Direct Sensitivity Testing Research Articles

Bioactivity against Staphylococcus aureus of New Nanoparticles Derived from Iron Oxide and Beta vulgaris Extracts and Synthesis Characterization

In this study an opportunity was obtained that combines the VITEK system and the detection system of clinical microbiology laboratories to reach the rapid microbial identification and sensitivity test for Staph aureus bacteria, where the results of the susceptibility test were compared to 3925 combinations of antibiotics. The total rate was for the normal antimicrobials as well as the category approval for direct sensitivity test. 92% with less than 3% significant errors and the average time required to identify the identity with a sensitivity test is 7.5 hours (3.0 SD hours), compared to an average of 32.3 hours 9-14 hours for the normal method. The study focuses on the effectiveness of anti-bacterial iron nanoparticles from Beta vulgaris extract in various concentrations (1 mg/ml. 2 mg/ml. 3 mg/ml.4 mg/ml. against Stphylococcus aureus. Where in an inhibition zone was obtained for the highest concentration of iron nanoparticles for Beta vulgaris when compared to other samples.

Direct antimicrobial susceptibility testing from positive blood culture bottles in laboratories lacking automated antimicrobial susceptibility testing systems

BackgroundTimely initiation of appropriate antimicrobial can improve the outcome in terms of reduced morbidity and mortality in addition to reduced health-care costs. Availability of early preliminary Antimicrobial Susceptibility Test (AST) report will be useful in directing antimicrobial therapy. The aim of the study was to correlate AST by disc diffusion method, directly from positively flagged blood culture bottles, with the AST by automated method. MethodsA total of 144 aerobic blood culture bottles flagged positive by the automated blood culture system were processed. The bacteria were pelleted by two-step centrifugation of the broth from the bottle and used to make a smear for Gram stain as well as an inoculum for antimicrobial sensitivity testing by Kirby Bauer disc diffusion method. Automated identification and AST were also carried out. ResultsOn direct staining, 94 samples showed gram-negative bacilli, 39 showed gram-positive cocci, and 11 showed yeasts or polymicrobial growth. In the case of gram-negative bacteria, there was 99% categorical agreement between direct sensitivity testing and automated sensitivity testing with 1% disagreement. Among the gram-positive cocci, there was 96% categorical agreement with 4% disagreement between the two methods. ConclusionHigh degree of agreement between the two methods is promising and applicable to situations where automated sensitivity testing is not available. Even if the systems are available, this method would prove useful as an adjunct to standard AST reporting. This sensitivity report can be generated earlier than the conventional AST, enabling choice of appropriate antimicrobial.

Comparative Evaluation of Antibiotic Susceptibility Testing on Vitek-2 Compact and Direct Sensitivity Test from Blood Cultures from a Tertiary Care Centre in South India

Comparative Evaluation of Antibiotic Susceptibility Testing on Vitek-2 Compact and Direct Sensitivity Test from Blood Cultures from a Tertiary Care Centre in South India

Evaluation of direct sensitivity testing as a method for early initiation of treatment in Gram-negative sepsis

Purpose: For antibiotic susceptibility results, conventional culture and sensitivity methods take 48 h after a blood culture are flagged positive by automated systems. Early initiation of targeted antibiotic therapy is essential for effective management of sepsis to reduce morbidity, mortality, cost of treatment and prevent antibiotic resistance. The objective of this study was to evaluate direct sensitivity test (DST) as a potential tool to get reliable antibiotic susceptibility results 24 h earlier. Materials and Methods: Blood cultures that flagged positive from 1st January 2015 to 30th June 2015 by BacT/ALERT were stained by Gram stain. All blood cultures with only one kind of Gram-negative bacteria by Gram stain were simultaneously cultured and sensitivity tests put up directly (DST) from the broth using disk-diffusion method according to the British Society of Antimicrobial Chemotherapy guidelines. DST results available next day were compared with conventional antibiotic susceptibility test (AST). Results of DST (test method) and AST (reference method) were compared for agreements or errors. Results: Of the fifty Gram-negative isolates tested, we observed 91.5% categorical agreement or no error (κ = 0.407, P < 0.001). Conclusions: DST using disk diffusion from positive blood culture broths helps initiate early targeted antibiotic therapy. There is a high concordance between DST and AST.

A method for early detection of antibiotic resistance in positive blood cultures: Experience from an oncology centre in eastern India

Purpose: For antibiotic susceptibility results, conventional culture and sensitivity methods takes 48 hours after a blood culture is flagged positive by automated systems. Early initiation of targeted antibiotic therapy is essential for effective management of sepsis to reduce morbidity, mortality, cost of treatment and prevent antibiotic resistance. Objective of this study was to evaluate Direct Sensitivity Test (DST) as a potential tool to get reliable antibiotic susceptibility results 24 hours earlier. Materials and Methods: Blood cultures flagged positive between May 2011 to December 2012 by BacT/ALERT were Gram stained. All uni-microbial gram-negative blood cultures were simultaneously cultured and processed for DST from broth using disk diffusion method using British Society of Antimicrobial Chemotherapy (BSAC) guidelines. DST results available next day were compared with conventional antibiotic susceptibility test (AST) performed by Vitek-2 on isolated colonies. Results of DST (test method) and AST (reference method) were compared for agreements or errors. Results: Of the 840 antibiotic gram-negative organism combinations tested, Categorical and essential agreements were 83.7% and 96.2% respectively. Minor, major and very major errors were 12.5%, 3.33% and 0.47%, respectively. Conclusions: DST using disk diffusion from positive blood culture broths helps to initiate early targeted antibiotic therapy. There is high concordance between DST and AST.

OC-024 Development and validation of a novel capture-fusion model for HCV replication

IntroductionHCV replicates poorly in vitro, so testing of novel antiviral therapies currently relies on modified viral replicons, based on genotype (G)1, or the G2 JFH-1 virus. A model allowing patient...

Blood culture gram stain, acridine orange stain and direct sensitivity-based antimicrobial therapy of bloodstream infection in patients with trauma

Purpose: The purpose of this study was to ascertain if the simple practice of Gram stain, acridine orange stain and direct sensitivity determination of positive blood culture bottles could be used to guide early and appropriate treatment in trauma patients with clinical suspicion of sepsis. The study also aimed to evaluate the error in interpreting antimicrobial sensitivity by direct method when compared to standard method and find out if specific antibiotic–organism combination had more discrepancies. Findings from consecutive episodes of blood stream infection at an Apex Trauma centre over a 12-month period are summarized. Materials and Methods: A total of 509 consecutive positive blood cultures were subjected to Gram staining. AO staining was done in BacT/ALERT-positive Gram-stain negative blood cultures. Direct sensitivity was performed from 369 blood culture broths, showing single type of growth in Gram and acridine orange staining. Results of direct sensitivity were compared to conventional sensitivity for errors. Results: No ‘very major’ discrepancy was found in this study. About 5.2 and 1.8% minor error rates were noted in gram-positive and gram-negative bacteria, respectively, while comparing the two methods. Most of the discrepancies in gram-negative bacteria were noted in β lactam – β lactamase inhibitor combinations. Direct sensitivity testing was not reliable for reporting of methicillin and vancomycin resistance in Staphylococci. Conclusions: Gram stain result together with direct sensitivity testing is required for optimizing initial antimicrobial therapy in trauma patients with clinical suspicion of sepsis. Gram staining and AO staining proved particularly helpful in the early detection of candidaemia.

190 CHANGES IN THE ETIOLOGIC AND ANTIBIOTIC RESISTANCE PROFILES OF BACTERIA CAUSING SPONTANEOUS PERITONITIS IN EGYPTIAN PATIENTS WITH LIVER CIRRHOSIS

To evaluate the recent changes in bacteria causing spontaneous bacterial peritonitis (SBP) in cirrhotic patients and its clinical significance on treatment, we compared the etiologic agents and their antibiotic resistance profiles over a four year period. In the prospective period of the study, 150 ascitic fluid (AF) samples obtained from SBP patients admitted consecutively to the Hepatology Department of Theodor Bilharz Research Institute during 2006-2007 were examined for polymorphnuclear leukocytes (PMLs) by blood cell counter and by a bedside dipstick test (Multistix SG10, Bayer). Blood and AF cultures were performed using BACTEC blood culture bottles and purified bacterial isolates were identified with a BBL Crystal Id System and software. Antibiotic sensitivity testing and extended-spectrum beta-lactamase (ESBL)- production were determined by disk diffusion and modified double disk synergy tests (MDDST) respectively. Genes encoding ESBLs were detected by PCR and typed by DNA sequencing. In the retrospective period of the study (20042005), the laboratory records of 140 episodes of SBP were examined for the culture positive rate, causes of SBP and their antibiotic resistance patterns recorded. Results showed that the overall culture positivity rate was significantly higher in prospective study period (32%) versus retrospective period (16.4 %) p<0.05 and the main bacterial isolates were E.coli, 47.8% and Klebsiella pneumoniae, 28.1% with no differences in the two study periods. Gram positive bacteria (GPB) were isolated more frequently in the prospective than retrospective period (25% versus 13%). Two opportunistic bacterial species (Staphylococcus haemolyticus and Pantoea agglomerans) were detected as a cause of SBP in the prospective period. Species identification of Pantoea isolate was confirmed by DNA extraction, sequencing of ribosomal RNA and phylogenetic analysis. ESBLs were detected among 17.6% of E. coli and Klebsiella isolates of the prospective period and all were of the CTX-M15 type. The rate of resistance to cefotaxime significantly increased from 45% to 72 % and to ciprofloxacin from 25% to 47% and treatment failure rate was 65% in recent years. No resistance was detected to imipenem over the entire study period. For the GPB, 50% were resistant to ampicilin/sulbactam, cefotaxime and gentamicin and one S. haemolyticus isolate was methicillin resistant. In conclusion the emergence of multidrug resistant opportunistic pathogens and ESBL-producing E. coli and Klebsiellae as causal agents of SBP, together with an increase in resistance to antibiotics commonly used for the empiric treatment of bacterial peritonitis have serious implications on patient management in our region. Rapid diagnosis of SBP by a bedside dipstick test and identification of the causative organism by culture using blood culture bottles and direct sensitivity testing to establish an effective antibiotic therapy is recommended.

Is primary sensitivity testing on urine samples valid?

One thousand eight hundred urine specimens were examined prospectively to determine the validity of primary sensitivity testing. Microscopic criteria assessing pyuria and microorganisms were developed for predicting the presence of urinary tract infection and thus suitability for direct sensitivity testing. The criteria selected gave a positive predictive value of 74.6% and a negative predictive value of 99.5%. Zone diameters by primary and standardized secondary methods were compared for each urinary pathogen to each antibiotic tested. Percentage agreement between primary and secondary sensitivity results varied between 100% for Enterobacteriaceae tested against Gentamicin to 95.2% for Enterococcus faecalis tested against Ampicillin. Seventeen discrepancies between primary and secondary test results were observed (error 2.0%) with only 3 of potential clinical significance (primary sensitive, secondary resistant). Although primary sensitivity testing has limitations, our study indicates that the results are, in the vast majority of cases, in agreement with secondary testing, and are probably adequate for the clinical management of uncomplicated urinary tract infections. Furthermore, as primary testing rarely produces false resistant results it may permit earlier modification of initial empiric therapy.

Urinary tract infection in general practice: Direct antibiotic sensitivity testing as a potential diagnostic method

Direct Antibiotic Sensitivity Testing (DST) is a rapid means of diagnosing urinary tract infection (UTI) and obtaining antibiotic sensitivity patterns of the infecting organisms. In this study 227 urine samples from general practice were analysed using this technique with those obtained using the standard laboratory method. DST was shown to be 94.6% sensitive, and 80.7% specific. Escherichia coli was the commonest infecting organism. Augmentin was the most effective antibiotic tested, all organisms tested in vitro, being susceptible. Direct Sensitivity Testing is rapid, inexpensive, easy to perform, highly sensitive and specific. It should be considered by general practitioners as an alternative to the problems and delays involved in sending urine samples to the laboratory and in awaiting the results.

Technique for the culture and direct sensitivity testing or large numbers of urine specimens.

A technique was required for batch culturing and direct sensitivity testing of urine specimens to reduce increasing demands on laboratory services. A comparison was made between the filter paper strip method and multipoint inoculator technique using a Denley inoculator (Denley Ltd, Billingshurst, Sussex). The results showed that multipoint inoculation was a rapid, economical, and reliable method for the handling of large numbers of urine samples.

Study on Direct Sensitivity Test of Tubercle Bacilli to the Various Anti-tuberculous Drugs 1. Inoculum Adjustment and Medium

Study on Direct Sensitivity Test of Tubercle Bacilli to the Various Anti-tuberculous Drugs 1. Inoculum Adjustment and Medium

A simple quantitative and qualitative microbiological screening test for bacteriuria.

A simple, accurate screening test for significant bacteriuria is described. It entails brief contact of a freshly voided specimen of urine with the surface of a solid culture medium lining the wall of a transparent disposable plastic container, incubating it at 37 degrees C for 24 hours, and counting colonies developing on a proscribed surface area. The method obviates errors due to contaminants, affords a limited species differentiation of the causative organisms, and provides a ready means of obtaining a direct sensitivity test on the responsible bacteria.

The detection of streptomycin, pas and isoniazid resistant tubercle bacilli by the direct method

A direct sensitivity test is described for detecting bacterial resistance to streptomycin, PAS and isoniazid using Lowenstein-Jensen medium and doubling dilutions of the drug. There was good agreement between the results of the direct test and the expected resistance of the cultures as judged by the chemotherapeutic history of the patients, provided there was confluent growth on the control tube of the direct test. If there was lighter growth, the direct test sometimes failed to detect presumed clinically resistant cultures. The total number of strains giving confluent growth on the control slope was small, 13 in the streptomycin tests, 9 in the PAS tests and 10 in the isoniazid tests. It cannot therefore be categorically stated that the present test will always detect resistant cultures. But the limited success suggests that the method might be tried on a larger scale.

A RAPlD DIRECT SENSITlVITY TEST WITH YOUMAN’S LIQUID MEDIA.

A description is made of a rapid direct sensitivity test using Youman's Liquid media. The result with this direct test and with indirect test on 135 positive sputum specimens are compared. The evidence of growth is judged by the presence of serpentine microcolonies by microscopy at 7th day of culture.There have been no growth in control tubes of 26 cases of direct test, and 8 cases of direst test were contaminated, In indirect test, there were 9cases of contamination and one case of no growth on control tube.Comparisons are made in remaining 101 cases. Results of both tests were identical in 84 cases, and there were one step difference in 17 cases, including 3 false resistances and 2 false sensitivities.