungal with or without vitrectomy when the vitreous is involved. Echinocandins, first-line for candidemia, penetrate the eye poorly.
Necrotizing soft-tissue infection. Subcutaneous injection (skin popping), black tar heroin, and intramuscular injection predispose to necrotizing fasciitis and clostridial myonecrosis. Pain out of proportion to the findings, rapid spread, crepitus, bullae, skin anesthesia, and shock demand emergent surgical debridement with vancomycin, piperacillin-tazobactam, and clindamycin, which suppresses toxin production; imaging must not delay the operating room.
Xylazine. This veterinary α2-agonist sedative, now common in the illicit fentanyl supply, causes deep sedation, bradycardia, and hypotension that naloxone does not reverse, so naloxone is still given for the opioid while breathing is supported. It also causes chronic necrotic ulcers with eschar, sometimes far from injection sites, which are treated with moist wound care and debridement; antibiotics are reserved for secondary infection.
Whole-person care
Screening and vaccination. Test for HIV (antigen/antibody), hepatitis C (antibody with reflex RNA), and hepatitis B (HBsAg, anti-HBs, anti-HBc). Vaccinate against hepatitis A and B, update tetanus, and offer HIV pre-exposure prophylaxis (daily oral emtricitabine-tenofovir disoproxil fumarate is the regimen studied for injection exposure). Ongoing drug use is not a reason to withhold curative direct-acting antiviral treatment for hepatitis C.
Harm reduction. Discharge every patient with naloxone, refer to syringe services programs (sterile equipment lowers HIV and HCV transmission without increasing drug use, and these programs link people to testing, vaccination, and treatment), advise never using alone, and provide fentanyl test strips and wound-care supplies.
Opioid use disorder. Starting buprenorphine or methadone in the hospital controls withdrawal, reduces patient-directed discharge and readmission, and lowers overdose deaths; it must continue without interruption after discharge. Detoxification alone lowers tolerance and raises overdose risk, and naltrexone cannot be started during active opioid dependence without precipitating withdrawal. Acute pain is treated adequately, with higher opioid doses when tolerance is present, and antibiotics or surgery are never made contingent on abstinence.
Completing antibiotics. When weeks of IV therapy or a PICC line is unsafe, impractical, or declined, a stable patient whose bacteremia has cleared can finish with a highly bioavailable oral regimen. Randomized trials in left-sided endocarditis (POET) and bone and joint infection (OVIVA) support partial oral therapy, and a completed oral course is far better than an abandoned IV one.