Bactericidal killing of meningococcal W strains isolated in Argentina by the sera of adolescents and infants immunized with 4-component meningococcal serogroup B vaccine (4CMenB).

Invasive meningococcal disease (IMD) is a life-threatening disease caused by meningococcal serogroups A, B, C, W, X, and Y, of which B and W are most common in Argentina. The 4-component meningococcal serogroup B (4CMenB) vaccine contains three purified recombinant protein antigens (Neisseria adhesin A [NadA], factor H binding protein [fHbp], and Neisserial Heparin Binding Antigen [NHBA]) and outer membrane vesicles (OMV), which is derived from the New Zealand epidemic strain and contains Porin A 1.4. These antigens are present and conserved in strains that belong to other serogroups. In this study, we show that 10/11 (91%) meningococcal serogroup W (MenW) strains selected to be representative of MenW isolates that caused IMD in Argentina during 2010-2011 were killed in bactericidal assays by the sera of adolescents and infants who had been immunized with the 4CMenB vaccine. We also show that MenW strains that caused IMD in Argentina during 2018-2021 were genetically similar to the earlier strains, indicating that the 4CMenB vaccine would likely still provide protection against current MenW strains. These data highlight the potential of 4CMenB vaccination to protect adolescents and infants against MenW strains that are endemic in Argentina.

Oropharyngeal meningococcal carriage in children and adolescents, a single center study in Buenos Aires, Argentina.

BACKGROUND: Neisseria meningitidis (Nm) pharyngeal carriage is a necessary condition for invasive disease. We present the first carriage study in children in Buenos Aires, Argentina, considering 2017 as a transition year. Aims: to assess the rate of Nm carriage, to determine genogroup, clonal complex and outer membrane protein distribution, to determine carriage risk factors by age. METHODS: Cross-sectional study including children 1-17 yrs, at Ricardo Gutiérrez Children's Hospital in Buenos Aires 2017. Oro-pharyngeal swabs were taken and cultured within a short time after collection. Genogroup was determined by PCR and clonal complex by MLST. Categorical variables were analyzed. RESULTS: A total of 1,751 children were included. Group 1: 943 children 1-9 yrs, 38 Nm were isolated; overall carriage 4.0%. Genogroup distribution: B 26.3%, W 5.3%, Y 2.6%, Z 5.3%, other groups 7.9% and capsule null (cnl) 52.6%. Participating in extracurricular activities was the only independent predictor of Nm carriage. Group 2: 808 children 10-17 yrs, 76 Nm were isolated; overall carriage 9.4%. Genogroup distribution: B 19.7%, C 5.3%, W 7.9%, Y 9.2%, Z 5.3%, other groups 7.9% and cnl 44.7%. Independent predictors of carriage: attending pubs/night clubs and passive smoking (adjusted OR: 0.55, 95%CI = 0.32-0.93; p = 0.025). CONCLUSIONS: Overall carriage was higher in 10-17 yrs. The isolates presenting the cnl locus were prevalent in both age groups and genogroup B was the second most frequent.

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.

Multicenter study for defining the breakpoint for rifampin resistance in Neisseria meningitidis by rpoB sequencing.

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.

PorA types in Neisseria meningitidis serogroup B isolated in Argentina from 2001 to 2003: implications for the design of an outer membrane protein-based vaccine.

Identification of Neisseria meningitidis PorA types remains important, as the PorA protein is a major immunogenic component of several meningococcal vaccines under development. In this study, 191 N. meningitidis serogroup B isolates collected in Argentina through active laboratory-based surveillance from 2001 to 2003 were serosubtyped. Nucleotide sequences of the porA variable region 1 (VR1) and VR2 regions were determined in 52 non-serosubtypeable isolates. A substantial number of distinct VR types were identified, and a new VR2 variant from the P1.16 family was described. This is the first report describing PorA types in N. meningitidis serogroup B isolates in Argentina. Furthermore, the wide diversity of subtypes detected by serosubtyping and genosubtyping reveals the difficulty in designing a useful outer-membrane vaccine applicable in this country. A possible mechanism responsible for altered PorA expression was analysed in two PorA types.