Blood Agar Plate Cultures Research Articles

An invitro comparison of antimicrobial efficacy of sodium hypochlorite gel with twin kleen irrigating solution against enterococcus feacalis

The Enterococcus faecalis (E. faecalis) is a normal inhabitant of the oral cavity and is the most commonly identified species in post treatment asymptomatic persistent endodontic diseases (both intra-radicular and extra- radicular). Its prevalence ranges from 24% to 77%. To completely eliminate microorganisms from the root canal system, combination of instrumentation and irrigation with antibacterial solutions is necessary. Hence, the purpose of this study was to evaluate and compare the antibacterial efficacy of sodium hypochlorite gel with twin kleen irrigating solution against E. faecalis.40 non-carious, single-rooted teeth with straight canals were selected and instrumented till F3 (30.06) ProTaper Universal (Dentsply Maillefer, Ballaigues, Switzerland). E faecalis was prepared and incubated in teeth and were randomly divided into four groups of 10 each, Group A – 5.25% NaOCl gel, Group B – Twin Kleen Irrigating solution, Group C – 3% NaOCl solution and Group D – Saline. Sterile paper points were used to collect the samples after irrigation and then they were transferred to blood agar culture plates to check the presence of E. faecalis. Significant statistical difference was seen between the four groups. The effect of 5.25% NaOCl gel was superior as compared to Twin Kleen irrigating solution.Under the limitations of this study, 5.25% NaOCl gel was effective in reducing E. faecalis count followed by Twin kleen irrigating solutions.

Trueperella pyogenes endocarditis in a Swiss farmer: a case report and review of the literature

BackgroundTrueperella pyogenes (T. pyogenes) is a bacterium that colonizes the skin and mucosal surfaces of various domestic and wild animals. It rarely leads to infections in humans, with only a few descriptions available in the literature.Case presentationA 71-year-old Swiss farmer with a history of recurring basal cell carcinoma and metastasized pancreatic neuroendocrine tumor presented with signs of sepsis after a three-day history of general weakness, malaise and fever. Clinical and echocardiographic findings, as well as persistent bacteremia were consistent with mitral valve endocarditis caused by T. pyogenes. The patient’s condition gradually improved under antibiotic treatment with piperacillin/tazobactam (empiric therapy of sepsis), and later penicillin G based on resistance testing. He was discharged after 13 days and continued outpatient antibiotic therapy with ceftriaxone, resulting in a total antibiotic treatment duration of six weeks. This is the first literature review of T. pyogenes endocarditis in humans. Among nine cases of T. pyogenes endocarditis, three patients had documented contact with farm animals and five had an underlying condition that compromised the immune system. While antibiotic resistance of T. pyogenes is an emerging concern, susceptibility to beta-lactam antibiotics seems to persist. The mortality of T. pyogenes endocarditis described in the literature was high, with 66% of patients not surviving the disease.ConclusionsT. pyogenes is a rare causative organism of infectious endocarditis in humans and descriptions are mainly restricted to case reports. In our review of the literature, we found that both an impaired immune system and contact with farm animals might be risk factors. Growth of T. pyogenes in blood cultures is unlikely to be missed during routine analysis, as it shows marked beta-hemolysis on blood agar culture plates, which generally leads to further characterization of the bacteria. Susceptibility to penicillin, ceftriaxone, and macrolides seems to be retained and the reported mortality in the few patients with T. pyogenes endocarditis is high.

Evaluation of BACTEC MGIT 960 system for recovery of Nocardia from clinical specimens

Nocardia spp. is an aerobic Gram-positive bacillus responsible for nocardiosis. Herein, we performed a retrospective study to evaluate the performance of BACTEC MGIT 960 system, in comparison with smear microscopy and blood agar plate (BAP) culture, to recover Nocardia from different clinical specimens. Furthermore, the inhibitory effect of antibiotics contained in MGIT 960 tube on Nocardia was also evaluated. The sensitivities for Nocardia recovery using smear microscopy, BAP culture, and MGIT 960 were 39.4% (54/137), 46.1% (99/215), and 81.3% (156/192), respectively. N. farcinica was the most detected species (60.4%, 136/225). In MGIT 960-recovered Nocardia strains, N. farcinica accounted for 76.9%. Furthermore, trimethoprim in MGIT 960 tube inhibited less N. farcinica growth than that of other Nocardia species, partially explaining why MGIT 960 recovered more N. farcinica from sputa. The current study demonstrated that MGIT 960 could recover Nocardia strains from heavily-contaminated samples if its components and antibiotics are redesigned.

Metagenomic Sequencing Revealed the Potential Pathogenic Threats of Banknotes.

Banknotes have long been suspected to be biologically “dirty” due to their frequent human contact, which may transmit human microbial pathogens. Still, it is an unsettled issue whether the microbes on banknotes pose a real threat to human health. In several previous studies, metagenomic sequencing was used to reveal the diversities of microbes on banknotes but live microorganism culture and functional verification were lacking. In this study, we collected banknotes of RMB in China as well as dollar bills in the United States and analyzed the microbial biodiversity and drug resistance genes carried by the identified microbes by metagenomic sequencing and in vitro culture methods. We identified eight major genera of drug-resistant bacteria through screening of 30 antibiotics, and the blood agar plate culture uncovered six pathogenic fungal species. Numerous phage and six dangerous viral sequences were also found. These results should substantiate our concern about the potential risk of banknotes to human health.

Hydrogen Peroxide Production by Streptococcus pneumoniae Results in Alpha-hemolysis by Oxidation of Oxy-hemoglobin to Met-hemoglobin.

Streptococcus pneumoniae and other streptococci produce a greenish halo on blood agar plates referred to as alpha-hemolysis. This phenotype is utilized by clinical microbiology laboratories to report culture findings of alpha-hemolytic streptococci, including S. pneumoniae, and other bacteria. The alpha-hemolysis halo on blood agar plates has been related to the hemolytic activity of pneumococcal pneumolysin (Ply) or, to a lesser extent, to lysis of erythrocytes by S. pneumoniae-produced hydrogen peroxide. We investigated the molecular basis of the alpha-hemolysis halo produced by S. pneumoniae Wild-type strains TIGR4, D39, R6, and EF3030 and isogenic derivative Δply mutants produced similar alpha-hemolytic halos on blood agar plates, while cultures of hydrogen peroxide knockout ΔspxB ΔlctO mutants lacked this characteristic halo. Moreover, in the presence of catalase, the alpha-hemolysis halo was absent in cultures of the wild-type (wt) and Δply mutant strains. Spectroscopic studies demonstrated that culture supernatants of TIGR4 released hemoglobin-bound heme (heme-hemoglobin) from erythrocytes and oxidized oxy-hemoglobin to met-hemoglobin within 30 min of incubation. As expected, given Ply hemolytic activity and that hydrogen peroxide contributes to the release of Ply, TIGR4Δply and ΔspxB ΔlctO isogenic mutants had significantly decreased release of heme-hemoglobin from erythrocytes. However, TIGR4Δply that produces hydrogen peroxide oxidized oxy-hemoglobin to met-hemoglobin, whereas TIGR4ΔspxB ΔlctO failed to produce oxidation of oxy-hemoglobin. Studies conducted with all other wt strains and isogenic mutants resulted in similar findings. We demonstrated that the so-called alpha-hemolysis halo is caused by the oxidation of oxy-hemoglobin (Fe+2) to a non-oxygen-binding met-hemoglobin (Fe+3) by S. pneumoniae-produced hydrogen peroxide.IMPORTANCE There is a misconception that alpha-hemolysis observed on blood agar plate cultures of Streptococcus pneumoniae and other alpha-hemolytic streptococci is produced by a hemolysin or, alternatively, by lysis of erythrocytes caused by hydrogen peroxide. We noticed in the course of our investigations that wild-type S. pneumoniae strains and hemolysin (e.g., pneumolysin) knockout mutants produced the alpha-hemolytic halo on blood agar plates. In contrast, hydrogen peroxide-defective mutants prepared in four different strains lacked the characteristic alpha-hemolysis halo. We also demonstrated that wild-type strains and pneumolysin mutants oxidized oxy-hemoglobin to met-hemoglobin. Hydrogen peroxide knockout mutants, however, failed to oxidize oxy-hemoglobin. Therefore, the greenish halo formed on cultures of S. pneumoniae and other so-called alpha-hemolytic streptococci is caused by the oxidation of oxy-hemoglobin produced by hydrogen peroxide. Oxidation of oxy-hemoglobin to the nonbinding oxygen form, met-hemoglobin, might occur in the lungs during pneumococcal pneumonia.

Comparative Study of the Antibacterial Effect of Nano-Silver Irrigant, Sodium Hypochlorite and chlorhexidine against Enterococcus Faecalis Biofilm

This study aimed to compare the antimicrobial effect of Nano-Silver Irrigant, Sodium Hypochlorite and Chlorohexidine against Enterococcus Faecalis bifilm. 60 Sixty, recently extracted, sound maxillary anterior teeth with completely formed apices and straight roots were selected in this study. Canals were instrumented using the Protaper Next system (Dentsply Sirona) 1 mm shorter from the apical foramen up to size X5 ( size# 50/06). Sterility of the teeth after complete root canal cleaning and shaping were achieved by autoclaving for 15 min at 121oC with the teeth immersed in distilled water. Enterococcus Faecalis Biofilm was prepared by mixing 5 mL of the bacterial inoculum with sterilized BHI, then inoculated in teeth samples for 60 days. Teeth were then divided after the incubation period into three groups; 20 teeth each, and were treated by delivering the each of the tested irrigating solution using sterile plastic syringes. The first group was treated with Nano-Silver 0.02mol/L (2000ppm) while the second was treated using with Sodium Hypochlorite (NaOCl) 5.25% and the third was treated usinwith Chlorohexidine (CHX) 2.0%. Serial rinses ensured 5 minutes contact period between the aseptic solution and the bacteria. Sterile paper points size 50 were introduced into the canals and maintained for 3 min for sample collection, after which the paper points were placed in test tubes containing 2ml of sterile saline and several dilutions were prepared. 100 µL of each dilution was applied to the blood agar culture plates and incubated at 37oC for 24 hours. A classical bacterial counting technique was used for each group after the treatment application for the recovery of viable E. faecalis on agar plates The results showed that the NaOCl had the highest antibacterial activity with high statistically significant difference with the other groups followed by the chlorhexidine group which also show statistically significant difference than the other two groups, then came the nano silver irrigant group which showed the lowest antibacterial activity among all the groups with statistically significant difference with them.

A study on the relationship between changes in serum hs-CRP levels and Chinese ischemic stroke subclassification

Objective: To explore the effects of combined application of culture supernatant of human umbilical cord mesenchymal stem cells (hUCMSCs) and ciprofloxacin on Staphylococcus aureus (SA) in vitro. Methods: hUCMSCs were isolated from umbilical cord tissues of full-term healthy fetuses after cesarean section and then cultured. Cells in the third passage were chosen for the use of experiment after identification. SA strains isolated from wounds of burn patients in our burn wards were used in the following experiment. Cells were divided into 0, 10, 100 and 1,000 ng/ml lipopolysaccharide (LPS) groups by use of the random number table (similarly hereinafter). Cells were cultured with culture medium containing mesenchymal stem cells (MSCs) after being treated with medium containing corresponding mass concentrations of LPS for 12 h. At post culture hour (PCH) 6, 12 and 24, 6 wells of culture supernatant of cells in each group were obtained to measure the content of LL-37 with enzyme-linked immunosorbent assay (ELISA). Ninety blood agar culture plates were divided into ciprofloxacin control group (CC), ciprofloxacin + supernatant group (CS), and ciprofloxacin + supernatant + LL-37 antibody group (CSL), with 30 blood agar culture plates in each group. Blood agar culture plates in group CC were coated with 1.5 × 10 8 colony forming unit (CFU)/ml bacteria solution prepared with normal saline. Blood agar culture plates in group CS were coated with 1.5 × 10 8 CFU/ml bacteria solution prepared with normal saline and hUCMSC culture supernatant (cultured by MSC culture medium, the same below) in double volume of normal saline. Blood agar culture plates in group CSL were coated with 1.5 × 10 8 CFU/ml bacteria solution prepared with normal saline, hUCMSC culture supernatant in double volume of normal saline, and 2.6 μL of LL-37 antibodies at the concentration of 2 μg/ml. At PCH 12, 24 and 48, 10 blood agar culture plates were taken out from each group to observe the distribution of SA colonies on blood agar culture plates and to measure diameters of zones of inhibition of ciprofloxacin. The minimum inhibitory concentration (MIC) of ciprofloxacin against SA in each group was recorded. Fractional inhibitory concentration (FIC) indexes of ciprofloxacin in group CS and group CSL at PCH 12, 24 and 48 were calculated, with the synergistic effect evaluated. Data were processed with factorial design ANOVA, one way ANOVA, LSD- t test, Kruskal-Wallis test and Mann-Whitney U test. Results: (1) At each PCH, the content of LL-37 in cell culture supernatant in 10 ng/ml LPS group, 100 ng/ml LPS group or 1,000 ng/ml LPS group was higher than that in 0 ng/ml LPS group (with t values ranging from 11.22 to 33.36, p values all below .01); the content of LL-37 in cell culture supernatant in either 100 ng/ml LPS group or 1,000 ng/ml LPS group was higher than that in 10 ng/ml LPS group (with t values ranging from 2.24 to 18.73, p < .05 or p < .01); the content of LL-37 in cell culture supernatant in 1,000 ng/ml LPS group was higher than that in 100 ng/ml LPS group (with t values ranging from 12.46 to 14.70, p values all below .01). (2) At PCH 12, 24 and 48, the bacterial colonies in groups CC, CS and CSL became integrated over time. In CC group, diameters of zones of inhibition of ciprofloxacin at PCH 12, 24 and 48 were 26 mm, 24 mm and 23 mm respectively, with no obvious changes. At PCH 12, 24 and 48, diameters of zones of inhibition of ciprofloxacin in groups CS and CSL were 82 mm, 71 mm, 68 mm and 74 mm, 59 mm, 56 mm respectively, which were significantly larger than those in group CC. (3) At each PCH, MIC of ciprofloxacin against SA in group CC was significantly higher than that in groups CS and CSL respectively (with Z values ranging from 6.22 to 6.71, p values all below .01); MIC of ciprofloxacin against SA in group CSL was significantly higher than that in group CS (with Z values all equal to 6.72, p values all below .01). (4) FIC indexes of ciprofloxacin in groups CS and CSL at PCH 12, 24 and 48 were 0.011, 0.032, 0.032 and 0.122, 0.350, 0.350, respectively. The results indicated that hUCMSC culture supernatant had a synergistically antibacterial effect when combined with ciprofloxacin. Conclusions: hUCMSCs can secrete LL-37, and the secretion level is improved with increase of LPS concentration. The combination of hUCMSC culture supernatant with ciprofloxacin can decrease the dosage of ciprofloxacin in resisting SA effectively. Once LL-37 is neutralized, the synergistically antibacterial effect of hUCMSC culture supernatant is decreased thereby.

Glass bead sterilizer comprehensively defeats hot air oven in orthodontic clinic

Background: It is necessary to 'try in' several bands before the correct one is selected. A possible concern with re-using such bands is the lack of cross-infection control. Aim and Objectives: To determine whether such bands could be successfully decontaminated with Glass bead sterilization so that they could be re-used without a cross-infection risk. Materials: Custom made molar bands were taken and buccal tubes,lingual sheath and lingual cleat were welded under strict aseptic conditions. Methods: Samples were divided into 2 groups i.e. A and B, based on mode for sterilization. Sterilized attachments were placed in each of 2 conical flask. The bacteria spores were inoculated into both flask under strict aseptic conditions. Bacteria Bacillus subtillis and Staphylococcus albus species were allowed to multiply in individual flasks filled with BHI broth for 24 hours. Bands from 1st group were placed in a glass bead sterilizer. For the 2 nd group i.e. hot air oven group, all bands were placed together. After sterilization bands were removed and placed in freshly sterilized 500ml conical flask containing BHI broth for 24 hours in the incubator. The following day randomly 4 attachments were selected from each group and streaked on blood agar culture plates. Results: After sterilization and on further incubation in BHI broth for 24 and 48 hrs. Respectively no growth was seen. Conclusion: 1 hr. of Hot Air Oven sterilization (excluding pre sterilization heat up time and post sterilization cooling time) at 190°C is as effective as 3 min of Chair side Glass Bead sterilization.

Anesthesiologist's hand hygiene and disinfection of reusable rubber tourniquet with alcohol swabs before intravascular cannulation.

Anesthesiologist's hand hygiene and disinfection of reusable rubber tourniquet with alcohol swabs before intravascular cannulation.

Performance of a Rapid Antigen-Detection Test and Throat Culture in Community Pediatric Offices: Implications for Management of Pharyngitis

The goals were to establish performance characteristics of a rapid antigen-detection test and blood agar plate culture performed and interpreted in community pediatric offices and to assess the effect of the pretest likelihood of group A streptococcus pharyngitis on test performance (spectrum bias). Two throat swabs were collected from 1848 children 3 to 18 years of age who were evaluated for acute pharyngitis between November 15, 2004, and May 15, 2005, in 6 community pediatric offices. One swab was used to perform the rapid antigen-detection test and a blood agar plate culture in the office and the other was sent to our laboratory for blood agar plate culture. Clinical findings were used to calculate the McIsaac score for each patient. The sensitivities of the office tests were calculated, with the hospital laboratory culture results as the criterion standard. Thirty percent of laboratory blood agar plate cultures yielded group A streptococcus (range among sites: 21%-36%). Rapid antigen-detection test sensitivity was 70% (range: 61%-80%). Office culture sensitivity was significantly greater, 81% (range: 71%-91%). Rapid antigen-detection test specificity was 98% (range: 98%-99.5%), and office culture specificity was 97% (range: 94%-99%), a difference that was not statistically significant. The sensitivity of a combined approach using the rapid antigen-detection test and back-up office culture was 85%. Among patients with McIsaac scores of >2, rapid antigen-detection test sensitivity was 78%, office culture sensitivity was 87%, and combined approach sensitivity was 91%. Positive diagnostic test results were significantly associated with McIsaac scores of >2. The sensitivity of the office culture was significantly greater than the sensitivity of the rapid antigen-detection test, but neither test was highly sensitive. The sensitivities of each diagnostic modality and the recommended combined approach were best among patients with greater pretest likelihood of group A streptococcus pharyngitis.

Rapid diagnosis of pharyngitis caused by group A streptococci.

Although commercial rapid antigen detection tests (RADTs) are more expensive than blood agar plate (BAP) cultures, the advantage they offer is the speed with which they provide results. Rapid identification and consequent prompt treatment of patients with pharyngitis due to group A beta-hemolytic streptococci (GABHS) can reduce the risk of spread of GABHS, can allow patients to return to school or work sooner, and may reduce the acute morbidity of this illness. In most studies, RADTs have been compared with BAP cultures as the criterion standard. However, these comparisons are complicated by the fact that there is no universally accepted procedure for performing a BAP culture. The great majority of the RADTs that are currently available have a high specificity (i.e., 95% or greater) and a sensitivity of between 70 and 90% compared with BAP cultures. Few published studies have compared the performance of various RADTs to each other or examined the performance of various RADTs in the office setting. There is also relatively little published information about how physicians in practice actually use RADTs, but the available information suggests that many physicians do not follow recommended guidelines. While the development of easy-to-perform RADTs for the diagnosis of GABHS pharyngitis has altered clinical practice substantially, only limited data about cost-effectiveness are currently available.

Rapid strep tests in the pediatric clinical setting

I T IS FRIDAY afternoon in a busy elementary school-based clinic, 7-year-old Crystal is referred due to a temperature of 102~ is complaining of a sore throat, pain with swallowing, headache, and stomach ache. Her physical exam reveals tonsillopharyngeal erythema, and tender, enlarged cervical lymph nodes. Tonsils are 2+ with slight patchy exudate. Crystal's family does not have a phone and there is no identified emergency contact. It will take considerable school resources to locate her mother. A routine throat culture result would be available Monday, but there is difficulty contacting Crystal's mother to either start an antibiotic if the culture is positive, or stop the antibiotic, if the culture is negative. Pharyngitis is a common symptom seen in pediatric populations. The most frequent cause of bacterial pharyngitis is group A beta-hemolytic streptococci (GABHS). Although the cause of pharyngitis is often viral, it is important to make an accurate diagnosis because GABHS can have acute morbidity and can lead to serious complications such as peritonsillar abscess, cervical lymphadenitis, rheumatic fever, and glomerulonephritis (Committee on Infectious Diseases of the AAP, 1997). Antimicrobial therapy should start as soon as possible in order to improve the clinical course of the GABHS illness and reduce the risk of transmission of the organism to others (Gerber, 1989; Randolph, Gerber, DeMeo, et al., 1985). The gold standard for diagnosis of GABHS pharyngitis is a throat swab specimen on a sheep blood agar plate. It is a highly accurate and sensitive test (Gerber, 1989). However, the disadvantage is the delay in obtaining results, often 24 to 48 hours later. This makes it particularly difficult with situations like the case scenario presented. The rapid antigen detection tests offer quick results in identifying GABHS pharyngitis. In 1988 Congress passed the Clinical Laboratory Improvement Amendments (CLIA) which set standards to improve the quality of clinical laboratory testing (National Committee for Clinical Laboratory Standards, 1992). This has allowed clinics to provide sophisticated scientific tests, such as the rapid strep test, to screen and confirm diagnoses or observations made by health care providers. All clinics that perform laboratory testing on-site hold a certificate from their state health department which authorizes testing, such as a nonculture Group A rapid strep screen. The rapid strep test takes a few minutes to perform and is easily read. The screens are only for use in the qualitative detection of GABHS; the rapid strep test does not differentiate between asymptomatic carriers and those patients with GABHS infection. Most of the current rapid strep screens have an excellent specificity of 95% or greater as compared with blood agar plate cultures (Gerber, 1989). Therefore, it is very unusual to get a false-positive result. If the rapid strep screen indicates a positive result, then antibiotic treatment should be instituted, (Gerber, 1997). The accuracy of the rapid antigen detection tests rely on staff who are well-trained in the steps involved in the screening test and good quality control procedures. The first step in the procedure is to take the throat specimen using only the swabs provided in the test kit box. Using a tongue blade to hold the tongue down, the specimen should be taken directly from the back of the throat, being careful not to touch the teeth, cheeks, gums, or tongue when inserting or removing the swab. The throat should be swabbed, not gently touched, and the specimen should be obtained from both tonsils (or fossae) and the posterior pharyngeal wall. If exudate is present, those areas should be collected

Does culture confirmation of high-sensitivity rapid streptococcal tests make sense? A medical decision analysis.

Since the 1990 publication of a decision analysis, in which the treatment of pharyngitis in children was evaluated, a number of assumptions important in that analysis have changed. Updating many of the assumptions and costs used in that analysis to reflect the conditions currently found in a large, suburban pediatric practice, a cost-effectiveness analysis was performed in which four strategies for the treatment of pharyngitis were considered: treat all, high-sensitivity antigen test, culture, and high-sensitivity antigen test with culture confirmation. Decision analysis. Using microbiology data from the 13 published studies in which a high-sensitivity antigen test (Strep A OIA; BioStar Inc., Boulder, CO) and blood agar plate culture were evaluated against a variety of gold standards, the sensitivity and specificity of the high-sensitivity antigen test were 89.1% and 95%, respectively. The sensitivity and specificity of blood agar plate throat culture were 83.4% and 99%, respectively. Penicillin V was used as the treatment of choice for uncomplicated pharyngitis; erythromycin was used in cases of penicillin allergy. Rates of suppurative and nonsuppurative complications reflect those currently seen in the United States. Other assumptions and cost data were taken from a large, suburban pediatric practice and its affiliated tertiary care medical center, except where noted. Despite the potential induction of resistance and the high number of allergic reactions associated with the treat-all strategy, this strategy had the lowest average cost per patient encounter and was the most cost-effective in terms of dollars per suppurative and nonsuppurative complication prevented. Of the strategies in which a diagnostic test was used, the high-sensitivity antigen test strategy had the lowest average cost and was the most cost-effective. The high-sensitivity antigen test with culture confirmation strategy had the highest average cost and was the least cost-effective. In the sensitivity analyses, a number of assumptions used in the original model were varied within a reasonable range. Under most conditions, the treat-all strategy remained the most cost-effective strategy used. One notable exception: when the wholesale cost of the antibiotic exceeded $10.76, as would be seen if any cephalosporin were used as the primary therapy of uncomplicated pharyngitis, the high-sensitivity antigen test strategy became the most cost-effective strategy. Under most conditions, the high-sensitivity antigen test strategy was the most cost-effective of the strategies in which a diagnostic test was used. Notable exceptions included: 1) conditions in which there was a low probability of streptococcal infection, 2) the use of an antigen test whose sensitivity is inferior to that of culture, and 3) during an epidemic of acute rheumatic fever. Culture confirmation of a negative high-sensitivity antigen test is the most cost-effective testing strategy only under conditions in which the probability of acute rheumatic fever approaches those levels last seen in the United States more than 40 years ago. Although most cost-effective, the treat-all strategy is not recommended because of concerns about antibiotic resistance, which could not be included in the model, and the high number of allergic reactions found in children who did not have streptococcal infection. Use of the high-sensitivity antigen test without culture confirmation of all negative results was the most cost-effective strategy in which a diagnostic test was used with respect to prevention of suppurative and nonsuppurative complications of streptococcal pharyngitis. Culture confirmation of negative high-sensitivity antigen tests was not cost-effective under any of those conditions currently seen in the United States.

Use of Optical Immunoassay to Diagnose Streptococcal Pharyngitis

<h3>To the Editor.</h3> —In the article by Dr Gerber and colleagues¹reporting an office-based multicenter investigation of the optical immunoassay (OIA) test for group A β-hemolytic streptococcal (GABHS) pharyngitis, the authors concluded that "with adequately trained personnel, negative OIA test results may not always need to be routinely confirmed with blood agar plate (BAP) cultures." We believe the authors' conclusions are based less on the quality of the testing personnel or the performance specifications of the OIA and more on the quality of the BAP culture procedure used in the study. Presumptive differentiation of GABHS and non—group A streptococci may be accomplished by the bacitracin test, in which a zone of inhibition is noted on a pure subculture of β-hemolytic colonies. Bacitracin disks placed on primary cultures on nonselective media, as was done in this study, may detect as little as 54% of group A streptococci.²We compared

Optical Immunoassay Test for Group A β-Hemolytic Streptococcal Pharyngitis

To compare the accuracy of an optical immunoassay (OIA) for the rapid diagnosis of group A streptococcal pharyngitis with blood agar plate (BAP) culture. Blinded comparison with criterion standard. A total of 6 private pediatricians' offices, 3 in Connecticut and 3 in Chicago, III. A total of 2113 consecutive patients with acute pharyngitis, 983 in Connecticut and 1130 in Chicago. The sensitivities and specificities of OIA and BAP culture (both performed and interpreted in the office) were determined using a research laboratory's interpretation of a combination of BAP culture and Todd-Hewitt broth (THB) culture of transport tube pledget as criterion standard. Among patients in Connecticut, the sensitivities of the OIA and BAP culture were 94% and 89%, respectively (P=.004), while the specificities were 96% and 99%, respectively (P=.001). Among patients in Chicago, the sensitivities of the OIA and BAP culture were 79% and 72%, respectively (P<.001), while the specificities were 89% and 99%, respectively (P<.001). In each of the 6 pediatricians' offices, the OIA was more sensitive than the BAP culture. Combining the data from Connecticut and Chicago, the overall sensitivities of the OIA and BAP culture were 84% and 78%, respectively (P<.001), while the specificities were 93% and 99%, respectively (P<.001). The results of this comprehensive office-based investigation suggest that with adequately trained personnel, negative OIA test results may not always need to be routinely confirmed with BAP cultures.

Evaluating Spatter And Aerosol Contamination During Dental Procedures

A pilot study evaluated the distribution of spatter and aerosols generated by high-speed instrumentation. In the first phase, fluorescent dye was added to the handpiece water supply. In the second, blood agar culture plates were placed in the operatory. Results show that contamination from spatter and aerosol dissemination remains a significant hazard for dental personnel.

Insensitivity of rapid antigen detection methods and single blood agar plate culture for diagnosing streptococcal pharyngitis: Wegner DL, Witte DL, Schrantz RD JAMA 266:695–697 Feb 1992

Insensitivity of rapid antigen detection methods and single blood agar plate culture for diagnosing streptococcal pharyngitis: Wegner DL, Witte DL, Schrantz RD JAMA 266:695–697 Feb 1992

Commercial antigen kits and a single blood agar plate culture were less sensitive for detecting streptococcal pharyngitis than a 2-plate culture method

Source Citation Wegner DL, Witte DL, Schrantz RD. Insensitivity of rapid antigen detection methods and single blood agar plate culture for diagnosing streptococcal pharyngitis. JAMA. 1992 Feb 5;267:695-7.

Insensitivity of rapid antigen detection methods and single blood agar plate culture for diagnosing streptococcal pharyngitis

Insensitivity of rapid antigen detection methods and single blood agar plate culture for diagnosing streptococcal pharyngitis

Insensitivity of Rapid Antigen Detection Methods and Single Blood Agar Plate Culture for Diagnosing Streptococcal Pharyngitis

To compare the sensitivity of five group A streptococcal antigen detection systems and single blood agar plate culture with a two-plate culture method for diagnosis of streptococcal pharyngitis. Two simultaneous throat swabs were obtained from consecutive patients with suspected streptococcal pharyngitis. One swab was tested for streptococcal antigen by physicians' office nurses and the other was cultured on both aerobic blood agar and anaerobic trimethoprim-sulfamethoxazole blood agar plates. Community office practice and community hospital laboratory. Consecutive outpatients seen by one of four pediatricians or a family practice physician. Results of rapid streptococcal antigen tests were compared with culture results either on a single aerobic blood agar plate or on the two-plate culture method. On throat swabs from 755 consecutive outpatients, the two-plate culture method detected 261 cases (defined as 100%) of group A streptococcal pharyngitis. The anaerobic trimethoprim-sulfamethoxazole plate alone, read at 1 and 2 days, detected 245 cases (94%). The blood agar plate used alone detected 189 cases (72%) at 2 days and 151 cases (58%) at 1 day. Antigen detection test results were positive for 106 throat specimens (41%), with individual kit sensitivity ranging from 31% to 50% compared with the two-plate culture method. Antigen detection test sensitivity decreased with decreasing colony counts. Antigen kit false-positivity rates varied from 0 to 28%. We conclude that the single blood agar plate culture and the antigen detection tests are insensitive, possibly leading the physician toward undertreatment and risking immunologic, local, or distant sequelae. The two-plate culture method should be the standard of practice to rule out streptococcal pharyngitis.