Evaluation of the 'HG Group B Streptococcus' loop-mediated isothermal amplification assay for accurate identification of Streptococcus agalactiae

This study evaluated the HiberGene Group B Streptococcus test, a CE-IVD-approved molecular assay for rapid detection of Streptococcus agalactiae [Group B Streptococcus (GBS)] in human clinical specimens. Performance of the assay in terms of specificity, sensitivity and genotype inclusivity was investigated using an extended specificity panel of 113 human and animal GBS isolates, and eight isolates from other streptococcal species, from the isolate collection of the German National Reference Center for Streptococci. Broth cultures were tested according to the manufacturer's protocol, including lysis, heat denaturation and isothermal amplification. All 104/104 (100 %) human GBS isolates of nine serotypes (Ia, Ib, II, III, IV, V, VI, VII, VIII and non-typeable) were correctly identified by the assay as GBS. Additionally, 7/9 (78 %) GBS isolates from elephants were also correctly identified. Six isolates of other streptococcal species/subspecies (Streptococcus anginosus, S. constellatus, S. castoreus, S. dysgalactiae and S. dysgalactiae equisimilis) were correctly reported as negative. Two S. pyogenes (Group A Streptococcus) isolates gave invalid results. The HG Group B Streptococcus assay identified human GBS isolates in culture with 100 % sensitivity.

Heterogeneity of penicillin-non-susceptible group B streptococci isolated from a single patient in Germany

OBJECTIVES

Streptococcus agalactiae [group B streptococci (GBS)] have been considered uniformly susceptible to penicillin. However, increasing reports from Asia and North America are documenting penicillin-non-susceptible GBS (PRGBS) with mutations in pbp genes. Here we report, to the best of our knowledge, the first two PRGBS isolates recovered in Europe (AC-13238-1 and AC-13238-2), isolated from the same patient.

METHODS

Two different colony morphologies of GBS were noted from a surgical abscess drainage sample. Both were serotyped and antimicrobial susceptibility testing was performed by different methodologies. High-throughput sequencing was done to compare the isolates at the genomic level, to identify their capsular type and ST, to evaluate mutations in the pbp genes and to compare the isolates with the genomes of other PRGBS isolates sharing the same serotype and ST.

RESULTS

Isolates AC-13238-1 and AC-13238-2 presented MICs above the EUCAST and CLSI breakpoints for penicillin susceptibility. Both shared the capsular type Ia operon and ST23. Genomic analysis uncovered differences between the two isolates in seven genes, including altered pbp genes. Deduced amino acid sequences revealed critical substitutions in PBP2X in both isolates. Comparison with serotype Ia clonal complex 23 PRGBS from the USA reinforced the similarity between AC-13238-1 and AC-13238-2, and their divergence from the US strains.

CONCLUSIONS

Our results support the in-host evolution of β-lactam-resistant GBS, with two PRGBS variants being isolated from one patient.

[Psychosis due to idiopathic basal ganglia calcification]

Idiopathic basal ganglia calcification is a rare neuropathological syndrome characterised by symmetrical and bilateral calcifications found primarily in the basal ganglia. Psychosis is describedas an acute presentation of idiopathic ganglia calcification. We describe the development of psychosis in a 48-year-old man, initially hospitalised on the neurology ward due to syncope. A ct scan of the brain showed bilateral, symmetrical calcification of the basal ganglia and nucleus dentatus. Laboratory research excluded other pathological disorders. The patient was referred to a psychiatric ward, where the administration of risperidone led to alleviation of his mental state. This case report underlines the importance of an accurate, comprehensive differential diagnosis and the associated significance of neuroimaging.

Protection of Escherichia coli cells against extreme turgor by activation of MscS and MscL mechanosensitive channels: identification of genes required for MscS activity

Mechanosensitive channels are ubiquitous amongst bacterial cells and have been proposed to have major roles in the adaptation to osmotic stress, in particular in the management of transitions from high to low osmolarity environments. Electrophysiological measurements have identified multiple channels in Escherichia coli cells. One gene, mscL, encoding a large conductance channel has previously been described, but null mutants were without well-defined phenotypes. Here, we report the characterization of a new gene family required for MscS function, YggB and KefA, which has enabled a rigorous test of the role of the channels. The channel determined by KefA does not appear to have a major role in managing the transition from high to low osmolarity. In contrast, analysis of mutants of E.coli lacking YggB and MscL shows that mechanosensitive channels are designed to open at a pressure change just below that which would cause cell disruption leading to death.