Quality in diagnostic microbiology: Experiential note to emphasize value of internal control programs (original) (raw)
Related papers
Evaluation of antibiotic susceptibility test results: how guilty a laboratory could be?
The Journal of the Egyptian Public Health Association, 2019
Background: The selection of an appropriate antimicrobial is a challenging task for clinicians. The Kirby-Bauer disk diffusion method is one of the most widely practiced antimicrobial susceptibility tests (AST). It is affected by many factors among which are the media used. Mueller-Hinton agar (MHA) is the standard medium recommended in guidelines. However, these guidelines are not strictly adhered to in some developing countries. Objectives: Validation of AST results on nutrient agar (NA) medium used as a substitute for MHA by some microbiology laboratories in Alexandria, Egypt. Methods: A total of 149 clinical bacterial isolates and 3 reference strains: Staphylococcus aureus (S. aureus) ATCC® 25923, Escherichia coli (E. coli) ATCC®25922, and Pseudomonas aeruginosa (P. aeruginosa) ATCC®27853 were comparatively challenged to antibiotics employing MHA and NA. Results: All antibiotics-reference bacterial strain challenges on NA compared to MHA were unacceptable (> 3 out of limit zones in 30 consecutive days). Considering clinical isolates, the frequency of very major, major, and minor errors on NA was highest in the case of P. aeruginosa (8.98%, 4.08%, and 14.7% respectively) followed by S. aureus (7.6%, 6%, and 8.8% respectively). On the other hand, the least frequency of errors was in the case of Enterobacteriaceae (0%, 0.4%, and 3.2% respectively). Conclusions and recommendations: Using NA in AST resulted in multiple errors and the high discrepancy in results compared to MHA making it unreliable for susceptibility testing. MHA should not be replaced by NA in AST. Following guidelines and QC measures for AST must be neither bypassed nor underestimated.
The Quality Assurance Program (QAP) of the Deutsches Krebsforschungszentrum (DKFZ) was a proficiency testing system developed to service the laboratory animal discipline. The QAP comprised the distribution of bacterial strains from various species of animals for identification to species level and antibiotic susceptibility testing (AST). Identification capabilities were below acceptable standards. This study evaluated AST results using the DKFZ compilations of test results for all bacterial strains showing the number of participants reporting the strain as resistant (R), sensitive (S) or intermediate susceptible (I) to each antibiotic substance used. Due to lack of information about methods used, it was assumed that what the majority of the participants reported (R or S) was the correct test result and that an opposite result was a major error (ME). MEs occurred in 1375 of 14,258 (9.7%) of test results and ME% ranged from 0% to 23.2% per bacterial group -agent group combination. Considerable variation in MEs was found within groups of bacteria and within groups of agents. In addition to poor performance in proper species classification, the quality of AST in laboratory animal diagnostic laboratories seems far below standards considered acceptable in human diagnostic microbiology.
Journal of Microbiological Methods, 2022
New techniques are needed to speed-up the identification and antimicrobial susceptibility testing (AST) of bacteria associated with bloodstream infections. Alfred 60/AST (Alifax®, Polverara, Italy) performs AST by light scattering directly from positive blood cultures. Methods: We evaluated Alfred 60/AST performances for 4 months. Each new episode of bacteraemia was included and AST were compared to either our rapid automated AST (Vitek® 2) or disk diffusion method. The discrepancies were investigated using Etest®. The time-to-result (TTR) was evaluated by comparing the blood volume inserted into Alfred 60/AST, i.e. 2 versus 7 blood drops. Taking into account the TTR, the workflow of positive blood cultures and the availability of AST results was studied in order to optimize the implementation of Alfred 60/AST. Results: A total of 249 samples and 1108 antibiotics for AST were tested. After exclusion of unavailable results, 1008 antibiotics were analysed. 94.9% (n = 957/1008) of the antibiotics showed categorical agreement. There were 14 very major errors (VME), 24 major errors (ME) and 13 minor errors (mE). The VME were mostly related to clindamycin (64.3%) whereas meropenem and piperacillin-tazobactam constituted the major part (37.5% and 61.5%) of ME and mE respectively. Results were highly reliable for Enterobacterales and enterococci. The mean TTR ranged between 4.3 and 6.3 h and was statistically 20 min faster when applying the 7 blood drops protocol. We showed that Alfred 60/AST could give relievable results within working hours for positive blood culture which are flagged the same day between 12:00 am and 12:00 pm. Conclusion: Our study confirmed that Alfred 60/AST gives reliable AST results in a short period of time, especially for Enterobacterales and enterococci. AST could thus be easily obtained the same day of a positive blood culture. Clinical impact studies are mandatory to validate a 24/24 working.
Due to the great deal of attention given to patient’s security, it is necessary to reduce non-conformities in pre-analytical phase, so the laboratories of medical bacteriology that can ensure the quality of examination results can contribute to diagnosis and prescription of treatment and patient safety. It is important that these laboratories collect and exploit statistics of the non-conformities rates which occur during pre-analytical phase in order to implement improvement plans. This study was done in a period of 10 months in a laboratory of bacteriology in a university hospital center. It aims to control the nonconformity rates of the biological samples found, show their nature and causes and to assess their criticality. Results obtained showed that overall rate of non-conformities identified in the year 2012 were 2.5% (310 samples from 12 398). 61% of the recorded errors concerned both the identification of biological samples and patient's identity. 29% was on conveyance an...
Annali dell'Istituto superiore di sanità, 2009
New technologies are revolutionizing diagnostic microbiology, but implementation of methodological advances in test evaluation has been extraordinarily slow. Published reports frequently fail to clearly distinguish between studies of analytical accuracy and those of clinical diagnostic performance. We argue that the evaluation of sensitivity and specificity, while necessary and occasionally problematic, is often inadequate to define the appropriate role of a new diagnostic test. To determine whether a test adds additional (incremental) value to the diagnostic information already available to the clinician, evaluation studies with a multivariable approach may also be needed. The impact of a test on patient outcome is best measured by a randomized controlled trial, but this may be unnecessary in certain well-defined situations. To improve the quality of published test evaluations close collaboration between clinicians, clinical microbiologists, and epidemiologists, as well as insisten...
Internal and external quality control in the medical microbiology laboratory
African Journal of Clinical and Experimental Microbiology
Culture media play a very important role in bacteriology as they are used in the isolation, identification and antimicrobial susceptibility testing. It is essential that the quality of media be safeguarded to have a successful microbiology laboratory. Microorganisms usually show typical morphological appearance and properties on solid media. Variations in the composition of the medium may alter this appearance and properties. There is therefore a need to ensure good quality media, which is capable of giving satisfactory results by ensuring a proper quality management system. Often times, majority of laboratories prepare their media for routine diagnostics and research purposes. Therefore, it is essential that certain parameters of media are checked thoroughly before they are considered suitable for laboratory use. Control methods are discussed in details in this report.
Antibacterial susceptibility testing in the clinical laboratory
Infectious Disease Clinics of North America, 2004
The clinical microbiology laboratory has a mandate to provide reliable, accurate susceptibility data in a time frame that is useful to the clinicians requesting the information to optimize clinical outcomes and, when possible, to reduce the emergence of resistance. This mandate is served by selective reporting of results to the ordering clinician from isolates obtained from individual patients and by providing collective data on local prevalence of resistance to be used for empiric therapy. To meet these challenges and responsibilities, clinical microbiologists must continuously assess and update susceptibility testing and reporting strategies. Although classical methods remain the workhorse of susceptibility testing, molecular methods are on the cusp of challenging their primacy.
Correct Diagnostics: Prerequisite for Prudent and Responsible Antimicrobial Administration
Asian Fisheries Science, 2020
Since bacterial diseases have an adverse impact on the profitability of aquaculture, causing direct and indirect losses, this review paper is assessing the importance of accurate diagnostics in prudent and responsible administration of antimicrobials. Diagnostics and treatment of bacterial diseases in aquaculture are inevitable factors in their responsible management and consequently contribute to the reduction of antimicrobial use (AMU) and prevention of antimicrobial resistance (AMR) development. To mitigate and prevent the losses, fast and accurate recognition and detection of bacterial pathogens are the main prerequisites. Monitoring programmes in all stages of production, from broodstock to fattening units, are needed to avoid long diagnostic processes and enable fast commencement of diagnostic procedures and responsible AMU. Moreover, preventive measures to reduce the risk of bacterial infection includes good aquaculture practices (GAP) and biosecurity measures, in the absence of specific immunoprophylaxis, or vaccination, against endemic bacterial diseases. Antimicrobial use may be considered as therapeutic, metaphylaxis, prophylaxis, and growth promotion. Antimicrobials are most often administered through bioenrichment of fish larvae or shrimp post larvae and medicated feed. The efficacy of the treatment via medicated feed depends on the rapid diagnosis and commencement of treatment, selection of appropriate antimicrobials, proper dosage, and duration of treatment. To prevent possible mistakes in AMU, it is necessary to avoid prophylactic use of antimicrobials, medication of viral infections, and repeated use of the same medicines.