Evaluation of the Cepheid Xpert SA Nasal Complete for direct detection of Staphylococcus aureus and methicillin-resistant Staphylococcus aureus in nasal swabs from pediatric patients.

Nasal carriers of Staphylococcus aureus (SA) are at increased risk for health-care associated infections with this organism. Timely detection of SA and Methicillin-resistant SA (MRSA) and subsequent decolonization are important components of infection control. While performance of nucleic acid amplification-based tests for detection of SA/MRSA in adults has been well-described, limited data are available in children. Our objective was to evaluate the performance of the Xpert SA in pediatric patients. Overall, for detection of SA, Xpert SA demonstrated a sensitivity and specificity of 95.1% and 93.5%, respectively and 87.8% sensitive and 98.1% specific for detection of MRSA. Performance in different age groups was similar but neonates had the lowest sensitivity and highest invalid rates. The Xpert SA is a rapid, reliable test to detect MSSA and MRSA nasal colonization in pediatric patients. Depending on the potential clinical impact, culture may be considered as a companion test to improve sensitivity.

Diagnosis of Pediatric Acute Adenovirus Infections: Is a Positive PCR Sufficient?

BACKGROUND: Human adenovirus (HAdV), especially species C (HAdV-C), can be detected incidentally by polymerase chain reaction in nasopharyngeal (NP) samples, making it difficult to interpret clinical significance of a positive result. We classified patients into groups based on HAdV culture positivity from respiratory specimens and the presence of an identified co-pathogen. We hypothesized that HAdV-C would be over-represented and viral burden would be lower in patients most likely to have incidental detection (ie, with a negative viral culture and documented co-pathogen). METHODS: Immunocompetent children with HAdV + nasopharyngeal specimens were classified into 4 groups: group I (HAdV culture (+) and no co-infection), group II (culture (+) and co-infection), group III (culture (-) and no co-infection) and group IV (culture (-) and co-infection). Viral burden (cycle threshold) and species were compared among groups. RESULTS: Of 483 nasopharyngeal specimens, HAdV was isolated in culture in 252 (52%); co-infection was found in 265 (55%) patients. Group I (most consistent with acute disease) had significantly lower cycle thresholds (median 23.9; interquarile range 22.2-28.1) compared with group IV (most consistent with incidental detection; median 37.3; interquarile range 35.3-38.9; P < 0.0001). HAdV-C accounted for 41% samples of group I and 83% of group IV (P < 0.0001). We identified a subset of 22 patients with bacterial or fungal co-pathogens, 18 of whom had no growth on viral culture (group IV) with a median cycle threshold of 37.4 (interquarile range 33.9-39.2). CONCLUSIONS: Species identification and viral burden may assist in interpretation of a positive HAdV result. Low viral burden with HAdV-C may be consistent with incidental detection.

Performance Characteristics of FilmArray Respiratory Panel v1.7 for Detection of Adenovirus in a Large Cohort of Pediatric Nasopharyngeal Samples: One Test May Not Fit All.

The FilmArray Respiratory Panel (RP) v1.7 assay has improved sensitivity for detection of human adenovirus (HAdV), compared to an earlier version (RP v1.6). RP v1.7 was designed for detection of species B, C, and E but may show variable detection of species A, D, and F. We sought to evaluate the clinical and analytical performance of RP v1.7 for detection of HAdV in a large pediatric cohort. Respiratory specimens obtained from a tertiary care children's hospital between February 2014 and February 2015 were tested for HAdV by RP v1.7. If the RP v1.7 results were negative for HAdV, then the specimens were reflexed to a HAdV-specific laboratory-developed PCR (LD-PCR) assay for confirmation. A subset of specimens underwent secondary confirmatory testing using another commercially available HAdV PCR assay and a molecular typing assay for species identification. Among 4,750 specimens, a total of 146 specimens (3.1%) were HAdV positive by RP v1.7. HAdV was detected by LD-PCR in an additional 220 specimens that were negative by RP v1.7. Overall, a nearly 5% increase in HAdV detection was observed when RP v1.7-negative specimens were reflexed to LD-PCR testing. RP v1.7 did not detect HAdV with either low viral burden (threshold cycle values of >30) or nonrespiratory species (species A, D, and F), as shown in both clinical and analytic data. While the level of sensitivity of RP v1.7 may be adequate for testing among otherwise healthy children, the decreased sensitivity may be problematic for immunocompromised patients, in whom low levels of HAdV in the respiratory tract may precede systemic infection and require early intervention.

Clinical and Virologic Characteristics May Aid Distinction of Acute Adenovirus Disease from Kawasaki Disease with Incidental Adenovirus Detection.

Incidental adenovirus detection in Kawasaki disease (KD) is important to differentiate from acute adenovirus disease. Twenty-four of 25 children with adenovirus disease and mimicking features of KD had <4 KD-like features, predominance of species B or E, and higher viral burden compared with those with KD and incidental adenovirus detection.

Occurrence of 3 Bordetella species during an outbreak of cough illness in Ohio: epidemiology, clinical features, laboratory findings and antimicrobial susceptibility.

BACKGROUND: An increase in laboratory diagnosis of pertussis was noted in central Ohio during 2010. Diagnosis was made using a polymerase chain reaction assay targeting the multicopy insertion sequence IS481, which is found in both Bordetella pertussis (Bp) and Bordetella holmesii (Bh). An increase in specimens testing positive for Bordetella parapertussis (Bpp) using insertion sequence IS1001 was also noted. METHODS: Nasopharyngeal swab specimens submitted April 1, 2010, to March 31, 2011, were tested using a multiplex polymerase chain reaction assay for Bp/Bh (IS481) and Bpp followed by singleplex assays for Bp and Bh. A subgroup of specimens was also cultured for Bordetella species, and antimicrobial susceptibility testing was performed on recovered organisms. Demographic and clinical features were compared for patients with Bp, Bh and Bpp. RESULTS: Of 520 IS481-positive specimens, 214 (41.1%) were positive for Bp, 79 (15.2%) were positive for Bh and 5 (1.0%) were positive for both Bp and Bh; 222 (42.7%) were negative for both targets. An additional 220 specimens were positive for Bpp. Among a sample of 155 IS481-positive specimens, 40, 15 and 0 were culture positive for Bp, Bh and Bpp, respectively. Among a sample of 55 BparaIS1001-positive (Bpp) specimens, 22, 0 and 0 were culture positive for Bpp, Bp and Bh, respectively. All Bordetella species were susceptible to macrolide antibiotics. Patients with Bh were older than patients with Bp, who were older than those positive for Bpp (mean ages: 12.0, 8.0 and 4.2 years, respectively; P < 0.001). One or more classic signs of pertussis (ie, paroxysmal cough, whoop, post-tussive emesis) were seen in 55.9% of 263 patients (59 Bp, 24 Bh, 80 Bpp and 100 negative for Bordetella species), but did not differ statistically among the groups (χ = 5.1, P = 0.17). CONCLUSIONS: All 3 Bordetella species, Bp, Bh and Bpp, were detected during on outbreak of pertussis-like cough illness. There were noted differences in age and seasonality, but clinical features at the time of presentation did not allow clear differentiation of these infections. All Bordetella species recovered from culture and tested were susceptible in vitro to macrolide antibiotics. Additional study is necessary to further characterize epidemiologic and clinical characteristics of Bh-associated cough illness and to determine potential co-occurrence of Bordetella species with other bacterial and viral respiratory tract pathogens.