A comparison of the Quidel Solana GAS assay, the Luminex Aries Group A Strep assay and the Focus Diagnostics Simplexa Group A Strep Direct assay for detection of Group A Streptococcus in throat swab specimens.

We compared three commercially available group A Streptococcus (GAS) nucleic acid amplification tests, the Quidel Solana GAS assay, the Luminex Aries Group A Strep assay and the Focus Diagnostics Simplexa Group A Strep Direct assay, with GAS bacterial culture. A true positive result was defined as one positive by culture or positive by ≥2/3 molecular methods. Two hundred eighty-seven throat swabs (207 children, 80 adults) were collected. The sensitivity of culture was 84.8% (95% CI 77.7-90.3%) with a specificity of 100% (95% CI 97.5-100%). The Solana assay sensitivity was 94.2% (95% CI 88.9-97.5%) with a specificity of 98.7% (95% CI 95.2-99.8%). Simplexa assay sensitivity was 99.3% (95% CI 96.0-99.9%) with a specificity of 95.3% (95% CI 90.6-98.1%). Aries assay sensitivity was 96.4% (95% CI 91.8-98.8%) with a specificity of 98.0% (95% CI 94.2-99.6%). In summary, all the molecular methods evaluated showed high sensitivity and specificity and were more sensitive than culture.

A comparison of the Quidel Solana HSV 1 + 2/VZV Assay, the Focus Diagnostics Simplexa HSV 1 & 2 Direct Assay and the Luminex Aries HSV 1&2 Assay for detection of herpes simplex virus 1 and 2 from swab specimens.

BACKGROUND: Molecular methods enable more rapid and sensitive detection of herpes simplex virus (HSV) than viral culture. OBJECTIVE: Three commercial molecular methods, all of which detect both HSV-1 and HSV-2, were compared to viral culture for the detection of HSV from swab specimens. STUDY DESIGN: Pediatric and adult patient viral swab specimens were cultured for HSV. Residual swab fluid was frozen at -80 °C until tested with the 3 molecular methods: the Quidel Solana HSV 1 + 2/VZV Assay, the Focus Diagnostics Simplexa HSV 1 & 2 Direct Assay and the Luminex Aries HSV 1&2 Assay. A true positive was defined as positive by culture or positive by ≥ 2/3 molecular methods. RESULTS: 177 specimens were studied. The sensitivity of culture was 81.3% (61/75, 95% CI 70.7-89.4%) and specificity was 100% (102/102, 95% CI 96.4-100%). The sensitivities of both the Solana and Simplexa were 100% (75/75, 95% CI 95.2-100%) and specificities were also both 100% (102/102, 95% CI 96.4-100%). The Aries had a sensitivity of 98.7% (74/75, 95% CI 92.8-99.97%) and specificity 99.0% (101/102, 95% CI 94.7-99.98%). All three molecular methods were significantly more sensitive than culture (p ≤ 0.0005 for Solana and Simplexa and p ≤ 0.0012 for Aries). CONCLUSION: All the molecular methods studied provided a significantly higher sensitivity than culture. In addition, the molecular methods took 1-2 hours to perform compared to a mean of 2.1 days for culture results. Use of any of the three molecular methods could lead to improved patient care.

Risk Factors for Methicillin-Resistant Staphylococcus aureus (MRSA) Colonization Among Patients Admitted to Obstetrical Units: A Nested Case-Control Study.

OBJECTIVE: Methicillin-resistant Staphylococcus aureus (MRSA) among obstetrical patients can increase birth complications for both mothers and infants, but little is known about the risk factors for MRSA in this population. The objective of this study was to determine the prevalence of MRSA among obstetrical patients and identify risk factors associated with MRSA colonization. METHODS: This nested case-control study used obstetrical patients with MRSA colonization identified through a universal screening program at The Ottawa Hospital (February 2008-January 2010). Cases and three matched controls were compared using chi-square tests for categorical variables, median and interquartile range (IQR), and Wilcoxon rank-sum tests for continuous variables. Conditional logistic regression using ORs and 95% CIs was used to identify risk factors. Standard microbiologic techniques and pulsed-field gel electrophoresis of the MRSA isolates from case patients were performed. RESULTS: Out of 11 478 obstetrical patients, 39 (0.34%) were MRSA colonized; 117 patients were selected as matched controls. The median age was 30 (IQR 27.5-35.00) and median length of stay was 2.55 days (IQR 1.95-3.24). Only MRSA cases had a previous MRSA infection (4 vs. 0). MRSA cases had significantly higher parity (median 3; IQR 2-5) compared with controls (median 2; IQR 1-3) (OR 1.52; 95% CI 1.22-1.90) CONCLUSION: This study identified a low prevalence of MRSA among obstetrical patients. Risk factors associated with MRSA colonization were previous MRSA infection and multiparity. Obstetrical patients who previously tested positive for MRSA should be placed on contact precautions at the time of hospital admission because this is a risk factor for future colonization.

Direct mecA polymerase chain reaction testing of blood culture bottles growing Gram-positive cocci and the clinical potential in optimizing antibiotic therapy for staphylococcal bacteremia.

This study evaluated the performance of direct mecA polymerase chain reaction (PCR) from blood culture bottles growing Gram-positive cocci in clusters and its role in optimization of antibiotic therapy. A total of 266 blood cultures including 121 methicillin-resistant and 122 methicillin-susceptible Staphylococci were tested for mecA. Compared to phenotypic testing, the overall performance of direct mecA PCR was 99% for sensitivity, specificity, positive predictive value, and negative predictive value, respectively. Assessment of antibiotic therapy upon microbiology reporting of direct mecA PCR results from 38 patients prior to (phase I) and 48 patients after implementation of testing and reporting (phase II) showed that the mean time to antibiotic optimization in phase II (0.9 ± 0.9 day) was significantly shorter than that in phase I (2.2 ± 3.2 days) (P < 0.05). Methicillin-susceptible staphylococcal bacteremias had significantly higher frequency of antibiotic adjustment upon direct mecA reporting, compared to methicillin-resistant staphylococcal bacteremias. Our study indicated that direct mecA PCR improved timely antibiotic optimization.

Tuberculosis, incarceration, and HIV at a crossroads in Guyana.

OBJECTIVES: The objective of this study was to describe the sociodemographic and clinical characteristics of patients dually infected with HIV and tuberculosis (TB) in Guyana. METHODS: The data for this study were obtained as part of a related project conducted to determine the prevalence of diabetes mellitus among TB patients in Guyana. From April to June 2006, a convenience sample of 100 patients was selected from those attending three TB clinics in Guyana and a structured questionnaire was used to collect relevant sociodemographic and risk factor data. The sociodemographic and clinical data of HIV-negative and HIV-positive patients with pulmonary TB were compared. Logistic regression was conducted to determine independent relationships between sociodemographic and clinical features. RESULTS: One hundred TB patients were considered for enrolment in the study, but since the HIV status was known for only 77 persons, these were included in the analysis. Thirty-one of the 77 (40.3%) were HIV-positive. Seventy-two of the 77 (93.5%) patients had pulmonary TB, 28 of whom were HIV-positive; the other five had extrapulmonary TB, three of whom were dually infected. Several social factors and clinical manifestations including incarceration at the time of TB diagnosis (p=0.01), cigarette smoking (p=0.05), homelessness (p=0.07), chest pain (p=0.001), hemoptysis (p=0.02), cough (p=0.08), and being acid-fast bacillus (AFB) sputum smear-positive (p=0.06) were associated with HIV-negative pulmonary TB. In the logistic regression model, HIV-negative TB patients demonstrated higher frequencies of complaints of chest pain (odds ratio (OR) 34.48, 95% confidence interval (CI) 4.35-250) and were more likely to be AFB sputum smear-positive (OR 11.97, 95% CI 1.91-74.76) than HIV-positive TB patients. CONCLUSIONS: Guyana is faced with a particularly high burden of HIV infection among TB patients. Given the impact of HIV on the clinical presentation of TB, physicians managing HIV patients should demonstrate a high level of suspicion for TB among these patients. Incarceration is a strong correlate of TB, overall.

Tuberculosis and diabetes in Guyana.

OBJECTIVES: This study was conducted to determine the prevalence of diabetes mellitus among tuberculosis (TB) patients attending three TB clinics in Guyana. METHODS: A cross-sectional study was conducted among TB patients attending TB clinics in three regions in Guyana. A structured questionnaire was used to collect demographic, clinical, and risk factor data. Random blood sugar testing was done using the OneTouch UltraSmart glucometer (LifeScan, Inc., 2002). RESULTS: One hundred TB patients were recruited; 90 had pulmonary TB and 10 had extrapulmonary disease. Fourteen patients were classified as diabetic: 12 had been previously diagnosed as diabetic by a physician and two had abnormally high random blood sugar at the time of enrolment. Of the 12 known diabetics, seven had been diagnosed before TB was discovered, three were identified at the time TB was diagnosed, and two after TB was diagnosed. All 14 diabetic patients presented with pulmonary TB. Thirty-one patients were HIV-positive and 28 of these had pulmonary TB, whereas three had extrapulmonary TB. None of the diabetics were infected with HIV. TB-diabetic patients tended to be older than non-diabetics (median age 44 vs. 36.5 years), were more likely to have been incarcerated at the time of TB diagnosis than non-diabetics (p=0.06), and were more likely to have an elevated (random) blood sugar level (p=0.02). Clinically, diabetes did not influence the presentation of TB. CONCLUSIONS: This study clearly highlights that diabetes and HIV are frequent in Guyanese TB patients. Routine screening of TB patients for diabetes and diabetic patients for TB should be speedily implemented. The National TB Programme should work closely with the diabetes clinics so that TB patients who are diabetics are optimally managed.

Infection with transmissible strains of Pseudomonas aeruginosa and clinical outcomes in adults with cystic fibrosis.

CONTEXT: Studies from Australia and the United Kingdom have shown that some patients with cystic fibrosis are infected with common transmissible strains of Pseudomonas aeruginosa. OBJECTIVES: To determine the prevalence and incidence of infection with transmissible strains of P. aeruginosa and whether presence of the organism was associated with adverse clinical outcomes in Canada. DESIGN, SETTING, AND PARTICIPANTS: Prospective observational cohort study of adult patients cared for at cystic fibrosis clinics in Ontario, Canada, with enrollment from September 2005 to September 2008. Sputum was collected at baseline, 3 months, and yearly thereafter for 3 years; and retrieved P. aeruginosa isolates were genotyped. Vital status (death or lung transplant) was assessed for all enrolled patients until December 31, 2009. MAIN OUTCOME MEASURES: Incidence and prevalence of P. aeruginosa isolation, rates of decline in lung function, and time to death or lung transplantation. RESULTS: Of the 446 patients with cystic fibrosis studied, 102 were discovered to be infected with 1 of 2 common transmissible strains of P. aeruginosa at study entry. Sixty-seven patients were infected with strain A (15%), 32 were infected with strain B (7%), and 3 were simultaneously infected with both strains (0.6%). Strain A was found to be genetically identical to the Liverpool epidemic strain but strain B has not been previously described as an epidemic strain. The incidence rate of new infections with these 2 transmissible strains was relatively low (7.0 per 1000 person-years; 95% confidence interval [CI], 1.8-12.2 per 1000 person-years). Compared with patients infected with unique strains of P. aeruginosa, patients infected with the Liverpool epidemic strain (strain A) and strain B had similar declines in lung function (difference in decline in percent predicted forced expiratory volume in the first second of expiration of 0.64% per year [95% CI, -1.52% to 2.80% per year] and 1.66% per year [95% CI, -1.00% to 4.30%], respectively). However, the 3-year rate of death or lung transplantation was greater in those infected with the Liverpool epidemic strain (18.6%) compared with those infected with unique strains (8.7%) (adjusted hazard ratio, 3.26 [95% CI, 1.41 to 7.54]; P = .01). CONCLUSIONS: A common strain of P. aeruginosa (Liverpool epidemic strain/strain A) infects patients with cystic fibrosis in Canada and the United Kingdom. Infection with this strain in adult Canadian patients with cystic fibrosis was associated with a greater risk of death or lung transplantation.

Repeat-based subtyping and grouping of Staphylococcus aureus from human infections and bovine mastitis using the R-domain of the clumping factor A gene.

Staphylococcus aureus has become an emerging public health concern. Markers capable of differentiating separate host-specific lineages are needed for tracing strain sources. Thus, a coding variable number tandem repeat-based typing was explored in this study, based on R-domain of clumping factor A (clfA) gene. DNA from isolates and strains of human infections and bovine mastitis were amplified and sequenced. Sequences of clfA from published strains were also analyzed. Results indicate that except one with 36 copies, 44 of the 55 R-domains had repeat copies between 44 and 57, whereas the remaining 10 had 59.5 to 73 copies. Furthermore, human isolates were polymorphic, while mastitis isolates were clonal. Phylogenetic grouping assigned host-specific strains into respective clusters. The repeats were stable during passages in milk, nutrient broth, and invasion of mammary cells showing suitability for typing. Our data show that the R-domain can be useful for typing and grouping host-specific lineages. Moreover, existence of variant repeats in human strains and the dominance of a clonal motif in mastitis may imply that a specific selection has occurred in the mammary gland.

A retrospective analysis of biofilm antibiotic susceptibility testing: a better predictor of clinical response in cystic fibrosis exacerbations.

BACKGROUND: Bacteria grow as biofilms within CF airways. However, antibiotic susceptibility testing is routinely performed on planktonically-growing bacteria. This study assessed whether CF patients infected with multiresistant organisms had improved clinical outcomes if given antibiotics that inhibited their biofilm-grown bacteria. METHODS: 110 patients with pulmonary exacerbations were treated with intravenous antibiotics based on susceptibility testing of planktonically-growing bacteria. A retrospective analysis was done using bacterial isolates grown from their sputum at exacerbation. Each isolate was grown as a biofilm and combination antibiotic susceptibility testing was performed. Clinical outcomes in patients treated with biofilm-susceptible antibiotics were compared to those that were not. RESULTS: 66 of 110 patients (60%) were treated with antibiotic combinations that inhibited all of their planktonically-grown bacterial isolates, however, when the same isolates were grown as biofilms, only 24 patients (22%) had all of their biofilm-grown isolates remaining susceptible to the antibiotics (P=<0.001 ). When patients with at least one biofilm-grown susceptible isolate (n=61) were compared to those with none (n=49), there was a significant decrease in sputum bacterial density (P=0.02) and length of stay (P=0.04) and a non-significant decrease in treatment failure. Survival analyses of time to next exacerbation showed non-significant trends favoring patients treated with biofilm-effective antibiotics. CONCLUSIONS: Most patients with CF exacerbations do not receive antibiotics that inhibit all biofilm-grown bacteria from their sputum at exacerbation. Patients treated with biofilm-effective therapy seemed to have improved clinical outcomes.

Pyrosequencing of a recA gene variable region for Burkholderia cepacia complex genomovar identification.

We developed an assay to identify Burkholderia cepacia complex genomovars by Pyrosequencing of a variable recA gene segment. Fifteen reference strains and 30 clinical isolates of B. cepacia complex were sequenced. Full 77-base pair target sequences were obtained from 44 of the 45 isolates, and BLAST queries of the sequences correctly identified the genomovar of these 44 isolates. Three Burkholderia multivorans isolates were identified as B. multivorans/Burkholderia ambifaria, indicating that additional identification methods may be needed for some B. multivorans strains.

Infection with Burkholderia cepacia complex bacteria and pulmonary exacerbations of cystic fibrosis.

BACKGROUND: Studies have shown that cystic fibrosis (CF) patients who are chronically infected with Burkholderia cepacia complex bacteria may potentially acquire new strains of B cepacia. Our objective was to determine whether pulmonary exacerbations of CF are associated with acquisition of new B cepacia strains or with B cepacia strain replacement. METHODS: Thirty-six patients from seven centers who were chronically infected with B cepacia complex bacteria were prospectively followed up over a 38-month period. Patients had sputum cultures performed every 3 months while clinically stable and at the time of a pulmonary exacerbation. Each B cepacia complex isolate was speciated by polymerase chain reaction amplification of the recA gene to determine species status and was genotyped by pulsed-field gel electrophoresis to determine strain type. RESULTS: Thirty-five of 36 patients (97%) had chronic infection with Burkholderia cenocepacia III-A during clinical stability. All 36 patients maintained the same species and strain of B cepacia complex at the time of exacerbation as was found during clinical stability. B cepacia complex isolates retrieved during exacerbations were significantly less susceptible to ciprofloxacin, chloramphenicol, piperacillin, meropenem, and tobramycin compared to isolates retrieved from the same patients during clinical stability. CONCLUSION: Adult CF patients infected with B cenocepacia maintain the same strain of B cenocepacia during exacerbations; pulmonary exacerbations are not caused by acquisition of a new B cepacia species or strain. B cepacia isolates retrieved during exacerbations may be more resistant to antibiotics.

Multiple combination bactericidal testing of staphylococcal biofilms from implant-associated infections.

Standardized susceptibility testing fails to predict in vivo resistance of device-related infections to antimicrobials. We assessed agents and combinations of antimicrobials against clinical isolates of Staphylococcus epidermidis and S. aureus (methicillin-resistant S. aureus and methicillin-sensitive S. aureus) retrieved from device-associated infections. Isolates were grown planktonically and as biofilms. Biofilm cultures of the organisms were found to be much more resistant to inhibitory and bactericidal effects of single and combination antibiotics than planktonic cultures (P < 0.001). Rifampin was the most common constituent of antibiotic combinations active against staphylococcal biofilms. Other frequently effective antimicrobials were vancomycin and fusidic acid. Susceptibility testing involving biofilm-associated bacteria suggests new options for combination antibiotic therapy.

Suboptimal clinical response to ciprofloxacin in patients with enteric fever due to Salmonella spp. with reduced fluoroquinolone susceptibility: a case series.

BACKGROUND: Salmonella spp. with reduced susceptibility to fluoroquinolones have higher than usual MICs to these agents but are still considered "susceptible" by NCCLS criteria. Delayed treatment response to fluoroquinolones has been noted, especially in cases of enteric fever due to such strains. We reviewed the ciprofloxacin susceptibility and clinical outcome of our recent enteric fever cases. METHODS: Salmonella enterica Serotype Typhi (S. Typhi) and Serotype Paratyphi (S. Paratyphi) blood culture isolates (1998-2002) were tested against nalidixic acid by disk diffusion (DD) and agar dilution (AD) and to ciprofloxacin by AD using NCCLS methods and interpretive criteria. Reduced fluoroquinolone susceptibility was defined as a ciprofloxacin MIC of 0.125-1.0 mg/L. The clinical records of patients treated with ciprofloxacin for isolates with reduced fluoroquinolone susceptibility were reviewed. RESULTS: Seven of 21 (33%) S. Typhi and S. Paratyphi isolates had reduced susceptibility to fluoroquinolones (MIC range 0.125-0.5 mg/L). All 7 were nalidixic acid resistant by DD (no zone) and by AD (MIC 128- >512 mg/L). The other 14 isolates were nalidixic acid susceptible and fully susceptible to ciprofloxacin (MIC range 0.015-0.03 mg/L). Five of the 7 cases were treated initially with oral ciprofloxacin. One patient remained febrile on IV ciprofloxacin until cefotaxime was added, with fever recurrence when cefotaxime was discontinued. Two continued on oral or IV ciprofloxacin alone but had prolonged fevers of 9-10 days duration, one was switched to IV beta-lactam therapy after remaining febrile for 3 days on oral/IV ciprofloxacin and one was treated successfully with oral ciprofloxacin. Four of the 5 required hospitalization. CONCLUSIONS: Our cases provide further evidence that reduced fluoroquinolone susceptibility of S. Typhi and S. Paratyphi is clinically significant. Laboratories should test extra-intestinal Salmonella spp. for reduced fluoroquinolone susceptibility.

Adult cystic fibrosis exacerbations and new strains of Pseudomonas aeruginosa.

We hypothesized that in adults with cystic fibrosis, the acquisition of a new strain of Pseudomonas aeruginosa may be associated with a pulmonary exacerbation. Eighty-four patients who were chronically infected with P. aeruginosa were prospectively followed from eight centers over a 26-month period. Patients had sputum cultures performed every 3 months while clinically stable and at the time of an exacerbation. Forty patients (48%) had an exacerbation requiring intravenous antibiotics during the study period, and in 36 of these patients, their P. aeruginosa isolates were genetically typeable by pulsed-field gel electrophoresis. In 34 of the 36 patients (94%), P. aeruginosa recovered during clinical stability and at exacerbation were of the same genotype. In only two patients (6%; 95% confidence interval, 0-18%) was a new P. aeruginosa clone cultured during an exacerbation that had not been cultured during clinical stability. There were no significant differences in antibiotic susceptibilities, measured as mean minimal inhibitory concentrations, for isolates retrieved during clinically stable periods compared with isolates retrieved during exacerbations. We conclude that for the majority of adult patients with cystic fibrosis a new pulmonary exacerbation is not caused by the acquisition of a new strain of P. aeruginosa.

Single and combination antibiotic susceptibilities of planktonic, adherent, and biofilm-grown Pseudomonas aeruginosa isolates cultured from sputa of adults with cystic fibrosis.

Evidence suggests that Pseudomonas aeruginosa bacteria form biofilms within the airways of adults with cystic fibrosis (CF). The objective of this study was to determine whether clinical isolates of P. aeruginosa recovered from adults with CF have similar susceptibilities to individual antibiotics and to antibiotic combinations when grown as adherent monolayers or as biofilms compared to when they are grown using planktonic methods. Twelve multiresistant P. aeruginosa isolates, one mucoid and one nonmucoid from each of six CF patients, were grown conventionally under planktonic conditions, as adherent bacterial monolayers, and as biofilms. Each bacterial isolate remained genotypically identical despite being cultured under planktonic, adherent, or biofilm growth conditions. Isolates grown as adherent monolayers and as biofilms were less susceptible to bactericidal killing by individual antibiotics compared to those grown planktonically. More importantly, biofilm-grown bacteria, but not adherent monolayer-grown bacteria, were significantly less susceptible to two- and three-drug combinations of antibiotics than were planktonically grown bacteria (P = 0.005). We conclude that biofilm-grown bacteria derived from patients with CF show decreased susceptibility to the bactericidal effects of antibiotic combinations than do adherent and planktonically grown bacteria.

An outbreak of vancomycin-resistant enterococci in a hematology-oncology unit: control by patient cohorting and terminal cleaning of the environment.

We describe the impact of enhanced infection control interventions on controlling the spread of vancomycin-resistant enterococci (VRE) in our hematology-oncology unit. Between April and September 1998, 13 patients on this unit were identified as having VRE. In addition to contact precautions, other measures that were needed to control the outbreak included closure of the unit to new admissions, creation of a cohort of VRE-positive patients and staff, and thorough cleaning of patients' rooms with 0.5% sodium hypochlorite.

Oxacillin susceptibility testing of coagulase-negative staphylococci using the disk diffusion method and the Vitek GPS-105 card.

One hundred and ninety-three isolates of coagulase-negative staphylococci (CoNS) were tested against oxacillin by agar dilution, disk diffusion, and Vitek (GPS-105 card), and the presence of the mecA gene determined by multiplex PCR. The results obtained by all testing methods were in agreement for 190 isolates. Two mecA-negative isolates (S. lugdunensis and S. haemolyticus) had MICs of < or = 0.25 microg/ml by agar dilution and Vitek but were resistant by disk diffusion. One mecA-positive isolate was resistant by Vitek and disk diffusion but had an agar dilution MIC of < or = 0.25 microg/ml. For the species of CoNS tested, oxacillin susceptibility results obtained with the Vitek GPS-105 card and disk diffusion correlated well with results obtained by National Committee for Clinical Laboratory Standards agar dilution and with the presence of the mecA gene.

Outbreak of burkholderia cepacia in the adult intensive care unit traced to contaminated indigo-carmine dye.

We report an unusual cluster of Burkholderia cepacia in patients. Environmental cultures identified indigo-carmine dye used in enteral feeding as the reservoir. Compared with the controls, the cases were significantly more likely to have received tube feedings tinted with this dye. This outbreak was terminated with the removal of the dye from hospital inventory.