Staphylococcal Infections Among Injection Drug Users

1
Staphylococcal Infections Among Injection Drug
Users

• Frederick L. Altice, M.D.
• Professor of Medicine
• Yale University School of Medicine

2
Background

• 13 million IDUs estimated worldwide 1
• Skin and soft tissue infections are the leading
  cause for ER visits and hospitalizations for IDUs
  (S aureus S pyogenes most common pathogens) 2
• S aureus nasal carriage occurs in 20 of people
  and associated with development of community- and
  nosocomial-acquired S aureus infections 3,4
• IDUs have a higher rate of S aureus colonization
  than the general population 3,5
• S aureus nasal carriage has been associated with
  ? development of subsequent infections in IDUs 5

1. UNODC, 2004 2. Palepu, CMAJ 2001 3.
Kluytmans, Clin Micro Rev 1997 4. von Eiff, NEJM
2001 5. Basetti, Infection 2004
3
S Aureus Expresses Many Potential Virulence
Factors

• Surface proteins that promote colonization of
  host tissues
• Factors that probably inhibit phagocytosis
  (capsule, immunoglobulin binding protein A)
• Toxins that damage host tissues and cause disease
  symptoms
• Coagulase-negative staphylococci are normally
  less virulent and express fewer virulence factors
• S epidermidis readily colonizes implanted devices

4
Skin and Soft Tissue Infections (SSTIs) Among IDUs

• Include local (cellulitis abscesses) and
  necrotizing (complicated abscesses, necrotizing
  fasciitis, pyomyositis, myonecrosis) SSTIs
• Most common organisms are S aureus gt S pyogenes gt
  polymicrobial infections
• Related to local tissue trauma, direct effect of
  drugs, tissue ischemia and inoculation of
  bacteria
• Increased risks skin popping, use of
  non-sterile needles, speedballs, booting,
  licking the needle
• Decreased risks use of alcohol preparation of
  skin
• Unclear association HIV and immunosuppression

Ebright, ID Clin NA, 2002
5
Skin and Soft Tissue Infections
6
Invasive Infections Among IDUs

• Most common cause is S aureus gtgt Strep gtgtgtgt GNRs
• Most commonly include bacteremia from local
  source (lungs, SSTIs), endocarditis and
  osteomyelitis
• Endocarditis more likely to be Right-Sided among
  IDUs than among non-IDUs
• Duration of antibiotics is prolonged though some
  evidence of shorter duration for right-sided
  infections

7
Invasive Infections
8
Emergence of MRSA

• Hospital-acquired MRSA (h-MRSA)
• Plasmid-mediated
• Not associated with toxin production
• Associated with recent hospitalization and use of
  antibiotics
• Highly resistant to most oral antibiotics, except
  linezolid
• Community-acquired MRSA (c-MRSA)
• Chromosomally-mediated
• Associated with toxin production
  (Panton-Valentine leukocidin)
• Person-to-person transmission and not associated
  with traditional risk factors IDUs, sexual
  contact and crowding athletes, prisoners,
  homeless shelters, day care centers)
• Sensitive to many oral antibiotics (TMP/SMZ,
  tetracycline, etc.)

9
Surveillance of S aureus and MRSA in the United
States

• Colonization 1
• S aureus 89.4 million (32) and MRSA 2.3
  million (0.8)
• Hospitalization
• ICUs (1974 2 1995 22 2004 64) 2
• 292,000 per year 126,000 (43) due to MRSA 3
• Skin and Soft Tissue Infections
• 12 million outpatient visits per year for SSTIs 4
• 76 of purulent infections in 11 ERs secondary to
  S aureus 5
• 78 of these due to MRSA with overall MRSA rate
  59
• Invasive Infections 6
• Occurs in 94,000 persons/year
• Mortality 19,000
• 86 are healthcare-associated

1. Kuehnert, JID, 2006 2. Klevens, CID, 2006
3. Kuehnert, Emerg ID, 2005 4. McCaig, Emerging
ID, 2006 5. Moran, NEJM, 2006 6. Klevens, JAMA,
2007
10
Staphylococcal Colonization Among IDUs is
Increasing in North America

• Nasal carriage screening in 2000 (N299) and 2006
  (N301) among active IDUs in Vancouver
• Increase in S aureus colonization 27.1 ? 39.5
• Increase in MRSA colonization 7.4 ? 18.6
• MRSA PFGE changed from primarily USA-500 (100)
  to USA-300 (75) with increasing susceptibility
  to TMP/SMZ and TCN with USA-300
• Trend toward increased recent antibiotic use
  (p.056) and hospitalization (p0.12) for MRSA
  vs. MSSA

Al-Rawahi GN, J Clin Microbiol, 2008
11
S Aureus Carriage Among IDUs in Methadone and
Heroin Maintenance Programs

• 2001 70 MM and 94 HM patients in Basel,
  Switzerland
• Nasal carriage higher in MM (43) than in HM
  (23) patients
• No difference in recent or remote hospitalization
• MM subjects more likely to have used antibiotics
  in previous month (12 vs 4), be HIV (20 vs
  6) and have no IDU (34 vs 0)
• In multivariate analysis, enrolled in MM was the
  only significant (AOR 2.27) correlate of S aureus
  colonization
• No MRSA isolated,1 but subsequent studies have
  demonstrated MRSA transmission between drug
  users2 and introduction of new MRSA strains3

1. Bassetti, Inf Control Hosp Epi, 2004 2. Qi, J
Clin Micro 2005 3. Fleisch, Infection, 2005
12
Colonization with MRSA in Opioid Dependent
Patients

• Case control study of 60 hospitalized opioid
  dependent (OD) and 60 non-drug users in Egypt
• Subjects with any CDC risk for h-MRSA excluded
  (time extended to five years for health care
  facility)
• Colonization higher in drug vs. non-drug users
  (30 vs 10)
• Increased risk associated with duration of drug
  use and use of non-prescription antibiotics
• 58 of active MRSA infections associated with
  colonization

El-Sharif, Exp Biol Med, 2008
13
Rapid Spread of MRSA in the Netherlands
No. Hospitals with MRSA PFT-16
No. MRSA Isolates
2000
2001
2002
Year
Wannet, J Clin Micro 2004
14
Hospitalization and S Aureus
15
Managing MRSA Colonization

• Colonization persists for years, despite
  treatment of infection
• Contact precautions and isolation of wounds
  recommended
• Controversy exists around universal screening,
  isolation and at eradication of the carrier state

16
Changing Epidemiology of Staphylococcal Infections
17
Summary

• IDUs exist on all continents and are more likely
  to be colonized with S aureus
• Morbidity and mortality related to S Aureus
  infections is greater among IDUs
• Colonization with S aureus, including MRSA, is
  associated with increased risk for infection
• Infection can be reduced with skin cleaning and
  sterile syringes
• MRSA prevalence is variable but growing in
  different regions of the world, thus requiring
  increased surveillance to guide clinical practice