Methicillin-Resistant Staphylococcus aureus Infection in the Texas Prison System

COVID-19 Case Fatality Rates in the Texas Prison System

The case fatality rate (CFR) is an important metric in the correctional setting because it permits assessment of the lethality of an infectious agent independent of its underlying variations in transmissibility and incidence. Several studies have reported that incarceration is associated with both increased COVID-19 incidence and mortality. CFR, sometimes referred to as infection fatality rate for COVID-19, was used to compare mortality in a population at two points in time. A retrospective cohort study design was used to assess age-adjusted mortality among people diagnosed with COVID-19 in the Texas prison system and the Texas nonincarcerated population from January 1, 2020, through December 31, 2021. For each 6-month period under study, the Texas prison population had a substantially lower age-adjusted CFR compared with the Texas nonincarcerated population. However, in the absence of information on underlying COVID-19 severity, comorbidities, and other potential confounding factors in these two populations, it is difficult to make strong inferences based on a comparison of their CFRs. Future research, with careful attention to bias and confounding, should examine the specific health system factors that may be used to reduce morbidity and mortality associated with infectious disease outbreaks in prisons.

Quality of Surgical Care Within the Criminal Justice Health Care System

Importance

Individuals who are incarcerated represent a vulnerable group due to concerns about their ability to provide voluntary and informed consent, and there are considerable legal protections regarding their participation in medical research. Little is known about the quality of surgical care received by this population.

Objective

To evaluate perioperative surgical care provided to patients who are incarcerated within the Texas Department of Criminal Justice (TDCJ) and compare their outcomes with that of the general nonincarcerated population.

Design, Setting, and Participants

This cohort study analyzed data from patients who were incarcerated within the TDCJ and underwent general or vascular surgery at the University of Texas Medical Branch (UTMB) from 2012 to 2021. Case-specific outcomes for a subset of these patients and for patients in the general academic medical center population were obtained from the American College of Surgeons National Quality Improvement Program (ACS-NSQIP) and compared. Additional quality metrics (mortality index, length of stay index, and excess hospital days) from the Vizient Clinical Data Base were analyzed for patients in the incarcerated and nonincarcerated groups who underwent surgery at UTMB in 2020 and 2021 to provide additional recent data. Patient-specific demographics, including age, sex, and comorbidities were not available for analysis within this data set.

Main Outcome and Measures

Perioperative outcomes (30-day morbidity, mortality, and readmission rates) were compared between the incarcerated and nonincarcerated groups using the Fisher exact test.

Results

The sample included data from 6675 patients who were incarcerated and underwent general or vascular surgery at UTMB from 2012 to 2021. The ACS-NSQIP included data (2012-2021) for 2304 patients who were incarcerated and 602 patients who were not and showed that outcomes were comparable between the TDCJ population and that of the general population treated at the academic medical center with regard to 30-day readmission (6.60% vs 5.65%) and mortality (0.91% vs 1.16%). However, 30-day morbidity was significantly higher in the TDCJ population (8.25% vs 5.48%, P = .01). The 2020 and 2021 data from the Vizient Clinical Data Base included 629 patients who were incarcerated and 2614 who were not and showed that the incarcerated and nonincarcerated populations did not differ with regard to 30-day readmission (12.52% vs 11.30%) or morbidity (1.91% vs 2.60%). Although the unadjusted mortality rate was significantly lower in the TDCJ population (1.27% vs 2.68%, P = .04), mortality indexes, which account for case mix index, were similar between the 2 populations (1.17 vs 1.12).

Conclusions and Relevance

Findings of this cohort study suggest that patients who are incarcerated have equivalent rates of mortality and readmission compared with a general academic medical center population. Future studies that focus on elucidating the potential factors associated with perioperative morbidity and exploring long-term surgical outcomes in the incarcerated population are warranted.

A cluster investigation of Candida auris among hospitalized incarcerated patients

Objective

Investigate and mitigate a cluster of Candida auris cases among incarcerated patients in a maximum-security prison hospital utilizing contact tracing, screening, whole genome sequencing, and environmental sampling and decontamination.

Design

Outbreak investigation.

Setting

Inpatient prison hospital affiliated with an academic tertiary referral center.

Patients

Inmates of the Texas Department of Criminal Justice.

Methods

Epidemiologic and environmental investigations were conducted including contact tracing, point prevalence surveys, and environmental sampling. Whole genome sequencing was performed on positive patient isolates.

Results

Following a clinical case of C. auris fungemia, 344 patients underwent C. auris surveillance screening. Eight (2.3%) patients were identified with C. auris colonization. All patients were male. Our index patient was the only clinical case and death. Whole genome sequencing was performed on the nine patient isolates. All isolates were clade III (Africa) and clustered together with the largest SNP difference being 21. Environmental cultures from 7 of 61 rooms (11.5%) were positive following terminal disinfection with bleach. Sites nearest to the patient were most often positive including the hospital bed rails and bedside table. The transmission cluster was successfully mitigated within 60 days of identification.

Conclusions

Implementation of an aggressive surveillance and decontamination program resulted in mitigation of a C. auris transmission cluster among our incarcerated patients. This investigation provides valuable insight into C. auris transmission in the incarcerated population, which is not considered a classic high-risk population as well as the challenges faced to stop transmission in a facility that requires the use of shared patient environments.

Genomic Analysis of Community Transmission Networks for MRSA among Females Entering a Large Inner-City Jail

Background

It is unclear if there are differences in MRSA risk between sexes in high-risk populations.

Methods

Females incarcerated at the Cook County Jail were enrolled within 72 hours of intake. Surveillance cultures (nares, throat, groin) were collected to determine prevalence of MRSA colonization. A survey was administered to identify colonization predictors. Univariate and multivariate analyses were performed to identify predictors of colonization at intake. Genomic sequencing was performed on MRSA colonization and archived clinical isolates.

Results

250 women were enrolled (70% AA, 15% Hispanic) with 70% previously in jail. The prevalence of MRSA colonization at intake was 20%, with 42% of those colonized solely in the throat or groin. Univariate predictors of MRSA colonization at entrance were illicit drug use, unstable housing, engaging in anal sex, recent exchange of sex for drugs/money, and a higher number of recent sexual partners. With multivariate adjustment for race/ethnicity, use of needles for illicit drugs was a significant predictor of MRSA. Use of illicit drugs was also associated with inclusion in a genomic cluster.

Nares colonization was significantly associated with not being in a genomic cluster (18.8% vs 78.6%, p<0.001), whereas exclusive extra-nasal colonization was associated (OR 15.89, p<0.001).

Conclusion

We found that a high proportion (20%) of females entered jail colonized with MRSA, suggesting that previously reported sex disparities of a lower risk in women may not apply to high-risk populations. Our findings suggest high-risk activities or venues in the community for MRSA, with potential for directing sex-specific interventions.

Type 2 diabetes mellitus and antibiotic-resistant infections: a systematic review and meta-analysis

BACKGROUND

Type 2 diabetes mellitus (T2DM) has been associated with infectious diseases; however, whether T2DM is associated with bacterial-resistant infections has not been thoroughly studied. We ascertained whether people with T2DM were more likely to experience resistant infections in comparison to T2DM-free individuals.

METHODS

Systematic review and random-effects meta-analysis. The search was conducted in Medline, Embase and Global Health. We selected observational studies in which the outcome was resistant infections (any site), and the exposure was T2DM. We studied adult subjects who could have been selected from population-based or hospital-based studies. I² was the metric of heterogeneity. We used the Newcastle-Ottawa risk of bias scale.

RESULTS

The search retrieved 3370 reports, 97 were studied in detail and 61 (449 247 subjects) were selected. Studies were mostly cross-sectional or case-control; several infection sites were studied, but mostly urinary tract and respiratory infections. The random-effects meta-analysis revealed that people with T2DM were twofold more likely to have urinary tract (OR=2.42; 95% CI 1.83 to 3.20; I² 19.1%) or respiratory (OR=2.35; 95% CI 1.49 to 3.69; I² 58.1%) resistant infections. Although evidence for other infection sites was heterogeneous, they consistently suggested that T2DM was associated with resistant infections.

CONCLUSIONS

Compelling evidence suggests that people with T2DM are more likely to experience antibiotic-resistant urinary tract and respiratory infections. The evidence for other infection sites was less conclusive but pointed to the same overall conclusion. These results could guide empirical treatment for patients with T2DM and infections.

Optimizing Treatment of Hand Infections: Is MRSA Coverage Always Necessary?

Multiple publications have highlighted the prevalence of methicillin resistant Staphylococcus aureus (MRSA) as a cause of hand infections. We hypothesized that these publications have shifted the empiric treatment of hand infections. The aim of this study was to identify the current standard of care, the most common causative bacteria, and factors leading to extended length of stay for hand infection patients at a suburban hospital to improve treatment and establish an optimized care protocol.

Methods

Retrospective cohort analysis was conducted to identify all patients admitted for hand infections over an 8-year period. A comprehensive chart review of each patient's hospital course was completed.

Results

A total of 70 patients were included. Maximum white blood cell count ≥ 12 was associated with a significantly longer hospital length of stay (9.1 days versus 5.4 days) compared to WBC values < 12 (P < 0.05). Also, 11 out of 23 (47.8%) underwent two or more incision and drainages (I&D's), compared with patients with maximum WBC < 12. Vancomycin use as an empiric antibiotic was widespread (68 patients, 97.1%), despite only 14 (20%) having MRSA positive cultures. Univariate analysis identified a significant increased likelihood for increased length of stay (P < 0.05) and rise in creatinine (P < 0.05) in patients with an initial vancomycin trough level > 20.

Conclusions

This analysis of hand infection treatment in a suburban hospital demonstrates the incidence of MRSA hand infections may not be universally high across institutions. Each hospital should review its own data to optimize hand infection treatment and its associated costs.

Methicillin Resistant Staphylococcus aureus and public fomites: a review

Staphylococcus genus is a Gram-positive coccus normally associated with skin and mucous membranes of warm-blooded animals. It is part of the commensal human microflora, or found in animals, or contaminating surfaces in the community and hospital settings. Staphylococcus aureus is the most pathogenic species belonging to this genus, as it possesses a collection of virulence factors that are expressed solely to evade the immune system. The increase in the misuse of antimicrobial agents predisposed S. aureus to develop antibiotic resistance, including the resistance to methicillin which led to the emergence of Methicillin-Resistant S. aureus (MRSA). MRSA is considered one of the most dangerous nosocomial pathogens causing many hard to treat infections in hospitals and was named as Hospital Associated MRSA (HA-MRSA). Over the past 20-25 years, MRSA was isolated from community settings and thus Community Associated MRSA (CA-MRSA) has emerged. Inside hospitals, MRSA has been isolated from fomites in contact with patients, as well as staff's protective and personal items. This review highlights the worldwide prevalence of MRSA on fomites within the contexts of hospital and community settings.

Drug Use Is Associated With Purulent Skin and Soft Tissue Infections in a Large Urban Jail: 2011-2015

Background

Skin and soft tissue infections (SSTIs) are a common problem in jails in the United States. This study aimed to identify factors associated with purulent SSTIs in the New York City jail system.

Methods

We conducted a case-control study of purulent SSTIs at the New York City jail. Cases were matched to controls by visit date to the jail’s urgent care clinic. Bivariate and multivariable analyses were conducted using conditional logistic regression.

Results

From April 2011 to April 2015, 1010 cases of SSTIs were identified and matched to 1010 controls. In multivariable analyses, report upon entry to jail of current injection drug use (odds ratio [OR], 2.76; 95% confidence interval [CI], 1.77–4.31), current snorting of drugs (OR, 1.50; 95% CI, 1.12–2.00), current heroin use (OR, 1.53; 95% CI, 1.08–2.17), current cocaine use (OR, 1.76; 95% CI, 1.18–2.65), and antibiotic use within the previous 6 months (OR, 4.05; 95% CI, 2.98–5.49) were significantly associated with SSTI diagnosis.

Conclusions

Skin and soft tissue infections were strongly associated with a history of drug use at jail entry. Targeting intravenous drug use may be a preventive strategy for SSTIs in this population. Strategies such as harm reduction programs may be investigated.

Epidemiology of Infectious Disease-Related Death After Release from Prison, Washington State, United States, and Queensland, Australia: A Cohort Study

OBJECTIVES

People in prison may be at high risk for infectious diseases and have an elevated risk of death immediately after release compared with later; their risk of death is elevated for at least a decade after release. We compared rates, characteristics, and prison-related risk factors for infectious disease-related mortality among people released from prisons in Queensland, Australia, and Washington State, United States, regions with analogous available data.

METHODS

We analyzed data from retrospective cohort studies of people released from prison in Queensland (1997-2007, n=37,180) and Washington State (1999-2009, n=76,208) and linked identifiers from each cohort to its respective national death index. We estimated infectious disease-related mortality rates (deaths per person-years in community) and examined associations using Cox proportional hazard models.

RESULTS

The most frequent infectious disease-related underlying cause of death after release from prison was pneumonia (43%, 23/54 deaths) in the Australian cohort and viral hepatitis (40%, 69/171 deaths) in the U.S. cohort. The infectious disease-related mortality rate was significantly higher in the U.S. cohort than in the Australian cohort (51.2 vs. 26.5 deaths per 100,000 person-years; incidence rate ratio = 1.93, 95% confidence interval 1.42, 2.62). In both cohorts, increasing age was strongly associated with mortality from infectious diseases.

CONCLUSION

Differences in the epidemiology of infectious disease-related mortality among people released from prison may reflect differences in patterns of community health service delivery in each region. These findings highlight the importance of preventing and treating hepatitis C and other infectious diseases during the transition from prison to the community.

The Intersecting Epidemics of Human Immunodeficiency Virus, Community-Associated Methicillin-Resistant Staphylococcus aureus, and Incarceration

Community-associated methicillin-resistant Staphylococcus aureus (MRSA) has had a significant impact on human immunodeficiency virus (HIV)-infected and incarcerated individuals. We examined electronic medical surveillance data from 2006 to 2011 and observed that even in a population of currently or recently incarcerated individuals, HIV status was a significant risk factor for MRSA infections and Hispanic ethnicity was protective.

Obesity as a Determinant of Staphylococcus aureus Colonization Among Inmates in Maximum-Security Prisons in New York State

Obesity increases a person's susceptibility to a variety of infections, including Staphylococcus aureus infections, which is an important cause of morbidity in correctional settings. Using a cross-sectional design, we assessed the association between obesity and S. aureus colonization, a risk factor for subsequent infection, in New York State maximum-security prisons (2011-2013). Anterior nares and oropharyngeal cultures were collected. Structured interviews and medical records were used to collect demographic, behavioral, and medical data. Body mass index (BMI; weight (kg)/height (m(2))) was categorized as 18.5-24.9, 25-29.9, 30-34.9, or ≥35. The association between BMI and S. aureus colonization was assessed using log-binomial regression. Thirty-eight percent of 638 female inmates and 26% of 794 male inmates had a BMI of 30 or higher. More than 40% of inmates were colonized. Female inmates with a BMI of 25-29.9 (prevalence ratio (PR) = 1.37, 95% confidence interval (CI): 1.06, 1.76), 30-34.9 (PR = 1.52, 95% CI: 1.17, 1.98), or ≥35 (PR = 1.49, 95% CI: 1.13, 1.96) had a higher likelihood of colonization than did those with a BMI of 18.5-24.9 after we controlled for age, educational level, smoking status, diabetes status, and presence of human immunodeficiency virus. Colonization was higher among male inmates with a BMI of 30-34.9 (PR = 1.27, 95% CI: 1.01, 1.61). Our findings demonstrate an association between BMI and S. aureus colonization among female prisoners. Potential contributory biologic and behavioral factors should be explored.

Methicillin-ResistantStaphylococcus aureusInfection and Colonization Among Hospitalized Prisoners

We assessed methicillin-resistantStaphylococcus aureus(MRSA) infection and colonization in hospitalized prisoners. Of 434 admission surveillance cultures, 58 (13%) were positive for MRSA. The sensitivity of admission surveillance cultures of samples from the anterior nares was 72% and increased to 84% when the calculation included cultures of wound samples. Hospitalized prisoners are at high risk for MRSA infection and colonization, and surveillance should include cultures of nares and wound samples.

Non-multidrug-resistant, methicillin-resistant Staphylococcus aureus in a neonatal unit

BACKGROUND

In the last decade, non-multiresistant methicillin-resistant Staphylococcus aureus (NM-MRSA) has been described as an important agent in bloodstream infections in our hospital.

METHODS

This prospective cohort study, conducted from February 2009 through January 2010 in the neonatal unit, evaluated 403 newborns (NB), their 382 mothers and 148 health care workers (HCW).

RESULTS

Approximately 217 NB (54%), 187 mothers (48%) and 87 HCW (59%) were colonized by S. aureus (SA). MRSA colonization was greater among NB (15%) than mothers (4.7%) and HCW (3.4%). Although mother-to-NB transmission occurred, in most cases mothers were not responsible for NB colonization. There were 2 predominant PFGE patterns among the NB and some mothers and HCW became colonized by them. Factors significantly associated with MRSA carriage by NB were lower level of maternal schooling (risk factor: odds ratio: 2.99; 95% confidence interval: 1.10-8.07) and maternal rhinosinusitis (protective factor: odds ratio: 0.33; 95% confidence interval:0.12-0.88). Among NB who remained hospitalized for more than 72 hours, breast feeding was protective (odds ratio: 0.22; 95% confidence interval: 0.05-0.98). All the isolates were NM-MRSA, carried few virulence factors and SCCmec types IVa and type IVd predominated.

CONCLUSIONS

Although there were no cases of infection, nosocomial transmission of MRSA clearly occurred in the neonatal unit, and this highlights the need for infection control practices such as hand hygiene to prevent cross-dissemination. Other healthcare practices, which are very basic but also ample in scope, may play a role, such as general education of women and breast feeding.

Prevalence of and risk factors for methicillin-resistant Staphylococcus aureus colonization in HIV infection: a meta-analysis

BACKGROUND

Human immunodeficiency virus (HIV)-infected individuals who are colonized with methicillin-resistant Staphylococcus aureus (MRSA) have increased risk for MRSA infection. We conducted a meta-analysis of published studies to estimate the prevalence of MRSA colonization in this population.

METHODS

We performed a systematic literature review and meta-analysis. The PubMed and Embase databases were searched and studies reporting prevalence of MRSA colonization among HIV-infected individuals were included.

RESULTS

Among 7940 citations, 32 studies reporting data on 6558 HIV-infected individuals were considered eligible for our meta-analysis. We found that 6.9% (95% confidence interval [CI], 4.8-9.3) of individuals with HIV infection are MRSA carriers, with the corresponding figure across North American studies being 8.8% (95% CI, 6.0-12.2). History of hospitalization during the previous 12 months was associated with a 3.1 times higher risk of MRSA colonization (risk ratio [RR], 3.11 [95% CI, 1.62-5.98]). Previous or current incarceration was also associated with a higher risk for carriage (RR, 1.77 [95% CI, 1.26-2.48]). Current antiretroviral therapy or use of trimethoprim-sulfamethoxazole did not impact the risk of MRSA carriage (RR, 1.02 [95% CI, .64-1.63] and 1.45 [95% CI, .69-3.03], respectively). Extranasal screening increased the detection of MRSA colonization by at least 31.6% (95% CI, 15.8-50.0). The added yield from groin screening was 19.3% (95% CI, 11.5-28.5), from perirectal screening 18.5% (95% CI, 7.4-33.2), and from throat cultures 17.5% (95% CI, 12.0-24).

CONCLUSIONS

Individuals with HIV infection constitute a highly vulnerable population for MRSA colonization, and prior exposure to hospital or incarceration are significant factors. Nasal screening alone will underestimate the rate of colonization by at least one-third.

Hand and nasal carriage of discordant Staphylococcus aureus isolates among urban jail detainees

In 928 Dallas County Jail detainees, nasal carriage of Staphylococcus aureus was found in 32.8% (26.5% methicillin-susceptible Staphylococcus aureus [MSSA] and 6.3% methicillin-resistant S. aureus [MRSA]), and hand carriage was found in 24.9% (20.7% MSSA and 4.1% MRSA). Among MRSA nasal carriers, 41% had hand MRSA carriage; 29% with hand MRSA carriage had no nasal S. aureus carriage. The prevalence of carriage was not associated with duration of the jail stay up to 180 days.

Impact of community-associated methicillin resistant Staphylococcus aureus on HIV-infected patients

Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has emerged as an increasingly important pathogen, causing infections in persons who have no significant healthcare exposures. Persons with human immunodeficiency virus (HIV) infection have been disproportionately affected by CA-MRSA, with increased colonization and infection documented. Several factors are likely involved in the increased CA-MRSA burden observed among HIV-infected patients, including immune factors as well as healthcare and community exposures. Proposed community exposures that have been associated with increased CA-MRSA risk include substance abuse, incarceration, geographic area of residence, and social networks. This article explores these associations and reviews the current knowledge of the epidemiology, pathogenesis, clinical manifestations, and treatment of CA-MRSA in HIV-infected persons.

Transmission of methicillin-resistant Staphylococcus aureus in the long term care facilities in Hong Kong

Background

The relative contribution of long term care facilities (LTCFs) and hospitals in the transmission of methicillin-resistant Staphylococcus aureus (MRSA) is unknown.

Methods

Concurrent MRSA screening and spa type analysis was performed in LTCFs and their network hospitals to estimate the rate of MRSA acquisition among residents during their stay in LTCFs and hospitals, by colonization pressure and MRSA transmission calculations.

Results

In 40 LTCFs, 436 (21.6%) of 2020 residents were identified as ‘MRSA-positive’. The incidence of MRSA transmission per 1000-colonization-days among the residents during their stay in LTCFs and hospitals were 309 and 113 respectively, while the colonization pressure in LTCFs and hospitals were 210 and 185 per 1000-patient-days respectively. MRSA spa type t1081 was the most commonly isolated linage in both LTCF residents (76/121, 62.8%) and hospitalized patients (51/87, 58.6%), while type t4677 was significantly associated with LTCF residents (24/121, 19.8%) compared with hospitalized patients (3/87, 3.4%) (p < 0.001). This suggested continuous transmission of MRSA t4677 among LTCF residents. Also, an inverse linear relationship between MRSA prevalence in LTCFs and the average living area per LTCF resident was observed (Pearson correlation −0.443, p = 0.004), with the odds of patients acquiring MRSA reduced by a factor of 0.90 for each 10 square feet increase in living area.

Conclusions

Our data suggest that MRSA transmission was more serious in LTCFs than in hospitals. Infection control should be focused on LTCFs in order to reduce the burden of MRSA carriers in healthcare settings.

Persistent nasal methicillin-resistant staphylococcus aureus carriage in hemodialysis outpatients: a predictor of worse outcome

Background

Nasal colonization with methicillin-resistant Staphylococcus aureus (MRSA) is a well defined risk factor for subsequent bacteremia and death in various groups of patients, but its impact on outcome in patients receiving long-term hemodialysis (HD) is under debate.

Methods

This prospective interventional cohort study (performed 2004 to 2010) enrolled 289 HD outpatients of an urban dialysis-unit. Nasal swab cultures for MRSA were performed in all patients upon first admission, at transfer from another dialysis facility or readmission after hospitalisation. Nasal MRSA carriers were treated in a separate ward and received mupirocin nasal ointment. Concomitant extra-nasal MRSA colonization was treated with 0.2% chlorhexidine mouth rinse (throat) or octenidine dihydrochloride containing antiseptic soaps and 2% chlorhexidine body washes (skin). Clinical data and outcome of carriers and noncarriers were systematically analyzed.

Results

The screening approach identified 34 nasal MRSA carriers (11.7%). Extra-nasal MRSA colonization was observed in 11/34 (32%) nasal MRSA carriers. History of malignancy and an increased Charlson Comorbidity Index were significant predictors for nasal MRSA carriers, whereas traditional risk factors for MRSA colonization or markers of inflammation or malnutrition were not able to discriminate. Kaplan-Meier analysis demonstrated significant survival differences between MRSA carriers and noncarriers. Mupirocin ointment persistently eliminated nasal MRSA colonization in 26/34 (73.5%) patients. Persistent nasal MRSA carriers with failure of this eradication approach had an extremely poor prognosis with an all-cause mortality rate >85%.

Conclusions

Nasal MRSA carriage with failure of mupirocin decolonization was associated with increased mortality despite a lack of overt clinical signs of infection. Further studies are needed to demonstrate whether nasal MRSA colonization represents a novel predictor of worse outcome or just another surrogate marker of the burden of comorbid diseases leading to fatal outcome in HD patients.

Impact of clinical severity index, infective pathogens, and initial empiric antibiotic use on hospital mortality in patients with ventilator-associated pneumonia

BACKGROUND

The prompt initial use of appropriate antibiotics should improve mortality rates in adults with ventilator-associated pneumonia (VAP). However, the incidence of multidrug-resistant (MDR) pathogen infections is on the rise, and the choice of the initial empiric antibiotic may be challenging. We investigated whether appropriate initial antibiotic therapy, infective pathogens, and the clinical severity index influence hospital mortality in patients with VAP and determined independent risk factors for the same.

METHODS

This study evaluated 163 adult patients (aged ≥ 18 years) at Chang Gung Memorial Hospital, Kaohsiung, Taiwan, from January 1, 2007, to January 31, 2008. Eligibility was evaluated based on criteria for VAP. Sequential Organ Failure Assessment (SOFA) scores, Acute Physiological Assessment and Chronic Health Evaluation II (APACHE II) scores, oxygenation index, underlying comorbidities, septic shock status, previous tracheostomy status, and factors related to pneumonia were collected for analysis.

RESULTS

Ninety-two patients survived from a total 163 patients with VAP during the course of their confinement in the intensive care unit. Multivariable logistic regression analysis identified that a pre-existing Charlson Comorbidity Index score (P = .011), initial oxygenation index (P = .025), SOFA score (P = .043), VAP caused by Acinetobacter baumanii (P = .030), and infection with MDR pathogens (P = .003) were independent risk factors for hospital mortality in patients with VAP.

CONCLUSION

High Charlson Comorbidity Index score, high initial oxygenation index, high SOFA score, and infection with Acinetobacter baumannii or MDR pathogens significantly affect hospital mortality in patients with VAP.

Outbreaks of infection caused by community-acquired methicillin-resistant Staphylococcus aureus in a Canadian correctional facility

BACKGROUND

Methicillin-resistant Staphylococcus aureus (MRSA) has been identified in prison settings in the United States. The present study investigated two clusters of skin and soft tissue infection caused by community-acquired (CA) MRSA in a correctional facility in southern Ontario.

METHODS

Outbreak investigations were conducted by the responsible public health authority. Strain relatedness was assessed through comparison of pulsed-field gel electrophoresis and antibiograms.

RESULTS

Two distinct outbreaks of CAMRSA-associated disease occurred in 2002 and 2004. Most patients presented with abscesses in the lower extremities. All isolates had identical DNA banding patterns on pulsed-field gel electrophoresis. One-half of the affected inmates resided in a cellblock with one other affected inmate. No other risk factors were identified.

CONCLUSIONS

One of the first outbreaks of CAMRSA infections in a correctional facility in Canada is documented. Taken in conjunction with outbreaks elsewhere, this suggests that residence in correctional facilities may be a risk factor for CAMRSA infection.

The rise of methicillin-resistant staphylococcus aureus in U.S. correctional populations

Methicillin-resistant Staphylococcus aureus (MRSA) is an emerging threat to public health, especially in correctional settings. Outbreaks have been seen in jails and prisons in Mississippi, California, Texas, and Georgia in recent years. Also, many correctional settings have seen an increase in MRSA infection greater than in the general population. This article examines the lessons that have been learned about MRSA in correctional settings and ponders what is yet to be learned about this disease in these populations.

Phenotypic and molecular characterization of Acinetobacter clinical isolates obtained from inmates of California correctional facilities

Acinetobacter spp. increasingly have been wreaking havoc in hospitals and communities worldwide. Although much has been reported regarding Acinetobacter isolates responsible for nosocomial infections, little is known about these organisms in correctional facilities. In this study, we performed species identification, examined the antibiotic resistance profiles, and determined the mechanisms of resistance and clonal relationships of 123 Acinetobacter isolates obtained from inmates of 20 California correctional facilities (CCFs). We found that 57.7% of the isolates belong to A. baumannii, followed by isolates of Acinetobacter genomic species 3 (gen. sp. 3; 23.6%) and of Acinetobacter gen. sp. 13TU (10.6%). Multidrug-resistant (MDR) CCF isolates were found in only six CCFs. Additionally, DNA sequences of gyrA and parC genes were consistent with fluoroquinolone (FQ) susceptibility phenotypes. Furthermore, the presence of class 1 integrons was detected in 15 CCF isolates, all of which are MDR. Integron-associated gene cassettes encode several aminoglycoside modification enzymes, which correlate with most of the aminoglycoside-resistant phenotypes. Antimicrobial susceptibility testing in the presence of Phe-Arg-β-naphthylamide dihydrochloride and 1-(1-naphthylmethyl)-piperazine indicated the involvement of efflux pumps in the FQ resistance of only a few CCF isolates. Finally, genetic profiling showed that there was no evidence of A. baumannii outbreaks in CCFs. Instead, our analyses revealed only limited clonal dissemination of mostly non-MDR A. baumannii strains in a few facilities. This study represents the first report to characterize phenotypic and molecular features of Acinetobacter isolates in correctional facilities, which provides a baseline for monitoring the antimicrobial resistance changes and dissemination patterns of these organisms in such specialized institutions.

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.

Community-based intervention to manage an outbreak of MRSA skin infections in a county jail

This article describes a community-based intervention to manage an outbreak of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) skin infections in a midwestern county jail. A systematic investigation conducted by a family medicine residency program identified 64 total cases and 19 MRSA cases between January 1 and December 31, 2007. Factors contributing to MRSA transmission included inadequate surveillance, lack of antibacterial soap, and a defective laundry process. All 19 isolates were CA-MRSA and all seven tested by pulsed-field gel electrophoresis (PFGE) were USA300. Four of the seven isolates showed variation of their PFGE patterns. A primary care approach using community-based resources effectively reduced the number of cases in this heterogeneous outbreak of CA-MRSA, with the last MRSA being isolated in October 2007.

Hand infections

Hand infections are very common and must be properly diagnosed and treated to minimize the potentially devastating functional complications. Acute hand infections include felon, paronychia, deep-space infections, septic arthritis, osteomyelitis, and necrotizing fasciitis. Chronic infections are usually caused by atypical mycobacteria and fungi. There are several conditions that mimic acute hand infections, and it is important to recognize them so that the appropriate treatment can be instilled. To prevent all these complications and poor outcome, prompt diagnosis and early institution of appropriate surgical management and antibiotic treatment are crucial.

Prevalence, risk factors, and molecular epidemiology of methicillin-resistant Staphylococcus aureus among newly arrested men in Baltimore, Maryland

BACKGROUND

Outbreaks of methicillin-resistant Staphylococcus aureus (MRSA) within prison populations seemingly attest to its spread within the corrections industry; however, the extent of MRSA colonization on arrest is unknown.

METHODS

This study determined the prevalence and risk factors of S aureus on arrest. Nasal swabs from 602 newly arrested men were evaluated. Risk factors were assessed through self-report. Molecular characterization of each isolate was completed.

RESULTS

The prevalence of S aureus nasal colonization was 40.4% (243/602). MRSA colonization was found in 15.8% (95/602) of the total population and in 39.1% (95/243) of the total S aureus isolates. Twenty-three skin infections were identified; of these, 11 (47.8%) were S aureus infections, with methicillin-susceptible S aureus (MSSA) in accounting for 3 cases (13.1%) and MRSA accounting for 8 cases (34.8%). In 2 cases (25%) of MRSA wound infection, the nasal colonizing strain was MSSA. By pulsed-field gel electrophoresis, 76 of 95 (80%) nasal isolates were found to be USA300 or related subtypes, with the other 19 (20%) being non-USA300 strains. The Panton-Valentine leukocidin gene was identified in 38 (97.4%) USA300 isolates and in 6 (31.6%) non-USA 300 isolates.

CONCLUSION

MRSA colonization is far greater in this sample than in the general public. USA300 subtypes are highly prevalent. History of previous arrest was not associated with increased MRSA prevalence. MRSA risk factors differed significantly between those with and without a history of previous arrest.

Long-term follow-up of methicillin-resistant Staphylococcus aureus molecular epidemiology after emergence of clone USA300 in San Francisco jail populations

We performed a longitudinal analysis of 502 unique methicillin-resistant Staphylococcus aureus (MRSA) clinical isolates originating from San Francisco jail inmates between 2000 and 2007. Strain USA300, first encountered in 2001, accounted for 82.1% (412/502) of MRSA infections. Non-USA300 MRSA strains were rarely found after 2005 (one isolate in 2006, three in 2007).

Skin and soft-tissue infections caused by community-acquired methicillin-resistant Staphylococcus aureus

Community-acquired methicillin-resistant Staphylococcus aureus (MRSA) infection has become epidemic. Skin and soft-tissue infections (SSTIs) are the most frequent forms of the disease. Obtainment of culture specimens is important for documentation of the presence of MRSA and for susceptibility testing to guide therapy. Purulent lesions should be drained whenever possible. In areas where community-acquired MRSA isolates are prevalent, uncomplicated SSTI in healthy individuals may be treated empirically with clindamycin, trimethoprim-sulfamethoxazole, or long-acting tetracyclines, although specific data supporting the efficacy of these treatments are lacking. In healthy patients with small purulent lesions, drainage alone may be sufficient. In patients with complicated SSTI requiring hospitalization or intravenous therapy, vancomycin is the drug of choice because of the low cost, efficacy, and safety. Linezolid, daptomycin, and tigecycline are also effective, although published studies on the last 2 agents for the treatment of SSTI due to MRSA are more limited. Dalbavancin, telavancin, and ceftobiprole are investigational agents that may expand our therapeutic options for the treatment of SSTI caused by MRSA.

Modelling an outbreak of an emerging pathogen

To illustrate the usefulness of mathematical models to the microbiology and medical communities, we explain how to construct and apply a simple transmission model of an emerging pathogen. We chose to model, as a case study, a large (>8,000 reported cases) on-going outbreak of community-acquired meticillin-resistant Staphylococcus aureus (CA-MRSA) in the Los Angeles County Jail. A major risk factor for CA-MRSA infection is incarceration. Here, we show how to design a within-jail transmission model of CA-MRSA, parameterize the model and reconstruct the outbreak. The model is then used to assess the severity of the outbreak, predict the epidemiological consequences of a catastrophic outbreak and design effective interventions for outbreak control.

Methicillin-resistant Staphylococcus aureus infection or colonization present at hospital admission: multivariable risk factor screening to increase efficiency of surveillance culturing

Identifying methicillin-resistant Staphylococcus aureus (MRSA) colonization or infection present at admission has become important in reducing subsequent nosocomial transmission, but the most efficient surveillance methods remain to be defined. We performed anterior nares surveillance cultures of all patients upon admission to and discharge from the general internal medicine floor in our community hospital over a 7-week period, and patients completed a questionnaire on MRSA risk factors. Of the 401 patients, 41 (10.2%) had MRSA upon admission. Of the 48 risk measures analyzed, 10 were significantly associated with admission MRSA, and 7 of these were independently associated in stepwise logistic regression analysis. Factor analysis identified eight latent variables that contained most of the predictive information in the 48 risk measures. Repeat logistic regression analysis including the latent variables revealed three independent risk measures for admission MRSA: a nursing home stay (relative risk [RR], 6.18; 95% confidence interval [95% CI], 3.56 to 10.72; P < 0.0001), prior MRSA infection (RR, 3.97; 95% CI, 1.94 to 8.12; P = 0.0002), and the third latent variable (factor 3; RR, 3.14; 95% CI, 1.56 to 6.31; P = 0.0013), representing the combined effects of homelessness, jail stay, promiscuity, intravenous drug use, and other drug use. Multivariable models had greater sensitivity at detecting admission MRSA than any single risk measure and allowed detection of 78% to 90% of admission MRSA from admission surveillance cultures on 46% to 58% of admissions. If confirmed in additional studies, multivariable questionnaire screening at admission might identify a subset of admissions for surveillance cultures that would more efficiently identify most admission MRSA.

Burden of methicillin-resistant Staphylococcus aureus: focus on clinical and economic outcomes

Infections caused by methicillin-resistant Staphylococcus aureus (MRSA) are a major public concern. Hospital-acquired MRSA rates have steadily increased over the past 25 years, and the bacterial strain is making inroads to the community. The morbidity and mortality burden of MRSA infection is compounded by delayed or inappropriate antibiotic treatment, taking a toll on health care resources that are already stretched thin. Vancomycin has historically been the drug of choice for this pathogen because its broad spectrum can address the multidrug resistance of most MRSA infections. Despite its sustained in vitro microbiologic inhibitory activity, researchers are beginning to question the continued utility of vancomycin for MRSA infections. Evidence against vancomycin is most notable with regard to nosocomial pneumonia and skin and soft tissue infections. In addition, because vancomycin must be administered intravenously, patients typically require prolonged hospitalization, which further increases the cost of MRSA treatment and exposes patients to additional nosocomial infections. Recent studies have shown that antibiotics with good bioavailability, such as linezolid, can be given orally to facilitate early hospital discharge, thus alleviating the economic burden of MRSA infections. Several agents have been developed over the past decade that have excellent in vitro activity against MRSA. Further studies are needed to determine if these drugs can better eradicate MRSA than vancomycin and remedy the adverse outcomes frequently observed with this organism.

Prospective comparison of methicillin-susceptible and methicillin-resistant community-associated Staphylococcus aureus infections in hospitalized patients

BACKGROUND

We sought to determine the proportion of community-associated Staphylococcus aureus infections due to methicillin-resistant S. aureus (CA-MRSA) at a large county hospital. In addition, we sought to identify the demographic and clinical risk factors associated with CA-MRSA infection.

METHODS

Patients were prospectively enrolled if they were admitted to Parkland Hospital and had a positive culture for S. aureus isolated within 72 h of admission. The patients were interviewed using a standardized data questionnaire. Data collected included patient demographics, clinical history, as well as health care and non-health care associated MRSA risk factors. Bacterial susceptibilities were verified through review of microbiology laboratory and pharmacy records. Isolates were tested for Panton-Valentine leukocidin (PVL) gene, SCCmec type, and for inducible clindamycin resistance.

RESULTS

One hundred and ninety-eight patients were interviewed prospectively, of which eight had colonization without active infection. One hundred and nineteen patients were infected with MRSA and 71 patients were infected with methicillin-susceptible S. aureus (MSSA). Patients with MRSA were more likely to be African-American and unemployed. Patients with MRSA most commonly presented with a skin or soft tissue infection (SSTI): 69% versus 45%, p=0.0012, while patients with MSSA were more likely to have infection of the respiratory tract: 11% versus 3%, p=0.02. Patients with MRSA were more likely to have used antibiotics in the past six months, been homeless, have a history of incarceration, have abused alcohol and have a history of infection with MRSA. In multivariate analysis, African-American race, antibiotics in the past six months, and a history of being homeless were associated with MRSA infection. Only 11 of 119 (9%) MRSA patients did not have at least one of these risk factors. PVL gene was present in 72 of 74 (97%) MRSA isolates and SCCmec type IV was present in 63 of 75 (84%) MRSA isolates.

CONCLUSIONS

The majority of patients hospitalized with community-associated S. aureus infections were due to MRSA, most of which involved an SSTI. African-American race, recent antibiotics and past homeless status predicted infection with MRSA; however, no clinical profile could reliably exclude MRSA. Clinicians should be aware of the increasing prevalence of CA-MRSA.

Increasing incidence of methicillin-resistant Staphylococcus aureus in hand infections: a 3-year county hospital experience

BACKGROUND

Staphylococcus aureus is the most common cause of skin and soft-tissue infections. Methicillin-resistant S. aureus and community-acquired methicillin-resistant S. aureus have shown an increase in prevalence among soft-tissue infections over the past several years, with overall rates approaching 50 percent at the authors' institution in 2002. The object of this study was to determine the incidence of methicillin-resistant S. aureus with respect to hand infections, the antibiotic resistance pattern of methicillin-resistant S. aureus isolates, and implications for a change in antibiotic treatment algorithms for hand infections.

METHODS

A retrospective chart review of 761 patients with hand infections tracked by International Classification of Diseases, 9th Revision codes for finger or hand abscesses from 2001 to 2003 was performed at Parkland Memorial Hospital, Dallas, Texas. Culture results were obtained from 436 patients and analyzed for type of organism, and sensitivity profiles were obtained for all methicillin-resistant S. aureus isolates.

RESULTS

The median age of 761 patients was 40 years (range, 16 to 77 years); 71 percent were male and 28 percent were female. Of the 436 cultures reviewed, 371 (85 percent) had organisms identified. Methicillin-resistant S. aureus was the dominant single organism in hand infections cultured in all 3 years. The overall methicillin-resistant S. aureus rate was 61 percent of all hand infections in 2003. The percentage of S. aureus isolates identified as methicillin-resistant S. aureus increased from 55 percent to 78 percent over 3 years, up from 34 percent in 2001. Fortunately, 86 percent of these methicillin-resistant S. aureus isolates demonstrated sensitivity to conventional antibiotics, but a trend of resistance is developing.

CONCLUSIONS

The incidence of community-acquired methicillin-resistant S. aureus increased from 34 percent to 61 percent over a 3-year period at the authors' county institution. An increasing trend of resistance patterns among conventional antibiotics was also demonstrated. As a result of this study, the treatment algorithm at Parkland Memorial Hospital has been modified to include abscess drainage accompanied by an antibiotic regimen targeted specifically at methicillin-resistant S. aureus. These data also have implications for broader application regarding simple skin infections and current antibiotic treatment algorithms.

Predictors of hospitalization for injection drug users seeking care for soft tissue infections

BACKGROUND

Soft tissue infections (STIs) from injection drug use are a common cause of Emergency Department visits, hospitalizations, and operating room procedures, yet little is known about factors that may predict the need for these costly medical services.

OBJECTIVE

To describe a cohort of injection drug users seeking Emergency Department care for STIs and to identify risk factors associated with hospitalization. We hypothesized that participants who delayed seeking care would be hospitalized more often than those who did not.

DESIGN

Cohort study using in-person structured interviews and medical record review. Logistic regression assessed the association between hospital admission and delay in seeking care as well as other demographic, clinical, and psychosocial factors.

PARTICIPANTS

Injection drug users who sought Emergency Department care for STIs from May 2001 to March 2002.

RESULTS

Of the 136 participants, 55 (40%) were admitted to the hospital. Delay in seeking care was not associated with hospital admission. Participants admitted for their infection were significantly more likely to be living in a shelter (P = .01) and to report being hospitalized 2 or more times in the past year (P < .01).

CONCLUSIONS

We identified a subpopulation of injection drug users, mostly living in shelters, who were hospitalized frequently in the past year and who were more likely to be hospitalized for their current infections compared to others. As members of this subpopulation can be easily identified and located, they may benefit from interventions to reduce the health care utilization resulting from these infections.

Management of Community-Associated Methicillin-ResistantStaphylococcus aureusInfections in Children

In recent years, community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) has emerged as a pathogen in children without established risk factors, and its prevalence in the United States is increasing. Although many CA-MRSA infections are mild, primarily involving the skin and soft tissues, the organism can cause serious, invasive, and life-threatening infections. To provide a comprehensive review of the epidemiology, clinical features, therapy, and prevention of CA-MRSA infections in children, we performed MEDLINE (1966-January 2006) and Cochrane Library searches, and reviewed abstracts for relevance to S. aureus infections. Only articles pertaining to CA-MRSA infections in pediatrics were closely examined. As a genetically distinct pathogen, CA-MRSA is generally susceptible to multiple non-beta-lactam antimicrobials. The optimal treatment for CA-MRSA infections in pediatric patients has not been well studied. Common antibiotics used include clindamycin, trimethoprim-sulfamethoxazole, vancomycin, and rifampin. Rational empiric antimicrobial therapy for infections caused by S. aureus requires consideration of the possibility of methicillin resistance. The local prevalence and susceptibilities of CA-MRSA, severity of infection, and individual risk factors should be considered in selecting treatment.

Quinupristin-dalfopristin resistance in Enterococcus faecium isolates from humans, farm animals, and grocery store meat in the United States

Three hundred sixty-one quinupristin-dalfopristin (Q-D)-resistant Enterococcus faecium (QDREF) isolates were isolated from humans, turkeys, chickens, swine, dairy and beef cattle from farms, chicken carcasses, and ground pork from grocery stores in the United States from 1995 to 2003. These isolates were evaluated by pulsed-field gel electrophoresis (PFGE) to determine possible commonality between QDREF isolates from human and animal sources. PCR was performed to detect the streptogramin resistance genes vatD, vatE, and vgbA and the macrolide resistance gene ermB to determine the genetic mechanism of resistance in these isolates. QDREF from humans did not have PFGE patterns similar to those from animal sources. vatE was found in 35%, 26%, and 2% of QDREF isolates from turkeys, chickens, and humans, respectively, and was not found in QDREF isolates from other sources. ermB was commonly found in QDREF isolates from all sources. Known streptogramin resistance genes were absent in the majority of isolates, suggesting the presence of other, as-yet-undetermined, mechanisms of Q-D resistance.

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.

Comorbidity risk-adjustment measures were developed and validated for studies of antibiotic-resistant infections

OBJECTIVES

Comorbidities are often included in risk-factor models for nosocomial antibiotic-resistant bacterial infections, and aggregate comorbidity measures are valuable because they allow one variable to represent many. This study aimed to develop new aggregate comorbidity measures based upon the Chronic Disease Score (CDS) for assessing the comorbidity-attributable risk of methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant enterococci (VRE) nosocomial infections.

STUDY DESIGN AND SETTING

For each outcome, two retrospective cohort studies of hospitalized patients were conducted. Outcomes were a first MRSA or VRE positive clinical culture obtained 48 hours or more postadmission. Each cohort was divided into development (July 1998-2001) and validation (August 2001-2003) samples. New comorbidity measures were created for MRSA (CDS-MRSA), VRE (CDS-VRE), or any nosocomial infection outcome (CDS-ID) using logistic regression and subsequently validated. Model discrimination was measured using the c-statistic.

RESULTS

Discrimination of the CDS-MRSA (c=0.60), CDS-VRE (c=0.65), and CDS-ID (MRSA: c=0.57; VRE: c=0.64) was greater than that of the original CDS (MRSA: c=0.52; VRE: c=0.57).

CONCLUSION

The CDS-MRSA, CDS-VRE, and CDS-ID are new infectious disease specific comorbidity risk-adjustment measures that will be useful for the quality of future epidemiologic studies of MRSA, VRE, and other infectious diseases.

Meticillin-resistant Staphylococcus aureus among US prisoners and military personnel: review and recommendations for future studies

We reviewed published work examining the prevalence and risk factors for meticillin-resistant Staphylococcus aureus (MRSA) infection in two high-risk groups: prisoners and military enlistees. Significant risk factors for infection included prison occupation, gender, comorbidities, prior skin infection, and previous antibiotic use. Although characteristics such as hygiene, physical contact, and crowding were postulated as risk factors for MRSA infection, there were few epidemiological studies supporting these factors. Most studies identified were retrospective in design and only one study used prospective surveillance for MRSA colonisation among all individuals residing within a single military setting. Our results suggest that there is a high incidence of MRSA infection among individuals in prisons and military settings, but surveys that quantify the prevalence of MRSA colonisation among individuals living within these specialised settings are needed. A thorough examination of MRSA acquisition and transmission patterns in prisons and military settings could help elucidate preventive strategies in other crowded and closed settings.

Activity of a new oral streptogramin, XRP2868, against gram-positive cocci harboring various mechanisms of resistance to streptogramins

The antibacterial activity of XRP2868, a new oral streptogramin composed of a combination of RPR132552 (streptogramin A) and RPR202868 (streptogramin B), was evaluated against a collection of clinical gram-positive isolates with characterized phenotypes and genotypes of streptogramin resistance. The effects of genes for resistance to streptogramin A or B on the activity of XRP2868 and its components were also tested by cloning these genes individually or in various combinations in gram-positive recipient strains susceptible to quinupristin-dalfopristin. The species tested included Staphylococcus aureus, coagulase-negative staphylococci, Enterococcus faecalis, Enterococcus faecium, Streptococcus pneumoniae, and other species of streptococci. XRP2868 was generally fourfold more potent than quinupristin-dalfopristin against S. aureus, E. faecium, and streptococci and had activity against E. faecalis (MICs = 0.25 to 1 microg/ml). XRP2868 appeared to be affected by the same mechanisms of resistance as those to quinupristin-dalfopristin. Nevertheless, the strong activity of factor A of the oral streptogramin enabled the combination to be very potent against streptogramin-susceptible staphylococci, streptococci, and E. faecium (MICs = 0.03 to 0.25 microg/ml) and to retain low MICs against the strains harboring a mechanism of resistance to factor A or factor B of the streptogramin. However, the combination of mechanisms of resistance to factors A and B caused an increase in the MICs of XRP2868, which reached 1 to 4 mug/ml. As with the other streptogramins, there was a reduction in the bactericidal effect of XRPR2868 when the staphylococcal strains acquired a constitutively expressed erm gene.

In vitro activity of linezolid against key gram-positive organisms isolated in the united states: results of the LEADER 2004 surveillance program

Since the approval of linezolid in 2000, sporadic reports of resistance have been given and a greater understanding of the underlying mechanisms of resistance has been gained. However, since these developments, an updated status of the in vitro activity of linezolid against gram-positive organisms from the United States has not been reported. The LEADER 2004 surveillance initiative was undertaken to obtain current and representative data on the activity of linezolid against key species, including isolates with significant resistance phenotypes. Organisms were isolated during 2004 and included 2,872 Staphylococcus aureus, 496 coagulase-negative staphylococcus (CNS), 428 Enterococcus faecalis, 196 Enterococcus faecium, and 422 Streptococcus pneumoniae isolates. All S. aureus isolates (54.2% oxacillin resistant) were susceptible to linezolid (MIC90 = 2 microg/ml); MIC distributions were consistent, regardless of oxacillin or multidrug resistance status. For CNS, one nonsusceptible isolate was encountered (Staphylococcus epidermidis; MIC = 32 microg/ml), but overall, the MIC(90) (1 microg/ml) was lower than that obtained with S. aureus. For E. faecalis and E. faecium, 99.5% and 96.4% of isolates, respectively, were linezolid susceptible. Both species had an MIC90 of 2 microg/ml, and MIC distributions did not vary with the vancomycin susceptibility status of the populations analyzed. Linezolid nonsusceptibility was not encountered among the S. pneumoniae isolates. These findings indicate that linezolid nonsusceptibility has remained rare among staphylococci and uncommon and sporadic among enterococci. Nonetheless, careful and ongoing monitoring of the in vitro effectiveness of linezolid will be needed so that any changes to the current status may be detected as soon as possible.

Emergence of Community-Associated Methicillin-Resistant Staphylococcus aureus USA300 Genotype as a Major Cause of Health Care--Associated Blood Stream Infections

BACKGROUND

Whether community-associated methicillin-resistant Staphylococcus aureus (MRSA) genotypes (e.g., USA300) are a major cause of bloodstream infections (BSIs) and health care-associated infections has been poorly defined.

METHODS

Consecutive MRSA isolates recovered from patients with BSIs were prospectively collected at an urban public hospital. Molecular typing studies were performed. Prevalence and risk factors for the MRSA USA300 genotype were assessed.

RESULTS

One hundred thirty-two cases of MRSA BSI were documented over 7.5 months in 2004 (incidence, 6.79 per 1000 admissions); 116 isolates were available for genotyping. Characteristics of the 116 evaluable cases included: a mean age 47 years; 62% were male, 82% were African American, and 22% were HIV seropositive. The crude in-hospital mortality rate was 22%. In 107 cases (92%), there was contact with a health care facility within the year prior to infection, and a nosocomial infection (defined as positive blood culture results obtained >48 h after admission) occurred in 49 cases (42%). PFGE demonstrated that 39 (34%) of the 116 isolates were the MRSA USA300 genotype; 34 (29%) were USA100; 42 (36%) were USA500; and 1 (1%) was USA800. MRSA USA300 accounted for 28% of health care-associated BSIs and 20% of nosocomial MRSA BSIs. In multivariate analysis, isolation of the USA300 genotype was associated with injectiondrug use (OR, 3.67; 95% CI, 1.10-12.28) and skin and soft tissue infection (OR, 4.26; 95% CI, 1.08-16.84). Patients who resided in long-term care facilities (OR, 0.09; 95% CI, 0.01-0.82) and those who were treated with antimicrobials in the prior year were less likely to have MRSA USA300 genotype recovered (OR, 0.10; 95% CI, 0.02-0.49).

CONCLUSIONS

MRSA USA300 genotype, the predominant cause of community-associated MRSA infections in our area (Atlanta, GA), has now emerged as a significant cause of health care-associated and nosocomial BSI. MRSA USA300 as a nosocomial pathogen presents new challenges to infection control programs.

Changes in antimicrobial susceptibility of native Enterococcus faecium in chickens fed virginiamycin

The extent of transfer of antimicrobial resistance from agricultural environments to humans is controversial. To assess the potential hazard posed by streptogramin use in food animals, this study evaluated the effect of virginiamycin exposure on antimicrobial resistance in Enterococcus faecium recovered from treated broilers. Four consecutive broiler feeding trials were conducted using animals raised on common litter. In the first three trials, one group of birds was fed virginiamycin continuously in feed at 20 g/ton, and a second group served as the nontreated control. In the fourth trial, antimicrobial-free feed was given to both groups. Fecal samples were cultured 1 day after chickens hatched and then at 1, 3, 5, and 7 weeks of age. Isolates from each time point were tested for susceptibility to a panel of different antimicrobials. Quinupristin/dalfopristin-resistant E. faecium appeared after 5 weeks of treatment in trial 1 and within 7 days of trials 2 to 4. Following removal of virginiamycin in trial 4, no resistant isolates were detected after 5 weeks. PCR failed to detect vat, vgb, or erm(B) in any of the streptogramin-resistant E. faecium isolates, whereas the msr(C) gene was detected in 97% of resistant isolates. In an experimental setting using broiler chickens, continuous virginiamycin exposure was required to maintain a stable streptogramin-resistant population of E. faecium in the animals. The bases of resistance could not be explained by known genetic determinants.

Frequent carriage of Panton-Valentine leucocidin genes by Staphylococcus aureus isolates from surgically drained abscesses

Between 1 February and 15 April 2002, 95 patients were admitted to Gaston Bourret Territorial Hospital (New Caledonia, France) for drainage of community-acquired soft tissue abscesses. Staphylococcus aureus was detected in 68 cases (72%). Two-thirds of the patients with S. aureus infection had furuncles, which were located on the limbs in 82% of cases. The median interval between symptom onset and hospital admission was 5.7 days. Three-quarters of the patients were Melanesians living in tribes. Fifty-four S. aureus isolates were screened for toxin genes. Panton-Valentine leucocidin (PVL) genes were detected in 48 isolates (89%), the exfoliative toxin A gene was detected in 1 isolate, and no toxin genes were detected in 4 isolates. S. aureus nasal carriage was detected in 39.7% of patients with S. aureus infections. Two infecting S. aureus strains and two nasal carriage strains were resistant to methicillin. Comparative pulsed-field gel electrophoresis, performed in 16 cases, showed that five of six patients with PVL-positive nasal carriage strains were infected by the same strains. In contrast, 8 of 10 patients with PVL-negative nasal carriage strains were infected by PVL-positive strains. PVL genes thus appear to be a major virulence factor in both primary and secondary S. aureus skin infections.

Utility of the Chronic Disease Score and Charlson Comorbidity Index as comorbidity measures for use in epidemiologic studies of antibiotic-resistant organisms

Comorbidity is a known risk factor for antibiotic-resistant bacterial infections. Although aggregate comorbidity measures are useful in epidemiologic research, none of the existing measures was developed for use with this outcome. This study compared the utility of two comorbidity measures, the Charlson Comorbidity Index and the Chronic Disease Score, in assessing the comorbidity-attributable risk of nosocomial infections with methicillin-resistant Staphylococcus aureus (MRSA) or vancomycin-resistant enterococci (VRE). Two case-control studies were conducted at the University of Maryland Medical System in Baltimore, Maryland. Cases were inpatients with a first positive clinical culture of MRSA or VRE at least 48 hours postadmission (July 1, 1998-July 1, 2001). Three inpatient controls were randomly selected per case. The MRSA study included 2,164 patients, and the VRE study included 1,948. The scores' discrimination and calibration were measured by using the c statistic and Hosmer-Lemeshow chi-square test. The Charlson Comorbidity Index (c = 0.653) and Chronic Disease Score (c = 0.608) were similar discriminators of MRSA and VRE (c = 0.670 and c = 0.647, respectively). Calibration of the scores was poor for both outcomes (p < 0.05). A revised comorbidity measure specific to resistant infections would likely provide a better assessment of the comorbidity-attributable risk of antibiotic-resistant infections.