scholarly journals Evaluation of penicillin G susceptibility testing methods for Staphylococcus lugdunensis

2020 ◽  
Vol 75 (5) ◽  
pp. 1206-1211
Author(s):  
Malin Hagstrand Aldman ◽  
Lisa I Påhlman
Keyword(s):  
Susceptibility Testing ◽  
Reference Method ◽  
Penicillin G ◽  
Diffusion Method ◽  
Disc Diffusion ◽  
Diffusion Test ◽  
Staphylococcus Lugdunensis ◽  
Susceptible Isolate ◽  
Focus Of Infection ◽  
Zone Edge

Abstract Background Staphylococcus lugdunensis belongs to the CoNS group, but is regarded to be more virulent than most other CoNS. It is also remarkably susceptible to antibiotics, including penicillin G. Objectives To evaluate different methods for penicillin susceptibility testing, to assess penicillin susceptibility rates among S. lugdunensis and to describe the clinical presentation including antibiotic treatment. Methods Clinical isolates of S. lugdunensis were tested for penicillin susceptibility using disc diffusion according to CLSI (10 U disc) and EUCAST (1 U disc), assessment of zone-edge appearance, nitrocefin test and Etest for MIC determination. PCR of the blaZ gene was used as a reference method. Results Of the 112 isolates included in the study, 67% were susceptible to penicillin G according to blaZ PCR. The EUCAST disc diffusion test had 100% sensitivity, whereas the CLSI method had one very major error with a false-susceptible isolate. When zone-edge appearance was included in the assessment, the false-susceptible isolate was correctly classified as resistant. Foreign-body infection was the most common focus of infection, affecting 49% of the participants. Only 4% of the patients were treated with penicillin G. Conclusions Penicillin susceptibility is common in S. lugdunensis and the disc diffusion method according to EUCAST had a higher sensitivity than that of CLSI. Assessment of zone-edge appearance could increase the sensitivity of the disc diffusion test. Penicillin susceptibility testing and treatment should be considered in S. lugdunensis infections.

Antimicrobial Susceptibility Testing for Staphylococcus lugdunensis

2021 ◽  
Author(s):  
Joanne S.K. Teh ◽  
Ioanna Pantelis ◽  
Xiao Chen ◽  
Tania Sadlon ◽  
Kelly Papanaoum ◽  
...  
Keyword(s):  
Antimicrobial Susceptibility ◽  
Susceptibility Testing ◽  
Resistant Isolate ◽  
Disc Diffusion ◽  
Broth Microdilution ◽  
Major Error ◽  
Staphylococcus Lugdunensis ◽  
Zone Diameter ◽  
Oxacillin Resistance ◽  
Zone Edge

Evaluation of penicillin and oxacillin susceptibility testing was conducted on two hundred Staphylococcus lugdunensis isolates. Disc diffusion with penicillin 1 IU (P1, EUCAST) and penicillin 10 IU (P10, CLSI) was compared with nitrocefin discs (Cefinase®) and automated broth microdilution (Vitek2®). Oxacillin susceptibility was extrapolated from cefoxitin 30μg disc diffusion (FOX) and compared with Vitek2®. Reference methods were blaZ and mecA PCR. Penicillin zone diameter and zone edge correlated with blaZ in all except two P10 susceptible isolates (VME; very major error) and one P1 resistant isolate (ME). One hundred and forty-eight isolates were blaZ -negative of which one hundred and forty-six and one hundred and forty-nine isolates were susceptible by P1 and P10 respectively. One hundred and twenty-seven isolates were penicillin susceptible by Vitek2®. Vitek2® overcalled resistance in twenty-one blaZ -negative, twenty P1 and twenty-two P10 susceptible isolates (Vitek2® ME rate, 14.2%). Two mecA -positive isolates were oxacillin resistant by FOX and Vitek2® (categorical agreement). However, eighteen FOX susceptible, mecA -negative isolates tested resistant by Vitek2®. In conclusion, Vitek2® over-estimated penicillin and oxacillin resistance compared with disc diffusion and PCR. Disc diffusion with zone edge interpretation was more accurate and specific than automated broth microdilution for S. lugdunensis in our study.

scholarly journals The EUCAST rapid disc diffusion method for antimicrobial susceptibility testing directly from positive blood culture bottles

2020 ◽  
Vol 75 (4) ◽  
pp. 968-978 ◽  
Author(s):  
Emma Jonasson ◽  
Erika Matuschek ◽  
Gunnar Kahlmeter
Keyword(s):  
Blood Culture ◽  
Positive Blood Culture ◽  
Antimicrobial Susceptibility ◽  
Susceptibility Testing ◽  
Reference Method ◽  
Bloodstream Infections ◽  
Error Rates ◽  
Antimicrobial Susceptibility Testing ◽  
Diffusion Method ◽  
Disc Diffusion

Abstract Objectives With increasing antimicrobial resistance, rapid antimicrobial susceptibility testing (RAST) becomes important, especially in patients with bloodstream infections. EUCAST decided to develop a standardized rapid method, based on EUCAST disc diffusion, to offer susceptibility reports within 4–8 h of a positive blood culture (BC). Methods BC bottles were spiked with clinical isolates (n = 332) of the seven most relevant sepsis pathogens with a variety of resistance mechanisms. RAST was performed directly from the bottle and zones read after 4, 6 and 8 h. Several variables were investigated, including the effect of using different BC bottles and of a 0–18 h delay between a positive signal and the performance of RAST. Results For five species, most inhibition zones could be read after 4 h. The proportion of results that could be interpreted increased from 75% at 4 h to 84% after 8 h. Categorical agreement against the reference method was good, with error rates of false susceptibility of 0.2%, 0.2% and 0.2% at 4, 6 and 8 h and false resistance of 1.2%, 0.2% and 0.1% at 4, 6 and 8 h, respectively. Conclusions With the EUCAST RAST method, reliable AST results can be delivered within 4–8 h of positivity of BC bottles for seven important bloodstream infection pathogens. To reduce the occurrence of errors and to absorb the variability caused by using a non-standardized inoculum, material from different manufacturers and workflow-related delays, we have introduced an area in which interpretation is not permitted, the Area of Technical Uncertainty.

Evaluation of methods for detection of β-lactamase production in MSSA

2021 ◽  
Author(s):  
Robert Skov ◽  
David R Lonsway ◽  
Jesper Larsen ◽  
Anders Rhod Larsen ◽  
Jurgita Samulioniené ◽  
...  
Keyword(s):  
Susceptibility Testing ◽  
Confirmatory Test ◽  
Disc Diffusion ◽  
Broth Microdilution ◽  
Confirmatory Tests ◽  
Correct Determination ◽  
Primary Test ◽  
Zone Edge ◽  
Evaluation Of Methods

Abstract Objectives Correct determination of penicillin susceptibility is pivotal for using penicillin in the treatment of Staphylococcus aureus infections. This study examines the performance of MIC determination, disc diffusion and a range of confirmatory tests for detection of penicillin susceptibility in S. aureus. Methods A total of 286 consecutive penicillin-susceptible S. aureus blood culture isolates as well as a challenge set of 62 MSSA isolates were investigated for the presence of the blaZ gene by PCR and subjected to penicillin-susceptibility testing using broth microdilution MIC determination, disc diffusion including reading of the zone edge, two nitrocefin tests and the cloverleaf test. Results Using PCR-based detection of blaZ as the gold standard, both broth microdilution MIC testing and disc diffusion testing resulted in a relatively low accuracy (82%–93%) with a sensitivity ranging from 49%–93%. Among the confirmatory tests, the cloverleaf test performed with 100% accuracy, while zone edge interpretation and nitrocefin-based tests increased the sensitivity of β-lactamase detection to 96%–98% and 82%–96% when using MIC determination or disc diffusion as primary test, respectively. Conclusions This investigation showed that reliable and accurate detection of β-lactamase production in S. aureus can be obtained by MIC determination or penicillin disc diffusion followed by interpretation of the zone edge as a confirmatory test for apparently penicillin-susceptible isolates. The more cumbersome cloverleaf test can also be used. Nitrocefin-based tests should not be used as the only test for confirmation of a presumptive β-lactamase-negative isolate.

scholarly journals Russia-made Mueller–Hinton agar: compliance with contemporary requirements

2019 ◽  
Vol 9 (2) ◽  
pp. 409-416
Author(s):  
L. V. Domotenko ◽  
I. S. Kosilova ◽  
A. P. Shepelin
Keyword(s):  
Quality Control ◽  
Antimicrobial Agents ◽  
Susceptibility Testing ◽  
Diffusion Method ◽  
Disc Diffusion ◽  
Disc Diffusion Method ◽  
Nutrient Media ◽  
Mueller Hinton ◽  
Mueller Hinton Agar

At present, a rise of antimicrobial resistance requires that susceptibility of infectious agents to antimicrobial agents could be accurately evaluated as related errors may lead to selecting improper therapeutics provoking spread of drug resistance. Pathogen sensitivity to antimicrobial agents is commonly determined by a disc diffusion method. A quality of nutrient medium used in assays plays a crucial role influencing final results. In Russia, it turned out that regulatory documents such as the nationwide guidelines and clinical recommendations outlining methodology for antimicrobial susceptibility testing underlay availability in domestic market few nutrient media, including Mueller–Hinton Agar, AGV medium etc. exhibiting sometimes unsatisfactory quality. To harmonize such methodology with international requirements, theStateResearchCenterfor Applied Microbiology and Biotechnology has developed a technology and promoted manufacture of Russia-made Mueller–Hinton agar satisfying requirements of EUCAST documents, clinical guidelines, and ISO/TS 16782:2016. The main objective of this study was to compare quality of new agar product with five similar foreign media while examining 11 test strains by disc diffusion method. As a result, some of nutrient media available to the Russian market turned out to be off-standard: not all of them satisfy to the EUCAST requirements and clinical guidelines since diameter distribution for growth inhibition recommended by EUCAST for quality control does not fit into permissible range. Moreover, susceptibility of P. aeruginosa ATCC 27853 to aminoglycosides, fluoroquinolones, Meropenem, as well as S. aureus ATSS 25923 and E. faecalis ATCC 29212 to tigecycline was assessed with certain mistakes. The data obtained by us were analyzed in accordance to the new document ISO/TS 16782:2016 “Clinical laboratory testing — criterion for acceptable lots of dehydrated Mueller–Hinton agar and broth for antimicrobial susceptibility testing”, not approved yet In Russia. To determine potential reason for deviation of data from reference range, we measured concentration of bivalent metals in all nutrient media examined by atomic emission spectrometry with inductively coupled plasma. We determined new patterns affecting reliability of results on microbial antibiotic susceptibility. A need to check intralaboratory quality control of nutrient media was emphasized.  

scholarly journals A study on Nalidixic Acid Resistant Salmonella among the patients attending Shree Birendra Hospital

2012 ◽  
Vol 10 (2) ◽  
pp. 1-3 ◽  
Author(s):  
Raina Chaudhary ◽  
Khagendra Sijapati ◽  
Sunil Kumar Singh
Keyword(s):  
Nalidixic Acid ◽  
Salmonella Enterica ◽  
Enteric Fever ◽  
Brain Heart Infusion ◽  
Public Health Problem ◽  
Diffusion Method ◽  
Disc Diffusion ◽  
Diffusion Test ◽  
Sensitivity Pattern

Introduction: Enteric fever is the commonest public health problem in developing countries like Nepal. Multi Drug Resistant Salmonella isolates are in vitro susceptible to Quinolone but exhibited a higher Minimum Inhibitory Concentration in vivo. Such phenomenon can be demonstrated by simple disc diffusion test of Nalidixic Acid which shows resistance. This study is conducted to determine prevalence of Nalidixic Acid Resistant Salmonella with their anti biotic sensitivity pattern at Shree Birendra Hospital, Chauni, kathmandu. Method: Of total 3945 blood samples from the patients suspected to have enteric fever were collected during the period of January 2011 to August 2011. Then it was mixed with Brain Heart Infusion , further processed according to standard methodology and their anti microbial susceptibility was performed by Kirby-Bauer disc diffusion method. Results: From 3945 samples, 280 (7.09%) showed positi ve growth, 114 (40.7%) Salmonella enterica serotype Typhi and 166 (59.2%) Salmonella enterica serotype Paratyphi A. a total of 221 (78.92%) were Nalidixic Acid Resistant Salmonella, all these strains were sensitive to Ciprofloxcin and Ofloxacin in disc diffusion test. Conclusion: Study showed a higher frequency of Nalidixic Acid Resistant Salmonella among the patients. screening of Nalidixic Acid disc diffusion test must be done as routine work for determination of low level resistance of Quinolone so as to decide the drug for the treatment of enteric fever. DOI: http://dx.doi.org/10.3126/mjsbh.v10i2.6453 Medical Journal of Shree Birendra Hospital July-Dec 2011 10(2) 1-3

Current Fluoroquinolone Susceptibility Criteria for Salmonella Needs Re-evaluation

2012 ◽  
Vol 10 (1) ◽  
pp. 66-71 ◽  
Author(s):  
D Acharya ◽  
S Malla ◽  
DR Bhatta ◽  
N Adhikari ◽  
SP Dumre
Keyword(s):  
Nalidixic Acid ◽  
Enteric Fever ◽  
Susceptibility Testing ◽  
Break Point ◽  
Resistance Rate ◽  
Diffusion Method ◽  
Dilution Method ◽  
Agar Dilution Method ◽  
Disc Diffusion ◽  
Zone Diameter

Background Disc diffusion technique is the routine susceptibility testing procedure for isolates of enteric fever, the most common clinical diagnosis among febrile patients in Nepal. Objective To evaluated the current fluoroquinolones (FQs) susceptibility criteria and nalidixic acid screening test in Salmonella enterica serovar Typhi and Paratyphi A. Methods S. Typhi and Paratyphi A strains isolated from 443 suspected enteric fever patients visiting National Public Health Laboratory (NPHL) during April through October 2008 were analyzed. All isolates were confirmed by standard microbiological procedures including serotyping. Antibiotic susceptibility testing was performed by using Kirby Bauer disc diffusion method and Clinical and Laboratory Standards Institute (CLSI) approved interpretive criteria. Agar dilution method was used to determine Minimum Inhibitory Concentration (MIC) of ciprofloxacin, ofloxacin and nalidixic acid. Result Out of 41 Salmonella isolates, 80.49% were nalidixic acid resistant, with S. Paratyphi A showing higher resistance rate (88.23%) compared to S. Typhi (75%). The difference in both MIC and zone diameter in nalidixic acid susceptible and nalidixic acid resistant isolates was found to be significant (P < 0.001) and decreased susceptibility to FQs was strongly correlated (sensitivity and specificity of 100%) with resistance to nalidixic acid. Regression analysis of MIC against zone diameter based on the current CLSI recommended guidelines suggests that accommodation of current susceptible and resistant MIC requires increase in the zone diameter of ciprofloxacin and ofloxacin. Conclusion Before using these drugs for management of enteric fever, appropriate identification of Salmonella isolates with reduced susceptibility to FQs is essential to limit the possible treatment failure and development of highly resistant strains. The current FQs susceptibility break point criteria for Salmonella need re-evaluation. KATHMANDU UNIVERSITY MEDICAL JOURNAL  VOL.10 | NO. 1 | ISSUE 37 | JAN - MAR 2012 | 24-29DOI: http://dx.doi.org/10.3126/kumj.v10i1.6909

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