In vitro susceptibility of Clostridium difficile to rifaximin and rifampin in 359 consecutive isolates at a university hospital in Houston, Texas

AimThis was an in vitro study to analyse the susceptibility of Clostridium difficile isolates to rifampin and rifaximin.MethodsStool samples from patients who had nosocomial diarrhoea and C difficile toxin B at a university hospital between August 2006 and December 2007 were cultured for C difficile. Susceptibility of C difficile isolates to rifaximin and rifampin was determined by agar dilution and E strips, respectively. C difficile isolates were analysed via PCR for genes encoding toxins A and B, for binary toxin (BT), and for partial deletions of the tcdC gene (tcdC-del).ResultsRifaximin exhibited high-level activity against 359 C difficile isolates, with MIC50 <0.01 μg/ml and MIC90 0.25 μg/ml; rifampin had MIC50 <0.002 μg/ml and MIC90 4 μg/ml. Among isolates analysed, 55 (15%) were positive for BT and tcdC-del. 28 (8% of 359) isolates were resistant to rifampin (≥32 μg/ml), of which 6 (2% of 359) were resistant to rifaximin and rifampin with MIC values ≥32 μg/ml. 2 of the 28 isolates resistant to rifampin were A+/B+/BT+/tcdC-del+, 5 were A+/B+/BT−/tcdC-del+, 4 were A+/B+/BT+/tcdC-del−, 13 were A+/B+/BT−/tcdC-del−, and 4 had no detectable toxin genes. Of the 11 isolates resistant to rifaximin alone, 1 was A+/B+/BT−/tcdC-del+, 2 were A+/B+/BT+/tcdC-del−, 6 were A+/B+/BT−/tcdC-del−, and 2 had no detectable toxin genes.ConclusionsThe study demonstrates that rifaximin has high-level activity against C difficile in vitro. Determination of resistance to rifampin by E strip did not predict rifaximin resistance.

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Fluoroquinolone resistance in Clostridium difficile isolates from a prospective study of C. difficile infections in Europe

Journal of Medical Microbiology ◽

10.1099/jmm.0.47738-0 ◽

2008 ◽

Vol 57 (6) ◽

pp. 784-789 ◽

Cited By ~ 85

Author(s):

Patrizia Spigaglia ◽

Fabrizio Barbanti ◽

Paola Mastrantonio ◽

Jon S. Brazier ◽

Frédéric Barbut ◽

...

Keyword(s):

Amino Acid ◽

Clostridium Difficile ◽

Prospective Study ◽

Amino Acid Substitution ◽

Amino Acid Change ◽

Fluoroquinolone Resistance ◽

Genes Encoding ◽

High Level ◽

A Prospective Study

The European Study Group on Clostridium difficile (ESGCD) conducted a prospective study in 2005 to monitor and characterize C. difficile strains circulating in European hospitals, collecting 411 isolates. Eighty-three of these isolates, showing resistance or intermediate resistance to moxifloxacin (MX), were selected for this study to assess susceptibility to other fluoroquinolones (FQs) and to analyse the gyr genes, encoding the DNA gyrase subunits GyrA and GyrB. Twenty MX-susceptible isolates from the surveillance study were included for comparison. Overall, one amino acid substitution in GyrA (Thr82 to Ile) and four different substitutions in GyrB (Ser416 to Ala, Asp426 to Asn, Asp426 to Val and Arg447 to Lys) were identified. A high level of resistance (MIC ≥32 μg ml−1) to MX, ciprofloxacin (CI), gatifloxacin (GA) and levofloxacin (LE) was found in 68 isolates showing the amino acid substitution Thr82 to Ile in GyrA, in eight isolates with the substitutions Thr82 to Ile in GyrA and Ser416 to Ala in GyrB, in two isolates showing the substitution Asp426 to Asn in GyrB and in one isolate with Asp426 to Val in GyrB. The remaining four isolates showed high MICs for CI and LE, but different MIC levels for MX and GA. In particular, intermediate levels of resistance to MX were shown by two isolates, one with the substitution Thr82 to Ile in GyrA, and one showing Asp426 to Asn in GyrB. The substitution Arg447 to Lys in GyrB was found in two strains resistant to MX, CI and LE but susceptible to GA. No substitutions in GyrA were found in the FQ-susceptible strains, whereas two strains showed the amino acid change Ser416 to Ala in GyrB. Thr82 to Ile was the most frequent amino acid change identified in the C. difficile isolates examined. In contrast to previous observations, 10 % of the isolates showed this substitution in association with Ser416 to Ala in GyrB. The other amino acid changes found were characteristic of a few strains belonging to certain types and/or countries. Two new substitutions for C. difficile, Ser416 to Ala and Arg447 to Lys, were found in GyrB. Whereas the former does not seem to have a key role in resistance, since it was also detected in susceptible strains, the latter substitution occurred in the same position where other amino acid variations take place in resistant Escherichia coli and other C. difficile strains. A large number of C. difficile isolates now show an alarming pattern of resistance to the majority of FQs currently used in hospitals and outpatient settings, therefore judicious use of these antibiotics and continuous monitoring of in vitro resistance are necessary.

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In vitro susceptibility of Clostridium difficile to rifaximin and rifampin in 359 consecutive isolates at a university hospital in Houston, Texas

Yearbook of Medicine ◽

10.1016/s0084-3873(10)79661-9 ◽

2010 ◽

Vol 2010 ◽

pp. 71-73

Author(s):

N.M. Khardori

Keyword(s):

Clostridium Difficile ◽

University Hospital ◽

In Vitro Susceptibility

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In Vitro Activities of 15 Antimicrobial Agents against 110 Toxigenic Clostridium difficile Clinical Isolates Collected from 1983 to 2004

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.01623-06 ◽

2007 ◽

Vol 51 (8) ◽

pp. 2716-2719 ◽

Cited By ~ 175

Author(s):

David W. Hecht ◽

Minerva A. Galang ◽

Susan P. Sambol ◽

James R. Osmolski ◽

Stuart Johnson ◽

...

Keyword(s):

Clostridium Difficile ◽

Antimicrobial Agents ◽

Treatment Strategies ◽

The United States ◽

Clinical Isolates ◽

Dilution Method ◽

Agar Dilution Method ◽

In Vitro Susceptibility ◽

Agar Dilution

ABSTRACT The incidence and severity of Clostridium difficile-associated disease (CDAD) is increasing, and standard treatment is not always effective. Therefore, more-effective antimicrobial agents and treatment strategies are needed. We used the agar dilution method to determine the in vitro susceptibility of the following antimicrobials against 110 toxigenic clinical isolates of C. difficile from 1983 to 2004, primarily from the United States: doripenem, meropenem, gatifloxacin, levofloxacin, moxifloxacin, OPT-80, ramoplanin, rifalazil, rifaximin, nitazoxanide, tizoxanide, tigecycline, vancomycin, tinidazole, and metronidazole. Included among the isolates tested were six strains of the toxinotype III, NAP1/BI/027 group implicated in recent U.S., Canadian, and European outbreaks. The most active agents in vitro were rifaximin, rifalazil, tizoxanide, nitazoxanide, and OPT-80 with MICs at which 50% of the isolates are inhibited (MIC50) and MIC90 values of 0.0075 and 0.015 μg/ml, 0.0075 and 0.03 μg/ml, 0.06 and 0.125 μg/ml, 0.06 and 0.125 μg/ml, 0.125 and 0.125 μg/ml, respectively. However, for three isolates the rifalazil and rifaximin MICs were very high (MIC of >256 μg/ml). Ramoplanin, vancomycin, doripenem, and meropenem were also very active in vitro with narrow MIC50 and MIC90 ranges. None of the isolates were resistant to metronidazole, the only agent for which there are breakpoints, with tinidazole showing nearly identical results. These in vitro susceptibility results are encouraging and support continued evaluation of selected antimicrobials in clinical trials of treatment for CDAD.

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Correlation between virulence gene expression and proton pump inhibitors and ambient pH in Clostridium difficile: results of an in vitro study

Journal of Medical Microbiology ◽

10.1099/jmm.0.059709-0 ◽

2013 ◽

Vol 62 (10) ◽

pp. 1517-1523 ◽

Cited By ~ 15

Author(s):

David B. Stewart ◽

John P. Hegarty

Keyword(s):

Gene Expression ◽

Clostridium Difficile ◽

Proton Pump Inhibitors ◽

Proton Pump ◽

Binary Toxin ◽

Toxin Gene ◽

Ribotype 027 ◽

Toxin Genes ◽

Positive Regulators

Proton pump inhibitors (PPIs) are associated with the development of Clostridium difficile infection in humans. Though it is assumed that PPIs mediate this effect through gastric acid suppression, there has been little investigation into whether PPIs, or ambient pH, might directly affect the expression of C. difficile toxin genes. In the present study, C. difficile ribotypes 001, 027 and 078 obtained from human subjects were grown under anaerobic conditions prepared at pHs of 5, 7.3 and 9. Matched trios were exposed to 100 µM and 200 µM of omeprazole along with PPI untreated controls. Custom designed reverse transcription quantitative PCR hydrolysis probes were used to assess C. difficile gene expression for toxins A (tcdA), B (tcdB) and binary toxin (cdtB), as well as their positive regulators (tcdR and cdtR), using rrsA, which encodes 16S rRNA, as a constitutively expressed reference gene. tcdC and codY, negative regulators of toxin expression, were also assessed. Basic pH resulted in greater expression of tcdA, and with PPI exposure a 120-fold higher expression was noted with ribotype 001. tcdB and cdtB expressions were much less responsive to pH or PPIs, though a clear response to acidic pH and PPI exposure was observed in ribotype 027. tcdC and codY expressions were largely unaffected, except with ribotype 027; low pH and PPIs resulted in their greater expression, though to a lesser degree than with toxin genes and their positive regulators. Non-neutral pH and PPI exposure appear to have an effect on C. difficile, one that has a net effect towards toxin gene expression.

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IN-VITRO SUSCEPTIBILITY TESTING BY AGAR DILUTION METHOD TO DETERMINE THE MINIMUM INHIBITORY CONCENTRATIONS OF AMPHOTERICIN B, FLUCONAZOLE AND KETOCONAZOLE AGAINST OCULAR FUNGAL ISOLATES

Indian Journal of Medical Microbiology ◽

10.1016/s0255-0857(21)02288-x ◽

2006 ◽

Vol 24 (4) ◽

pp. 273-279

Author(s):

KL Therese ◽

R Bagyalakshmi ◽

HN Madhavan ◽

P Deepa

Keyword(s):

Amphotericin B ◽

Susceptibility Testing ◽

Dilution Method ◽

Agar Dilution Method ◽

In Vitro Susceptibility ◽

Minimum Inhibitory Concentrations ◽

Fungal Isolates ◽

Agar Dilution ◽

In Vitro Susceptibility Testing

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Characterizations of Clinical Isolates of Clostridium difficile by Toxin Genotypes and by Susceptibility to 12 Antimicrobial Agents, Including Fidaxomicin (OPT-80) and Rifaximin: a Multicenter Study in Taiwan

Antimicrobial Agents and Chemotherapy ◽

10.1128/aac.00191-12 ◽

2012 ◽

Vol 56 (7) ◽

pp. 3943-3949 ◽

Cited By ~ 34

Author(s):

Chun-Hsing Liao ◽

Wen-Chien Ko ◽

Jang-Jih Lu ◽

Po-Ren Hsueh

Keyword(s):

Clostridium Difficile ◽

Care Setting ◽

Antimicrobial Agents ◽

Teaching Hospitals ◽

Binary Toxin ◽

Content Type ◽

Vancomycin Mics ◽

Major Teaching ◽

Southern Taiwan

ABSTRACTA total of 403 nonduplicate isolates ofClostridium difficilewere collected at three major teaching hospitals representing northern, central, and southern Taiwan from January 2005 to December 2010. Of these 403 isolates, 170 (42.2%) were presumed to be nontoxigenic due to the absence of genes for toxins A or B or binary toxin. The remaining 233 (57.8%) isolates carried toxin A and B genes, and 39 (16.7%) of these also had binary toxin genes. The MIC90of all isolates for fidaxomicin and rifaximin was 0.5 μg/ml (range, ≤0.015 to 0.5 μg/ml) and >128 μg/ml (range, ≤0.015 to >128 μg/ml), respectively. All isolates were susceptible to metronidazole (MIC90of 0.5 μg/ml; range, ≤0.03 to 4 μg/ml). Two isolates had reduced susceptibility to vancomycin (MICs, 4 μg/ml). Only 13.6% of isolates were susceptible to clindamycin (MIC of ≤2 μg/ml). Nonsusceptibility to moxifloxacin (n= 81, 20.1%) was accompanied by single or multiple mutations ingyrAandgyrBgenes in all but eight moxifloxacin-nonsusceptible isolates. Two previously unreportedgyrBmutations might independently confer resistance (MIC, 16 μg/ml), Ser416 to Ala and Glu466 to Lys. Moxifloxacin-resistant isolates were cross-resistant to ciprofloxacin and levofloxacin, but some moxifloxacin-nonsusceptible isolates remained susceptible to gemifloxacin or nemonoxacin at 0.5 μg/ml. This study found the diversity of toxigenic and nontoxigenic strains ofC. difficilein the health care setting in Taiwan. All isolates tested were susceptible to metronidazole and vancomycin. Fidaxomicin exhibited potentin vitroactivity against all isolates tested, while the more than 10% of Taiwanese isolates with rifaximin MICs of ≥128 μg/ml raises concerns.

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Enhancement of cell-mediated cytotoxicity by Clostridium difficile toxin A: An in vitro study

Toxicon ◽

10.1016/0041-0101(91)90016-k ◽

1991 ◽

Vol 29 (4-5) ◽

pp. 417-428 ◽

Cited By ~ 9

Author(s):

W. Malorni ◽

S. Paradisi ◽

M.L. Dupuis ◽

C. Fiorentini ◽

C. Ramoni

Keyword(s):

Clostridium Difficile ◽

In Vitro Study ◽

Vitro Study ◽

Toxin A ◽

Clostridium Difficile Toxin ◽

Clostridium Difficile Toxin A

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Evaluation of the Cepheid Xpert C. difficile/Epiand Meridian Bioscienceillumigene C. difficile Assays for Detecting Clostridium difficile Ribotype 033 Strains

Journal of Clinical Microbiology ◽

10.1128/jcm.03297-14 ◽

2014 ◽

Vol 53 (3) ◽

pp. 973-975 ◽

Cited By ~ 14

Author(s):

Grace O. Androga ◽

Alan M. McGovern ◽

Briony Elliott ◽

Barbara J. Chang ◽

Timothy T. Perkins ◽

...

Keyword(s):

Clostridium Difficile ◽

Binary Toxin ◽

Content Type ◽

Toxin Genes ◽

Production Animals

Clostridium difficilePCR ribotype 033 (RT033) is found in the gastrointestinal tracts of production animals and, occasionally, humans. TheillumigeneC. difficileassay (Meridian Bioscience, Inc.) failed to detect any of 52C. difficileRT033 isolates, while all strains signaled positive for the binary toxin genes but were reported as negative forC. difficileby the XpertC. difficile/Epiassay (Cepheid).

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1582. In Vitro Activity of Ceftolozane/Tazobactam against Enterobacterales and Pseudomonas aeruginosa Isolates from Geriatric Patients in the Asia/Pacific region – SMART 2016-2018

Open Forum Infectious Diseases ◽

10.1093/ofid/ofaa439.1762 ◽

2020 ◽

Vol 7 (Supplement_1) ◽

pp. S788-S789

Author(s):

Sibylle Lob ◽

Meredith Hackel ◽

Wei-Ting Chen ◽

Yivonne Khoo ◽

Kanchan Balwani ◽

...

Keyword(s):

Hong Kong ◽

Urinary Tract ◽

Length Of Hospital Stay ◽

Asia Pacific ◽

Surveillance Program ◽

Independent Contractor ◽

In Vitro Susceptibility ◽

Specimen Collection ◽

Genes Encoding

Abstract Background Ceftolozane/tazobactam (C/T) is an antipseudomonal cephalosporin combined with a β-lactamase inhibitor approved by FDA and EMA for complicated urinary tract and intraabdominal infections, and hospital-acquired and ventilator-associated bacterial pneumonia. We evaluated the activity of C/T against isolates collected from patients ≥65 years old as part of the SMART surveillance program in Asia/Pacific. Methods In 2016-2018, 49 clinical laboratories in Australia, Hong Kong, Malaysia, New Zealand, Philippines, Singapore, Korea, Taiwan, Thailand, and Vietnam each collected up to 250 consecutive gram-negative pathogens per year. Susceptibility was determined using CLSI broth microdilution and breakpoints. C/T-nonsusceptible (NS) Enterobacterales (ENT) and P. aeruginosa (PA) isolates were screened by PCR and sequenced for genes encoding β-lactamases (except ENT from 1 site in Taiwan). Results 2082 PA (68.3% lower respiratory tract, 12.7% intraabdominal, 15.1% urinary tract, and 3.0% bloodstream infection isolates) and 8181 ENT isolates (29.8%, 27.8%, 32.5%, and 9.2%, respectively) were collected from patients ≥65 years old. In vitro susceptibility of PA and ENT stratified by length of hospital stay at time of specimen collection (LOS) is shown (Table). C/T maintained activity against 75.5% of 518 P/T-NS, 67.9% of 395 cefepime-NS, and 71.6% of 377 meropenem-NS PA isolates. Among 136 C/T-NS PA isolates, 44.9% carried metallo-β-lactamases (MBL), 0.7% KPC, 1.5% GES carbapenemases, 5.9% only ESBL, and in 47.1% no acquired β-lactamases were detected. Among 878 characterized C/T-NS ENT, 14.1% carried MBL, 5.2% KPC, 3.3% OXA-48-like carbapenemases, and 53.5% AmpC and/or ESBL; no acquired β-lactamases were detected in 23.8% of isolates, of which 89.5% were species with intrinsic AmpC. Table Conclusion Susceptibility of PA and ENT to all studied agents was lower for isolates collected ≥48 than < 48 hours post-admission. C/T was active against >92% of PA in both strata, 7-29 percentage points higher than the studied comparators except amikacin, and against >84% of ENT, 4-30% higher than the comparators except meropenem and amikacin. C/T is a potential new treatment option for older patients with infections caused by ENT and PA in Asia/Pacific. Disclosures Sibylle Lob, PhD, IHMA (Employee)Pfizer, Inc. (Consultant) Wei-Ting Chen, MD, Merck, Sharp & Dohme, Taiwan (Employee) Yivonne Khoo, PhD, Merck, Sharp & Dohme, Malaysia (Employee) Kanchan Balwani, MBBS, MS, Merck, Sharp & Dohme, Hong Kong (Employee) Katherine Young, MS, Merck & Co., Inc. (Employee, Shareholder)Merck & Co., Inc. (Employee, Shareholder) Mary Motyl, PhD, Merck & Co, Inc (Employee, Shareholder) Daniel F. Sahm, PhD, IHMA (Employee)Pfizer, Inc. (Consultant)Shionogi & Co., Ltd. (Independent Contractor)

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