Since the introduction of 10-valent pneumococcal conjugate vaccine (PCV10) into the Finnish national vaccination program in September 2010, the incidence of invasive pneumococcal disease in children ...has decreased steeply in Finland. We studied the antimicrobial susceptibility of invasive and non-invasive
Streptococcus pneumoniae
(pneumococcus) isolated in the Helsinki Metropolitan Area during 2009–2014. We divided the data into two age groups: isolates from patients <5 years old and ≥5 years old. We also studied the serotype distribution of invasive isolates and of a subset of non-invasive multidrug-resistant isolates. The invasive isolate numbers recovered from patients aged <5 years old declined from 33/228 (15%) in 2009 to 8/208 (4%) in 2014 (
p
< 0.001) and non-invasive isolate numbers declined during the same time period from 221/595 (37%) to 119/432 (28%) (
p
< 0.001). At the same time, the proportion of penicillin non-susceptible non-invasive isolates in this age group decreased from 25% (56/220) to 13% (15/119) (
p
= 0.001) and multidrug-resistant isolates from 22% (49/220) to 6% (7/119) (
p
< 0.001), respectively. The number of PCV10 serotype isolates also decreased among the serotyped multidrug-resistant non-invasive isolates. Among patients aged ≥5 years old, the isolate numbers did not show a similar decreasing trend compared to the younger group and, further, the number of non-PCV10 serotype isolates increased in invasive cases. To conclude, the antimicrobial non-susceptibility of pneumococcus has decreased markedly, especially among young patients (<5 years old), following PCV10 implementation in Finland.
Serotype 6D of Streptococcus pneumoniae has been reported in Asia and the Fijian islands among nasopharyngeal carriage isolates. We now report a 6D isolate from a Finnish adult with invasive ...pneumococcal disease. Interestingly, the Finnish isolate and Asian isolate capsule gene loci are almost identical.
Multidrug-resistance among
Streptococcus pneumoniae
isolates, especially of serotype 19A, has increased in several countries recently. Even before the introduction of the pneumococcal conjugate ...vaccine into the Finnish National Vaccination Programme, the proportion of multidrug-resistant (MDR) pneumococci had doubled from 2007 to 2008, when it reached 3.6% in Southern Finland. Our aim was to look for a possible association between antimicrobial susceptibility and clonality among the MDR isolates. Twelve non-invasive isolates non-susceptible to penicillin, erythromycin, clindamycin, trimethoprim/sulfamethoxazole, and doxycycline from 2008 were available for serotyping, genotyping by multilocus sequence typing (MLST), and detection of genes encoding macrolide resistance and adherence-promoting pili. Two isolates were also resistant to ceftriaxone. Five serotypes, 19F, 19A, 6B, 23F, and 14, and six genotypes from three genetic lineages were found, among which CC320 was the largest. All isolates in this study carried the
erm
(B) macrolide resistance gene, and the CC320 isolates additionally carried the
mef
(A/E) macrolide resistance gene. Eleven isolates carried pilus islet 1, while the CC320 isolates also carried the pilus islet 2 genes. The findings emphasize the importance of the careful monitoring of antimicrobial susceptibility and serotype distribution among pneumococci, especially now that antimicrobials and pneumococcal vaccines are in widespread use.
The purpose of this study was to determine the prevalence of acquired antimicrobial resistance in
Streptococcus pneumoniae
isolated from nasopharyngeal swabs and blood and cerebrospinal fluid (CSF) ...specimens of 3,028 children hospitalized with signs or symptoms of pneumonia, sepsis, or meningitis in rural Philippines between 1994 and 2000. Pneumococci were identified using standard methods, serotyped, and their susceptibility to oxacillin, erythromycin, tetracycline, chloramphenicol, and trimethoprim-sulfamethoxazole was determined using the disk diffusion method. Penicillin minimum inhibitory concentrations (MICs) of the oxacillin-resistant isolates were further tested. The clonality of the penicillin-nonsusceptible (PNSP) isolates was analyzed using pulsed-field gel electrophoresis (PFGE) and multi-locus sequence typing (MLST). Altogether 1,048 isolates were analyzed, of which 35 were invasive and 1,013 nasopharyngeal isolates. None was resistant, but 22 (2.1%) were intermediately resistant to penicillin, 4 (0.2%) were resistant to chloramphenicol, 3 (0.2%) to erythromycin, 39 (3.7%) to tetracycline, and 4 (0.2%) to trimethoprim/sulfamethoxazole. Twelve of the 22 PNSP isolates were of serotype 14 and of sequence type 63. These included the two invasive PNSP isolates. PFGE profiling further identified three separate clusters among the sequence of type 63, serotype 14 (ST63
14
) isolates. Antimicrobial resistance in both invasive and nasopharyngeal pneumococcal pediatric isolates in rural Philippines is rare. In spite of this remote setting, the PNSP isolates of the serotype 14 clusters were of ST63 type, which has been described previously on other continents.
Methicillin-resistant Staphylococcus aureus (MRSA) strains from Finland covering years 1997-1999 were studied for the presence of Panton-Valentine leukocidin (PVL) gene loci, and the clinically ...well-defined community-acquired MRSA (CA-MRSA) strains (n = 108) also for staphylococcal chromosomal cassette mec (SCCmec) and multilocus sequence types (MLST). Only a minority (12%) of the CA-MRSA strains contained the PVL gene loci and possessed genotypes formerly described as typical to CA-MRSA strains. The majority of these strains were heterogenous by MLST and pulsed-field gel electrophoresis (PFGE) analysis but, however, harboured the SCCmec cassette type IV. In conclusion, it seems doubtful to consider only molecular characteristics such as the presence of PVL genes as definite markers for CA-MRSA strains.
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.
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.
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.
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.
Abstract
The in vivo role for RNase H1 in mammalian mitochondria has been much debated. Loss of RNase H1 is embryonic lethal and to further study its role in mtDNA expression we characterized a ...conditional knockout of Rnaseh1 in mouse heart. We report that RNase H1 is essential for processing of RNA primers to allow site-specific initiation of mtDNA replication. Without RNase H1, the RNA:DNA hybrids at the replication origins are not processed and mtDNA replication is initiated at non-canonical sites and becomes impaired. Importantly, RNase H1 is also needed for replication completion and in its absence linear deleted mtDNA molecules extending between the two origins of mtDNA replication are formed accompanied by mtDNA depletion. The steady-state levels of mitochondrial transcripts follow the levels of mtDNA, and RNA processing is not altered in the absence of RNase H1. Finally, we report the first patient with a homozygous pathogenic mutation in the hybrid-binding domain of RNase H1 causing impaired mtDNA replication. In contrast to catalytically inactive variants of RNase H1, this mutant version has enhanced enzyme activity but shows impaired primer formation. This finding shows that the RNase H1 activity must be strictly controlled to allow proper regulation of mtDNA replication.
The regulation of mitochondrial RNA life cycles and their roles in ribosome biogenesis and energy metabolism are not fully understood. We used CRISPR/Cas9 to generate heart- and ...skeletal-muscle-specific knockout mice of the pentatricopeptide repeat domain protein 1, PTCD1, and show that its loss leads to severe cardiomyopathy and premature death. Our detailed transcriptome-wide and functional analyses of these mice enabled us to identify the molecular role of PTCD1 as a 16S rRNA-binding protein essential for its stability, pseudouridylation, and correct biogenesis of the mitochondrial large ribosomal subunit. We show that impaired mitoribosome biogenesis can have retrograde signaling effects on nuclear gene expression through the transcriptional activation of the mTOR pathway and upregulation of cytoplasmic protein synthesis and pro-survival factors in the absence of mitochondrial translation. Taken together, our data show that impaired assembly of the mitoribosome exerts its consequences via differential regulation of mitochondrial and cytoplasmic protein synthesis.
Display omitted
•CRISPR/Cas9-engineered intron-exon boundaries enable conditional knockout of Ptcd1•PTCD1 is required for the stability of the 16S rRNA•Pseudouridinylation of the 16S rRNA requires PTCD1•Impaired mitoribosome biogenesis activates the mTOR pathway
Perks et al. engineered intron-exon boundaries using CRISPR/Cas9 to conditionally knock out Ptcd1 in mice. The RNA-binding protein PTCD1 is essential for heart function and regulates the stability and maturation of the 16S rRNA. PTCD1 is required for mitoribosome biogenesis, mitochondrial function, and coordinated nuclear transcription.
Mitochondria are vital in providing cellular energy via their oxidative phosphorylation system, which requires the coordinated expression of genes encoded by both the nuclear and mitochondrial ...genomes (mtDNA). Transcription of the circular mammalian mtDNA depends on a single mitochondrial RNA polymerase (POLRMT). Although the transcription initiation process is well understood, it is debated whether POLRMT also serves as the primase for the initiation of mtDNA replication. In the nucleus, the RNA polymerases needed for gene expression have no such role. Conditional knockout of Polrmt in the heart results in severe mitochondrial dysfunction causing dilated cardiomyopathy in young mice. We further studied the molecular consequences of different expression levels of POLRMT and found that POLRMT is essential for primer synthesis to initiate mtDNA replication in vivo. Furthermore, transcription initiation for primer formation has priority over gene expression. Surprisingly, mitochondrial transcription factor A (TFAM) exists in an mtDNA-free pool in the Polrmt knockout mice. TFAM levels remain unchanged despite strong mtDNA depletion, and TFAM is thus protected from degradation of the AAA(+) Lon protease in the absence of POLRMT. Last, we report that mitochondrial transcription elongation factor may compensate for a partial depletion of POLRMT in heterozygous Polrmt knockout mice, indicating a direct regulatory role of this factor in transcription. In conclusion, we present in vivo evidence that POLRMT has a key regulatory role in the replication of mammalian mtDNA and is part of a transcriptional mechanism that provides a switch between primer formation for mtDNA replication and mitochondrial gene expression.
PDF
