Potential Heavy Metals Pollution Contribution from Wash-Off of Urban Road-Dust.

Based on the different particle sizes of street dust, the potential pollution load of heavy metals from dry and wet atmospheric deposition to surface runoff in different functional areas of Zhengzhou city was estimated by using the rain-scour heavy metal index model. Compared to the EA, IA, and CA areas, RA and PA have a higher potential contribution to heavy metal runoff pollution from Road deposited sediments (RDS) than the other watersheds. Zhengzhou utilized the RDS index model to calculate pollution loads in various areas around Zhengzhou (EA, IA, CA, PA, and RA). In the different land-use areas, the RDS indices for pollutant load (RDSindex,load) and pollutant strength (RDSindex,strength) varied greatly, and the RDS index strength values increased. RDSindex,load fell in the following order: IA > RA > PA > EA. Because the RDS index incorporates RDS characteristics such as the amount of RDS, grain sizes present, RDS mobility, and associated metals, the RDSindex,load and RDSindex,strength results did not merely match variability in the amounts of RDS found or metal concentrations in the RDS in various land-use areas. Metal's presence in the dust is a direct health risk for humans and warrants immediate and effective pollution control and prevention measures in the city.

Assessment and source apportionment of water-soluble heavy metals in road dust of Zhengzhou, China.

The water-soluble concentration of heavy metals in road dust poses a considerable hazard to public health. The primary goals of the study were estimation of water-soluble contents of heavy metal, estimation of pollution indices, and source apportionment of water-soluble contents of heavy metals using UNMIX model from the road dust of Zhengzhou city. To accomplish this, inductively coupled plasma atomic emission spectroscopy (ICP-AES) was used to determine concentrations of eight heavy metals (Cr, Cu, Ni, Zn, Cd, As, Pb, and Hg), and it has been observed that Cu and Zn were the metals with the highest concentration, while Hg, Cd, and Pb were in the lowest concentration range of metals. Pollution indices, geo-accumulation index (Igeo), contamination factor (CF), and Nemerow synthetic pollution index (PIN) were calculated to assess the contamination level of water-soluble contents of these hazardous heavy metals. Igeo classified the contamination risk into a spectrum of categories ranging from unpolluted (Cr and Pb) to high polluted (Cu and Cd). For the CF results, the concentration of Cr and Pb was found to be low, similar to Igeo, while the concentrations of three heavy metals, Cu, Cd, and Hg, were found to be extremely high or excessive. The results of the PIN assessment indicated that there was an enormous risk of Hg contamination in the city and that Cu, Cd, and Zn were all within a few percent of the Hg pollution level and hence fell into the high pollution group. The UNMIX model was used for source apportionment of dissolved heavy metals and showed: Source 1 (natural sources, 10%), Source 2 (copper mine tailing contamination, 19%), and Source 3 (agricultural activities22%). Source 4 accounted for (air pollution, 15%) of the total and Source 5 accounted for (industrial activity, 34%). It is imperative that immediate and comprehensive pollution control and preventive measures be implemented in the city due to the presence of metal in the dust.

Fault-tolerance in metric dimension of boron nanotubes lattices.

The concept of resolving set and metric basis has been very successful because of multi-purpose applications both in computer and mathematical sciences. A system in which failure of any single unit, another chain of units not containing the faulty unit can replace the originally used chain is called a fault-tolerant self-stable system. Recent research studies reveal that the problem of finding metric dimension is NP-hard for general graphs and the problem of computing the exact values of fault-tolerant metric dimension seems to be even harder although some bounds can be computed rather easily. In this article, we compute closed formulas for the fault-tolerant metric dimension of lattices of two types of boron nanotubes, namely triangular and alpha boron. These lattices are formed by cutting the tubes vertically. We conclude that both tubes have constant fault tolerance metric dimension 4.

Interspecific Differences in Physiological and Biochemical Traits Drive the Water Stress Tolerance in Young Morus alba L. and Conocarpus erectus L. Saplings.

Mitigating climate change requires the identification of tree species that can tolerate water stress with fewer negative impacts on plant productivity. Therefore, the study aimed to evaluate the water stress tolerance of young saplings of C. erectus and M. alba under three soil water deficit treatments (control, CK, 90% field capacity, FC, medium stress MS, 60% FC and high stress, HS, 30% FC) under controlled conditions. Results showed that leaf and stem dry weight decreased significantly in both species under MS and HS. However, root dry weight and root/shoot ratio increased, and total dry weight remained similar to CK under MS in C. erectus saplings. Stomatal conductance, CO2 assimilation rate decreased, and intrinsic water use efficiency increased significantly in both species under MS and HS treatments. The concentration of hydrogen peroxide, superoxide radical, malondialdehyde and electrolyte leakage increased in both the species under soil water deficit but was highest in M. alba. The concentration of antioxidative enzymes like superoxide dismutase, peroxidase, catalase, and ascorbate peroxidase also increased in both species under MS and HS but was highest in C. erectus. Therefore, results suggest that C. erectus saplings depicted a better tolerance to MS due to an effective antioxidative enzyme system.

Increased antioxidative enzyme activity mediates the phytoaccumulation potential of Pb in four agroforestry tree species: a case study under municipal and industrial wastewater irrigation.

Wastewater used as irrigation water is causing heavy metal accumulation in the agro-ecosystems. A greenhouse study was conducted to compare the phytoaccumulation ability of four agroforestry tree species under different wastewater treatments. Three-month-old potted seedlings of Morus alba, Acacia nilotica, Acacia ampliceps, and Azadirachta indica were irrigation with tap water (C), municipal wastewater (MWW), and industrial wastewater (IWW). Results showed that MWW had a positive and IWW had a negative impact on biomass production in all the species. Acacia ampliceps showed the highest increment (65%) and showed the lowest decrease (5%) in total biomass under both MWW and IWW treatment. Pb concentration was also found highest in the leaves, stem and roots of Azadirachta indica (108.5, 46.2, 180.5 mg kg-1, respectively) under IWW. Production of H2O2 was highest in IWW treatment with almost 148% increase observed in Azadirachta indica. Similarly, the production of antioxidative enzymes (Superoxide dismutase, Catalase and Peroxidase) was also highest in Azadirachta indica under IWW. Therefore, results suggest that along with high increment in total biomass, both Acacia ampliceps and Azadirachta indica showed high Pb concentration and an effective antioxidative defense mechanism and thus, can be used for planting in soils irrigated with MWW and IWW.

Metric basis and metric dimension of 1-pentagonal carbon nanocone networks.

Resolving set and metric basis has become an integral part in combinatorial chemistry and molecular topology. It has a lot of applications in computer, chemistry, pharmacy and mathematical disciplines. A subset S of the vertex set V of a connected graph G resolves G if all vertices of G have different representations with respect to S. A metric basis for G is a resolving set having minimum cardinal number and this cardinal number is called the metric dimension of G. In present work, we find a metric basis and also metric dimension of 1-pentagonal carbon nanocones. We conclude that only three vertices are minimal requirement for the unique identification of all vertices in this network.

Short- and Intermediate-Term Outcomes in Living-Related Renal Transplant Donors.

OBJECTIVES: The aim of the present study was to evaluate the short- and intermediate-term outcomes of living-related kidney donors in terms of renal function and postnephrectomy complications at a single center in Pakistan. MATERIALS AND METHODS: Our study included healthy donors who underwent unilateral nephroureterectomy for living-related renal transplant procedures at the Sindh Institute of Urology and Transplantation (Karachi, Pakistan) between January 2005 and January 2006. All patients were evaluated for early postoperative complications and renal functions at last follow-up. The mean follow-up duration was 1.7 ± 1.3 years. RESULTS: A total of 256 living-related donors underwent nephroureterectomy during the study period, which included 142 men (55.5%) and 114 women (44.5%). The mean age of donors was 33.7 ± 10.0 years. Most donors were between 21 and 40 years old. Of total donors, most were siblings (n = 143, 55.8%), followed by offspring, parents, and spouses. Left nephrectomy was performed in 206 donors (80.4%) and right in 50 donors (19.5%). There were no deaths during transplant. The mean postoperative hospital stay was 6.37 ± 0.95 days. A total of 38 donors (14.8%) had one or more surgical complication. Hypertension developed in 25 (9.7%) and diabetes mellitus in 9 donors (5%). Creatinine clearance was > 90 mL/min in 96 (41%), 60 to 90 mL/min in 120 (51%), and ≤ 60 mL/min in 18 donors (8%). CONCLUSIONS: Living-related donor nephrectomy remains a valuable source of kidneys for transplant procedures and carries a small risk. With careful donor selection and good surgical management, operative complications can be minimized.

Long-term Safety of Living Kidney Donation in an Emerging Economy.

BACKGROUND: Long-term follow-up and management of donors was undertaken in a specialist kidney transplant unit in Pakistan to identify risk and prevent adverse outcomes in living related kidney donors. METHODS: In an observation cohort study between 1985 and 2012, 3748 donors were offered free medical follow-up and treatment 6 to 12 months after donation and annually thereafter. Each visit included history, physical examination, blood tests for renal, lipid, glucose profiles, and 24-hour urine for proteinuria and creatinine clearance. Preventive intervention was undertaken for new onset clinical conditions. Donor outcomes were compared with 90 nondonor healthy siblings matched for age, sex, and body mass index. RESULTS: Of the 3748 donors, 2696 (72%) were in regular yearly follow-up for up to 27 years (median, 5.6; interquartile range, 7.9). Eleven (0.4%) died 4 to 22 years after donation with all-cause mortality of 4.0/10 000 person years. Six (0.2%) developed end-stage renal disease 5 to 17 years after donation, (2.7/10 000 person years). Proteinuria greater than 1000 mg/24 hours developed in 28 patients (1%), hypertension in 371 patients (13.7%), and diabetes in 95 patients (3.6%). Therapeutic intervention-controlled protein was less than 1000 mg/24 hours, blood pressure was below 140/90 mm Hg, and glycemic control in 85% up to 15 years after onset. Creatinine clearance fell from 109.8 ± 22.3 mL/min per 1.73 m predonation to 78 ± 17 at 1 year, 84 ± 19 at 5 years, and 70 ± 20 at 25 years. Comparison of 90 nondonor sibling and donor pairs showed significantly higher fasting glucose and hypertension in nondonors. CONCLUSIONS: Long-term follow-up of donors has demonstrated end-stage renal disease in 0.6% at 25 years. Regular follow-up identified new onset of disease and allowed interventions that may have prevented adverse outcomes.

The epidemiology, antibiotic resistance and post-discharge course of peritonsillar abscesses in London, Ontario.

BACKGROUND: Peritonsillar abscesses (PTA) are a common complication of tonsillitis. Recent global epidemiological data regarding PTAs have demonstrated increasing antimicrobial resistance patterns. No similar studies have been conducted in Canada and no Canadian study has examined the post-discharge course of treated patients. METHODS: A prospective observational study of the epidemiology, antibiotic resistance and post-discharge course of patients presenting with a peritonsillar abscess to the Emergency Department in London, Ontario over one year. A follow-up telephone survey was conducted 2-3 weeks after abscess drainage. RESULTS: 60 patients were diagnosed with an abscess, giving an incidence of 12/100,000. 46 patients were enrolled in the study; the average duration of symptoms prior to presentation was 6 days, with 51% treated with antibiotics prior to presentation. Streptococcus pyogenes and Streptococcus anginosus were present in 56% of isolates and of those, 7/23 (32%) of specimens demonstrated resistance to clindamycin. Eight patients were treated with clindamycin and had a culture that was resistant, yet only one had recurrence. Telephone follow-up was possible for 38 patients: 51% of patients reported a return to solid food within 2 days, and 75% reported no pain by 5 days. Resolution of trismus took a week or longer for 51%. INTERPRETATION: Clindamycin resistance was identified in a third of Streptococcus isolates, which should be taken into account when prescribing antibiotics. Routine culture appears unnecessary as patients recover quickly from outpatient drainage and empiric therapy, with less pain than expected, but trismus takes time to resolve.

Antibiotic prescribing practices for catheter urine culture results.

BACKGROUND: The literature suggests that positive results of catheter urine cultures frequently lead to unnecessary antimicrobial prescribing, which therefore represents an important target for stewardship. OBJECTIVE: To assess the appropriateness of antibiotic prescribing in response to the results of urine cultures from patients with indwelling urinary catheters. METHODS: This retrospective study was conducted at a tertiary care centre and involved adults with indwelling urinary catheters from whom urine specimens were obtained for culture. Patients with positive or negative culture results were identified from microbiology laboratory reports. The medical records of consecutive patients were screened to select a sample of 80 inpatients (40 per group). Abstracted patient histories were independently evaluated by an expert panel of 3 infectious diseases consultants blinded to the decisions of prescribers and of fellow panelists. The primary end point was concordance of each patient's treatment decision (with respect to the indication) between the expert panel (based on majority agreement, i.e., at least 2 of the 3 expert panelists) and the prescriber. The secondary end points were unnecessary days of therapy and selected outcomes over a predefined period after urine was obtained for culture. RESULTS: A total of 591 charts were screened to generate the targeted number of patients. Baseline demographic characteristics were comparable for the 2 groups, except antibiotic exposure before urine collection was significantly more frequent for the group with negative culture results. The treatment decision was concordant in 40% (16/40) of the patients with a positive culture result and 85% (34/40) of those with a negative culture result (p < 0.001). The most common reason for discordance was administration of antibiotics when not indicated (23 of 24 patients with a positive result and 5 of 6 patients with a negative result), which accounted for 165 and 32 unnecessary days of therapy per 1000 inpatient-days, respectively (p < 0.001). Adverse effects occurred in 2 of the 23 patients with a positive result who received antibiotics that were not indicated. CONCLUSIONS: Appropriateness of antibiotic prescribing, as measured by concordance of decisions between the expert panel and prescribers, was more common among patients with negative urine culture results than among those with positive results. However, there is an opportunity to improve prescribing for both groups through antimicrobial stewardship initiatives. Unnecessary days of therapy and adverse effects were more common in patients with a positive culture result.

CONTEXTE: Selon la littérature, des résultats positifs à des cultures d'échantillons d'urine prélevés à partir d'une sonde vésicale entraînent souvent la prescription inutile d'antibiotiques; par conséquent, cette situation représente un objet important de gestion responsable des antimicrobiens. OBJECTIF: Évaluer la pertinence de la prescription d'antibiotiques sur la base de résultats des cultures d'échantillons d'urine prélevés chez les patients porteurs d'une sonde vésicale à demeure. MÉTHODES: La présente étude rétrospective a été menée dans un établissement de soins tertiaires auprès de patients adultes porteurs d'une sonde vésicale à demeure chez qui on a prélevé des échantillons d'urine à des fins de culture. Les patients avec des résultats de culture positifs ou négatifs ont été repérés à partir des rapports de microbiologie. Les dossiers médicaux d'une série consécutive de patients ont été examinés afin de choisir un échantillon de 80 patients hospitalisés (40 par groupe). Les historiques abrégés des patients ont été évalués indépendamment par un panel d'experts composé de trois consultants en maladies infectieuses qui ignoraient la décision des prescripteurs et les résultats des évaluations de leurs collègues panélistes. Le paramètre d'évaluation principal était la concordance de la décision thérapeutique (quant à l'indication) pour chaque patient entre le panel d'experts (selon un accord majoritaire, c.-à-d. au moins deux des trois panélistes experts) et le prescripteur. Les paramètres d'évaluation secondaires étaient le nombre de jours de traitement inutiles et certains résultats cliniques sur une période prédéterminée après l'obtention d'un échantillon d'urine à des fins de culture. RÉSULTATS: Un total de 591 dossiers de patients ont été analysés afin d'obtenir le nombre cible de patients pour l'étude. Les caractéristiques démographiques initiales étaient comparables dans les deux groupes, sauf l'exposition aux antibiotiques avant le prélèvement d'urine qui était significativement plus fréquente dans le groupe de patients ayant obtenu des résultats de culture négatifs. La décision thérapeutique concordait pour 40 % (16/40) des patients ayant obtenu des résultats positifs à la culture d'urine et pour 85 % (34/40) de ceux qui avaient obtenu des résultats négatifs (p < 0,001). La raison la plus fréquente expliquant la discordance entre les décisions thérapeutiques était l'administration non indiquée d'antibiotiques, une circonstance observée chez 23 patients sur 24 ayant obtenu des résultats positifs et 5 patients sur 6 ayant obtenu des résultats négatifs. Ces cas ont contribué respectivement à un total de 165 et de 32 jours de traitement inutiles par 1000 journées-patients hospitalisés (p < 0,001). Des effets indésirables sont survenus chez deux des 23 patients ayant obtenu un résultat positif et reçu des antibiotiques non indiqués. CONCLUSIONS: La pertinence de la prescription d'antibiotiques, telle qu'elle a été mesurée en fonction de la concordance des décisions entre le panel d'experts et les prescripteurs, était plus fréquente dans le cas des patients ayant obtenu des résultats négatifs à la culture d'urine que chez ceux dont ces résultats étaient positifs. Cependant, des mesures pour la gestion responsable des antimicrobiens pourraient améliorer la prescription dans les deux groupes. Le nombre de jours de traitement inutiles et les effets indésirables étaient plus fréquents chez les patients ayant obtenu des résultats positifs à la culture. [Traduction par l'éditeur].

Recurrent late-onset group B Streptococcus sepsis in a preterm infant acquired by expressed breastmilk transmission: a case report.

Group B Streptococcus is a known cause of neonatal sepsis, being more common in the early period by maternal genital tract transmission and less so in the late neonatal period, ascribed to intestinal colonization or horizontal transmission. Although breastmilk transmission of Group B Streptococcus has rarely been reported in the past, most cases are of patients nursed on the mother's breast and less commonly in expressed breastmilk-fed infants. This case describes a preterm infant (born at a gestational age of 24 weeks 6 days) in the neonatal intensive care unit who acquired recurrent late-onset sepsis with Group B Streptococcus with the mother's expressed breastmilk culture growing the same organism that was later matched to the infant's isolate. The mother had presented with features of mastitis only during the second episode of sepsis and was then treated with oral antibiotics. The infant was fed on formula feeds after the second incidence and remained healthy, being discharged on a regular follow-up plan at 39 weeks corrected gestational age.

Attitudes toward vaccination for pandemic H1N1 and seasonal influenza in patients with hematologic malignancies.

BACKGROUND: Patients with hematologic malignancies are at increased risk of influenza and its complications. Despite current health recommendations and evidence favoring influenza vaccination, vaccination rates remain low in cancer patients. OBJECTIVE: The purpose of this study was to determine which factors influenced vaccination rates. METHODS: During the 2009-2010 pandemic H1N1 and seasonal influenza season, we surveyed patients with hematologic malignancies in a Canadian cancer center. Of the patients participating in our study (n = 129), 66% and 57% received the H1N1 pandemic influenza and seasonal influenza vaccines, respectively. RESULTS: A number of reasons for vaccination refusal were reported, most relating to general skepticism about the safety and efficacy of vaccination. Physician advice was also a factor influencing vaccination rates in patients. The vaccination rate for seasonal influenza was 39% in patients < 65 years old, significantly lower than the rate of 73% reported for patients aged > or = 65 years (P < 0.0001). CONCLUSION: Future education programs should target younger patient populations and health-care workers, focusing on vaccine safety and efficacy in the high-risk cancer population.

Comparison of community-associated and health care-associated methicillin-resistant Staphylococcus aureus in Canada: results of the CANWARD 2007-2009 study.

This study assessed the demographics, antimicrobial susceptibility, and molecular epidemiology of community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) and health care-associated MRSA (HA-MRSA) in Canadian hospitals between 2007 and 2009. Among 3589 S. aureus, 889 (24.8%) were MRSA; 224 (25.2%) were CA-MRSA genotypes and 644 (72.4%) were HA-MRSA genotypes. The prevalence of CA-MRSA genotypes increased from 19.5% in 2007 to 31.9% in 2009 (P < .001). CMRSA10/USA300 (73.7%) was the predominant CA-MRSA epidemic type; the most common HA-MRSA epidemic type was CMRSA2/USA100/800 (83.5%). CA-MRSA genotypes carried SCCmec type IVa (98.2%) and were largely agr type I (73.2%). Most HA-MRSA genotypes were SCCmec type II (81.2%) and agr type II (83.4%). Panton-Valentine leukocidin was detected in 201/224 (89.7%) CA-MRSA genotypes and 3/644 (0.5%) HA-MRSA genotypes. An increase in vancomycin minimum inhibitory concentration (MIC) was observed in HA-MRSA genotypes overall, with 1.3% (4/305) of strains in 2007 and 4.6% (7/152) in 2009 exhibiting vancomycin MICs of 2 µg/mL. No MRSA resistance occurred with linezolid, daptomycin, or tigecycline. In conclusion, CA-MRSA genotypes represented 25.2% of all MRSA and continue to increase in prevalence in Canadian hospitals.

Susceptibility patterns of coagulase-negative staphylococci to several newer antimicrobial agents in comparison with vancomycin and oxacillin.

Coagulase-negative staphylococci (CoNS) have emerged as important nosocomial pathogens. CoNS resistance to meticillin and other semisynthetic penicillins is now common. Elevated vancomycin minimal inhibitory concentrations (MICs) have been reported and are associated with worse treatment outcomes. Several newer antibiotics have recently become available for the treatment of Gram-positive infections. The purpose of this study was to assess the in vitro activity of telavancin, daptomycin, linezolid and tigecycline in comparison with oxacillin and vancomycin against 653 non-duplicate clinical isolates of CoNS by the agar dilution method. The greatest variability in MIC was observed for oxacillin. Presence of the mecA gene conferred higher MICs for oxacillin but did not influence MICs to all other antibiotics tested. Telavancin tended to have MICs that were 1-2 dilutions lower than vancomycin. Daptomycin had good activity against all isolates. Staphylococcus haemolyticus, Staphylococcus hominis subsp. novobiosepticus, Staphylococcus saprophyticus, Staphylococcus schleiferi and Staphylococcus simulans were the most daptomycin-susceptible CoNS species tested. The validity of the agar dilution method for daptomycin was confirmed, with >90% isolates having MICs that were within 1 dilution of parallel Etest results. Within-species MIC variation was most restricted for linezolid and tigecycline, with the exception of Staphylococcus epidermidis and Staphylococcus haemolyticus that demonstrated higher overall MICs to tigecycline.

Methicillin-resistant Staphylococcus aureus in skin and soft tissue infections presenting to the Emergency Department of a Canadian Academic Health Care Center.

OBJECTIVES: This study aimed to estimate the city-wide prevalence of methicillin-resistant Staphylococcus aureus (MRSA) in patients (≥18 years old) presenting with skin and soft tissue infections (SSTIs) to the emergency departments (EDs) of a Canadian Academic Health Care Center. Secondary objectives were to identify demographic and clinical variables associated with MRSA, and determine MRSA antimicrobial susceptibilities and genotypes. METHODS: This prospective observational study was conducted over 2 months. Participants completed a Health and Lifestyle Questionnaire. Cultures of the infection site, nares, and throat were obtained and MRSA isolates were confirmed by polymerase chain reaction. Patient characteristics were summarized using descriptive statistics and MRSA prevalence and 95% confidence intervals were estimated using standard equations. Backwards stepwise multivariate logistic regression models determined predictor variables independently associated with MRSA colonization or infection. RESULTS: Of 205 patients, 35 (17.1%) were infected or colonized with MRSA. Seventy-eight (38.0%) of the infection site cultures grew S. aureus of which 27 (34.6%) were MRSA. Incarceration, known exposure to MRSA and involvement in competitive sports were significant predictors of MRSA SSTIs. Antimicrobial susceptibility among MRSA isolates was trimethoprim/sulfamethoxazole, vancomycin, gentamicin, and linezolid 100%, clindamycin 75%, ciprofloxacin 59.3%, and erythromycin 7.4%. Sixty-nine percent of MRSA cases fit the clinical definition of community associated; subsequently 77% were confirmed as CMRSA 10, a recognized community-acquired MRSA. CONCLUSION: Community-acquired -MRSA is a significant pathogen of SSTIs in EDs of a Canadian teaching center. MRSA should be considered when initiating empiric antibiotic therapy, particularly in patients with risk factors.

Comparison of three phenotypic techniques for detection of methicillin resistance in Staphylococcus spp. reveals a species-dependent performance.

OBJECTIVES: To evaluate the usefulness of the cefoxitin screen in Vitek 2 Gram-positive panels for recognizing methicillin-resistant strains of staphylococci. METHODS: Seven hundred and ninety-nine non-duplicate isolates of Staphylococcus aureus and coagulase-negative strains were included in the study. Methicillin resistance was measured using PCR for the mecA gene, the CLSI cefoxitin disc diffusion method, the Vitek 2 cefoxitin screen and the Vitek 2 oxacillin susceptibility test. RESULTS: Compared with the molecular detection of methicillin resistance the overall sensitivities and specificities of the phenotypic tests for cefoxitin disc diffusion were 94.9% and 97.0%, for Vitek 2 cefoxitin screen were 94.6% and 93.5% and for Vitek 2 oxacillin susceptibility test were 93.8% and 77.9%. The cephamycin tests (cefoxitin disc diffusion and Vitek 2 screen) were not able to identify mecA-positive strains of Staphylococcus simulans. In addition, the performance of the Vitek 2 system was poor against Staphylococcus cohnii subspecies, Staphylococcus hominis hominis and Staphylococcus saprophyticus. CONCLUSIONS: Overall, the performance of the Vitek 2 system for differentiating mecA-positive staphylococci was comparable to PCR and the CLSI disc diffusion method; however, performance was species-dependent. Thus, before accepting the results produced by Vitek 2, species identification may be required.

Evaluation of a new chromogenic medium for the detection of methicillin-resistant Staphylococcus aureus carriage on nasal and perianal specimens.

A new chromogenic medium, denim blue (DB), was compared with methicillin-resistant Staphylococcus aureus (MRSA) Select (MRSAS) for detection of MRSA from surveillance specimens. On DB, MRSA colonies are larger (0.57-0.8 versus 0.45-0.6 mm at 18 and 24 h, respectively). Despite this, sensitivities of DB were 77% and 96% at 18 and 24 h, respectively, and those of MRSAS were 63% and 97.5%. Specificities were significantly higher for MRSAS than DB. The study demonstrates that DB and MRSA are equal for the detection of MRSA from surveillance specimens provided the plates are read after 24 h of incubation. Positive predictive values of both media were less than 95% requiring confirmation of MRSA, by another method, from all new patients.

Performance of TechLab C. DIFF QUIK CHEK and TechLab C. DIFFICILE TOX A/B II for the detection of Clostridium difficile in stool samples.

UNLABELLED: Two membrane-bound enzyme immunoassays by TechLab, Blacksburg, VA, were evaluated and compared with the Triage Micro C. difficile Panel (Biosite Diagnostics, San Diego, CA), with culture, and with cytotoxic assay. The TechLab panels were C. DIFF QUIK CHEK (QC-GDH) and C. DIFFICILE TOX A/B II (QC-toxinA/B), which detect glutamate dehydrogenase (GDH) and Clostridium difficile toxins A and B, respectively. The Triage Panel detects GDH (TR-GDH) and toxin A (TR-toxinA). METHODS: Stool samples were inoculated onto CCFA plates (Q-Labs, Quebec, Canada) after alcohol shock, and suspected colonies were identified by the MicroScreen C. difficile latex slide agglutination test (Microgen Bioproducts, Surrey, UK). TR-GDH, TR-toxinA, QC-GDH, and QC-toxinA/B tests were performed according to the manufacturers' instructions on all the samples. Samples positive for GDH or culture but negative for TR-toxinA and QC-toxinA/B were further tested by cytotoxin assay (CTA). CTA was also performed on samples that caused blackening of the Triage Micro C. difficile Panel. RESULTS: A total of 313 of 401 stool samples were negative for GDH and toxins (78%). Eighty-eight samples were positive either for GDH or culture or both. Thirteen of these could not be evaluated for C. difficile-associated diarrhea (CDAD) because CTA test was not performed. Toxin/s was detected at least by one method in 46 (11.8%) of 388 samples that were positive for culture or GDH and were considered diagnostic of CDAD. The QC-GDH was more sensitive than culture and TR-GDH for the detection of C. difficile. However, in 18GDH-positive samples positive for either of the Triage or TechLab immunoassays, the culture remained negative. Ten (2%) results of the Triage immunoassays could not be evaluated because of discoloration of the panels. QC-GDH (93.5%) was more sensitive for detecting the presence of toxin-producing C. difficile than TR-GDH (79.5%). TR-toxinA was more specific for detecting the presence of toxin-producing C. difficile than QC-toxinA/B (100% and 96.9%, respectively). CONCLUSIONS: The GDH tests had a faster turnaround time than the traditional culture methods. QC-GDH was most sensitive for the detection C. difficile-positive stools and was easy to use.

Prospective comparison of a new chromogenic medium, MRSASelect, to CHROMagar MRSA and mannitol-salt medium supplemented with oxacillin or cefoxitin for detection of methicillin-resistant Staphylococcus aureus.

MRSASelect agar was compared to CHROMagar, mannitol-salt agar with oxacillin, and mannitol-salt agar with cefoxitin (MSA-CFOX) for the isolation of methicillin-resistant Staphylococcus aureus (MRSA). The sensitivities and specificities were 97.3% and 99.8%, 82.9% and 99.1%, 80.2% and 79%, and 99.1% and 84.8%, respectively. MSA-CFOX and MRSASelect had a high sensitivity. MRSASelect, however, was more specific and proved to be a more reliable and rapid medium for the detection of MRSA.