Charles Garrigan

Multicenter Evaluation of Clinical Diagnostic Methods for Detection and Isolation of Campylobacter spp. from Stool

ABSTRACT The use of culture-independent diagnostic tests (CIDTs), such as stool antigen tests, as standalone tests for the detection of Campylobacter in stool is increasing. We conducted a prospective, multicenter study to evaluate the performance of stool antigen CIDTs compared to culture and PCR for Campylobacter detection. Between July and October 2010, we tested 2,767 stool specimens from patients with gastrointestinal illness with the following methods: four types of Campylobacter selective media, four commercial stool antigen assays, and a commercial PCR assay. Illnesses from which specimens were positive by one or more culture media or at least one CIDT and PCR were designated “cases.” A total of 95 specimens (3.4%) met the case definition. The stool antigen CIDTs ranged from 79.6% to 87.6% in sensitivity, 95.9 to 99.5% in specificity, and 41.3 to 84.3% in positive predictive value. Culture alone detected 80/89 (89.9% sensitivity) Campylobacter jejuni/Campylobacter coli-positive cases. Of the 209 noncases that were positive by at least one CIDT, only one (0.48%) was positive by all four stool antigen tests, and 73% were positive by just one stool antigen test. The questionable relevance of unconfirmed positive stool antigen CIDT results was supported by the finding that noncases were less likely than cases to have gastrointestinal symptoms. Thus, while the tests were convenient to use, the sensitivity, specificity, and positive predictive value of Campylobacter stool antigen tests were highly variable. Given the relatively low incidence of Campylobacter disease and the generally poor diagnostic test characteristics, this study calls into question the use of commercially available stool antigen CIDTs as standalone tests for direct detection of Campylobacter in stool.

Use of a Combination Biomarker Algorithm To Identify Medical Intensive Care Unit Patients with Suspected Sepsis at Very Low Likelihood of Bacterial Infection

ABSTRACT Sepsis remains a diagnostic challenge in the intensive care unit (ICU), and the use of biomarkers may help in differentiating bacterial sepsis from other causes of systemic inflammatory syndrome (SIRS). The goal of this study was to assess test characteristics of a number of biomarkers for identifying ICU patients with a very low likelihood of bacterial sepsis. A prospective cohort study was conducted in a medical ICU of a university hospital. Immunocompetent patients with presumed bacterial sepsis were consecutively enrolled from January 2012 to May 2013. Concentrations of nine biomarkers (α-2 macroglobulin, C-reactive protein [CRP], ferritin, fibrinogen, haptoglobin, procalcitonin [PCT], serum amyloid A, serum amyloid P, and tissue plasminogen activator) were determined at baseline and at 24 h, 48 h, and 72 h after enrollment. Performance characteristics were calculated for various combinations of biomarkers for discrimination of bacterial sepsis from other causes of SIRS. Seventy patients were included during the study period; 31 (44%) had bacterial sepsis, and 39 (56%) had other causes of SIRS. PCT and CRP values were significantly higher at all measured time points in patients with bacterial sepsis. A number of combinations of PCT and CRP, using various cutoff values and measurement time points, demonstrated high negative predictive values (81.1% to 85.7%) and specificities (63.2% to 79.5%) for diagnosing bacterial sepsis. Combinations of PCT and CRP demonstrated a high ability to discriminate bacterial sepsis from other causes of SIRS in medical ICU patients. Future studies should focus on the use of these algorithms to improve antibiotic use in the ICU setting.

A Pragmatic Biomarker-Driven Algorithm to Guide Antibiotic Use in the Pediatric Intensive Care Unit: The Optimizing Antibiotic Strategies in Sepsis (OASIS) Study

Background. Biomarkers that identify critically ill children with systemic inflammatory response syndrome (SIRS) at low risk for bacterial infection may help clinicians reduce unnecessary antibiotic use. Methods. We conducted a prospective cohort study of children with SIRS and suspected infection admitted to a pediatric intensive care unit from January 5, 2012 to March 7, 2014. We enrolled patients upon initiation of new antibiotics (Time 0) and measured a panel of 8 serum biomarkers daily over 72 hours. Microbiology, imaging, and clinical data were reviewed to classify bacterial infections using Centers for Disease Control and Prevention definitions. We identified cut points of biomarker combinations to maximize the negative predictive value (NPV) and specificity for bacterial infection. Excess antibiotics were calculated as days of therapy beyond day 2 after SIRS onset in patients without bacterial infection. Results. Infections were identified in 46 of 85 patients: bacterial (n = 22) and viral (24), whereas 39 patients had no infection identified. At Time 0, C-reactive protein (CRP) <5 mg/dL plus serum amyloid A <15.0 µg/mL had an NPV of 0.92 (95% confidence interval [CI], 0.79-1.0) and specificity of 0.54 (95% CI, 0.42-0.66) to identify patients without bacterial infection, whereas CRP <4 mg/dL plus procalcitonin <1.75 ng/mL had an NPV of 0.90 (95% CI, 0.79-1.0) and specificity of 0.43 (95% CI, 0.30-0.55). Patients without bacterial infection received a mean of 3.8 excess days of therapy. Conclusions. Early measurement of select biomarkers can identify children with SIRS in whom antibiotics might be safely discontinued when there is no other objective evidence of infection at 48 hours.

Combined biomarkers discriminate a low likelihood of bacterial infection among surgical intensive care unit patients with suspected sepsis

Among surgical intensive care unit (SICU) patients, it is difficult to distinguish bacterial sepsis from other causes of systemic inflammatory response syndrome (SIRS). Biomarkers have proven useful to identify the presence of bacterial infection. We enrolled a prospective cohort of 69 SICU patients with suspected sepsis and assayed the concentrations of 9 biomarkers (α-2 macroglobulin [A2M], C-reactive protein, ferritin, fibrinogen, haptoglobin, procalcitonin [PCT], serum amyloid A, serum amyloid P, and tissue plasminogen activator) at baseline, 24, 48, and 72hours. Forty-two patients (61%) had bacterial sepsis by chart review. A2M concentrations were significantly lower, and PCT concentrations were significantly higher in subjects with bacterial sepsis at 3 of 4 time points. Using optimal cutoff values, the combination of baseline A2M and 72-hour PCT achieved a negative predictive value of 75% (95% confidence interval, 54-96%). The combination of A2M and PCT discriminated bacterial sepsis from other SIRS among SICU patients with suspected sepsis.

Epidemiology and characteristics of Escherichia coli sequence type 131 (ST131) from long-term care facility residents colonized intestinally with fluoroquinolone-resistant Escherichia coli

The objective of this study was to evaluate molecular and epidemiologic factors associated with Escherichia coli sequence type 131 (ST131) among long-term care facility (LTCF) residents who acquired gastrointestinal tract colonization with fluoroquinolone-resistant E. coli (FQREC). Colonizing isolates from 37 residents who newly developed FQREC colonization at three LTCFs from 2006 to 2008 were evaluated. Twenty-nine (78%) of 37 total FQREC colonizing isolates were ST131. Most ST131 isolates had a distinctive combination of gyrA and parC replacement mutations. The ST131 and non-ST131 isolates differed significantly for the prevalence of many individual virulence factors but not for the proportion that qualified molecularly as extraintestinal pathogenic E. coli (ExPEC) or aggregate virulence factor scores. E. coli ST131 was highly prevalent among LTCF residents with FQREC colonization. Future studies should determine the risk factors for infection among ST131-colonized residents, and assess the potential for increased transmissibility of ST131 in the long-term care setting.

Distribution of Campylobacter jejuni capsular types, 2007-2012, Philadelphia, PA.

The distribution of Campylobacter jejuni capsular serotypes in the Philadelphia region from 2007 to 2012 was determined using molecular methods. Compared with the last U.S. survey in 1990, there does not appear to be a major shift in circulating capsular types.