Injection Drug Use–Related Infections

Key Features

Essentials of Diagnosis

• Common infections that occur with greater frequency in persons who inject drugs

  • Skin infections

  • Hepatitis A, B, C, D

  • Aspiration pneumonia

  • Tuberculosis

  • Pulmonary septic emboli

  • Sexually transmitted diseases

  • HIV/AIDS

  • Infective endocarditis

  • Osteomyelitis

  • Septic arthritis

General Considerations

SKIN INFECTIONS

• Associated with poor hygiene and use of nonsterile injection technique

• Most common organisms

  • Staphylococcus aureus (including methicillin-resistant strains)

  • Oral flora (streptococci, Eikenella, Fusobacterium, Peptostreptococcus)

• Enteric gram-negative organisms are less common except in those who inject into the groin

HEPATITIS

• Very common among persons who inject drugs habitually

• Transmissible both by the parenteral (hepatitis B, C, and D) and by the fecal–oral route (hepatitis A)

• Multiple episodes of hepatitis with different agents can occur

ASPIRATION PNEUMONIA

• Results from altered consciousness associated with drug use

• Mixed aerobic and anaerobic mouth flora are usually involved

TUBERCULOSIS

• Infection with HIV has fostered the spread of tuberculosis

PULMONARY SEPTIC EMBOLI

• From venous thrombi or right-sided endocarditis

SEXUALLY TRANSMITTED DISEASES

• Related to the practice of exchanging sex for drugs

• Syphilis, gonorrhea, and chancroid are the most common

HIV/AIDS

• High incidence among persons who inject drugs, among their sexual contacts, and among the offspring of infected women

INFECTIVE ENDOCARDITIS

• Most common organisms

  • S aureus

  • Candida (usually C albicans or C parapsilosis)

  • Enterococcus faecalis

  • Other streptococci

  • Gram-negative bacteria (especially Pseudomonas and Serratia marcescens)

• Right-sided heart involvement

  • Common

  • Infection of more than one valve is not infrequent

OTHER VASCULAR INFECTIONS

• Septic thrombophlebitis

• Mycotic aneurysms result from direct trauma to a vessel with secondary infection

• Aneurysms result from hematogenous spread of organisms

OSTEOMYELITIS AND SEPTIC ARTHRITIS

• Osteomyelitis usually results from hematogenous distribution of injected organisms or septic venous thrombi

• While staphylococci—often methicillin-resistant—are common organisms, also found are Serratia, Pseudomonas, Candida (often not C albicans), and other pathogens rarely encountered in spontaneous bone or joint disease

Demographics

• More than 2 million persons in North America are estimated to have used injection drugs in the past year

Clinical Findings

Symptoms and Signs

SKIN INFECTIONS

• Cellulitis and subcutaneous abscesses occur most commonly, particularly in association with subcutaneous ("skin-popping") or intramuscular injections and the use of cocaine and heroin mixtures (probably due to ...