647. Investigation of Heteroresistance Among Klebsiella pneumoniae (KP) Inner Colonies (IC) Observed During Fosfomycin Disk Diffusion (DD) Testing

Abstract Background During fosfomycin DD testing, the frequent occurrence of non-susceptible IC within the zone of inhibition of susceptible isolates has been noted. The Clinical & Laboratory Standards Institute (CLSI) and European Committee on Antimicrobial Susceptibility Testing (EUCAST) have contradicting recommendations on how IC should be interpreted; CLSI recommends considering IC when interpreting DD results whereas EUCAST recommends ignoring them. This study sought to identify the susceptibility of these IC and to understand whether heteroresistance contributes to the appearance of IC during fosfomycin DD. Methods This study included a convenience sample of 71 KP clinical isolates from 3 United States locations. During DD testing, 58 (81.7%) of these isolates displayed at least one IC. Broth microdilution (BMD) minimal inhibitory concentration (MIC) testing, using extrapolated CLSI Escherichia coli breakpoints, was performed on a subset (n=32) of the IC in duplicate for comparison to the corresponding parent MIC values. This was followed by a modified disk elution screening test for heteroresistance to compare the frequency of low level resistance (LLR) and high level resistance (HLR) between the susceptible isolates that produced resistant IC (n=6) and those that did not produce any IC (n=3). Results The MIC range for the IC isolates (128 to > 1024 μg/mL) increased as compared to the parent isolates (< 2 to > 256 μg/mL) and MIC50/90 increased from the parent (128/ > 256 μg/mL) to IC (1024/ > 1024 μg/mL) isolates. All IC isolates had a resistant MIC value vs. 46.5% of parent isolates, and over 90% of IC isolates had an MIC at least 2 dilutions higher than their corresponding parent isolate. Heteroresistance screening found all tested isolates to be positive for LLR, and 8 of 9 positive for HLR, while the one HLR-negative isolate was IC-producing. Conclusion IC were frequent during fosfomycin DD testing and were commonly more resistant than their corresponding KP parent isolates. A small subset of these isolates tested via a modified disk elution test displayed either LLR or HLR regardless of the absence of IC. These results call for further investigation among a larger isolate set to understand what mechanisms are responsible for the frequency of IC and their increased fosfomycin resistance. Disclosures All Authors: No reported disclosures

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Activity of isavuconazole and other triazole derivatives against clinical isolates of Aspergillus fumigatus

Postępy Higieny i Medycyny Doświadczalnej ◽

10.5604/01.3001.0013.0511 ◽

2019 ◽

Vol 73 ◽

pp. 76-80

Author(s):

Urszula Nawrot ◽

Katarzyna Włodarczyk ◽

Marzenna Bartoszewicz ◽

Sylwia Balicka ◽

Monika Pomorska-Wesołowska ◽

...

Keyword(s):

Aspergillus Fumigatus ◽

Susceptibility Testing ◽

Inhibitory Concentration ◽

Acquired Resistance ◽

Clinical Samples ◽

Triazole Derivatives ◽

European Committee ◽

Microdilution Method ◽

Resistant Strains ◽

Mic Value

Aspergillus fumigatus is the most frequent pathogen of the genus Asperillus, which is highly susceptible to triazole derivatives, especially to isavuconazole and voriconazole. Many countries face a growing problem of infections due to A. fumigatus showing acquired resistance to one or several triazoles. In medical centres, monitoring the susceptibility of isolated Aspergillus spp. is recommended. Aim: The aim of this study was to collect and test triazole susceptibility of Aspergillus fumigatus obtained from clinical samples, which were investigated in diagnostic laboratories located in Wrocław, Warszawa and Ruda Śląska (Poland). In addition, 5 resistant A. fumigatus strains with TR34/L98H mutation were included. Material/Methods: The microdilution method, according to the European Committee on Antimicrobial Susceptibility Testing (EUCAST) was applied to test susceptibility to isavuconazole (ISV), voriconazole (VOR), posaconazole (POS) and itraconazole (ITR). Results: During a period of 24 months, a total number of 75 A. fumigatus isolates were collected. Most of the strains were obtained from lower respiratory tract specimens (58/75; 77%), from patients hospitalized on pulmonology (41%) or intensive care and surgery units (29%). No isolate resistant to ISV or other triazoles was found. The minimal inhibitory concentration (MIC) value of ISV ranged from 0.125 to 1 mg/L (mean 0.4 ±0.15 mg/L) in triazole susceptible isolates, whereas among triazole-resistant strains, three showed a MIC of 8 mg/L and two had a MIC of 4 mg/L. Conclusions: A. fumigatus isolates carrying the mutation TR34/L98H are cross-resistant to ISV. The acquired resistance is very rare in our region (0-4%), which supports of use of triazole derivatives (VOR, ISV) in the therapy of aspergillosis.

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Antimicrobial susceptibility of Neisseria gonorrhoeae in Barcelona during a five-year period, 2013 to 2017

Eurosurveillance ◽

10.2807/1560-7917.es.2020.25.42.1900576 ◽

2020 ◽

Vol 25 (42) ◽

Cited By ~ 1

Author(s):

Paula Salmerón ◽

Belén Viñado ◽

Rachid El Ouazzani ◽

Marta Hernández ◽

María Jesús Barbera ◽

...

Keyword(s):

Neisseria Gonorrhoeae ◽

Antimicrobial Susceptibility ◽

Susceptibility Testing ◽

Testing Time ◽

Susceptibility Data ◽

European Committee ◽

Clinical Breakpoints ◽

High Level ◽

Resistance Rates ◽

Level Resistance

Introduction Increasing rates of antimicrobial resistance in Neisseria gonorrhoeae cause problems for treating gonorrhoea. Aim This observational study aimed to describe isolates from all patients found infected with N. gonorrhoeae, in Barcelona, Spain, between 2013 and 2017, and with available antimicrobial susceptibility data. Methods Minimum inhibitory concentrations (MICs) of penicillin (PEN), cefixime (CFM), ceftriaxone (CRO), azithromycin (AZM), ciprofloxacin (CIP), spectinomycin (SPT), fosfomycin (FOF) and gentamicin (GEN) were determined by E-test. Susceptibility was assessed using clinical breakpoints from the European Committee on Antimicrobial Susceptibility Testing. Time trends for PEN, CFM, AZM and CIP were investigated using logistic regression. Results Of 1,979 patients with infection (2,036 isolates), 1,888 (95.4%) were men. Patient median age was 32 years. The proportions of isolates resistant to extended-spectrum cephalosporins were low, with 0.3% (5/1,982) resistant to CRO and 4.9% (98/1,985) to CFM. AZM resistance prevalence was 2.7% (52/1,981), including 16 isolates detected in 2016 and 2017, with high-level resistance. For CIP, 51.3% (1,018/1,986) of isolates were resistant, and for PEN, 20.1% (399/1,985). All isolates were susceptible to SPT. MIC50 and MIC90 values of GEN were 4 and 6 mg/L and of FOF 12 and 24 mg/L, respectively. Between 2013 and 2017, PEN and CFM resistance rates each decreased from 28.1% (92/327) to 12.2% (70/572) and from 8.3% (27/327) to 4.4% (25/572) (p ≤ 0.0073). In contrast, AZM resistance prevalence appeared to increase from 1.5% in 2014 (5/340) to 3.0% (17/572) in 2017. No trend was identified for CIP. Conclusion Antimicrobial susceptibility surveillance is important to timely detect new phenotypes and trends.

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E-Test or Agar Dilution for Metronidazole Susceptibility Testing of Helicobacter Pylori: Importance of the Prevalence of Metronidazole Resistance

10.21203/rs.3.rs-677597/v1 ◽

2021 ◽

Author(s):

Jinnan Chen ◽

Yu Huang ◽

Zhaohui Ding ◽

Xiao Liang ◽

Hong Lu

Keyword(s):

Helicobacter Pylori ◽

Susceptibility Testing ◽

Resistance Rate ◽

Test Method ◽

Major Error ◽

Metronidazole Resistance ◽

Agar Dilution ◽

H Pylori ◽

High Level ◽

Level Resistance

Abstract Background: A number of studies have shown that E-test overestimated the presence of Helicobacter pylori (H. pylori) resistance compared to agar dilution.Objective: The purpose of this study was to explore whether E-test could be an alternative for agar dilution to detect the metronidazole susceptibility of H. pylori.Method: E-test and agar dilution were used to assess susceptibility of H. pylori to metronidazole, clarithromycin and levofloxacin in 281 clinical isolates obtained from China where resistance was high. Cohen kappa analysis, McNemar test, essential and categorical agreement analysis were performed for these two methods. Results: Overall, the result of E-test showed similar prevalence of resistance rate to all antibiotics compared with agar dilution. The essential agreement (EA) of E-test method and agar dilution in the evaluation susceptibility of H. pylori to clarithromycin and levofloxacin were moderate, with 89.0% and 79.7% respectively, but only 45.9% for metronidazole. Results showed categorical agreement (CA) between E-test and agar dilution were 100% for both clarithromycin and levofloxacin. As for metronidazole, the CA was 98.7%, no major error was identified, and rate of very major error was 1.8%.Conclusion: E-test can be an alternative method to detect the metronidazole susceptibility of H. pylori in regions where high-level resistance is common.

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Evaluation of Antimicrobial Activity and Synergistic Effect of Spices against Few Selected Pathogens

Tribhuvan University Journal of Microbiology ◽

10.3126/tujm.v6i0.26573 ◽

2019 ◽

Vol 6 ◽

pp. 10-18

Author(s):

Renuka Maharjan ◽

Saru Thapa ◽

Amrit Acharya

Keyword(s):

Antimicrobial Activity ◽

Synergistic Effect ◽

Inhibitory Concentration ◽

Agar Plate ◽

Ethanolic Extract ◽

Fractional Inhibitory Concentration ◽

Zone Of Inhibition ◽

Soxhlet Apparatus ◽

Mic Value

Objectives: The main objective of this study was to evaluate antimicrobial activity of ethanolic extract of spices along with determination of its synergistic effect against few selected pathogens. Methods: In this study, ethanolic extract of 5 different spices; Zingiber officinale (Ginger), Allium sativum (Garlic), Curcuma longa (Turmeric), Capsicum annum (Chili) and Allium cepa (Onion) were obtained by using Soxhlet apparatus. The ethanolic extract was concentrated by evaporation and different concentrations of extract were prepared in Dimethy Sulphoxide (DMSO) solvent. Test organisms included mainly pathogens i.e. Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae. The antimicrobial activities of the extracts were determined by well diffusion technique both individually and in combination. On the other hand, Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) was determined by serial dilution technique. The result were interpreted on the basis of the fact that the growth occurs in positive control and other tubes with inadequate amount of extract whereas the lowest concentration of agent that inhibits growth of organism, detected by lack of visible turbidity by inhibition of 99% is designed as the MIC. The MBC is identified by determining the lowest concentration of extract solution that reduces the viability of the initial bacterial inoculum by a predetermined reduction such as ≥99.9%. Likewise, for determination of Fractional Inhibitory Concentration Index (FICI), two extracts were combined along with standardized inoculum of bacterial strain. Tubes without visible turbidity were streaked on agar plate and observed for 99.9% killing. Results: All the tested extract of spices were found effective against S. aureus and K. pneumoniae only. The highest zone of inhibition (ZOI) was found in chili extract (ZOI=26 mm) against S. aureus whereas lowest zone of inhibition was found in garlic extract against K. pneumoniae (ZOI=12mm). Similarly, highest ZOI was produced by combined extract of both Turmeric and Ginger (ZOI= 26 mm). Turmeric extract was found to be effective against S. aureus (MIC value = 62.5 mg /ml and MBC value = 31.25 mg/ml) and K. pneumoniae (MIC value 125 mg/ml and MBC value = 62.5 mg/ml). The Fractional Inhibitory Concentration (FIC) values of combined extract suggested synergistic and additive effect (0.5<FIC<1). Chili and ginger were effective with FIC value of 0.25. Conclusion: To recapitulate, the extract of spices can be used to prevent the pathogenic organism.

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Hyper-Aerotolerant Campylobacter coli from Duck Sources and Its Potential Threat to Public Health: Virulence, Antimicrobial Resistance, and Genetic Relatedness

Microorganisms ◽

10.3390/microorganisms7110579 ◽

2019 ◽

Vol 7 (11) ◽

pp. 579 ◽

Cited By ~ 2

Author(s):

Jae-Ho Guk ◽

Junhyung Kim ◽

Hyokeun Song ◽

Jinshil Kim ◽

Jae-Uk An ◽

...

Keyword(s):

Public Health ◽

Antimicrobial Resistance ◽

Inhibitory Concentration ◽

Genetic Relatedness ◽

Control Strategies ◽

Campylobacter Coli ◽

Potential Threat ◽

High Level ◽

Sequence Types ◽

Level Resistance

Campylobacter, a common foodborne human pathogen, is considered sensitive to oxygen. Recently, aerotolerant (AT) Campylobacter jejuni with the ability to survive under aerobic stress has been reported. Here, we investigated the prevalence of hyper-aerotolerant (HAT) Campylobacter coli from duck sources (118 carcasses and meat) and its characteristics to assess potential impacts on public health. Half of 56 C. coli isolates were HAT and most harbored various virulence genes including flaA, cadF, cdtA, ceuB, and wlaN. Moreover, 98.2% of C. coli isolates showed resistance to quinolones, including ciprofloxacin (CIP), and nine (16.1%) showed high-level resistance to ciprofloxacin (Minimum Inhibitory Concentration, MIC ≥ 32 μg/mL) and most of these were HAT. Based on genetic relatedness between C. coli from duck sources and those from human sources (PubMLST and NCBI), HAT isolates sharing the same MLST sequence types were significantly more prevalent than those not sharing the same sequence types as those from human sources. Therefore, HAT C. coli is prevalent in duck sources, and is most likely transmitted to humans through the food chain given its aerotolerance. This being so, it might pose a threat to public health given its virulence and antimicrobial resistance (AMR). This study will assist in improving control strategies to reduce farm-to-table HAT C. coli transmission to humans.

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Human isolates of apramycin-resistant Escherichia coli which contain the genes for the AAC(3)IV enzyme

Epidemiology and Infection ◽

10.1017/s0950268800068175 ◽

1993 ◽

Vol 110 (2) ◽

pp. 253-259 ◽

Cited By ~ 15

Author(s):

J. E. B. Hunter ◽

C. A. Hart ◽

J. C. Shelley ◽

J. R. Walton ◽

M. Bennett

Keyword(s):

Escherichia Coli ◽

Minimal Inhibitory Concentration ◽

Inhibitory Concentration ◽

Aminoglycoside Antibiotic ◽

Dna Probe ◽

Conjugative Plasmid ◽

E Coli ◽

High Level ◽

Level Resistance

SUMMARYGentamicin-resistant Escherichia coli isolated at different periods from patients in two hospitals were tested for resistance to the aminoglycoside antibiotic apramycin. Twenty-four of 93 (26%) gentamicin-resistant isolates collected from the Royal Liverpool Hospital between 1981 and 1990 were resistant to apramycin. Thirteen isolates were highly resistant to apramycin (minimal inhibitory concentration (MIC) ≥ 1024 μg/ml). were also resistant to gentamicin, netilmicin and tobramycin, and hybridized with a DNA probe derived from the aminoglycoside acetyltransferase (3)IV (AAC(3)IV) gene. The proportion of gentamicinresistant isolates which had high level resistance to apramycin increased from 7% in 1981–5 to 24% in 1986–90.Twelve gentamicin-resistant E. coli from Guy's and St Thomas's Hospital isolated between 1977 and 1980 were also tested for resistance to apramycin. For five of these isolates the MICs of apramycin was 32–256 μg/ml. None was shown to have a conjugative plasmid carrying resistance to apramycin and only one hybridized with the DNA probe for the AAC(3)IV enzyme.

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Sparfloxacin Resistance in Clinical Isolates ofStreptococcus pneumoniae: Involvement of Multiple Mutations in gyrA and parC Genes

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.42.9.2193 ◽

1998 ◽

Vol 42 (9) ◽

pp. 2193-2196 ◽

Cited By ~ 28

Author(s):

Hideki Taba ◽

Nobuchika Kusano

Keyword(s):

Streptococcus Pneumoniae ◽

Amino Acid ◽

Antimicrobial Susceptibility ◽

Susceptibility Testing ◽

Clinical Isolates ◽

Amino Acid Substitutions ◽

Sequencing Analysis ◽

High Level ◽

Additional Nucleotide ◽

Level Resistance

ABSTRACT Antimicrobial susceptibility testing revealed among 150 clinical isolates of Streptococcus pneumoniae 4 pneumococcal isolates with resistance to fluoroquinolones (MIC of ciprofloxacin, ≥32 μg/ml; MIC of sparfloxacin, ≥16 μg/ml). Gene amplification and sequencing analysis of gyrA andparC revealed nucleotide changes leading to amino acid substitutions in both GyrA and ParC of all four fluoroquinolone-resistant isolates. In the case of strains 182 and 674 for which sparfloxacin MICs were 16 and 64 μg/ml, respectively, nucleotide changes were detected at codon 81 in gyrA and codon 79 in parC; these changes led to an Ser→Phe substitution in GyrA and an Ser→Phe substitution in ParC. Strains 354 and 252, for which sparfloxacin MICs were 128 μg/ml, revealed multiple mutations in both gyrA and parC. These strains exhibited nucleotide changes at codon 85 leading to a Glu→Lys substitution in GyrA, in addition to Ser-79→Tyr and Lys-137→Asn substitutions in ParC. Moreover, strain 252 showed additional nucleotide changes at codon 93, which led to a Trp→Arg substitution in GyrA. These results suggest that sparfloxacin resistance could be due to the multiple mutations in GyrA and ParC. However, it is possible that other yet unidentified mutations may also be involved in the high-level resistance to fluoroquinolones in S. pneumoniae.

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Penicillin- and Cephalosporin-Resistant Streptococcus pneumoniae: An Emerging Microbial Threat

PEDIATRICS ◽

10.1542/peds.93.3.500 ◽

1994 ◽

Vol 93 (3) ◽

pp. 500-503 ◽

Cited By ~ 1

Author(s):

Robert J. Leggiadro

Keyword(s):

Streptococcus Pneumoniae ◽

Pneumococcal Disease ◽

Inhibitory Concentration ◽

Penicillin Resistance ◽

Cell Wall Synthesis ◽

Penicillin Binding Proteins ◽

Clinical Challenge ◽

Recent Developments ◽

High Level ◽

Level Resistance

Recent reports from South Africa,1 Spain,2 Hungary,3 Texas,4-6 and Memphis7,8 document an increasing incidence of penicillin-resistant Streptococcus pneumoniae infections in children. The emergence of penicillin-resistant pneumococci that also demonstrate decreased susceptibility to extended-spectrum cephalosporins presents an even greater clinical challenge.6-9 This commentary reviews recent developments in the epidemiology, identification, and management of penicillin- and cephalosporin-resistant pneumococcal disease in children. Pneumococcal susceptibility to penicillin is defined as a minimal inhibitory concentration (MIC) <0.1 µg/mL. Intermediate (relative) penicillin resistance is defined as an MIC from 0.1 to 1.0 µg/mL and high-level resistance as an MIC >1.0 µ/mL. Pneumococcal penicillin resistance is mediated by alterations in penicillin-binding proteins involved in cell wall synthesis.10

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Antimicrobial Susceptibilities of Group B Streptococci Isolated from Patients with Invasive Disease: 10-Year Perspective

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.45.12.3623-3624.2001 ◽

2001 ◽

Vol 45 (12) ◽

pp. 3623-3624 ◽

Cited By ~ 45

Author(s):

David R. Murdoch ◽

L. Barth Reller

Keyword(s):

Antimicrobial Susceptibility ◽

Susceptibility Testing ◽

Invasive Disease ◽

Antimicrobial Susceptibility Testing ◽

Streptococcal Infections ◽

Group B Streptococci ◽

Treatment And Prevention ◽

Group B ◽

High Level ◽

Level Resistance

ABSTRACT Antimicrobial susceptibility testing of 192 group B streptococcal isolates from patients with invasive disease demonstrated that 31 (16%) were resistant to erythromycin and 17 (9%) were resistant to clindamycin. One isolate demonstrated high-level resistance to streptomycin, but none was highly resistant to gentamicin. Erythromycin and clindamycin are no longer reliable empirical alternatives to penicillin for the treatment and prevention of group B streptococcal infections.

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2166. Performance Study on the New ETEST® Piperacillin/Tazobactam (P/T) MIC Strip

Open Forum Infectious Diseases ◽

10.1093/ofid/ofz360.1846 ◽

2019 ◽

Vol 6 (Supplement_2) ◽

pp. S735-S735

Author(s):

Roland Martelin ◽

Edwige Pillon ◽

Emilie Cutivet ◽

Marion Pompilio ◽

Diane Halimi ◽

...

Keyword(s):

Susceptibility Testing ◽

Inhibitory Concentration ◽

Reference Method ◽

Error Rates ◽

Performance Study ◽

First Line ◽

Severe Infections ◽

Agar Dilution ◽

Resistant Strains ◽

High Level

Abstract Background Piperacillin/Tazobactam combination is a first-line antibiotic and carbapenem sparing option for severe infections due to Enterobacteriaceae, Pseudomonas aeruginosa and Acinetobacter baumannii. ETEST® strips allow to determine antimicrobial Minimum Inhibitory Concentration (MIC). ETEST® Piperacillin/Tazobactam (Ptc) was developped in 1995 against agar dilution reference method. Since then, resistance to Piperacillin/Tazobactam has been increasing and broth microdilution (BMD) substituted for agar dilution as the reference method. The new ETEST® P/T strip for determining MIC of Enterobacteriaceae, P. aeruginosa and A. baumannii was developed against BMD using a panel of recent strains well genotypically characterized. The aim of this study was to compare the performance of both strips on a panel of challenging strains harboring different-resistant mechanisms. Methods A total of 64 strains were tested using ETEST® P/T, ETEST® PTc and BMD: 48 Enterobacteriaceae including 25 resistant strains and 16 P. aeruginosa including 11 resistant strains. The results were analyzed for essential (EA) and category (CA) agreements, minor (mE), major (ME) and very major (VME) error rates using FDA/CLSI 2019 breakpoints (Enterobacteriaceae, P. aeruginosa: ≤ 16/4(S); ≥ 128/4(R) µg/mL). Results Although the panel of strains was challenging including different resistant mechanisms (acquired penicillinase, high-level cephalosporinase, acquired cephalosporinase, ESBL, carbapenemase), the new ETEST® P/T performance was significantly improved for Enterobacteriaceae with an EA at 92,2% without ME or VME. This improvement was also linked to the easiest reading (significant decrease of microcolonies in the ellipse zone). For P. aeruginosa, the performance was similar between the two strips but the new ETEST® P/T was better correlated with the BMD and showed an EA of 100%. The results are summarized in the table. Conclusion The new ETEST® P/T improved the MIC determination and resistance detection, as well as the reading of MIC end points for the routine use. This study emphasizes the need to check the performance of the antimicrobial susceptibility testing products by testing strains reflecting the current epidemiology. Disclosures All authors: No reported disclosures.

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