Multicenter inter-laboratory analysis of routine susceptibility testing with a challenge panel of resistant strains

ABSTRACT We performed susceptibility testing with Shigella sonnei isolates from imported and domestic cases of infection in Japan during 2001 and 2002. Some S. sonnei isolates were resistant to nalidixic acid, tetracycline, and trimethoprim-sulfamethoxazole. Most of the nalidixic acid-resistant strains showed reduced susceptibility to fluoroquinolones but did not show fluoroquinolone resistance.

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Evidence of Another Anthropic Impact on Iguana delicatissima from the Lesser Antilles: The Presence of Antibiotic Resistant Enterobacteria

Antibiotics ◽

10.3390/antibiotics10080885 ◽

2021 ◽

Vol 10 (8) ◽

pp. 885

Author(s):

Gustavo Di Lallo ◽

Marco Maria D’Andrea ◽

Samanta Sennati ◽

Maria Cristina Thaller ◽

Luciana Migliore ◽

...

Keyword(s):

Antibiotic Resistance ◽

Animal Species ◽

Susceptibility Testing ◽

Acquired Resistance ◽

Climatic Conditions ◽

Antibiotic Resistant ◽

Associated Bacteria ◽

Improper Use ◽

Resistant Strains ◽

Drug Resistant Strains

The improper use of antibiotics by humans may promote the dissemination of resistance in wildlife. The persistence and spread of acquired antibiotic resistance and human-associated bacteria in the environment, while representing a threat to wildlife, can also be exploited as a tool to monitor the extent of human impact, particularly on endangered animal species. Hence, we investigated both the associated enterobacterial species and the presence of acquired resistance traits in the cloacal microbiota of the critically endangered lesser Antillean iguana (Iguana delicatissima), by comparing two separate populations living in similar climatic conditions but exposed to different anthropic pressures. A combination of techniques, including direct plating, DNA sequencing and antimicrobial susceptibility testing allowed us to characterize the dominant enterobacterial populations, the antibiotic resistant strains and their profiles. A higher frequency of Escherichia coli was found in the samples from the more anthropized site, where multi-drug resistant strains were also isolated. These results confirm how human-associated bacteria as well as their antibiotic-resistance determinants may be transferred to wildlife, which, in turn, may act as a reservoir of antibiotic resistance.

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Macrolide-resistant phenotypes of invasive streptococcus pneumoniae isolates in Serbia

Archives of Biological Sciences ◽

10.2298/abs1204377g ◽

2012 ◽

Vol 64 (4) ◽

pp. 1377-1382

Author(s):

Ina Gajic ◽

Natasa Opavski ◽

Vera Mijac ◽

L. Ranin

Keyword(s):

Streptococcus Pneumoniae ◽

Susceptibility Testing ◽

Reference Laboratory ◽

National Reference ◽

The Past ◽

Triple Test ◽

Resistance To Penicillin ◽

Resistant Strains ◽

Resistance Rates ◽

Susceptibility Patterns

Macrolide resistance in Streptococcus pneumoniae has emerged as an important worldwide problem over the past decade. The aim of this study was to investigate macrolide-resistant phenotypes and the antimicrobial susceptibility patterns of invasive pneumococci in Serbia. A total of 68 invasive pneumococcal strains, collected from 2009 to 2011, were sent from regional laboratories to the National Reference Laboratory. Susceptibility testing was performed using the VITEK2 system and phenotypes were determined by triple-test. Overall penicillin and erythromycin nonsusceptibility rates were 26% and 43%, respectively. Resistance rates were higher in children than in adults. Co-resistance to penicillin and erythromycin was detected in 18% strains. Resistance rates to the third generation of cephalosporins, TMP-SXT and tetracycline were 16%, 37% and 29%, respectively. All isolates were fully susceptible to vancomycin, linezolid, fluoroquinolones, telithromycin and rifampicin. Twenty-two isolates (79%) an expressed macrolide-lincosamide-streptogramin B (MLSB) resistance phenotype and M phenotype was found in 21% of macrolide resistant strains.

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Variation in erythromycin and clindamycin susceptibilities of Streptococcus pneumoniae by four test methods.

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.41.1.129 ◽

1997 ◽

Vol 41 (1) ◽

pp. 129-134 ◽

Cited By ~ 39

Author(s):

E L Fasola ◽

S Bajaksouzian ◽

P C Appelbaum ◽

M R Jacobs

Keyword(s):

Streptococcus Pneumoniae ◽

Susceptibility Testing ◽

Ambient Air ◽

Test Methods ◽

Disk Diffusion ◽

Broth Microdilution ◽

Microdilution Method ◽

Broth Microdilution Method ◽

Agar Dilution ◽

Resistant Strains

Susceptibilities of 124 strains of Streptococcus pneumoniae to erythromycin and clindamycin were determined by the National Committee for the Clinical Laboratory Standards (NCCLS) broth microdilution method, with incubation for 20 to 24 h in ambient air and with modifications of this method by incubation for up to 48 h in air and CO2. Strains were also tested by agar dilution, E-test, and disk diffusion; good correlation was obtained with these methods, with clear separation into bimodal populations of susceptible and resistant stains. The broth microdilution method, however, using incubation in air for 24 h (NCCLS method), misclassified 4 of 92 erythromycin-resistant strains (1 as susceptible and 3 as intermediate) and 25 of 58 clindamycin-resistant strains (all as susceptible). With the exception of one strain with clindamycin, susceptible and resistant strains were correctly classified by the microdilution method with incubation in CO2 for 24 h or in ambient air for 48 h. Disk diffusion, agar dilution, and E-test methods with incubation in 5% CO2 are therefore reliable methods for susceptibility testing of pneumococci against these agents. However, the NCCLS microdilution method, which specifies incubation for 20 to 24 h in ambient air, produced significant very major errors (43%) clindamycin. Modification of the microdilution method by incubation in 5% CO2 or by extension of incubation time in ambient air to 48 h corrected these errors. Disk diffusion, however, was shown to be a simple, convenient, and reliable method for susceptibility testing of pneumococci to erythromycin and clindamycin and is suggested as the method of choice for these agents.

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Antimicrobial susceptibility and molecular characterization of Salmonella serovar Ndolo isolated from outbreaks in cattle and horses

Ciência Rural ◽

10.1590/0103-8478cr20180688 ◽

2018 ◽

Vol 48 (12) ◽

Cited By ~ 2

Author(s):

Carolina Pantuzza Ramos ◽

Rafael Gariglio Clark Xavier ◽

Carlos Augusto Gomes Leal ◽

Elias Jorge Facury Filho ◽

Antonio Ultimo de Carvalho ◽

...

Keyword(s):

Clavulanic Acid ◽

Antimicrobial Susceptibility ◽

Virulence Genes ◽

Susceptibility Testing ◽

Domestic Animals ◽

Amoxicillin Clavulanic Acid ◽

Resistant Strains ◽

Human Infections ◽

First Time

ABSTRACT: The present study aimed to describe and characterize, for the first time, two outbreaks of salmonellosis caused by Salmonella Ndolo in foals and calves in Brazil and compare the isolated strains with S. Ndolo previously identified in asymptomatic reptiles. The affected calves and foals presented fever, lethargy, and profuse diarrhea. Isolated strains were subjected to antimicrobial susceptibility testing, characterized according to virulence genes, and fingerprinted by ERIC-PCR. Salmonella Ndolo was identified in fecal samples from two foals and four calves. One isolate from a calf was resistant to amoxicillin/clavulanic acid, trimethoprim/sulfamethoxazole, and florfenicol. Strains from two other calves were resistant to oxytetracycline. All virulence genes tested were present in the isolates, and two major clusters of closely related strains were identified by ERIC-PCR, each per outbreak. This is the first report of Salmonella Ndolo infection in domestic and symptomatic animals. Previously, this serovar had been identified only in human infections. The presence of relevant virulence genes in all Salmonella Ndolo isolates and the detection of antimicrobial multi-resistant strains highlighted the importance of monitoring serovars associated with salmonellosis in domestic animals.

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Comparative Evaluation of Colistin Susceptibility Testing Methods among Carbapenem-Nonsusceptible Klebsiella pneumoniae and Acinetobacter baumannii Clinical Isolates

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00868-15 ◽

2015 ◽

Vol 59 (8) ◽

pp. 4625-4630 ◽

Cited By ~ 57

Author(s):

Konstantina Dafopoulou ◽

Olympia Zarkotou ◽

Evangelia Dimitroulia ◽

Christos Hadjichristodoulou ◽

Vasiliki Gennimata ◽

...

Keyword(s):

Klebsiella Pneumoniae ◽

Acinetobacter Baumannii ◽

Susceptibility Testing ◽

Reference Method ◽

Test Strip ◽

Clinical Isolates ◽

Content Type ◽

Gradient Diffusion ◽

Agar Dilution ◽

Resistant Strains

ABSTRACTWe compared six colistin susceptibility testing (ST) methods on 61 carbapenem-nonsusceptibleKlebsiella pneumoniae(n= 41) andAcinetobacter baumannii(n= 20) clinical isolates with provisionally elevated colistin MICs by routine ST. Colistin MICs were determined by broth microdilution (BMD), BMD with 0.002% polysorbate 80 (P80) (BMD-P80), agar dilution (AD), Etest, Vitek2, and MIC test strip (MTS). BMD was used as the reference method for comparison. The EUCAST-recommended susceptible and resistant breakpoints of ≤2 and >2 μg/ml, respectively, were applied for bothK. pneumoniaeandA. baumannii. The proportions of colistin-resistant strains were 95.1, 77, 96.7, 57.4, 65.6, and 98.4% by BMD, BMD-P80, AD, Etest, MTS, and Vitek2, respectively. The Etest and MTS methods produced excessive rates of very major errors (VMEs) (39.3 and 31.1%, respectively), while BMD-P80 produced 18% VMEs, AD produced 3.3% VMEs, and Vitek2 produced no VMEs. Major errors (MEs) were rather limited by all tested methods. These data show that gradient diffusion methods may lead to inappropriate colistin therapy. Clinical laboratories should consider the use of automated systems, such as Vitek2, or dilution methods for colistin ST.

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SUSCEPTIBILITY TEST FOR FUNGI: CLINICAL AND LABORATORIAL CORRELATIONS IN MEDICAL MYCOLOGY

Revista do Instituto de Medicina Tropical de São Paulo ◽

10.1590/s0036-46652015000700011 ◽

2015 ◽

Vol 57 (suppl 19) ◽

pp. 57-64 ◽

Cited By ~ 57

Author(s):

Ana ALASTRUEY-IZQUIERDO ◽

Marcia S.C. MELHEM ◽

Lucas X. BONFIETTI ◽

Juan L. RODRIGUEZ-TUDELA

Keyword(s):

Susceptibility Testing ◽

Fungal Infections ◽

Antifungal Susceptibility ◽

Fungal Species ◽

Medical Mycology ◽

Candida Spp ◽

Disease Epidemiology ◽

Resistant Strains ◽

European Standards

SUMMARYDuring recent decades, antifungal susceptibility testing has become standardized and nowadays has the same role of the antibacterial susceptibility testing in microbiology laboratories. American and European standards have been developed, as well as equivalent commercial systems which are more appropriate for clinical laboratories. The detection of resistant strains by means of these systems has allowed the study and understanding of the molecular basis and the mechanisms of resistance of fungal species to antifungal agents. In addition, many studies on the correlation of in vitro results with the outcome of patients have been performed, reaching the conclusion that infections caused by resistant strains have worse outcome than those caused by susceptible fungal isolates. These studies have allowed the development of interpretative breakpoints for Candida spp. and Aspergillus spp., the most frequent agents of fungal infections in the world. In summary, antifungal susceptibility tests have become essential tools to guide the treatment of fungal diseases, to know the local and global disease epidemiology, and to identify resistance to antifungals.

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Non-pncAGene-Mutated but Pyrazinamide-Resistant Mycobacterium tuberculosis: Why Is That?

Journal of Clinical Microbiology ◽

10.1128/jcm.02532-16 ◽

2017 ◽

Vol 55 (6) ◽

pp. 1920-1927 ◽

Cited By ~ 20

Author(s):

Jim Werngren ◽

Erik Alm ◽

Mikael Mansjö

Keyword(s):

Susceptibility Testing ◽

Gene Mutations ◽

Drug Susceptibility ◽

Multidrug Resistant ◽

Drug Susceptibility Testing ◽

Molecular Techniques ◽

Content Type ◽

Resistant Strains ◽

Clear Majority

ABSTRACTPyrazinamide (PZA) is a key component for the effective treatment of drug-susceptible and PZA-susceptible multidrug-resistant (MDRPZA-S) tuberculosis (TB).pncAgene mutations are usually detected in a clear majority (>90%) of PZA-resistant strains but obviously not in all. Rapid and reliable PZA drug susceptibility testing (DST) is critical whenever PZA is to be used in a treatment regimen, not least for the treatment of MDRPZA-STB. In this study, we selected 26 PZA-resistant isolates reported to carry a wild-typepncAgene. To confirm resistance, susceptibility testing was repeated using 100 mg/liter and 200 mg/liter PZA for all the 26 isolates and Sanger sequencing was repeated on the 18 isolates that remained PZA resistant. Apart from the eight isolates initially misclassified as PZA resistant, the retests identified three factors responsible for the phenotype-genotype discrepancy:panDorrpsAmutations identified by whole-genome sequencing (WGS) (n= 7), heteroresistance (n= 8), and mixed populations withMycobacterium avium(n= 3). Additionally, we performed WGS on 400 PZA-susceptible isolates and 15 consecutive MDRPZA-Rclinical isolates. Of the 400 PZA-susceptible isolates, only 1 harbored a nonsynonymouspncAmutation (Thr87Met), whereas a nonsynonymousrpsAmutation was found in 17 isolates. None of these isolates carried a nonsynonymouspanDmutation, while all 15 of the MDRPZA-Risolates harbored a nonsynonymouspncAmutation. Our findings indicate that it is necessary to consider the occurrence ofpanDmutations in PZA-resistant isolates, as well as heteroresistance, for the development and evaluation of new molecular techniques to ensure high-quality DST performance. The identification of nonsynonymousrpsAmutations in both PZA-susceptible and PZA-resistant isolates also implies that further studies are needed in order to determine the role ofrpsAin PZA resistance.

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The Profile of Microbiological Pathogens in Diabetic Foot Ulcers

Frontiers in Medicine ◽

10.3389/fmed.2021.656467 ◽

2021 ◽

Vol 8 ◽

Author(s):

Wei Chai ◽

Yuqing Wang ◽

Huancheng Zheng ◽

Song Yue ◽

Yan Liu ◽

...

Keyword(s):

Diabetic Foot ◽

Antibiotic Susceptibility ◽

Susceptibility Testing ◽

Limb Amputation ◽

Foot Ulcers ◽

Diabetic Foot Ulcers ◽

Antibiotic Resistant ◽

Resistant Strains ◽

Pathogen Spectrum ◽

Main Complication

Diabetic foot, a main complication of diabetes mellitus, renders the foot susceptible to infection, and may eventually lead to non-traumatic limb amputation due to the deterioration of diabetic foot ulcers (DFUs). Characterizing the pathogen spectrum and antibiotic susceptibility is critical for the effective treatment of DFUs. In the current study, the characteristics and antibiotic susceptibility of the pathogen spectrum were analyzed. Secretions from the DFUs of 102 patients were cultured, and dominant pathogens were identified by using test cards. Antibiotic susceptibility of dominant pathogens was assayed by the Kirby–Bauer assay. We found that the dominant pathogens varied with age, duration of diabetes, blood sugar control, and the initial cause of ulcers. Moreover, the dominant pathogens were susceptible to at least one antibiotic. However, the antibacterial efficacy of several commonly used antibiotics decreased from 2016 to 2019. Our study indicates that the identification of dominant pathogens and antibiotic susceptibility testing is essential for the treatment of DFUs with effective antibiotics, while the abuse of antibiotics should be strictly restrained to reduce the generation of antibiotic-resistant strains.

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Hazard of agricultural triazole fungicide: Does cyproconazole induce voriconazole resistance in Aspergillus fumigatus isolates?

Current Medical Mycology ◽

10.18502/cmm.6.4.5329 ◽

2021 ◽

Author(s):

Maryam Moazeni ◽

Elaheh Ghobahi Katomjani ◽

Iman Haghani ◽

Mojtaba Nabili ◽

Hamid Badali ◽

...

Keyword(s):

Aspergillus Fumigatus ◽

Susceptibility Testing ◽

Antifungal Susceptibility ◽

Homology Model ◽

In Vitro Activity ◽

Environmental Isolates ◽

Microdilution Method ◽

Broth Microdilution Method ◽

Resistant Strains

Background and Purpose: The present study aimed to evaluate the effect of cyproconazole, the most used fungicide in Iranian wheat farms, on the induction of voriconazole resistance in Aspergillus fumigatus isolates. Materials and Methods: A collection of 20 clinical and environmental isolates were selected for investigation of the in vitro activity of fungicides. The minimum inhibitory concentrations (MICs) were determined by the documented broth microdilution method M38-A2 (CLSI, 2008). Induction experiments were performed and the possibly induced isolate(s) were subjected to antifungal susceptibility testing, sequencing of the CYP51A promoter, and full coding gene. Furthermore, CYP51-protein homology modeling and docking modes were evaluated using SWISS-MODEL (https://swissmodel.expasy.org/) and SEESAR software (version 9.1). Results: Among 10 susceptible isolates, only one strain showed a high MIC value against voriconazole (MIC=4μg/ml) after 25 passages. Nevertheless, sequencing of the CYP51A promoter and full coding gene did not reveal any mutations. Cyproconazole, which has three nitrogen atoms in the aromatic ring, coordinated to the iron atom of heme through a hydrogen bond contact to residue Lys147 present in the active site of the A. fumigates Cyp51 homology model. Conclusion: Cyproconazole is being applied extensively in wheat farms in Iran. According to the results, cyproconazole may not play a key role in the induction of azole resistance in the isolates through the environmental route. However, the potential ability of the fungicide to induce medically triazole-resistant strains over a long period of application should not be neglected.

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