International links between Streptococcus pneumoniae vaccine serotype 4 sequence type (ST) 801 in Northern European shipyard outbreaks of invasive pneumococcal disease

BACKGROUND

Pneumococcal disease outbreaks of vaccine preventable serotype 4 sequence type (ST)801 in shipyards have been reported in several countries. We aimed to use genomics to establish any international links between them.

METHODS

Sequence data from ST801-related outbreak isolates from Norway (n = 17), Finland (n = 11) and Northern Ireland (n = 2) were combined with invasive pneumococcal disease surveillance from the respective countries, and ST801-related genomes from an international collection (n = 41 of > 40,000), totalling 106 genomes. Raw data were mapped and recombination excluded before phylogenetic dating.

RESULTS

Outbreak isolates were relatively diverse, with up to 100 SNPs (single nucleotide polymorphisms) and a common ancestor estimated around the year 2000. However, 19 Norwegian and Finnish isolates were nearly indistinguishable (0-2 SNPs) with the common ancestor dated around 2017.

CONCLUSION

The total diversity of ST801 within the outbreaks could not be explained by recent transmission alone, suggesting that harsh environmental and associated living conditions reported in the shipyards may facilitate invasion of colonising pneumococci. However, near identical strains in the Norwegian and Finnish outbreaks does suggest that transmission between international shipyards also contributed to those outbreaks. This indicates the need for improved preventative measures in this working population including pneumococcal vaccination.

Murine monoclonal antibodies to PorA of Neisseria meningitidis show reduced protective activity in vivo against B:15:P1.7,16 subtype variants in an infant rat infection model

The major outer membrane protein PorA of Neisseria meningitidis is the target for bactericidal serosubtyping antibodies and is currently considered as a potential vaccine candidate against group B meningococcal disease. Although the minor antigenic variability of the PorA has been increasingly recognized and described, its implication for vaccine design remains unclear. In this study, the protective activity of murine monoclonal PorA specific antibodies against four isogenic meningococcal P1.7,16 target strains, the prototype P1.7,16a and three loop 4 point mutation variants (designated P1.7,16b to d) constructed from reference strain H44/76 (B:15:P1.7,16a), was evaluated in the infant rat infection model. All monoclonal antibodies had been obtained by immunization of mice with outer membrane protein preparations from meningococcal serosubtype P1.7,16 reference strain H44/76. A challenge dose of 10(5)cfu/pup was given i.p. 1-2 h after the i.p. injection of 1:100 diluted antibodies, and the development of bacteremia was assessed by culturing blood samples taken 6 h after challenge. MN14C11.6, a reference monoclonal antibody for serosubtype P1.7 epitope located in predicted loop 1 (VR1) identical in all the variants, was equally protective against all loop 4 variants. The three P1.16 specific monoclonal antibodies tested (MN5C11G, MN12H2 and 62D12-8) all completely protected animals against the prototype P1.7,16a, variably against the P1.7,16b and P1.7,16c, but not against the P1.7,16d variant. Our findings therefore suggest that certain subtype variants may escape protection in vivo conferred by PorA specific antibodies.

The infant rat model adapted to evaluate human sera for protective immunity to group B meningococci

The infant rat infection model previously developed to evaluate protective ability of passively administered murine antibodies to group B meningococcal (MenB) surface antigens was adapted for human sera. Several challenge doses were tested, aiming at sensitive detection of protection with little interassay variability. Doses of 10(5) and 10(6) colony forming units of strain IH5341 (MenB:15:P1.7,16) injected intraperitoneally gave consistently high levels of bacteremia and meningitis developed in 6 h in 50-100% of the pups. A monoclonal antibody mAb735 to the MenB capsule, injected 1-2 h before bacterial challenge, gave full protection at a dose of 2 microg/pup. Sera from adult volunteers immunized with a MenB outer membrane vesicle vaccine reproducibly reduced bacterial counts in the blood and cerebrospinal fluid, whereas a normal human serum, lacking bactericidal and opsonophagocidal activity, was unprotective.

Behavioral sensitivity and ethanol potentiation of the N-methyl-D-aspartate receptor antagonist MK-801 in a rat line selected for high ethanol sensitivity

The role of the N-methyl-D-aspartate (NMDA) receptors in differential ethanol sensitivity of the alcohol-insensitive [alcohol-tolerant (AT)] and alcohol-sensitive [alcohol-nontolerant (ANT)] rat lines selected for low and high sensitivity to ethanol-induced (2 g/kg) motor impairment was studied in behavioral and neurochemical experiments. A noncompetitive antagonist of the NMDA receptor, dizocilpine maleate (MK-801; 0.2 mg/kg), impaired motor function in ANT rats, but not in AT rats, in a tilting plane test. The impairment was further potentiated by a dose (0.75 g/kg) of ethanol, which alone was inactive. This effect was apparently not associated with the locomotor stimulation produced by MK-801 (0.1 and 0.2 mg/kg), because stimulation did not differ between the rat lines. Locomotor stimulation was potentiated by the low ethanol dose in both rat lines. Ethanol treatment decreased the cerebellar and hippocampal cGMP concentrations both with and without MK-801 pretreatment in both rat lines. In situ hybridization using oligonucleotide probes specific for NMDA receptor subunit mRNAs NR1 and NR2A, B, C, and D revealed no clear differences in brain regional expression between ANT and AT rates. These results indicate that the alcohol-sensitive ANT rats are very sensitive to a low dose of ethanol in the presence of NMDA receptor antagonism, consistent with the hypothesis that this receptor system is involved in acute ethanol intoxication.

Pharmacologic actions of subtype-selective and novel GABAergic ligands in rat lines with differential sensitivity to ethanol

Alcohol-nontolerant (ANT) rats, produced by selective breeding for high sensitivity to motor-impairing effects of ethanol, have a point mutation in the cerebellar gamma-aminobutyric acid type A (GABAA) receptor alpha 6 subunit, which has been proposed to underlie enhanced sensitivity to benzodiazepine agonists as well. We compared ANT and alcohol-tolerant (AT) rats using behavioral and neurochemical methods to assess the significance of alpha 6- and non alpha 6-containing GABAA receptor subtypes. Motor performance in a tilting plane test was largely unaffected by a type I benzodiazepine receptor-preferring agonist, zolpidem [1-10 mg/kg, intraperitoneally (IP)], partial benzodiazepine agonists bretazenil and ZG-63 (both at 40 mg/kg, IP), and a novel broad-spectrum anticonvulsant loreclezole (40 mg/kg, IP) in both ANT and AT rats. In contrast, diazepam (10 mg/kg, IP) impaired performance of the ANT but not AT animals. These data, supported by results from brain regional autoradiography of [3H]Ro15-4513 and membrane binding of [3H]ZG-63 and [35S]TBPS as influenced by these ligands, strongly suggest that only ligands with full agonist actions on mutant (ANT) but not wild-type (AT) alpha 6-containing GABAA receptors are able to produce motor impairment in the ANT rats.