Controlled clinical comparison of new pediatric medium with adsorbent polymeric beads (PF Plus) versus charcoal-containing PF medium in the BacT/alert blood culture system.

We conducted a controlled clinical comparison of PF Plus, the new pediatric medium with adsorbent polymeric beads, versus the charcoal-containing PF medium in the BacT/Alert blood culture system. A total of 2,381 pediatric cultures were enrolled, and 1,703 (71.5%) were deemed to be compliant and acceptable for analysis. Seventy-two cultures (4.2%) had a positive result with 80 clinically significant microorganisms. The results showed that the PF Plus medium yielded more clinically significant microorganisms than the BacT/Alert system (P < 0.05). In addition, the PF Plus bottle yielded positive results an average of 5.0 h earlier than the PF bottle for compliant clinically significant cultures (18.3 h versus 23.2 h, P = 0.004). PF Plus is an improved medium for detecting microorganisms that cause pediatric bloodstream infections.

Better tests, better care: improved diagnostics for infectious diseases.

In this IDSA policy paper, we review the current diagnostic landscape, including unmet needs and emerging technologies, and assess the challenges to the development and clinical integration of improved tests. To fulfill the promise of emerging diagnostics, IDSA presents recommendations that address a host of identified barriers. Achieving these goals will require the engagement and coordination of a number of stakeholders, including Congress, funding and regulatory bodies, public health agencies, the diagnostics industry, healthcare systems, professional societies, and individual clinicians.

Bacteremic disseminated tuberculosis in sub-saharan Africa: a prospective cohort study.

BACKGROUND: Disseminated tuberculosis is a major health problem in countries where generalized human immunodeficiency virus (HIV) infection epidemics coincide with high tuberculosis incidence rates; data are limited on patient outcomes beyond the inpatient period. METHODS: We enrolled consecutive eligible febrile inpatients in Moshi, Tanzania, from 10 March 2006 through 28 August 2010; those with Mycobacterium tuberculosis bacteremia were followed up monthly for 12 months. Survival, predictors of bacteremic disseminated tuberculosis, and predictors of death were assessed. Antiretroviral therapy (ART) and tuberculosis treatment were provided. RESULTS: A total of 508 participants were enrolled; 29 (5.7%) had M. tuberculosis isolated by blood culture. The median age of all study participants was 37.4 years (range, 13.6-104.8 years). Cough lasting >1 month (odds ratio [OR], 13.5; P< .001), fever lasting >1 month (OR, 7.8; P = .001), weight loss of >10% (OR, 10.0; P = .001), lymphadenopathy (OR 6.8; P = .002), HIV infection (OR, undefined; P < .001), and lower CD4 cell count and total lymphocyte count were associated with bacteremic disseminated tuberculosis. Fifty percent of participants with M. tuberculosis bacteremia died within 36 days of enrollment. Lower CD4 cell count (OR, 0.88; P = .049) and lower total lymphocyte count (OR, 0.76; P = .050) were associated with death. Magnitude of mycobacteremia tended to be higher among those with lower CD4 cell counts, but did not predict death. CONCLUSIONS: In the era of free ART and access to tuberculosis treatment, almost one half of patients with M. tuberculosis bacteremia may die within a month of hospitalization. Simple clinical assessments can help to identify those with the condition. Advanced immunosuppression predicts death. Efforts should focus on early diagnosis and treatment of HIV infection, tuberculosis, and disseminated disease.

Streptococcal pharyngitis leading to corneal ulceration.

PURPOSE: To report a patient with a history of exposure keratopathy who presented with bilateral bacterial keratitis associated with streptococcal pharyngitis and use of bilevel positive airway pressure (BiPAP). DESIGN: Case report. METHODS: Pulsed-field gel electrophoresis of patient isolates from ocular and pharyngeal cultures. RESULTS: Ocular and oropharyngeal cultures from a 24-month-old child with a history of cerebral palsy on BiPAP at night revealed the same strain of Streptococcus pyogenes. CONCLUSIONS: Use of mechanical ventilation, such as BiPAP, may precipitate inoculation of eye with respiratory or oropharyngeal pathogens. To the authors' knowledge this is the first report demonstrating the association between concurrent streptococcal pharygitis, keratitis, and use of BiPAP.

Performance of nucleic acid amplification following extraction of 5 milliliters of whole blood for diagnosis of Mycobacterium tuberculosis bacteremia.

To investigate the performance of a nucleic acid amplification test (NAAT) for the diagnosis of Mycobacterium tuberculosis bacteremia, 5-ml aliquots of blood were inoculated into bioMérieux mycobacterial (MB) bottles and incubated, and 5-ml aliquots of blood were extracted and tested by real-time PCR. Of 25 samples from patients with M. tuberculosis bacteremia, 9 (36.0%) were positive and 1 (1.5%) of 66 control samples was positive by NAAT. The NAAT shows promise, but modifications should focus on improving sensitivity.

Transmission of MRSA between companion animals and infected human patients presenting to outpatient medical care facilities.

Methicillin-resistant Staphylococcus aureus (MRSA) is a significant pathogen in both human and veterinary medicine. The importance of companion animals as reservoirs of human infections is currently unknown. The companion animals of 49 MRSA-infected outpatients (cases) were screened for MRSA carriage, and their bacterial isolates were compared with those of the infected patients using Pulsed-Field Gel Electrophoresis (PFGE). Rates of MRSA among the companion animals of MRSA-infected patients were compared to rates of MRSA among companion animals of pet guardians attending a "veterinary wellness clinic" (controls). MRSA was isolated from at least one companion animal in 4/49 (8.2%) households of MRSA-infected outpatients vs. none of the pets of the 50 uninfected human controls. Using PFGE, patient-pets MRSA isolates were identical for three pairs and discordant for one pair (suggested MRSA inter-specie transmission p-value = 0.1175). These results suggest that companion animals of MRSA-infected patients can be culture-positive for MRSA, representing a potential source of infection or re-infection for humans. Further studies are required to better understand the epidemiology of MRSA human-animal inter-specie transmission.

Polymorphisms in fibronectin binding protein A of Staphylococcus aureus are associated with infection of cardiovascular devices.

Medical implants, like cardiovascular devices, improve the quality of life for countless individuals but may become infected with bacteria like Staphylococcus aureus. Such infections take the form of a biofilm, a structured community of bacterial cells adherent to the surface of a solid substrate. Every biofilm begins with an attractive force or bond between bacterium and substratum. We used atomic force microscopy to probe experimentally forces between a fibronectin-coated surface (i.e., proxy for an implanted cardiac device) and fibronectin-binding receptors on the surface of individual living bacteria from each of 80 clinical isolates of S. aureus. These isolates originated from humans with infected cardiac devices (CDI; n = 26), uninfected cardiac devices (n = 20), and the anterior nares of asymptomatic subjects (n = 34). CDI isolates exhibited a distinct binding-force signature and had specific single amino acid polymorphisms in fibronectin-binding protein A corresponding to E652D, H782Q, and K786N. In silico molecular dynamics simulations demonstrate that residues D652, Q782, and N786 in fibronectin-binding protein A form extra hydrogen bonds with fibronectin, complementing the higher binding force and energy measured by atomic force microscopy for the CDI isolates. This study is significant, because it links pathogenic bacteria biofilms from the length scale of bonds acting across a nanometer-scale space to the clinical presentation of disease at the human dimension.

Methicillin-susceptible Staphylococcus aureus endocarditis isolates are associated with clonal complex 30 genotype and a distinct repertoire of enterotoxins and adhesins.

BACKGROUND: Using multinational collections of methicillin-susceptible Staphylococcus aureus (MSSA) isolates from infective endocarditis (IE) and soft tissue infections (STIs), we sought to (1) validate the finding that S. aureus in clonal complex (CC) 30 is associated with hematogenous complications and (2) test the hypothesis that specific genetic characteristics in S. aureus are associated with infection severity. METHODS: IE and STI isolates from 2 cohorts were frequency matched by geographic origin. Isolates underwent spa typing to infer CC and multiplex polymerase chain reaction for presence of virulence genes. RESULTS: 114 isolate pairs were genotyped. IE isolates were more likely to be CC30 (19.5% vs 6.2%; P = .005) and to contain 3 adhesins (clfB, cna, map/eap; P < .0001 for all) and 5 enterotoxins (tst, sea, sed, see, and sei; P ≤ .005 for all). CC30 isolates were more likely to contain cna, tst, sea, see, seg, and chp (P < .05 for all). CONCLUSIONS: MSSA IE isolates were significantly more likely to be CC30 and to possess a distinct repertoire of virulence genes than MSSA STI isolates from the same region. The genetic basis of this association requires further study.

Controlled comparison of BacT/Alert MB system, manual Myco/F lytic procedure, and isolator 10 system for diagnosis of Mycobacterium tuberculosis Bacteremia.

We compared the performance of the BacT/Alert MB system, that of the manual Bactec Myco/F Lytic procedure, and that of the Isolator 10 lysis-centrifugation system in the detection of Mycobacterium tuberculosis bacteremia. Mean times to detection were 16.4 days for BacT/Alert MB versus 20.0 days for Myco/F Lytic, 16.5 days for BacT/Alert MB versus 23.8 days for Isolator 10, and 21.1 days for Bactec Myco/F Lytic versus 22.7 days for Isolator 10. There were no significant differences in yields. The mean (range) magnitude of mycobacteremia was 30.0 (0.4, 90.0) CFU/ml and was correlated with the time to positivity in the BacT/Alert MB system (r = -0.4920). M. tuberculosis bacteremia was detected more rapidly in a continuously monitored liquid blood culture system, but the mean time to positivity exceeded 3 weeks.

Quantitation of Candida CFU in initial positive blood cultures.

One potential limitation of DNA-based molecular diagnostic tests for Candida bloodstream infection (BSI) is organism burden, which is not sufficiently characterized. We hypothesized that the number of CFU per milliliter (CFU/ml) present in an episode of Candida BSI is too low for reliable DNA-based diagnostics. In this study, we determined Candida burden in the first positive blood culture and explored factors that affect organism numbers and patient outcomes. We reviewed records of consecutive patients with a positive blood culture for Candida in the lysis-centrifugation blood culture system (Isolator, Wampole Laboratories, Cranbury, NJ) from 1987 to 1991. Descriptive statistics and logistic regression analyses were performed. One hundred fifty-two episodes of Candida BSI were analyzed. Patient characteristics included adult age (72%), indwelling central venous catheters (83%), recent surgery (29%), neutropenia (24%), transplant (14%), and other immune suppression (21%). Rates of treatment success and 30-day mortality for candidemia were each 51%. The median CFU/ml was 1 (mode 0.1, range 0.1 to >1,000). In the multivariate analysis, pediatric patients were more likely than adults to have high organism burdens (odds ratio [OR], 10.7; 95% confidence interval [95% CI], 4.3 to 26.5). Initial organism density did not affect patient outcome. Candida CFU/ml in the first positive blood culture of a BSI episode varies greatly; >50% of cultures had ≤1 CFU/ml, a concentration below the experimental yeast cell threshold for reliable DNA-based diagnostics. DNA-based diagnostics for Candida BSI will be challenged by low organism density and the need for sufficient specimen volume; future research on alternate targets is warranted.

Potential associations between severity of infection and the presence of virulence-associated genes in clinical strains of Staphylococcus aureus.

BACKGROUND: The clinical spectrum of Staphylococcus aureus infection ranges from asymptomatic nasal carriage to osteomyelitis, infective endocarditis (IE) and death. In this study, we evaluate potential association between the presence of specific genes in a collection of prospectively characterized S. aureus clinical isolates and clinical outcome. METHODOLOGY/PRINCIPAL FINDINGS: Two hundred thirty-nine S. aureus isolates (121 methicillin-resistant S. aureus [MRSA] and 118 methicillin-susceptible S. aureus [MSSA]) were screened by array comparative genomic hybridization (aCGH) to identify genes implicated in complicated infections. After adjustment for multiple tests, 226 genes were significantly associated with severity of infection. Of these 226 genes, 185 were not in the SCCmec element. Within the 185 non-SCCmec genes, 171 were less common and 14 more common in the complicated infection group. Among the 41 genes in the SCCmec element, 37 were more common and 4 were less common in the complicated group. A total of 51 of the 2014 sequences evaluated, 14 non-SCCmec and 37 SCCmec, were identified as genes of interest. CONCLUSIONS/SIGNIFICANCE: Of the 171 genes less common in complicated infections, 152 are of unknown function and may contribute to attenuation of virulence. The 14 non-SCCmec genes more common in complicated infections include bacteriophage-encoded genes such as regulatory factors and autolysins with potential roles in tissue adhesion or biofilm formation.

The clinical and prognostic importance of positive blood cultures in adults.

BACKGROUND: Bloodstream infections are a major cause of morbidity and mortality in adults. Bloodstream infections should be reassessed periodically because of increased antibiotic resistance, more patients receiving immunomodulatory therapy, improved antiretroviral therapy, and acquisition of infection in health care settings other than hospitals. METHODS: We conducted retrospective assessment by infectious disease physicians of hospitalized adults with positive blood cultures at 3 academic medical centers. RESULTS: Two thousand two hundred seventy positive blood culture episodes occurred in 1706 patients. Of 2669 isolates, 51% represented true infection, 41% contamination, and 8% unknown clinical significance. Although coagulase-negative staphylococci were most common, only 10% were clinically significant. Among 1225 true bloodstream infections, the most frequent isolates were Staphylococcus aureus, Escherichia coli, Enterococcus spp., Klebsiella pneumoniae, coagulase-negative staphylococci, Pseudomonas aeruginosa, Candida albicans, Enterobacter cloacae, and Serratia marcescens. Intravenous catheters were the most common primary source of bloodstream infection (23% of episodes). Most (81%) bloodstream infections were acquired in the hospital or other health care settings. Crude and attributable in-hospital case-fatality ratios were 20% and 12%, respectively, lower than in previous studies. Increasing age, hypotension, absence of fever, hospital acquisition, extreme white blood cell count values, and the presence of the acquired immunodeficiency syndrome, malignancy, or renal disease were significantly associated with an increased risk of in-hospital attributable death in multivariable analysis. CONCLUSIONS: The proportion of bloodstream infections due to intravenous catheters is continuing to increase. Most episodes were acquired in the hospital or other health care setting. In-hospital case-fatality ratios have decreased compared with previous studies. Several previously identified factors associated with an increased mortality remain statistically significant.

The (1,3){beta}-D-glucan test as an aid to early diagnosis of invasive fungal infections following lung transplantation.

The Fungitell assay for (1,3)ß-D-glucan (BG) detection in serum has been evaluated in patients with invasive fungal infections (IFIs) and healthy controls and for the early diagnosis of IFI in cancer patients. We evaluated the BG assay for the detection of IFI in lung transplant recipients. Serial serum samples were prospectively collected from patients undergoing lung transplants at Duke Hospital. Fungal infections were classified according to revised European Organization for Research and Treatment of Cancer/Mycoses Study Group criteria. A receiver operator characteristic (ROC) curve was generated; possible causes for false-positive and false-negative tests were investigated by linear regression analysis. Seven hundred fifty-six serum specimens from 59 subjects without IFI and 41 specimens from 14 patients with proven or probable IFI were tested. The area under the ROC curve was 0.69. Based on a 60-pg/ml positive cutoff, per-patient sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were 64%, 9%, 14%, and 50%, respectively; per-test estimates were 71%, 59%, 9%, and 97%, respectively. The majority (92%) of patients not diagnosed with an IFI had at least one BG level of ≥60 pg/ml, and 90% had at least one BG level of ≥80 pg/ml. Respiratory colonization with mold and hemodialysis significantly affected mean BG levels. In conclusion, the accuracy of the BG test is marginal and its utility as a tool for the early diagnosis of IFI is questionable in the lung transplant population. Although the NPV of the BG test is high, the low PPV limits its utility as a screening tool for early diagnosis of IFI.

Dissemination of an Enterococcus Inc18-Like vanA plasmid associated with vancomycin-resistant Staphylococcus aureus.

Of the 9 vancomycin-resistant Staphylococcus aureus (VRSA) cases reported to date in the literature, 7 occurred in Michigan. In 5 of the 7 Michigan VRSA cases, an Inc18-like vanA plasmid was identified in the VRSA isolate and/or an associated vancomycin-resistant Enterococcus (VRE) isolate from the same patient. This plasmid may play a critical role in the emergence of VRSA. We studied the geographical distribution of the plasmid by testing 1,641 VRE isolates from three separate collections by PCR for plasmid-specific genes traA, repR, and vanA. Isolates from one collection (phase 2) were recovered from surveillance cultures collected in 17 hospitals in 13 states. All VRE isolates from 2 Michigan institutions (n = 386) and between 60 and 70 VRE isolates (n = 883) from the other hospitals were tested. Fifteen VRE isolates (3.9%) from Michigan were positive for an Inc18-like vanA plasmid (9 E. faecalis [12.5%], 3 E. faecium [1.0%], 2 E. avium, and 1 E. raffinosus). Six VRE isolates (0.6%) from outside Michigan were positive (3 E. faecalis [2.7%] and 3 E. faecium [0.4%]). Of all E. faecalis isolates tested, 6.0% were positive for the plasmid, compared to 0.6% for E. faecium and 3.0% for other spp. Fourteen of the 15 plasmid-positive isolates from Michigan had the same Tn1546 insertion site location as the VRSA-associated Inc18-like plasmid, whereas 5 of 6 plasmid-positive isolates from outside Michigan differed in this characteristic. Most plasmid-positive E. faecalis isolates demonstrated diverse patterns by PFGE, with the exception of three pairs with indistinguishable patterns, suggesting that the plasmid is mobile in nature. Although VRE isolates with the VRSA-associated Inc18-like vanA plasmid were more common in Michigan, they remain rare. Periodic surveillance of VRE isolates for the plasmid may be useful in predicting the occurrence of VRSA.

Multicenter study to determine disk diffusion and broth microdilution criteria for prediction of high- and low-level mupirocin resistance in Staphylococcus aureus.

Mupirocin susceptibility testing of Staphylococcus aureus has become more important as mupirocin is used more widely to suppress or eliminate S. aureus colonization and prevent subsequent health care- and community-associated infections. The present multicenter study evaluated two susceptibility testing screening methods to detect mupirocin high-level resistance (HLR), broth microdilution (BMD) MICs of >or=512 microg/ml, and a 6-mm zone diameter for a disk diffusion (DD) test with a 200-microg disk. Initial testing indicated that with Clinical and Laboratory Standards Institute methods for BMD and DD testing, the optimal conditions for the detection of mupirocin HLR were 24 h of incubation and reading of the DD zone diameters with transmitted light. Using the presence or absence of mupA as the "gold standard" for HLR, the sensitivity and specificity of a single-well 256 microg/ml BMD test were 97 and 99%, respectively, and those for the 200-microg disk test were 98 and 99%, respectively. Testing with two disks, 200 microg and 5 microg, was evaluated for its ability to distinguish HLR isolates (MICs >or= 512 microg/ml), low-level-resistant (LLR) isolates (MICs = 8 to 256 microg/ml), and susceptible isolates (MICs

Correlation of cefoxitin MICs with the presence of mecA in Staphylococcus spp.

This report describes the results of an 11-laboratory study to determine if a cefoxitin broth microdilution MIC test could predict the presence of mecA in staphylococci. Using breakpoints of < or = 4 microg/ml for mecA-negative and > or = 6 or 8 microg/ml for mecA-positive isolates, sensitivity and specificity based on mecA or presumed mecA for Staphylococcus aureus at 18 h of incubation were 99.7 to 100% in three cation-adjusted Mueller-Hinton broths tested. For coagulase-negative strains at 24 h of incubation, breakpoints of < or = 2 microg/ml for mecA-negative and > or = 4 microg/ml for mecA-positive isolates gave sensitivity and specificity of 94 to 99% and 69 to 80%, respectively.

Staphylococcus aureus bacteremia among patients with health care-associated fever.

BACKGROUND: Although Staphylococcus aureus bacteremia is a common, serious infection, accurately identifying febrile patients with this diagnosis at the time of initial evaluation is difficult. The purpose of this investigation was to define clinical characteristics present at the time of the initial recognition of fever that were associated with the presence of any bloodstream infection and, in particular, with S. aureus bacteremia. METHODS: All patients > or =18 years of age with a new episode of health care-associated fever (temperature > or =38 degrees C) and at least one blood culture drawn were eligible for enrollment into this prospective multicenter cohort study. Multivariable analyses were conducted and internally validated scoring systems were developed to categorize the risk of bacteremia. RESULTS: Of 1015 patients enrolled, 181 patients (17.8%) had clinically significant bacteremia, including 77 patients (7.6%) with S. aureus bacteremia. Clinical characteristics associated with S. aureus bacteremia were the presence of a hemodialysis graft or shunt (odds ratio [OR] 3.22; 95% confidence interval [CI], 1.85-5.61), chills (OR 2.38; 95% CI, 1.43-3.98), and a history of S. aureus infection (OR 2.68; 95% CI, 1.38-5.20). Peripheral vascular catheters were inversely associated with S. aureus bacteremia (OR 0.42; 95% CI, 0.26-0.69). Clinical characteristics associated with any bloodstream infection were central venous access, chills, history of S. aureus infection, and hemodialysis access. CONCLUSIONS: Among patients with health care-associated fever, the presence of easily recognizable clinical characteristics at the time of obtaining the initial blood cultures can help to identify patients at increased risk for any bloodstream infection, in particular for S. aureus bacteremia.

Murine typhus and febrile illness, Nepal.

Murine typhus was diagnosed by PCR in 50 (7%) of 756 adults with febrile illness seeking treatment at Patan Hospital in Kathmandu, Nepal. Of patients with murine typhus, 64% were women, 86% were residents of Kathmandu, and 90% were unwell during the winter. No characteristics clearly distinguished typhus patients from those with blood culture-positive enteric fever.