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Lodi L, Rubino C, Ricci S, Indolfi G, Giovannini M, Consales G, Magazzini S, Lai F, Vasarri P, Conti A, Brunelli T, Moriondo M, Azzari C. Neisseria meningitidis with H552Y substitution on rpoB gene shows attenuated behavior in vivo: report of a rifampicin-resistant case following chemoprophylaxis. J Chemother 2020; 32:98-102. [PMID: 32037986 DOI: 10.1080/1120009x.2020.1723967] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
Abstract
We present the first Italian reported case of an invasive meningococcal disease with rifampicin-resistance (Rif-R)secondary to chemoprophylaxis. The case is entered in a cluster of two IMDs registered in Tuscany, Italy, in November 2019 caused by two non-differentiable group-C Neisseria meningitidis belonging to ST-11 clonal-complex. The contact case, differently from the index, harbored H552Y mutation on rpoB gene which is known to confer Rif-R putting a high-cost fee on bacterial fitness. The extremely mild clinical presentation in the contact can constitute an in vivo demonstration of the virulence attenuation observed in vitro for H552Ymutants. Clinicians should be aware of the possibility of secondary cases with induced Rif-R and keep a high level of suspicion on contacts who received rifampicin-chemoprophylaxis. Molecular characterization of Rif-R should be performed routinely directly on biological samples and not only on isolates, in order to rapidly detect rare cases of resistance and consequently modify chemoprophylaxis for contacts.
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Affiliation(s)
- Lorenzo Lodi
- Post-graduate School of Pediatrics, University of Florence, Florence, Italy
| | - Chiara Rubino
- Post-graduate School of Pediatrics, University of Florence, Florence, Italy
| | - Silvia Ricci
- Department of Health Sciences, University of Florence and Meyer Children's University Hospital, Florence, Italy
| | - Giuseppe Indolfi
- Department of Pediatrics, Meyer Children's University Hospital, Florence, Italy
| | - Mattia Giovannini
- Post-graduate School of Pediatrics, University of Florence, Florence, Italy
| | | | - Simone Magazzini
- Department of Intensive Care Unit, Santo Stefano Hospital, Prato, Italy
| | - Franco Lai
- Department of Intensive Care Unit, Santo Stefano Hospital, Prato, Italy
| | | | - Antonella Conti
- Clinical Chemistry and Microbiology Laboratory, Santo Stefano Hospital, Prato, Italy
| | - Tamara Brunelli
- Clinical Chemistry and Microbiology Laboratory, Santo Stefano Hospital, Prato, Italy
| | - Maria Moriondo
- Department of Health Sciences, University of Florence and Meyer Children's University Hospital, Florence, Italy
| | - Chiara Azzari
- Department of Health Sciences, University of Florence and Meyer Children's University Hospital, Florence, Italy
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Gorla MC, Pinhata JMW, Dias UJ, de Moraes C, Lemos AP. Surveillance of antimicrobial resistance in Neisseria meningitidis strains isolated from invasive cases in Brazil from 2009 to 2016. J Med Microbiol 2018; 67:750-756. [PMID: 29717974 DOI: 10.1099/jmm.0.000743] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
PURPOSE To describe the antimicrobial resistance profile of Neisseria meningitidis isolates causing invasive disease in Brazil from 2009 to 2016. METHODOLOGY Among 3548 N. meningitidis isolates received, 2888 (81.4 %) were analysed for antimicrobial resistance using the broth microdilution technique, as recommended by the Clinical and Laboratory Standards Institute. Isolates were tested for ciprofloxacin, chloramphenicol, ceftriaxone, penicillin G, ampicillin and rifampin. RESULTS All the isolates tested were susceptible to ceftriaxone, while 953 (33.0 %), 1307 (45.3 %) and 2 (0.07 %) isolates were penicillin G-, ampicillin- and rifampin-intermediate, respectively. Resistance to rifampin, ciprofloxacin and chloramphenicol was shown by three isolates (0.1 %), two isolates (0.07 %) and one (0.03 %) isolate, respectively. Although no isolates were resistant to penicillin G in the period of 2009-2016, our results show an upward trend in minimum inhibitory concentrations (MICs) for this drug as of 2010 (P<0.001). There was no significant difference between different gender and age groups of patients for reduced susceptibility to penicillin G. There was a higher frequency of isolates with reduced susceptibility to penicillin G in the South and Southeast regions (P<0.001). This reduced susceptibility was also associated with serotype 19 inside serogroup B (P<0.001). CONCLUSION Despite the decrease in susceptibility to penicillin G and ampicillin observed from 2010, the overall resistance of N. meningitidis isolates to the antimicrobials tested remained uncommon and sporadic, confirming their efficacy for chemoprophylaxis or treatment of invasive meningococcal disease (IMD) in Brazil. Continued surveillance of N. meningitidis antimicrobial susceptibility profiles is important in order to monitor variations in resistance either geographically, over time or in association with emergent clones.
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Affiliation(s)
- Maria Cecília Gorla
- Bacteriology Department, Adolfo Lutz Institute, Av. Dr Arnaldo, 351, São Paulo, CEP 01246-902, SP, Brazil
| | | | - Ueslei José Dias
- Bacteriology Department, Adolfo Lutz Institute, Av. Dr Arnaldo, 351, São Paulo, CEP 01246-902, SP, Brazil
| | - Camile de Moraes
- Secretariat of Health Surveillance, Ministry of Health, Esplanada dos Ministérios, Bloco G, Brasília, Federal District CEP 70058-900, Brazil
| | - Ana Paula Lemos
- Bacteriology Department, Adolfo Lutz Institute, Av. Dr Arnaldo, 351, São Paulo, CEP 01246-902, SP, Brazil
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Colicchio R, Pagliuca C, Pastore G, Cicatiello AG, Pagliarulo C, Talà A, Scaglione E, Sammartino JC, Bucci C, Alifano P, Salvatore P. Fitness Cost of Rifampin Resistance in Neisseria meningitidis: In Vitro Study of Mechanisms Associated with rpoB H553Y Mutation. Antimicrob Agents Chemother 2015; 59:7637-49. [PMID: 26416867 PMCID: PMC4649176 DOI: 10.1128/aac.01746-15] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2015] [Accepted: 09/23/2015] [Indexed: 12/14/2022] Open
Abstract
Rifampin chemoprophylaxis against Neisseria meningitidis infections led to the onset of rifampin resistance in clinical isolates harboring point mutations in the rpoB gene, coding for the RNA polymerase β chain. These resistant strains are rare in medical practice, suggesting their decreased fitness in the human host. In this study, we isolated rifampin-resistant rpoB mutants from hypervirulent serogroup C strain 93/4286 and analyzed their different properties, including the ability to grow/survive in different culture media and in differentiated THP-1 human monocytes and to compete with the wild-type strain in vitro. Our results demonstrate that different rpoB mutations (H553Y, H553R, and S549F) may have different effects, ranging from low- to high-cost effects, on bacterial fitness in vitro. Moreover, we found that the S549F mutation confers temperature sensitivity, possibly explaining why it is observed very rarely in clinical isolates. Comparative high-throughput RNA sequencing analysis of bacteria grown in chemically defined medium demonstrated that the low-cost H553Y substitution resulted in global transcriptional changes that functionally mimic the stringent response. Interestingly, many virulence-associated genes, including those coding for meningococcal type IV pili, porin A, adhesins/invasins, IgA protease, two-partner secretion system HrpA/HrpB, enzymes involved in resistance to oxidative injury, lipooligosaccharide sialylation, and capsular polysaccharide biosynthesis, were downregulated in the H553Y mutant compared to their level of expression in the wild-type strain. These data might account for the reduced capacity of this mutant to grow/survive in differentiated THP-1 cells and explain the rarity of H553Y mutants among clinical isolates.
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Affiliation(s)
- Roberta Colicchio
- Department of Molecular Medicine and Medical Biotechnology, Federico II University Medical School, Naples, Italy SDN-Foundation, Naples, Italy
| | - Chiara Pagliuca
- Department of Molecular Medicine and Medical Biotechnology, Federico II University Medical School, Naples, Italy Ceinge Advanced Biotechnologies, Naples, Italy
| | - Gabiria Pastore
- Department of Sciences and Technologies, University of Sannio, Benevento, Italy
| | | | - Caterina Pagliarulo
- Department of Sciences and Technologies, University of Sannio, Benevento, Italy
| | - Adelfia Talà
- Department of Biological and Environmental Sciences and Technologies, University of Salento, Lecce, Italy
| | - Elena Scaglione
- Department of Molecular Medicine and Medical Biotechnology, Federico II University Medical School, Naples, Italy
| | - Josè Camilla Sammartino
- Department of Molecular Medicine and Medical Biotechnology, Federico II University Medical School, Naples, Italy
| | - Cecilia Bucci
- Department of Biological and Environmental Sciences and Technologies, University of Salento, Lecce, Italy
| | - Pietro Alifano
- Department of Biological and Environmental Sciences and Technologies, University of Salento, Lecce, Italy
| | - Paola Salvatore
- Department of Molecular Medicine and Medical Biotechnology, Federico II University Medical School, Naples, Italy Ceinge Advanced Biotechnologies, Naples, Italy
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Rifaximin in the treatment of irritable bowel syndrome: is there a high risk for development of antimicrobial resistance? J Clin Gastroenterol 2013; 47:205-11. [PMID: 23340064 DOI: 10.1097/mcg.0b013e31827559a3] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Irritable bowel syndrome (IBS), a chronic, nonfatal illness is commonly encountered in clinical practice; however, treatment options are limited and often ineffectual. Despite this, there is increasing evidence that bacterial overgrowth in the bowel (dysbiosis) may be an etiological factor in IBS. This has lead to studies in which the antibiotic agent rifaximin has been used to reduce the microbial burden in the bowel, to some extent alleviating the symptoms of IBS. Rifaximin is a member of the rifamycin class of antibiotics, which when administered orally has the distinctions of being gut specific coupled with poor systemic absorption, characteristics that are suggested to limit the development of bacterial resistance. The rifamycins are currently used to treat serious human diseases including tuberculosis, meningococcal disease, methicillin-resistant Staphylococcus aureus and Clostridium difficile infections. The use of rifamycins in the treatment of these diseases is associated with the development of antibiotic resistance over time. When considering the importance of the rifamycins in the treatment of serious human diseases, the large number of patients affected by IBS, and the lack of scientific evidence available on the development of antibiotic resistance to rifaximin over the long-term when used in the gut, it is advisable that the use of rifaximin as a therapy for IBS should be limited to single, acute, short-term treatment.
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Resolution of a meningococcal disease outbreak from whole-genome sequence data with rapid Web-based analysis methods. J Clin Microbiol 2012; 50:3046-53. [PMID: 22785191 DOI: 10.1128/jcm.01312-12] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The increase in the capacity and reduction in cost of whole-genome sequencing methods present the imminent prospect of such data being used routinely in real time for investigations of bacterial disease outbreaks. For this to be realized, however, it is necessary that generic, portable, and robust analysis frameworks be available, which can be readily interpreted and used in real time by microbiologists, clinicians, and public health epidemiologists. We have achieved this with a set of analysis tools integrated into the PubMLST.org website, which can in principle be used for the analysis of any pathogen. The approach is demonstrated with genomic data from isolates obtained during a well-characterized meningococcal disease outbreak at the University of Southampton, United Kingdom, that occurred in 1997. Whole-genome sequence data were collected, de novo assembled, and deposited into the PubMLST Neisseria BIGSdb database, which automatically annotated the sequences. This enabled the immediate and backwards-compatible classification of the isolates with a number of schemes, including the following: conventional, extended, and ribosomal multilocus sequence typing (MLST, eMLST, and rMLST); antigen gene sequence typing (AGST); analysis based on genes conferring antibiotic susceptibility. The isolates were also compared to a reference isolate belonging to the same clonal complex (ST-11) at 1,975 loci. Visualization of the data with the NeighborNet algorithm, implemented in SplitsTree 4 within the PubMLST website, permitted complete resolution of the outbreak and related isolates, demonstrating that multiple closely related but distinct strains were simultaneously present in asymptomatic carriage and disease, with two causing disease and one responsible for the outbreak itself.
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Ion torrent personal genome machine sequencing for genomic typing of Neisseria meningitidis for rapid determination of multiple layers of typing information. J Clin Microbiol 2012; 50:1889-94. [PMID: 22461678 DOI: 10.1128/jcm.00038-12] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Neisseria meningitidis causes invasive meningococcal disease in infants, toddlers, and adolescents worldwide. DNA sequence-based typing, including multilocus sequence typing, analysis of genetic determinants of antibiotic resistance, and sequence typing of vaccine antigens, has become the standard for molecular epidemiology of the organism. However, PCR of multiple targets and consecutive Sanger sequencing provide logistic constraints to reference laboratories. Taking advantage of the recent development of benchtop next-generation sequencers (NGSs) and of BIGSdb, a database accommodating and analyzing genome sequence data, we therefore explored the feasibility and accuracy of Ion Torrent Personal Genome Machine (PGM) sequencing for genomic typing of meningococci. Three strains from a previous meningococcus serogroup B community outbreak were selected to compare conventional typing results with data generated by semiconductor chip-based sequencing. In addition, sequencing of the meningococcal type strain MC58 provided information about the general performance of the technology. The PGM technology generated sequence information for all target genes addressed. The results were 100% concordant with conventional typing results, with no further editing being necessary. In addition, the amount of typing information, i.e., nucleotides and target genes analyzed, could be substantially increased by the combined use of genome sequencing and BIGSdb compared to conventional methods. In the near future, affordable and fast benchtop NGS machines like the PGM might enable reference laboratories to switch to genomic typing on a routine basis. This will reduce workloads and rapidly provide information for laboratory surveillance, outbreak investigation, assessment of vaccine preventability, and antibiotic resistance gene monitoring.
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Evolutionary changes in antimicrobial resistance of invasive Neisseria meningitidis isolates in Belgium from 2000 to 2010: increasing prevalence of penicillin nonsusceptibility. Antimicrob Agents Chemother 2012; 56:2268-72. [PMID: 22290951 DOI: 10.1128/aac.06310-11] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022] Open
Abstract
This study was conducted to evaluate the evolution of the antimicrobial susceptibility of Neisseria meningitidis causing invasive diseases in Belgium in the period of January 2000 to December 2010. A total of 1,933 cases of N. meningitidis from invasive infections were analyzed by antimicrobial susceptibility testing at the Belgian Meningococcal Reference Centre. The majority of strains were susceptible to antibiotics that are currently used for the treatment and prophylaxis of meningococcal disease, but the prevalence of clinical isolates with reduced susceptibility to penicillin increased over the years. The phenotyping, genotyping, and determination of MICs of penicillin G were performed. The systematic shift of the curves toward higher penicillin MICs in the susceptible population indicated that this population became less sensitive to penicillin in this period. A 402-bp DNA fragment in the 3' end of penA was sequenced for the 296 nonsusceptible meningococcal strains isolated between 2000 and 2010 to examine the genetic diversity and evolution of their penA gene. In conclusion, the data obtained in our study support the statement that the position of penicillin G as a first choice in the treatment of invasive meningococcal diseases in Belgium should be reexamined. Despite an important number of isolates displaying a reduced susceptibility to penicillin, at present the expanded-spectrum cephalosporins, such as ceftriaxone, are not affected. The follow-up of the evolutionary changes in antimicrobial resistance has also proved to be essential for the recommendation of an appropriate antimicrobial treatment for invasive meningococcal diseases.
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Harrison OB, Brueggemann AB, Caugant DA, van der Ende A, Frosch M, Gray S, Heuberger S, Krizova P, Olcen P, Slack M, Taha MK, Maiden MCJ. Molecular typing methods for outbreak detection and surveillance of invasive disease caused by Neisseria meningitidis, Haemophilus influenzae and Streptococcus pneumoniae, a review. MICROBIOLOGY (READING, ENGLAND) 2011; 157:2181-2195. [PMID: 21622526 PMCID: PMC3980633 DOI: 10.1099/mic.0.050518-0] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Invasive disease caused by the encapsulated bacteria Neisseria meningitidis, Haemophilus influenzae and Streptococcus pneumoniae remains an important cause of morbidity and mortality worldwide, despite the introduction of successful conjugate polysaccharide vaccines that target disease-associated strains. In addition, resistance, or more accurately reduced susceptibility, to therapeutic antibiotics is spreading in populations of these organisms. There is therefore a continuing requirement for the surveillance of vaccine and non-vaccine antigens and antibiotic susceptibilities among isolates from invasive disease, which is only partially met by conventional methods. This need can be met with molecular and especially nucleotide sequence-based typing methods, which are fully developed in the case of N. meningitidis and which could be more widely deployed in clinical laboratories for S. pneumoniae and H. influenzae.
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Affiliation(s)
- Odile B. Harrison
- Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK
| | | | - Dominique A. Caugant
- Department of Bacteriology and Immunology, Norwegian Institute of Public Health, PO Box 4404 Nydalen, NO-0403 Oslo, Norway
| | - Arie van der Ende
- Academic Medical Center, Department of Medical Microbiology, Reference Laboratory for Bacterial Meningitis, PO Box 22660, 1100 DD Amsterdam, The Netherlands
| | - Matthias Frosch
- Institut für Hygiene und Mikrobiologie, Universität Würzburg, Josef-Schneider Strasse 2, 97080 Würzburg, Germany
| | - Stephen Gray
- Meningococcal Reference Unit, Health Protection Agency, PO Box 209, Clinical Sciences Building 2, Manchester Royal Infirmary, Oxford Road, Manchester M13 9WZ, UK
| | - Sigrid Heuberger
- Österreichische Agentur für Gesundheit und Ernährungssicherheit GmbH, Bereich Humanmedizin, Institut für medizinische Mikrobiologie und Hygiene, Beethovenstraße 6, A-8010 Graz, Austria
| | - Paula Krizova
- National Reference Laboratory for Meningococcal Infections, National Institute of Public Health, Srobarova 48, Prague, Czech Republic
| | - Per Olcen
- Department of Laboratory Medicine, Clinical Microbiology and Immunology, Orebro University Hospital, SE-701 85 Orebro, Sweden
| | - Mary Slack
- Respiratory and Systemic Infection Laboratory, Health Protection Agency Centre for Infections, 61 Colindale Avenue, London NW9 5EQ, UK
| | | | - Martin C. J Maiden
- Department of Zoology, University of Oxford, South Parks Road, Oxford OX1 3PS, UK
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Antimicrobial susceptibility of Neisseria meningitidis strains isolated from meningitis cases in Brazil from 2006 to 2008. Enferm Infecc Microbiol Clin 2011; 29:85-9. [DOI: 10.1016/j.eimc.2010.07.016] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2010] [Revised: 06/21/2010] [Accepted: 07/06/2010] [Indexed: 11/18/2022]
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Neri A, Mignogna G, Fazio C, Giorgi A, Schininà ME, Stefanelli P. Neisseria meningitidis rifampicin resistant strains: analysis of protein differentially expressed. BMC Microbiol 2010; 10:246. [PMID: 20868485 PMCID: PMC2955632 DOI: 10.1186/1471-2180-10-246] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2010] [Accepted: 09/24/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Several mutations have been described as responsible for rifampicin resistance in Neisseria meningitidis. However, the intriguing question on why these strains are so rare remains open. The aim of this study was to investigate the protein content and to identify differential expression in specific proteins in two rifampicin resistant and one susceptible meningococci using two-dimensional electrophoresis (2-DE) combined with mass spectrometry. RESULTS In our experimental conditions, able to resolve soluble proteins with an isoelectric point between 4 and 7, twenty-three proteins have been found differentially expressed in the two resistant strains compared to the susceptible. Some of them, involved in the main metabolic pathways, showed an increased expression, mainly in the catabolism of pyruvate and in the tricarboxylic acid cycle. A decreased expression of proteins belonging to gene regulation and to those involved in the folding of polypeptides has also been observed. 2-DE analysis showed the presence of four proteins displaying a shift in their isoelectric point in both resistant strains, confirmed by the presence of amino acid changes in the sequence analysis, absent in the susceptible. CONCLUSIONS The analysis of differentially expressed proteins suggests that an intricate series of events occurs in N. meningitidis rifampicin resistant strains and the results here reported may be considered a starting point in understanding their decreased invasion capacity. In fact, they support the hypothesis that the presence of more than one protein differentially expressed, having a role in the metabolism of the meningococcus, influences its ability to infect and to spread in the population. Different reports have described and discussed how a drug resistant pathogen shows a high biological cost for survival and that may also explain why, for some pathogens, the rate of resistant organisms is relatively low considering the widespread use of a particular drug. This seems the case of rifampicin resistant meningococci.
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Affiliation(s)
- Arianna Neri
- Department of Infectious, Parasitic and Immune-mediated Diseases, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Rome, Italy
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Multicenter study for defining the breakpoint for rifampin resistance in Neisseria meningitidis by rpoB sequencing. Antimicrob Agents Chemother 2010; 54:3651-8. [PMID: 20606072 DOI: 10.1128/aac.00315-10] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Identification of clinical isolates of Neisseria meningitidis that are resistant to rifampin is important to avoid prophylaxis failure in contacts of patients, but it is hindered by the absence of a breakpoint for resistance, despite many efforts toward standardization. We examined a large number (n = 392) of clinical meningococcal isolates, spanning 25 years (1984 to 2009), that were collected in 11 European countries, Argentina, and the Central African Republic. The collection comprises all clinical isolates with MICs of > or = 0.25 mg/liter (n = 161) received by the national reference laboratories for meningococci in the participating countries. Representative isolates displaying rifampin MICs of < 0.25 mg/liter were also examined (n = 231). Typing of isolates was performed, and a 660-bp DNA fragment of the rpoB gene was sequenced. Sequences differing by at least one nucleotide were defined as unique rpoB alleles. The geometric mean of the MICs was calculated for isolates displaying the same allele. The clinical isolates displaying rifampin MICs of > 1 mg/liter possessed rpoB alleles with nonsynonymous mutations at four critical amino acid residues, D542, H552, S548, and S557, that were absent in the alleles found in all isolates with MICs of < or = 1 mg/liter. Rifampin-susceptible isolates could be defined as those with MICs of < or = 1 mg/liter. The rpoB allele sequence and isolate data have been incorporated into the PubMLST Neisseria database (http://pubmlst.org/neisseria/). The rifampin-resistant isolates belonged to diverse genetic lineages and were associated with lower levels of bacteremia and inflammatory cytokines in mice. This biological cost may explain the lack of clonal expansion of these isolates.
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