Samia Arshad

Analysis of pathogen and host factors related to clinical outcomes in patients with hospital-acquired pneumonia due to methicillin-resistant Staphylococcus aureus

ABSTRACT Methicillin-resistant Staphylococcus aureus (MRSA) is a major cause of nosocomial pneumonia. To characterize pathogen-derived and host-related factors in intensive care unit (ICU) patients with MRSA pneumonia, we evaluated the Improving Medicine through Pathway Assessment of Critical Therapy in Hospital-Acquired Pneumonia (IMPACT-HAP) database. We performed multivariate regression analyses of 28-day mortality and clinical response using univariate analysis variables at a P level of <0.25. In isolates from 251 patients, the most common molecular characteristics were USA100 (55.0%) and USA300 (23.9%), SCCmec types II (64.1%) and IV (33.1%), and agr I (36.7%) and II (61.8%). Panton-Valentine leukocidin (PVL) was present in 21.9%, and vancomycin heteroresistance was present in 15.9%. Mortality occurred in 37.1% of patients; factors in the univariate analysis were age, APACHE II score, AIDS, cardiac disease, vascular disease, diabetes, SCCmec type II, PVL negativity, and higher vancomycin MIC (all P values were <0.05). In multivariate analysis, independent predictors were APACHE II score (odds ratio [OR], 1.090; 95% confidence interval [CI], 1.041 to 1.141; P < 0.001) and age (OR, 1.024; 95% CI, 1.003 to 1.046; P = 0.02). Clinical failure occurred in 36.8% of 201 evaluable patients; the only independent predictor was APACHE II score (OR, 1.082; 95% CI, 1.031 to 1.136; P = 0.002). In summary, APACHE II score (mortality, clinical failure) and age (mortality) were the only independent predictors, which is consistent with severity of illness in ICU patients with MRSA pneumonia. Interestingly, our univariate findings suggest that both pathogen and host factors influence outcomes. As the epidemiology of MRSA pneumonia continues to evolve, both pathogen- and host-related factors should be considered when describing epidemiological trends and outcomes of therapeutic interventions.

Prevalence of and Risk Factors for Vancomycin-Resistant Staphylococcus aureus Precursor Organisms in Southeastern Michigan

We assessed for vancomycin-resistant Staphylococcus aureus (VRSA) precursor organisms in southeastern Michigan, an area known to have VRSA. The prevalence was 2.5% (pSK41-positive methicillin-resistant S. aureus, 2009-2011) and 1.5% (Inc18-positive vancomycin-resistant Enterococcus, 2006-2013); Inc18 prevalence significantly decreased after 2009 (3.7% to 0.82%). Risk factors for pSK41 included intravenous vancomycin exposure.

The impact of obesity and timely antiviral administration on severe influenza outcomes among hospitalized adults

Obesity was identified as a risk factor for severe influenza during the 2009 influenza A(H1N1)pandemic, but evidence of this association has been mixed since. Post‐pandemic antiviral treatment guidelines may have increased antiviral treatment among obese individuals. A prospective study of adults hospitalized with laboratory‐confirmed influenza in Detroit, Michigan in 2011‐2012 and 2012‐2013 was conducted. Patient information was collected from interviews and medical chart abstraction. Obese (BMI ≥ 30) and non‐obese (BMI < 30) participants were compared. Late antiviral treatment (>2 days from symptom onset), obesity (30 ≤ BMI < 40), and morbid obesity (BMI ≥ 40) were evaluated as predictors of lower respiratory tract disease (LRD), ICU admission, and length of stay (LOS) using logistic regression and inverse probability weighted models. Forty‐eight participants were included in the study after exclusions and all patients received antiviral treatment. Participants who were obese were significantly more likely to have a cough and to take steroids than non‐obese participants, and had a shorter time from hospital admission to antiviral treatment (median time from admission to treatment of 0 days for obese patients and 1 day for non‐obese patients [P = 0.001]). In all models, late antiviral treatment was associated with increased odds of LRD (OR: 3.9 [1.1,15.9] in fully adjusted model). After adjustment for treatment timing, the odds of ICU admission (OR: 6.4 [0.8,58.2] to 7.9 [0.9, 87.1]) and LRD (OR: 3.3 [0.5, 23.5] to 4.0 [0.6, 35.0]) associated with morbid obesity increased. Obese individuals were treated with antivirals earlier than others. Late antiviral treatment was associated with severe influenza in the hospital.

Predictors of Mortality in Cancer Patients With Methicillin-Resistant Staphylococcus aureus Bloodstream Infection

Background: Methicillin-resistant Staphylococcus aureus (MRSA) is a common healthcare associated infection, with a high mortality rate. Patients with active cancer have a high risk of bloodstream infection (BSI) and MRSA infection due to immune suppression from chemoradiation and frequent exposure to the healthcare environment. Data is lacking on the level of mortality for cancer patients with MRSA BSI, and so the aim of this study is to assess the mortality related to MRSA BSI in cancer patients. Methods: This is a retrospective study performed in an integrated 4 hospital health system in Southeast Michigan. We evaluated 1173 consecutive individual patients with MRSA BSI over a 9 year period, from July 2005 to June 2014. Demographic, clinical, and microbiology data were obtained via review of electronic medical records. Patients were screened for having active cancer within 30-days before MRSA BSI. MRSA strain types were identified using pulse-field gel electrophoresis (PFGE) and patterns were compared using Bionumerics software. Isolates were considered to be in the same PFGE group if they had ≥80% similarity using the Dice coefficient. Isolate groups are based on categories set by the CDC. Results: We identified 92 patients (46 males) with active cancer who had a MRSA BSI. The average age of patients was 66 years, 62 patients had solid tumors (45 with metastasis), and 30 hematologic malignancy. Treatment included chemotherapy in 40.2% of patients, radiotherapy in 19.6%, and steroids in 27.2%. All-cause mortality 30 days after index blood culture was 35.87%. Charlson score was ≥3 in 95% of patients. Vancomycin MIC by E-test was ≤ 1.5 μg/ml in 84% of MRSA isolates. USA 100 was the most common strain in 52.7% of BSIs, followed by USA 300 at 30.8%, and USA 600 at 1.1%. Three factors on univariate analysis were statistically significant predictors of mortality: treatment with steroids 30-days before MRSA BSI (p=0.006), ICU admission during hospitalization for MRSA BSI (p=0.02), and patients with acute renal failure during MRSA BSI (p=0.02). Conclusion: Our data show that patients with active cancer and MRSA BSI have high mortality of 35.87%. Recent treatment with steroids, admission to the ICU, and acute renal failure are significant predictors of mortality.

733Vancomycin-Resistant Enterococcus (VRE) faecium Bloodstream Infections and Mortality

– A retrospective review of medical records was performed from 2010-2013 of all VRE faecium bloodstream infections from individual patients at a single 900 bed teaching hospital in Detroit – 166 VRE faecium isolates, collected from 2010-2013, were evaluated – Identification and susceptibility of isolates was performed in the microbiology laboratory using Vitek 2 (bioMerieux, Durham, NC) – Baseline demographics and characteristics, risk factors, and therapeutic antibiotic regimens used were evaluated to assess 90-day all-cause mortality

Evaluation of in vitro susceptibility trends to vancomycin and daptomycin by strain type of Staphylococcus aureus causing bloodstream infections

In total, 718 consecutive clinical meticillin-resistant Staphylococcus aureus (MRSA) isolates from 2006 to 2010 and 417 clinical meticillin-susceptible S. aureus (MSSA) isolates from mid-2007 to 2010 were evaluated. Isolates were from blood cultures obtained from separate patients in Detroit, MI, and were tested for in vitro susceptibility trends to vancomycin and daptomycin by molecular strain type. The MRSA pulsed-field gel electrophoresis (PFGE) results showed that 290 (40.4%) were USA100, 296 (41.2%) were USA300 and the remaining isolates were non-USA100/300. Vancomycin minimum inhibitory concentrations (MICs) by Etest [mean±standard deviation (S.D.) 1.55±0.26mg/L] in MRSA isolates showed no significant change over the 5-year period within all strain types, whilst daptomycin MICs by Etest (mean±S.D. 0.51±0.25mg/L) showed a significant downward trend across time (r=-0.243; P<0.001), with this trend occurring among all PFGE groups. For MSSA, a significant decrease in MICs to vancomycin was found by Etest (r=-0.160; P=0.001) and conversely a significant increase in daptomycin MICs by Etest was found (r=0.146; P=0.028). The results of this study showed that changes in MIC were not specific to strain molecular type. For vancomycin, there was no change in MRSA MICs and a decrease in MSSA MICs for blood isolates. For daptomycin, MICs decreased in MRSA and increased in MSSA blood isolates over the study period.

USA600 methicillin-resistant staphylococcus aureus in ICU patients with pneumonia: A case-control study design to evaluate epidemiology and outcomes of an emerging strain

BackgroundMethicillin-resistant Staphylococcus aureus (MRSA) infections are associated with severe necrotizing syndromes and high mortality, accounting for 20% to 40% of all hospital-acquired pneumonia and ventilator-associated pneumonia. There is insufficient data on comparative outcomes by specific strain characteristics in MRSA isolates in patients with pneumonia. MethodsClinical outcomes of patients with USA600 (ST45) MRSA strain were compared with other sequence types in MRSA pneumonia from 5 different hospitals in a retrospective case-control study. Patients were identified through review of microbiology laboratory records and through the Improving Medicine through Pathway Assessment of Critical Therapy in Hospital-Acquired Pneumonia database. Pulsed-field gel electrophoresis of SmaI-digested genomic DNA was performed on all isolates using a CHEF-DR III (BioRad). Pulsed-field gel electrophoresis patterns were compared using BioNumerics software (Applied Maths). ResultsTwo hundred fifty-one consecutive patients with MRSA pneumonia were evaluable for an all-cause 28-day mortality and 14-day failure outcome. Prevalence of USA600 was 8% (21). Laboratory characteristics of USA600 isolates were 100% (21) Panton-Valentine leukocidin toxin negative, agr I type, 67% (14) heteroresistant to vancomycin, and higher rates of SCCmec type II versus SCCmec type IVa, 95% versus 5%. Twenty-eight–day mortality rates were USA600 (52.4%), USA100 (ST5; 29%), and USA300 (ST8; 32%); and 14-day failure rates were USA600 (50%), USA100 (37%), and USA300 (27%), respectively. ConclusionsThis is the first comparative observational study of its kind, with evidence of a much higher failure rate (>50%) within patients with USA600 MRSA pneumonia. The high mortality rate in this subset warrants further investigation of factors of this emerging strain that may predict mortality and failure outcomes.

Methicillin-resistant staphylococcus aureus pneumonia what is the optimal duration of treatment?

BackgroundMethicillin-resistant Staphylococcus aureus (MRSA) pneumonia is associated with high morbidity and mortality. There is no consensus about the length of therapy. Current Infectious Diseases Society of America consensus guidelines recommend 7 to 21 days for duration. MethodsIn a retrospective study conducted in a 900-bed teaching hospital in urban Detroit over a 26-month period, we evaluated the charts of 706 patients with positive MRSA respiratory cultures. We studied 115 patients with MRSA pneumonia. ResultsThe mean ± SD age for the patients was 64.36 ± 14.44 years; 67 patients (58.77 %) were women, 44 patients (38.26%) had multilobar pneumonia. Patients were treated with either vancomycin or linezolid or treatment was switched between those 2 agents. The mean ± SD treatment duration was 13.1 ± 7.1 days. The overall 28-day mortality rate was 28.73% (n = 32). Among the 83 patients who survived to 28 days, 9 patients (10.8%) received treatment for less than 8 days, 33 patients (39.8%) received treatment for 8 to 13 days, 26 patients (31.3%) received treatment for 14 to 20 days, and 15 patients (18.1%) received treatment for more than 20 days. Among the 32 patients who did not survive to 28 days, 11 patients (34.4%) received treatment for less than 8 days, 14 patients (43.8%) received treatment for 8 to 13 days, 6 patients (18.8%) received treatment for 14 to 20 days, and 1 patient (3.1%) received treatment for more than 20 days; P < 0.001. ConclusionThe nonsurvivors were treated for shorter durations than survivors, indicating that MRSA pneumonia requires longer treatment durations (≥14 days).