A Series of Skin and Soft Tissue Infections Due to Methicillin-Resistant Staphylococcus aureus in HIV-Infected Patients

Decreasing Incidence of Skin and Soft-tissue Infections in 86 US Emergency Departments, 2009-2014

Background

The incidence of skin and soft-tissue infections (SSTIs), for which human immunodeficiency virus (HIV) is a significant risk factor, in United States emergency departments (EDs) increased dramatically after 2000 with the emergence of community-associated methicillin-resistant Staphylococcus aureus. Few studies have examined SSTI incidence among HIV-infected and non-HIV-infected patients in the United States after 2010.

Methods

Data were obtained for patient encounters at all academic medical center EDs affiliated with the Vizient clinical data warehouse assigned an SSTI-associated code based on the International Classification of Diseases, Ninth Revision, between 1 January 2009 and 31 December 2014. The rate was calculated per 1000 ED encounters by year and stratified by SSTI, HIV infection, or both, and by age group, race, payer type, and region of care. Poisson regression was used to assess temporal change over the study period.

Results

In 2009-2014, a total of 47317 HIV-associated and 820440 SSTI-associated encounters were recorded among 25239781 ED patient encounters. The rate of SSTIs decreased by 8% among all patients and by 14.6%, among those with HIV infection. The SSTI incidence overall decreased from 32.0 to 29.7 per 1000 ED encounters between 2009 and 2014. HIV-infected patients had a significantly higher rate of SSTIs than HIV-uninfected patients (adjusted rate ratio, 1.91; 95% confidence interval, 1.84-1.99).

Conclusions

The decline in SSTI incidence in US EDs between 2009 and 2014 is a remarkable epidemiologic shift from the increase in SSTIs after 2000, and further research is necessary to assess reasons for this decrease.

Protective immunity in recurrent Staphylococcus aureus infection reflects localized immune signatures and macrophage-conferred memory

Staphylococcus aureus is the leading cause of skin and skin structure infection (SSSI), a primary portal of entry for invasive infection. Our prior studies discovered a role for protective innate memory against recurrent methicillin-resistant S. aureus (MRSA) SSSI. In the present study, the dynamics and mechanisms of this response were explored in recurrent SSSI in WT mice. Priming by prior infection reduced skin lesion severity and MRSA burden, and protected against dissemination at day 7 but not day 2. Cytokine and cellular signatures in SSSI differed at day 2 versus 7, and were distinct in skin versus blood or spleen. Cytokines associated with protection in skin included increased IL-17, IL-6, monokine inducible by IFN-γ (MIG), and RANTES, while increased IP-10 correlated with protection from dissemination. Cellular signatures of protection included increased Th17, M1 macrophage, and dendritic cell populations in abscesses, and total macrophages in lymph nodes. Priming potentiated S. aureus-specific phagocytic killing by bone marrow-derived macrophages in vitro, and their adoptive transfer into naïve skin afforded protective efficacy in vivo. Present findings indicate that protective immunity in recurrent S. aureus infection is locally targeted, and involves specific memory conferred by macrophages. These insights provide targets for vaccine and immunotherapeutic development against MRSA.

Innate Immune Memory Contributes to Host Defense against Recurrent Skin and Skin Structure Infections Caused by Methicillin-Resistant Staphylococcus aureus

Staphylococcus aureus is the leading cause of skin and skin structure infections (SSSI). The high frequency of recurring SSSI due to S. aureus, including methicillin-resistant S. aureus (MRSA) strains, despite high titers of specific antibodies and circulating T cells, implies that traditional adaptive immunity imparts incomplete protection. We hypothesized that innate immune memory contributes to the protective host defense against recurring MRSA infection. To test this hypothesis, SSSI was induced in wild-type and rag1^-/- mice in the BALB/c and C57BL/6 backgrounds. Prior infection (priming) of wild-type and rag1^-/- mice of either background afforded protection against repeat infection, as evidenced by reduced abscess severities and decreased CFU densities compared to those in naive controls. Interestingly, protection was greater on the previously infected flank than on the naive flank for wild-type and rag1^-/- mice. For wild-type mice, protective efficacy corresponded to increased infiltration of neutrophils (polymorphonuclear leukocytes [PMN]), macrophages (MΦ), Langerin⁺ dendritic cells (LDC), and natural killer (NK) cells. Protection was associated with the induction of interleukin-17A (IL-17A), IL-22, and gamma interferon (IFN-γ) as well as the antimicrobial peptides CRAMP and mβD-3. Priming also protected rag1^-/- mice against recurring SSSI, with increased MΦ and LDC infiltration and induction of IL-22, CRAMP, and mβD-3. These findings suggest that innate immune memory, mediated by specific cellular and molecular programs, likely contributes to the localized host defense in recurrent MRSA SSSI. These insights support the development of targeted immunotherapeutic strategies to address the challenge of MRSA infection.

Nonredundant Roles of Interleukin-17A (IL-17A) and IL-22 in Murine Host Defense against Cutaneous and Hematogenous Infection Due to Methicillin-Resistant Staphylococcus aureus

Staphylococcus aureus is the leading cause of skin and skin structure infections (SSSI) in humans. Moreover, the high frequency of recurring SSSI due to S. aureus, particularly methicillin-resistant S. aureus (MRSA) strains, suggests that infection induces suboptimal anamnestic defenses. The present study addresses the hypothesis that interleukin-17A (IL-17A) and IL-22 play distinct roles in immunity to cutaneous and invasive MRSA infection in a mouse model of SSSI. Mice were treated with specific neutralizing antibodies against IL-17A and/or IL-22 and infected with MRSA, after which the severity of infection and host immune response were determined. Neutralization of either IL-17A or IL-22 reduced T cell and neutrophil infiltration and host defense peptide elaboration in lesions. These events corresponded with increased abscess severity, MRSA viability, and CFU density in skin. Interestingly, combined inhibition of IL-17A and IL-22 did not worsen abscesses but did increase gamma interferon (IFN-γ) expression at these sites. The inhibition of IL-22 led to a reduction in IL-17A expression, but not vice versa. These results suggest that the expression of IL-17A is at least partially dependent on IL-22 in this model. Inhibition of IL-17A but not IL-22 led to hematogenous dissemination to kidneys, which correlated with decreased T cell infiltration in renal tissue. Collectively, these findings indicate that IL-17A and IL-22 have complementary but nonredundant roles in host defense against cutaneous versus hematogenous infection. These insights may support targeted immune enhancement or other novel approaches to address the challenge of MRSA infection.

Recurrent skin and soft tissue infections in HIV-infected patients during a 5-year period: incidence and risk factors in a retrospective cohort study

Background

Skin and soft tissue infections (SSTIs) are common in the era of community-associated methicillin resistant Staphylococcus aureus among HIV-infected patients. Recurrent infections are frequent. Risk factors for recurrence after an initial SSTI have not been well-studied.

Methods

Retrospective cohort study, single center, 2005–2009. Paper and electronic medical records were reviewed by one of several physicians. Subjects with initial SSTI were followed until the time of SSTI recurrence. Standard descriptive statistics were calculated to describe the characteristics of subjects who did and did not develop a recurrent SSTI. Kaplan-Meier methods were used to estimate the risk of recurrent SSTI. A Cox regression model was developed to identify predictors of SSTI recurrence.

Results

133 SSTIs occurred in 87 individuals. 85 subjects were followed after their initial SSTI, of whom 30 (35.3 %) had a recurrent SSTI in 118.3 person-years of follow-up, for an incidence of second SSTI of 253.6 SSTIs/1000 person-years (95 % CI 166.8-385.7). The 1-year Kaplan-Meier estimated risk of a second SSTI was 29.2 % (95 % CI 20.3–41.0 %), while the 3-year risk was 47.0 % (95 % CI 34.4–61.6 %). Risk factors for recurrent SSTI in a multivariable Cox regression model were non-hepatitis liver disease (HR 3.44; 95 % CI 1.02–11.5; p = 0.05), the presence of an intravenous catheter (HR 6.50; 95 % CI 1.47–28.7; p = 0.01), and a history of intravenous drug use (IVDU) (HR 2.80; 95 % CI 1.02-7.65; p = 0.05); African-American race was associated with decreased risk of recurrent SSTI (HR 0.12; 95 % CI 0.04-0.41; p < 0.01). Some evidence was present for HIV viral load ≥ 1000 copies/mL as an independent risk factor for recurrent SSTI (HR 2.21; 95 % CI 0.99-4.94; p = 0.05). Hemodialysis, currently taking HAART, CD4+ count, trimethoprim-sulfamethoxazole or azithromycin use, initial SSTI type, diabetes mellitus, incision and drainage of the original SSTI, or self-report of being a man who has sex with men were not associated with recurrence.

Conclusion

Of HIV-infected patients with an SSTI, nearly 1/3 had a recurrent SSTI within 1 year. Risk factors for recurrent SSTI were non-hepatitis liver disease, intravenous catheter presence, a history of IVDU, and non-African-American race. Low CD4+ count was not a significant risk factor for recurrence.

Trends in annual incidence of methicillin-resistant Staphylococcus aureus (MRSA) infection in HIV-infected and HIV-uninfected patients

We describe trends in incidence rates of methicillin-resistant Staphylococcus aureus (MRSA) in HIV-infected and HIV-uninfected patients enrolled in a large northern California Health Plan, and the ratio of MRSA to methicillin-susceptible S. aureus (MSSA) case counts. Between 1995 and 2010, 1549 MRSA infections were diagnosed in 14060 HIV-infected patients (11·0%) compared to 89546 MRSA infections in 6597396 HIV-uninfected patients (1·4%) (P = 0·00). A steady rise in MRSA infection rates began in 1995 in HIV-uninfected patients, peaking at 396·5 infections/100000 person-years in 2007. A more rapid rise in MRSA infection rates occurred in the HIV-infected group after 2000, peaking at 3592·8 infections/100000 in 2005. A declining trend in MRSA rates may have begun in 2008-2009. Comparing the ratio of MRSA to MSSA case counts, we observed that HIV-infected patients shouldered a greater burden of MRSA infection during most years of study follow-up compared to HIV-uninfected patients.

Coagulase-negative staphylococci in an HIV-infected child causing pancytopaenia

Although coagulase-negative staphylococci (CONS) constitute normal flora of the human body, some species can produce human infections, particularly when the host defense is breached. There is little evidence of the pathogenicity of CONS in HIV-infected individuals. We present the case of a 14-year-old HIV-infected boy who presented with a right lower zone pneumonia and a cutaneous abscess, following which he developed pancytopaenia due to underlying CONS infection that responded to antibiotic treatment.

Methicillin-Resistant Staphylococcus aureus Infections in Human Immunodeficiency Virus-Infected Children and Adolescents

Background. Methicillin-resistant Staphylococcus aureus (MRSA) infection incidence has increased in healthy US children. Our objective was to evaluate MRSA incidence and correlates in HIV-infected youth. Methods. The CDC-sponsored LEGACY study is a US multicenter chart abstraction study of HIV-infected youth. We identified MRSA infections among participants with ≥1 visit during 2006. We used bivariate and multivariable analyses to compare sociodemographic and HIV clinical factors between MRSA cases and noncases. Results. Fourteen MRSA infections (1 invasive, 12 soft tissue, 1 indeterminate) occurred among 1,813 subjects (11.1 infections/1,000 patient-years (PY), 95% CI: 11.06–11.14). Most (86%) isolates were clindamycin susceptible. Compared with noncases, MRSA cases were more likely older (17 versus 14 years), black (100% versus 69%), behaviorally HIV infected (43% versus 17%), and in Maryland (43% versus 7%) and had viral loads (VL) >1000 copies/mL (86% versus 51%) and lower mean CD4% (18% versus 27%) (all P < 0.05). In multivariate analysis, independent risk factors were Maryland care site (adjusted odds ratio (aOR) = 9.0), VL >1000 copies/mL (aOR = 5.9), and black race (aOR undefined). Conclusions. MRSA occurred at a rate of 11.1 infections/1,000 PY in HIV-infected youth but invasive disease was uncommon. Geographic location, black race, and increased VL, but not immunosuppression, were independently associated with MRSA risk.

Recurrent community-acquired methicillin-resistant Staphylococcus aureus infections in an HIV-infected person

HIV-infected persons are at heightened risk for recurrent community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections, but there are limited data regarding the molecular characterization of these events. We describe an HIV-infected patient with 24 soft tissue infections and multiple colonization events. Molecular genotyping from 33 nonduplicate isolates showed all strains were USA300, Panton-Valentine leukocidin (PVL) and arginine catabolic mobile element (ACME) positive, and genetically related.

Recurrent skin and soft tissue infections due to methicillin-resistant Staphylococcus aureus requiring operative debridement

BACKGROUND

The aim of this study was to examine clinical factors associated with the recurrence of community-onset skin and soft tissue infections caused by methicillin-resistant Staphylococcus aureus.

METHODS

An observational case-comparison study based on a retrospective review of medical records was conducted in a public health system. All patients with community-onset skin and soft tissue infections caused by methicillin-resistant S aureus who underwent operative debridement from January 1999 to December 2003 were included. The outcome of interest was recurrence within 1 year.

RESULTS

Two hundred fifty-three patients met the criteria for inclusion. Fifty-three (21%) patients returned with recurrent episodes. These patients were compared with 200 patients (79%) who did not develop recurrence. On multivariate analysis, factors independently predictive of recurrence were medical history of abscess requiring surgical debridement within the previous year (adjusted odds ratio, 2.6; 95% confidence interval, 1.4-5.0; P = .002) and obesity (adjusted odds ratio, 3.4; 95% confidence interval, 1.4-8.8; P = .008).

CONCLUSIONS

Patients with obesity or histories of methicillin-resistant S aureus infection are at significantly increased risk for recurrent soft tissue infection.

Community-associated methicillin-resistant Staphylococcus aureus: epidemiology and clinical consequences of an emerging epidemic

Staphylococcus aureus is an important cause of skin and soft-tissue infections (SSTIs), endovascular infections, pneumonia, septic arthritis, endocarditis, osteomyelitis, foreign-body infections, and sepsis. Methicillin-resistant S. aureus (MRSA) isolates were once confined largely to hospitals, other health care environments, and patients frequenting these facilities. Since the mid-1990s, however, there has been an explosion in the number of MRSA infections reported in populations lacking risk factors for exposure to the health care system. This increase in the incidence of MRSA infection has been associated with the recognition of new MRSA clones known as community-associated MRSA (CA-MRSA). CA-MRSA strains differ from the older, health care-associated MRSA strains; they infect a different group of patients, they cause different clinical syndromes, they differ in antimicrobial susceptibility patterns, they spread rapidly among healthy people in the community, and they frequently cause infections in health care environments as well. This review details what is known about the epidemiology of CA-MRSA strains and the clinical spectrum of infectious syndromes associated with them that ranges from a commensal state to severe, overwhelming infection. It also addresses the therapy of these infections and strategies for their prevention.

Recurrent community-associated methicillin-resistant Staphylococcus aureus infections among HIV-infected persons: incidence and risk factors

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) infections are well described among the general population, but little is known regarding the incidence of and predictors for recurrent CA-MRSA infections among HIV-infected persons. We retrospectively evaluated HIV-infected patients seen at the Naval Medical Center San Diego from January 1, 2000 to June 30, 2007 for wound culture-proven MRSA infections defined as community-associated based on Centers for Disease Control and Prevention (CDC) criteria. Data on skin/soft tissue infections (SSTIs) following an initial CA-MRSA infection were collected by review of medical records and culture results. Patients with or without recurrent infections were compared for predictors of recurrence using multivariate logistic regression models. Thirty-one (6.8%) of 458 patients with HIV had wound culture-proven CA-MRSA SSTIs for an incidence rate of 12.3 infections per 1000 person-years. Those who developed a MRSA infection had a mean age of 40 years, 97% were male, 58% were Caucasian, 23% were Hispanic, 16% were African American, and 3% were other; demographics were similar to the overall study population. Fourteen (41%) HIV patients with an initial MRSA infection had recurrent SSTIs; of these, seven (21%) had culture-confirmed recurrent CA-MRSA. The median time between infection recurrences was 4 months (range, 1-20 months). Suppressed HIV-1 RNA levels of less than 1000 copies per milliliter (odds ratio [OR] 0.14, p = 0.03) was associated with a lower rate of SSTI recurrence. In summary, HIV-infected persons have a high incidence of CA-MRSA skin/soft tissue infections and a high rate of recurrence. HIV control may be associated with a reduced risk of recurrent skin/soft tissue infections.

Prevalence of and risk factors for methicillin-resistant Staphylococcus aureus (MRSA) nasal colonization in HIV-infected ambulatory patients

BACKGROUND

Estimates of the prevalence of colonization with methicillin-resistant Staphylococcus aureus (MRSA) vary in HIV-infected patients.

METHODS

HIV clinic patients were prospectively cultured. Bilateral nasal and axillary swabs were plated on BBL CHROMagar MRSA media. Molecular typing was done by pulse-field gel electrophoresis, and staphylococcal cassette chromosomemec typing was determined. A patient questionnaire was conducted to ascertain potential MRSA risk factors; medical records were reviewed.

RESULTS

Fifteen of 146 (10.3%) patients had MRSA nasal colonization; 1 also had axillary colonization. Twelve of 15 isolates were staphylococcal cassette chromosomemec type IV, and 8 of 14 were USA300 or USA400 genotype. MRSA colonization was associated with lower CD4 cell count, not receiving current or recent antibiotics, history of prior MRSA or methicillin-susceptible Staphylococcus aureus infection (P < 0.05 for all), and a trend toward history of hospitalization or emergency department visit in the past year (P = 0.064). Current use of trimethoprim-sulfamethoxazole was protective for colonization: 0 of 29 trimethoprim-sulfamethoxazole recipients were colonized versus 15 of 117 nonrecipients, P = 0.04. In a multivariate logistic regression model, prior infection with either methicillin-susceptible S. aureus (odds ratio = 32.4, 95% confidence interval 3.04 to 345.42) or MRSA (odds ratio = 9.71, 95% confidence interval 2.20 to 43.01), not receiving current or recent antibiotics (odds ratio = 0.026, 95% confidence interval 0.002 to 0.412), and lower CD4 count (odds ratio 0.996, 95% confidence interval 0.992 to 0.999) were associated with MRSA colonization.

DISCUSSION

The prevalence of MRSA nasal colonization was relatively high compared with prior studies; axillary colonization was rare. Prior staphylococcal infection (methicillin-susceptible S. aureus or MRSA), not receiving antibiotics, and lower CD4 count were associated with MRSA nasal colonization. Trimethoprim-sulfamethoxazole seemed to be protective of MRSA colonization.

The incidence of and risk factors for MRSA bacteraemia in an HIV-infected cohort in the HAART era

OBJECTIVES

To define the incidence and risk factors for methicillin resistant Staphylococcus aureus (MRSA) bacteraemia in an HIV-infected population.

METHODS

From January 1, 2000 to December 31, 2004, we conducted a retrospective cohort study. We identified all cases of Staphylococcus aureus bacteraemia (SAB), including MRSA, among patients enrolled in the Johns Hopkins Hospital out-patient HIV clinic. A conditional logistic regression model was used to identify risk factors for MRSA bacteraemia compared with methicillin-sensitive SAB and no bacteraemia in unmatched (1:1) and matched (1:4) nested case-control analyses, respectively.

RESULTS

Of 4607 patients followed for a total of 11 020 person-years (PY) of follow-up, 216 episodes of SAB occurred (incidence: 19.6 cases per 1000 PY), including 94 cases (43.5%) which were methicillin-resistant. The incidence of MRSA bacteraemia increased from 5.3 per 1000 PY in 2000-2001 to 11.9 per 1000 PY in 2003-2004 (P=0.001). Multivariate analysis demonstrated that independent predictors of MRSA bacteraemia (vs. no bacteraemia) were injection drug use (IDU), end-stage renal disease (ESRD) and CD4 count <200 cells/microL.

CONCLUSIONS

MRSA bacteraemia was an increasingly common diagnosis in our HIV-infected cohort, especially in patients with history of IDU, low CD4 cell count and ESRD.

Penile cellulitis due to community-acquired methicillin-resistant Staphylococcus aureus in an HIV-positive man

This is a study of aggressive penile cellulitis in an HIV-positive man due to community-acquired methicillin-resistant Staphylococcus aureus. Discussion focuses on the importance of recognizing this pathogen in the sexual health setting and possible causes of penile cellulitis.

Community-associated methicillin-resistant Staphylococcus aureus in the patient with HIV infection

The prevalence of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has increased alarmingly in both the general population and the HIV-infected community. We look at the background of MRSA including the mechanisms of resistance, genetics, and trends in the individual with HIV infection. Numerous studies have investigated the risk factors for CA-MRSA. Other studies have further characterized the incidence of and risk factors for MRSA infections in the HIV community. Although one might not readily associate advanced HIV infection with increased susceptibility to bacterial pathogens, a number of studies have explained the mechanisms of this B-cell-mediated susceptibility. Invasive MRSA infections have spread into communities, are increasingly prevalent, and pose a public health challenge for their containment, prevention, and treatment.

Community-onset methicillin-resistant Staphylococcus aureus in an urban HIV clinic

OBJECTIVES

To determine the proportion of skin/soft tissue infections (SSTIs) and to determine risks for MRSA infection caused by methicillin-resistant Staphylococcus aureus (MRSA) in HIV-infected out-patients.

METHODS

We conducted a prospective study of SSTIs in HIV-infected out-patients. A questionnaire was used to record MRSA risk factors and treatment. In vitro testing for antibiotic susceptibility, inducible clindamycin resistance, panton-valentine leucocidin (PVL) toxin, and the staphylococcal chromosomal cassette mec (SCCmec) type was performed using standardized methods. Treatment outcomes included resolution of primary site of infection, nonresolution of infection and reinfection and were confirmed at clinic visit and/or telephone follow-up.

RESULTS

Forty-one of 44 patients had an SSTI caused by MRSA. African-Americans comprised 21 of 41 MRSA patients. The median CD4 count of MRSA patients was 411 cells/microL. Four patients required hospitalization and three patients had secondary bacteraemia. Twenty-one of 41 MRSA patients had healthcare-associated (HCA) MRSA risk factors including a history of prior MRSA infection (n=9) and hospitalization within 6 months (n=11). Other prevalent MRSA risk factors included receipt of systemic antibiotics within 6 months (n=21) and previous incarceration (n=19). Twenty-two patients had a significant non-HIV-related comorbid illness. The majority of isolates were susceptible to trimethoprim-sulfamethoxazole, tetracycline, and clindamycin. Inducible clindamycin resistance was detected in 0 of 16 erythromycin-resistant, clindamycin-susceptible MRSA isolates. Twenty-one of 24 isolates tested positive for SCCmec type IV. Twenty-four of 24 isolates tested positive for the PVL gene. Antibiotic treatment was discordant (bacteria nonsusceptible to antibiotic used) in eight MRSA patients. The primary SSTI resolved in 37 of 40 MRSA patients. Recurrence of infection at a site other than the primary site was relatively common (11 patients).

CONCLUSIONS

We found a high rate of MRSA causing SSTI in community-dwelling patients. The majority of isolates were positive for PVL and SCCmec IV, which is typical of community-associated MRSA isolates causing SSTIs in the general population. Inducible clindamycin resistance was not detected. Most patients had MRSA risk factors. The initial site of infection resolved in most cases but subsequent MRSA infection was relatively common.