Rates of community-acquired MRSA (methicillin-resistant Staphylococcus aureus) infections in
patients with HIV appear to be declining. A US study conducted between 2002 and
2009, and published in the online edition of AIDS, showed that rates of MRSA increased steadily until 2007, but
have fallen sharply since.
Gay and other men who have sex with men (MSM) and injecting
drug users (IDU) had a higher risk of MRSA than other patients. A low CD4 cell
count and younger age were also risk factors for the infection.
“Our findings reproduce those of other studies that have
reported immunodeficiency, MSM, IDU and younger age as independent risk factors
for MRSA infections in HIV patients,” comment the investigators.
Taking HIV therapy appeared to reduce the risk of infection
Information on rates of MRSA infections and its risk factors
among HIV-positive patients attending the Atlanta Veteran’s Affairs Medical
Center were collected between 2002 and 2009.
The study involved individuals receiving inpatient and
A total of 168 individuals were diagnosed with 226 MRSA
infections during the study. These patients represented 11% of the entire HIV
cohort receiving care at the clinic.
Most (99%) of the patients were men, 84% were black, and
their median age was 45. The median CD4 cell count at the time MRSA infection
was diagnosed was 325 cells/mm3.
However, 40 infections occurred in individuals with CD4 cell
counts below 50 cells/mm3 and a further 46 in patients whose CD4
cell count was between 51 and 200 cells/mm3.
Half the patients were taking antiretroviral therapy at the
time of MRSA diagnosis.
Nearly all the infections (94%) were community acquired.
There were 184 skin and soft tissue infections. Most of
these affected the extremities (42%) or the anogenital region (32%). Other
common sites of infection were the face (12%) and scalp (7%). A quarter of
patients experienced a recurrence of their MRSA infection.
Higher rates of MRSA infections were seen in gay and other
MSM (3.43 cases per 100 person years) and injecting drug users (3.69 cases per
100 person years) than in individuals from other HIV risk groups (1.51 cases
per 100 person years; comparison, p < 0.0001).
Patients with a CD4 cell count below 50 cells/mm3
had a high incidence of MRSA (4.17 cases per 100 person years), and rates of
the infection were also high among patients with a CD4 cell count between
51 and 200 cells/mm3 (1.39 cases per 100 person years). However,
incidence of the infection was markedly lower for individuals with better-preserved
immunity (0.81 cases per 100 person years; comparison p < 0.0001).
Patients under 60 had a markedly higher incidence of MRSA
than older individuals (2.85 vs 0.81 per 100 person years; p < 0.004).
Much lower incidence of MRSA was seen in patients who were
taking HIV therapy than those who were not (1.81 vs 5.10 cases per 100 person
years, p < 0.0001).
“To our knowledge, this study is the first to suggest HAART
may result in a reduced risk of MRSA infections,” comment the investigators. They
suggest that possible reasons for this finding include control of viral load or
better immune status.
Infection rates peaked in 2007 at 5.10 cases per 100 person
years, but by 2009 had fallen to a little over 1.5 cases per 100 person years.
The investigators note that this fall mirrors the decline in MRSA rates seen in
the general population.
“Whether the observed decrease in incidence in parallel with
this nationwide downward trend is the result of local changes in infection
control practices, or any HIV-specific factors will need to be prospectively
studied,” conclude the authors.