Emergence of Neisseria meningitidis with decreased susceptibility to ciprofloxacin in Argentina

Molecular detection of fluoroquinolone-resistant Neisseria meningitidis by using mismatched PCR-restriction fragment length polymorphism technique

Ciprofloxacin (CIP) is a commonly used antibiotic for meningococcal chemoprophylaxis, and the mutations in the quinolone resistance-determining region of gyrA are associated with CIP-resistant Neisseria meningitidis. Here, we established a mismatched PCR-restriction fragment length polymorphism (RFLP) assay to detect a mutation at codon 91 of gyrA, followed by high-level CIP-resistant meningococci. We designed PCR-RFLP primers to detect the T91I mutation in gyrA by introducing an artificial AciI cleavage site. This assay was performed using 26 N. meningitidis strains whose gyrA sequences have been characterized. The amplified 160 bp PCR product from gyrA was digested into three fragments (80, 66, and 14 bp) when there was no mutation, or two fragments (146 and 14 bp) when there was a mutation at codon 91. A correlation was observed between the mismatched PCR-RFLP assay and gyrA sequencing. This rapid, simple, and accurate assay has the potential to detect CIP-resistant N. meningitidis in clinical microbiology laboratories, contributing to the appropriate antibiotic selection for meningococcal chemoprophylaxis, will help maintain an effective treatment for close contacts of IMD patients, and prevent the spread of CIP-resistant N. meningitidis.

Meningococcal Quinolone Resistance Originated from Several Commensal Neisseria Species

Quinolone resistance is increasing in Neisseria meningitidis, with its prevalence in China being high (>70%), but its origin remains unknown. The aim of this study was to investigate the donors of mutation-harboring gyrA alleles in N. meningitidis A total of 198 N. meningitidis isolates and 293 commensal Neisseria isolates were collected between 2005 and 2018 in Shanghai, China. The MICs of ciprofloxacin were determined using the agar dilution method. The resistance-associated genes gyrA and parC were sequenced for all isolates, while a few isolates were sequenced on the Illumina platform. The prevalences of quinolone resistance in the N. meningitidis and commensal Neisseria isolates were 67.7% (134/198) and 99.3% (291/293), respectively. All 134 quinolone-resistant N. meningitidis isolates possessed mutations in T91 (n = 123) and/or D95 (n = 12) of GyrA, with 7 isolates also harboring ParC mutations and exhibiting higher MICs. Phylogenetic analysis of the gyrA sequence identified six clusters. Among the 71 mutation-harboring gyrA alleles found in 221 N. meningitidis isolates and genomes (n = 221), 12 alleles (n = 103, 46.6%) were included in the N. meningitidis cluster, while 20 alleles (n = 56) were included in the N. lactamica cluster, 27 alleles (n = 49) were included in the N. cinerea cluster, and 9 alleles (n = 10) were included in the N. subflava cluster. Genomic analyses identified the exact N. lactamica donors of seven mutation-harboring gyrA alleles (gyrA92, gyrA97, gyrA98, gyrA114, gyrA116, gyrA151, and gyrA230) and the N. subflava donor isolate of gyrA171, with the sizes of the recombinant fragments ranging from 634 to 7,499 bp. Transformation of gyrA fragments from these donor strains into a meningococcal isolate increased its ciprofloxacin MIC from 0.004 μg/ml to 0.125 or 0.19 μg/ml and to 0.5 μg/ml with further transformation of an additional ParC mutation. Over half of the quinolone-resistant N. meningitidis isolates acquired resistance by horizontal gene transfer from three commensal Neisseria species. Quinolone resistance in N. meningitidis increases in a stepwise manner.

Prevalence, sequence type, and quinolone resistance of Neisseria lactamica carried in children younger than 15 years in Shanghai, China

OBJECTIVE

Neisseria lactamica has an important influence on carriage and antimicrobial susceptibility of N. meningitidis, a major pathogen of septicemia and meningitis. In China, quinolone resistance is highly prevalent in N. meningitidis but unknown in N. lactamica. This study investigates the carriage rate, sequence type, and ciprofloxacin resistance of N. lactamica in children in China.

METHODS

During 2014-2016, throat swabs were collected from 2,239 children in Shanghai. The ciprofloxacin minimum inhibitory concentrations of the isolates were determined by the agar dilution method.

RESULTS

The overall carriage rate of N. lactamica was higher (8.9%) than that of N. meningitidis (0.9%) and peaked at two years (37.1%). The resistance frequency of N. lactamica to ciprofloxacin was 98.5% (197/200). There were 65 sequence types (STs). Clonal complex (cc) 640 (45.5%) dominated, while ST-14031 was predominant (37%, 74/200). All isolates possessed a GyrA mutation; 17 isolates (8.5%) harbored additionally a ParC mutation. Assigned to 39 different alleles, the gyrA sequences from these N. lactamica isolates formed an N. lactamica cluster, which also included eight alleles from N. meningitidis.

CONCLUSION

The N. lactamica isolates in China showed distinct characteristics with lower genetic diversity and a much higher prevalence of quinolone resistance than in other countries.

Surveillance of antimicrobial resistance in Neisseria meningitidis strains isolated from invasive cases in Brazil from 2009 to 2016

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.

Emergence of resistance to ciprofloxacin in Neisseria meningitidis in Brazil

To prevent secondary invasive meningococcal disease (IMD) cases and outbreaks, antimicrobial prophylaxis of high-risk contacts is indicated. This study reports two ciprofloxacin-resistant Neisseria meningitidis strains in Brazil. The 3523 N. meningitidis isolates collected throughout Brazil from 2009 to 2016 were evaluated for antimicrobial resistance. Meningococcal isolates showing minimal inhibitory concentrations, MICs≥0.125µg ml^-1 to ciprofloxacin, were analysed to determine the presence of mutations in the quinolone resistance-determining regions (QRDRs) of gyrA and parC genes. Two ciprofloxacin-resistant N. meningitidis isolates were found, both presenting a single mutation in the quinolone resistance-determining region of the gyrA gene. These results confirmed that ciprofloxacin is still a first-line drug for chemoprophylaxis. However, we highlight the importance of continued surveillance to monitor the trends of N. meningitidis susceptibility profiles to the antimicrobials recommended for chemoprophylaxis and IMD treatment.

Ciprofloxacin-resistant Neisseria meningitidis in Canada: likely imported strains

The prevalence of ciprofloxacin-resistant Neisseria meningitidis in Canada was studied by testing 346 isolates received at the National Microbiology Laboratory during the calendar years 2013 to 2015. Of the 277 individual invasive and 69 noninvasive isolates tested, only 2 serogroup C (MenC) isolates were found to be resistant to ciprofloxacin. Both MenC were typed as sequence type (ST)-4821, a unique clone found mainly in China, thus suggesting both isolates might be from travel-related or imported cases. This prompted us to also examine 6 serogroup A (MenA) isolates in our collection, since MenA is not currently endemic in Canada. Three MenA from 2006 were resistant to ciprofloxacin and they were typed as ST-4789. A ciprofloxacin-resistant MenA strain of ST-4789 was responsible for a meningococcal disease outbreak in Delhi, India, in 2005 to 2006. The 2 MenC and 3 MenA ciprofloxacin-resistant N. meningitidis were from patients residing in British Columbia.

Population-Based Surveillance of Neisseria meningitidis Antimicrobial Resistance in the United States

Isolates of Neisseria meningitidis collected in 2004, 2008, 2010, and 2011 from an active population-based surveillance system in the United States were tested for susceptibility to antimicrobials used for treatment and chemoprophylaxis of meningococcal disease. Susceptibility remains high and stable.

Background. Antimicrobial treatment and chemoprophylaxis of patients and their close contacts is critical to reduce the morbidity and mortality and prevent secondary cases of meningococcal disease. Through the 1990's, the prevalence of antimicrobial resistance to commonly used antimicrobials among Neisseria meningitidis was low in the United States. Susceptibility testing was performed to ascertain whether the proportions of isolates with reduced susceptibility to antimicrobials commonly used for N meningitidis have increased since 2004 in the United States.

Methods. Antimicrobial susceptibility testing was performed by broth microdilution on 466 isolates of N meningitidis collected in 2004, 2008, 2010, and 2011 from an active, population-based surveillance system for susceptibility to ceftriaxone, ciprofloxacin, penicillin G, rifampin, and azithromycin. The molecular mechanism of reduced susceptibility was investigated for isolates with intermediate or resistant phenotypes.

Results. All isolates were susceptible to ceftriaxone and azithromycin, 10.3% were penicillin G intermediate (range, 8% in 2008–16.7% in 2010), and <1% were ciprofloxacin, rifampin, or penicillin G resistant. Of the penicillin G intermediate or resistant isolates, 63% contained mutations in the penA gene associated with reduced susceptibility to penicillin G. All ciprofloxacin-resistant isolates contained mutations in the gyrA gene associated with reduced susceptibility.

Conclusions. Resistance of N meningitidis to antimicrobials used for empirical treatment of meningitis in the United States has not been detected, and resistance to penicillin G and chemoprophylaxis agents remains uncommon. Therapeutic agent recommendations remain valid. Although periodic surveillance is warranted to monitor trends in susceptibility, routine clinical testing may be of little use.

Shifts in the Antibiotic Susceptibility, Serogroups, and Clonal Complexes of Neisseria meningitidis in Shanghai, China: A Time Trend Analysis of the Pre-Quinolone and Quinolone Eras

BACKGROUND

Fluoroquinolones have been used broadly since the end of the 1980s and have been recommended for Neisseria meningitidis prophylaxis since 2005 in China. The aim of this study was to determine whether and how N. meningitidis antimicrobial susceptibility, serogroup prevalence, and clonal complex (CC) prevalence shifted in association with the introduction and expanding use of quinolones in Shanghai, a region with a traditionally high incidence of invasive disease due to N. meningitidis.

METHODS AND FINDINGS

A total of 374 N. meningitidis isolates collected by the Shanghai Municipal Center for Disease Control and Prevention between 1965 and 2013 were studied. Shifts in the serogroups and CCs were observed, from predominantly serogroup A CC5 (84%) in 1965-1973 to serogroup A CC1 (58%) in 1974-1985, then to serogroup C or B CC4821 (62%) in 2005-2013. The rates of ciprofloxacin nonsusceptibility in N. meningitidis disease isolates increased from 0% in 1965-1985 to 84% (31/37) in 2005-2013 (p < 0.001). Among the ciprofloxacin-nonsusceptible isolates, 87% (27/31) were assigned to either CC4821 (n = 20) or CC5 (n = 7). The two predominant ciprofloxacin-resistant clones were designated ChinaCC4821-R1-C/B and ChinaCC5-R14-A. The ChinaCC4821-R1-C/B clone acquired ciprofloxacin resistance by a point mutation, and was present in 52% (16/31) of the ciprofloxacin-nonsusceptible disease isolates. The ChinaCC5-R14-A clone acquired ciprofloxacin resistance by horizontal gene transfer, and was found in 23% (7/31) of the ciprofloxacin-nonsusceptible disease isolates. The ciprofloxacin nonsusceptibility rate was 47% (7/15) among isolates from asymptomatic carriers, and nonsusceptibility was associated with diverse multi-locus sequence typing profiles and pulsed-field gel electrophoresis patterns. As detected after 2005, ciprofloxacin-nonsusceptible strains were shared between some of the patients and their close contacts. A limitation of this study is that isolates from 1986-2004 were not available and that only a small sample of convenience isolates from 1965-1985 were available.

CONCLUSIONS

The increasing prevalence of ciprofloxacin resistance since 2005 in Shanghai was associated with the spread of hypervirulent lineages CC4821 and CC5. Two resistant meningococcal clones ChinaCC4821-R1-C/B and ChinaCC5-R14-A have emerged in Shanghai during the quinolone era. Ciprofloxacin should be utilized with caution for the chemoprophylaxis of N. meningitidis in China.

Genetic diversity and clonal characteristics of ciprofloxacin-resistant meningococcal strains in China

The purpose of the present study was to identify the clonal characteristics and gyrA gene diversity of ciprofloxacin-resistant meningococcal strains in China. One hundred and forty-one ciprofloxacin-resistant and 103 ciprofloxacin-susceptible meningococcal strains were selected for multilocus sequence typing. Of these, 54 ciprofloxacin-resistant and 42 ciprofloxacin-susceptible strains were selected for gyrA gene sequencing. Of the three clonal complexes prevalent in China, serogroup A of ST-5 complex (CC5) and serogroup C/B strains of CC4821 had a high proportion of ciprofloxacin resistance, whereas CC11 serogroup W strains were all susceptible. Nucleotide and amino acid sequences of the gyrA gene among ciprofloxacin-resistant strains showed more diversity than those among ciprofloxacin-susceptible strains. All ciprofloxacin-resistant strains had a T91I mutation and the ciprofloxacin-susceptible strains had no T91I mutation. Phylogenetic analysis showed that the gyrA gene sequences of CC4821 serogroup B/C strains, CC11 serogroup W, CC1 serogroup A, ciprofloxacin-susceptible CC5 serogroup A and reference strains had high similarity. By contrast, the ciprofloxacin-resistant CC5 serogroup A strains had a highly conserved gyrA gene sequence which was different (94.8% similarity) from that in the above strains. The results of our investigation showed that the high proportion of ciprofloxacin resistance in Neisseria meningitidis is associated with certain sequence types (STs) or clonal complexes (CCs). The prevalence of certain CCs with a high proportion of ciprofloxacin resistance can facilitate the spread of ciprofloxacin resistance.

Phenotypic and genotypic characteristics of Neisseria meningitidis disease-causing strains in Argentina, 2010

Phenotypic and genotypic characterization of 133 isolates of Neisseria meningitidis obtained from meningococcal disease cases in Argentina during 2010 were performed by the National Reference Laboratory as part of a project coordinated by the PAHO within the SIREVA II network. Serogroup, serotype, serosubtype and MLST characterization were performed. Minimum Inhibitory Concentration to penicillin, ampicillin, ceftriaxone, rifampin, chloramphenicol, tetracycline and ciprofloxacin were determined and interpreted according to CLSI guidelines. Almost 49% of isolates were W135, and two serotype:serosubtype combinations, W135:2a:P1.5,2:ST-11 and W135:2a:P1.2:ST-11 accounted for 78% of all W135 isolates. Serogroup B accounted for 42.1% of isolates, and was both phenotypically and genotypically diverse. Serogroup C isolates represented 5.3% of the dataset, and one isolate belonging to the ST-198 complex was non-groupable. Isolates belonged mainly to the ST-11 complex (48%) and to a lesser extent to the ST-865 (18%), ST-32 (9,8%) and the ST-35 complexes (9%). Intermediate resistance to penicillin and ampicillin was detected in 35.4% and 33.1% of isolates respectively. Two W135:2a:P1.5,2:ST-11:ST-11 isolates presented resistance to ciprofloxacin associated with a mutation in the QRDR of gyrA gene Thr91-Ile. These data show serogroup W135 was the first cause of disease in Argentina in 2010, and was strongly associated with the W135:2a:P1.5,2:ST-11 epidemic clone. Serogroup B was the second cause of disease and isolates belonging to this serogroup were phenotypically and genotypically diverse. The presence of isolates with intermediate resistance to penicillin and the presence of fluorquinolone-resistant isolates highlight the necessity and importance of maintaining and strengthening National Surveillance Programs.

Target gene sequencing to define the susceptibility of Neisseria meningitidis to ciprofloxacin

Meningococcal gyrA gene sequence data, MICs, and mouse infection were used to define the ciprofloxacin breakpoint for Neisseria meningitidis. Residue T91 or D95 of GyrA was altered in all meningococcal isolates with MICs of ≥ 0.064 μg/ml but not among isolates with MICs of ≤ 0.032 μg/ml. Experimental infection of ciprofloxacin-treated mice showed slower bacterial clearance when GyrA was altered. These data suggest a MIC of ≥ 0.064 μg/ml as the ciprofloxacin breakpoint for meningococci and argue for the molecular detection of ciprofloxacin resistance.

Evaluation of quinolone resistance-determining region mutations and efflux pump expression in Neisseria meningitidis resistant to fluoroquinolones

Three Neisseria meningitidis serotype B strains displaying elevated ciprofloxacin MIC values (0.06 and 0.25 μg/mL) and a GyrA alteration at T91I have been described in the United States by Wu et al. [Wu et al., (2009) Emergence of ciprofloxacin-resistant Neisseria meningitidis in North America. N. Engl. J. Med. 360:886-892] and were further evaluated here by reference broth microdilution against fluoroquinolones (FQ) and other antimicrobial agents. Additional quinolone resistance-determining region (QRDR) mutations and alterations in structure and expression of the mtrCDE efflux system, including its intergenic regions, were also analyzed. Two strains showed ciprofloxacin and levofloxacin MIC values at 0.25 μg/mL, and 1 strain had a ciprofloxacin MIC at 0.06 μg/mL. In addition to T91I, the 2 strains displaying higher FQ MIC values also possessed a T173A alteration on GyrA. All components of the efflux pump mtrCDE (also associated with rifampin resistance) were intact, excluding the presence of insertions/deletions within the pump operon. The promoter region (mtrR) was fully sequenced and was distinct from FQ-susceptible controls. Isolates with higher ciprofloxacin MIC values had identical promoter region, whereas the isolate displaying a lower ciprofloxacin MIC value possessed a different sequence. Expression experiments showed discrepancies of the mRNA in pump components. The most remarkable difference was for the outer membrane protein encoded by mtrE that was hyperexpressed (>3600× elevated compared to control) in the strain displaying a ciprofloxacin MIC value of 0.06 μg/mL. These results confirm that T91I alteration on GyrA had an important role in elevating ciprofloxacin MIC values; however, additional resistance determinants, including other gyrA mutations, also contribute to higher FQ MIC levels. Alterations in expression of mtrCED pump appear to have minimal influence on ciprofloxacin resistance, and this finding was supported by low rifampin susceptible-level results (MIC, ≤0.008 to 0.03 μg/mL).

Resistance surveillance studies: a multifaceted problem--the fluoroquinolone example

INTRODUCTION

This review summarizes data on the fluoroquinolone resistance epidemiology published in the previous 5 years.

MATERIALS AND METHODS

The data reviewed are stratified according to the different prescription patterns by either primary- or tertiary-care givers and by indication. Global surveillance studies demonstrate that fluoroquinolone- resistance rates increased in the past several years in almost all bacterial species except Staphylococcus pneumoniae and Haemophilus influenzae causing community-acquired respiratory tract infections (CARTIs), as well as Enterobacteriaceae causing community-acquired urinary tract infections. Geographically and quantitatively varying fluoroquinolone resistance rates were recorded among Gram-positive and Gram-negative pathogens causing healthcare-associated respiratory tract infections. One- to two-thirds of Enterobacteriaceae producing extended-spectrum β-lactamases (ESBLs) were fluoroquinolone resistant too, thus, limiting the fluoroquinolone use in the treatment of community- as well as healthcare-acquired urinary tract and intra-abdominal infections. The remaining ESBL-producing or plasmid-mediated quinolone resistance mechanisms harboring Enterobacteriaceae were low-level quinolone resistant. Furthermore, 10-30 % of H. influenzae and S. pneumoniae causing CARTIs harbored first-step quinolone resistance determining region (QRDR) mutations. These mutants pass susceptibility testing unnoticed and are primed to acquire high-level fluoroquinolone resistance rapidly, thus, putting the patient at risk. The continued increase in fluoroquinolone resistance affects patient management and necessitates changes in some current guidelines for the treatment of intra-abdominal infections or even precludes the use of fluoroquinolones in certain indications like gonorrhea and pelvic inflammatory diseases in those geographic areas in which fluoroquinolone resistance rates and/or ESBL production is high. Fluoroquinolone resistance has been selected among the commensal flora colonizing the gut, nose, oropharynx, and skin, so that horizontal gene transfer between the commensal flora and the offending pathogen as well as inter- and intraspecies recombinations contribute to the emergence and spread of fluoroquinolone resistance among pathogenic streptococci. Although interspecies recombinations are not yet the major cause for the emergence of fluoroquinolone resistance, its existence indicates that a large reservoir of fluoroquinolone resistance exists. Thus, a scenario resembling that of a worldwide spread of β-lactam resistance in pneumococci is conceivable. However, many resistance surveillance studies suffer from inaccuracies like the sampling of a selected patient population, restricted geographical sampling, and undefined requirements of the user, so that the results are biased. The number of national centers is most often limited with one to two participating laboratories, so that such studies are point prevalence but not surveillance studies. Selected samples are analyzed predominantly as either hospitalized patients or patients at risk or those in whom therapy failed are sampled; however, fluoroquinolones are most frequently prescribed by the general practitioner. Selected sampling results in a significant over-estimation of fluoroquinolone resistance in outpatients. Furthermore, the requirements of the users are often not met; the prescribing physician, the microbiologist, the infection control specialist, public health and regulatory authorities, and the pharmaceutical industry have diverse interests, which, however, are not addressed by different designs of a surveillance study. Tools should be developed to provide customer-specific datasets.

CONCLUSION

Consequently, most surveillance studies suffer from well recognized but uncorrected biases or inaccuracies. Nevertheless, they provide important information that allows the identification of trends in pathogen incidence and antimicrobial resistance.

Deletion of the Correia element in the mtr gene complex of Neisseria meningitidis

The mtr gene complex in Neisseria meningitidis encodes an efflux pump that is responsible for export of antibacterial hydrophobic agents. The promoter region of the mtrCDE operon harbours an insertion sequence known as a Correia element, and a binding site for the integration host factor (IHF) is present at the centre of the Correia element. It has been suggested that the expression of the mtrCDE operon in meningococci is subject to transcriptional regulation by the IHF and post-transcriptional regulation by cleavage in the inverted repeat of the Correia element. The promoter region of the mtrCDE operon as well as the association of changes at that point with decreased susceptibility to antimicrobial drugs in 606 Neisseria meningitidis strains were analysed in this study. Two different deletions were present in the analysed region. The first one, found in seven strains, corresponded to absence of the Correia element. The second one, affecting the −10 region and first 100 bp of the mtrR gene and present in 57 isolates, was only found in ST-1624 isolates. None of the deletions were associated with decreased susceptibility to antimicrobial drugs. Although most of the meningococcal strains carry the Correia element at that position, its deletion is not an exception.

Determination of CEM-101 activity tested against clinical isolates of Neisseria meningitidis from a worldwide collection

The activity of CEM-101, a fluoroketolide, was compared to those of 11 other antimicrobial agents using the reference broth microdilution method tested against 103 Neisseria meningitidis strains, including ciprofloxacin-nonsusceptible isolates with confirmed gyrA (T91I) mutations. Among the tested isolates, 79.6% were serogroup B or C and all isolates were susceptible to ceftriaxone, azithromycin, minocycline, and rifampin. However, penicillin-nonsusceptible strains were observed (15.5%) and susceptibility to trimethoprim-sulfamethoxazole was only 50.5%. CEM-101 was the most active macrolide-like compound (MIC(90), < or = 0.015 microg/ml) compared with MIC(90)s of telithromycin (MIC(90), 0.03 microg/ml), azithromycin and clarithromycin (MIC(90), 0.12 microg/ml), and erythromycin (MIC(90), 0.25 microg/ml). CEM-101 could provide a potent alternative for the prophylaxis of meningococcal disease.

Antibiotic susceptibility and characteristics of Neisseria meningitidis isolates from the African meningitis belt, 2000 to 2006: phenotypic and genotypic perspectives

Up-to-date information regarding the antibiotic susceptibility of Neisseria meningitidis strains from African countries is highly limited. Our aim was to comprehensively describe the antibiotic susceptibilities of a selection of N. meningitidis isolates recovered between 2000 and 2006 from 18 African countries, mainly those within the meningitis belt. Susceptibilities to 11 antibiotics were determined using Etest for 137 N. meningitidis isolates (stringently selected from 693 available isolates). The isolates were also characterized by serogrouping, multilocus sequence typing, genosubtyping, and penA allele identification. All N. meningitidis isolates were susceptible to ceftriaxone, chloramphenicol, and ciprofloxacin. No isolate produced beta-lactamase. Only three isolates (2%) displayed reduced susceptibility to penicillin G. The two isolates with the highest penicillin G MICs were the only isolates showing reduced susceptibility to ampicillin and cefuroxime. One of these isolates was also resistant to penicillin V. One percent of isolates displayed reduced susceptibility to rifampin, while 52% of the isolates were resistant to tetracycline, 74% were resistant to erythromycin, and 94% were resistant to sulfadiazine. The MICs of rifampin and tetracycline seemed to be associated with the serogroup of the isolates. In total, 18 sequence types (STs), 10 genosubtypes, and 8 different penA alleles were identified; the most common were ST-7, P1.20,9,35-1, and penA4, respectively. A high level of correlation was found between ST, genosubtype, and penA allele. In conclusion, N. meningitidis isolates from the African meningitis belt remain highly susceptible to the antibiotics used. Regarding beta-lactam antibiotics, rare isolates showed a reduced susceptibility to penicillins, but the expanded-spectrum cephalosporins are not affected at present.

Ciprofloxacin-resistant Neisseria meningitidis, Delhi, India

Decreased susceptibility of Neisseria meningitidis isolates to ciprofloxacin emerged from an outbreak in Delhi, India. Results of antimicrobial susceptibility testing of the meningococcal isolates to ciprofloxacin and further sequencing of DNA gyrase A quinolone-resistance–determining region confirmed the emergence of ciprofloxacin resistance in the outbreak.

Pyrosequencing of the DNA gyrase gene in Neisseria species: effective indicator of ciprofloxacin resistance in Neisseria gonorrhoeae

The quinolone resistance determining region (QRDR) of the gyrA gene in ciprofloxacin-susceptible strains (n=53) and strains of Neisseria spp. with reduced susceptibility (n=70) was determined by the pyrosequencing method. Results showed that the QRDR of the gyrA gene is an effective molecular indicator of resistance to ciprofloxacin in Neisseria gonorrhoeae, and presumably in Neisseria meningitidis, but not in all other Neisseria spp. This sequence was not unique for N. gonorrhoeae and seems unsuitable for species verification of N. gonorrhoeae. However, whether it is also possible to use this region for verification depends on the specificity of the primary screening method used.

Antibiotic resistant meningococci in Europe: Any need to act?

Meningococcal disease is a serious and rapidly progressing illness. It is therefore very important to monitor changes in the level of antibiotic susceptibility among clinical isolates. Different aspects such as interpretation of laboratory results, determination of breakpoints predicting treatment failure as well as definition of susceptibility levels in clinical samples using molecular methods are critical points for the surveillance of antibiotic resistance in Neisseria meningitidis. Within the strategic framework outlined by the EU.MenNet project, several objectives were identified to analyze 'The spread of antibiotic resistant meningococci in Europe', including the extent of antimicrobial resistance, its association with particular meningococcal lineages and geographical areas, as well as molecular characterization of the mechanisms involved, particularly in penicillin resistance. A heterogeneous figure for the frequency of intermediate resistance to penicillin appears across Europe. This heterogeneity may reflect different clonal lineages and/or uneven access to antibiotics in each country. In addition, the use of different criteria for the methodology used for definition cannot be avoided. The description of five specific changes associated with intermediate resistance to penicillin also allows the design of PCR-based tools to objectify results and for application in clinical samples.

Resistance testing of meningococci: the recommendations of the European Monitoring Group on Meningococci

One of the most controversial topics concerning Neisseria meningitidis is the definition of antimicrobial resistance. A process of harmonization, promoted by the European Monitoring Group on Meningococci (EMGM), is already in progress. There are several aspects of the MIC definition for meningococcal strains for which a consensus is needed, as follows. (1) What methods can be used? At present, both the Etest and agar dilution methods are recommended by the EMGM. Microdilution, also a recommended method, is not used across Europe. (2) What media produce the most reliable data? The use of Mueller-Hinton medium supplemented with 5% blood is recommended for the MIC determination of N. meningitidis by both Etest and agar dilution method. (3) What is the minimum set of antimicrobial agents to be tested? A minimum set should include rifampicin, ciprofloxacin (or another quinolone), penicillin, ampicillin and ceftriaxone. (4) What are the most suitable breakpoints for definition? There is no widely accepted robust evidence base for the definition of breakpoints. Although progress has been made in achieving a standardized methodology, we are still far from obtaining common breakpoints for antimicrobial resistance definition. These differences will imply inability for building a common epidemiologic figure about drug resistance.

Interlaboratory comparison of PCR-based methods for detection of penicillin G susceptibility in Neisseria meningitidis

We carried out a study for the nonculture detection of susceptibility of Neisseria meningitis to penicillin G in three laboratories of the European Monitoring Group on Meningococci (EMGM). Thirteen clinical samples (cerebrospinal fluids) and corresponding bacterial isolates from 13 cases of invasive meningococcal infection were distributed to the three laboratories. The MICs of penicillin G were determined for the isolates. Each laboratory used an "in-house" PCR-based method to determine alterations to the penA gene, which is associated with a reduced susceptibility to penicillin G. Nucleotide sequences from the 3' end of the penA gene were also determined. We observed a good correlation between genotyping of penA and the phenotypic determination (MIC) of susceptibility to penicillin G. The results obtained by the three methods for penA in the samples correlated very well with those obtained in bacterial isolates and with sequence data. The kappa coefficient that was used to estimate the level of agreement between genotypic results varied between 0.65 and 1, indicating a good agreement. This suggests that genotyping can predict susceptibility of N. meningitidis to penicillin G. These data strongly suggest that genotyping of penA should be used to determine meningococcal susceptibility to penicillin G in culture-negative cases. Although the nucleotide sequence of penA may be the gold standard in genotyping of penA, the less expensive PCR-based approach reported in this study may be quicker when a large number of isolates and clinical samples need to be tested.