Megapneumonia Coinfection: pneumococcus, Mycoplasma pneumoniae,

We report a young girl who died of Streptococcus pneumoniae 19A pneumonia, septic shock, and hemolytic uremic syndrome despite prior pneumococcal vaccination, appropriate antibiotics, and aggressive intensive care support. Serotype 19A is not covered by the 7- or 10-valent pneumococcal vaccines. Mycoplasma pneumoniae and metapneumovirus were simultaneously detected by PCR in the nasopharyngeal and tracheal aspirates. The pneumococcus is penicillin sensitive. Although infections with each of these pathogens alone are typically mild, this case highlights that co-infection with the triple respiratory pathogens possibly contributed to the fatal outcome of this child. Also, the new policy in Hong Kong to use PCV13 may help prevent further cases of serotype 19A infections

Subspecies typing of Streptococcus agalactiae based on ribosomal subunit protein mass variation by MALDI-TOF MS

Background: A ribosomal subunit protein (rsp)-based matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) method was developed for fast subspecies-level typing of Streptococcus agalactiae (Group B Streptococcus, GBS), a major cause of neonatal sepsis and meningitis. Methods: A total of 796 GBS whole genome sequences, covering the genetic diversity of the global GBS population, were used to in silico predict molecular mass variability of 28 rsp and to identify unique rsp mass combinations, termed “rsp-profiles”. The in silico established GBS typing scheme was validated by MALDI-TOF MS analysis of GBS isolates at two independent research sites in Europe and South East Asia. Results: We identified in silico 62 rsp-profiles, with the majority (>80%) of the 796 GBS isolates displaying one of the six rsp-profiles 1-6. These dominant rsp-profiles classify GBS strains in high concordance with the core-genome based phylogenetic clustering. Validation of our approach by in-house MALDI-TOF MS analysis of 248 GBS isolates and external analysis of 8 GBS isolates showed that across different laboratories and MALDI-TOF MS platforms, the 28 rsp were detected reliably in the mass spectra, allowing assignment of clinical isolates to rsp-profiles at high sensitivity (99%) and specificity (97%). Our approach distinguishes the major phylogenetic GBS genotypes, identifies hyper-virulent strains, predicts the probable capsular serotype and surface protein variants and distinguishes between GBS genotypes of human and animal origin. Conclusion: We combine the information depth of whole genome sequences with the highly cost efficient, rapid and robust MALDI-TOF MS approach facilitating high-throughput, inter-laboratory, large-scale GBS epidemiological and clinical studies based on pre-defined rsp-profiles

Comparative transcriptomics of multidrug-resistant Acinetobacter baumannii in response to antibiotic treatments

Abstract Multidrug-resistant Acinetobacter baumannii, a major hospital-acquired pathogen, is a serious health threat and poses a great challenge to healthcare providers. Although there have been many genomic studies on the evolution and antibiotic resistance of this species, there have been very limited transcriptome studies on its responses to antibiotics. We conducted a comparative transcriptomic study on 12 strains with different growth rates and antibiotic resistance profiles, including 3 fast-growing pan-drug-resistant strains, under separate treatment with 3 antibiotics, namely amikacin, imipenem, and meropenem. We performed deep sequencing using a strand-specific RNA-sequencing protocol, and used de novo transcriptome assembly to analyze gene expression in the form of polycistronic transcripts. Our results indicated that genes associated with transposable elements generally showed higher levels of expression under antibiotic-treated conditions, and many of these transposon-associated genes have previously been linked to drug resistance. Using co-expressed transposon genes as markers, we further identified and experimentally validated two novel genes of which overexpression conferred significant increases in amikacin resistance. To the best of our knowledge, this study represents the first comparative transcriptomic analysis of multidrug-resistant A. baumannii under different antibiotic treatments, and revealed a new relationship between transposons and antibiotic resistance

Population structure and virulence gene profiles of Streptococcus agalactiae collected from different hosts worldwide

Streptococcus agalactiae is a leading cause of morbidity and mortality among neonates and causes severe infections in pregnant women and nonpregnant predisposed adults, in addition to various animal species worldwide. Still, information on the population structure of S. agalactiae and the geographical distribution of different clones is limited. Further data are urgently needed to identify particularly successful clones and obtain insights into possible routes of transmission within one host species and across species borders. We aimed to determine the population structure and virulence gene profiles of S. agalactiae strains from a diverse set of sources and geographical origins. To this end, 373 S. agalactiae isolates obtained from humans and animals from five different continents were typed by DNA microarray profiling. A total of 242 different S. agalactiae strains were identified and further analyzed. Particularly successful clonal lineages, hybridization patterns, and strains were identified that were spread across different continents and/or were present in more than one host species. In particular, several strains were detected in both humans and cattle, and several canine strains were also detected in samples from human, bovine, and porcine hosts. The findings of our study suggest that although S. agalactiae is well adapted to various hosts including humans, cattle, dogs, rodents, and fish, interspecies transmission is possible and occurs between humans and cows, dogs, and rabbits. The virulence and resistance gene profiles presented enable new insights into interspecies transmission and make a crucial contribution to the identification of suitable targets for therapeutic agents and vaccines

A simple, rapid typing method for Streptococcus agalactiae based on ribosomal subunit proteins by MALDI-TOF MS

Streptococcus agalactiae (Group B Streptococcus, GBS), is a frequent human colonizer and a leading cause of neonatal meningitis as well as an emerging pathogen in non-pregnant adults. GBS possesses a broad animal host spectrum, and recent studies proved atypical GBS genotypes can cause human invasive diseases through animal sources as food-borne zoonotic infections. We applied a MALDI-TOF MS typing method, based on molecular weight variations of predefined 28 ribosomal subunit proteins (rsp) to classify GBS strains of varying serotypes into major phylogenetic lineages. A total of 249 GBS isolates of representative and varying capsular serotypes from patients and animal food sources (fish and pig) collected during 2016-2018 in Hong Kong were analysed. Over 84% (143/171) noninvasive carriage GBS strains from patients were readily typed into 5 globally dominant rsp-profiles. Among GBS strains from food animals, over 90% (57/63) of fish and 13% (2/15) of pig GBS matched with existing rsp-profiles, while the remainder were classified into two novel rsp-profiles and we failed to assign a fish strain into any cluster. MALDI-TOF MS allowed for high-throughput screening and simultaneous detection of novel, so far not well described GBS genotypes. The method shown here is rapid, simple, readily transferable and adapted for use in a diagnostic microbiology laboratory with potential for the surveillance of emerging GBS genotypes with zoonotic potential

Role of Two-Component System Response Regulator bceR in the Antimicrobial Resistance, Virulence, Biofilm Formation, and Stress Response of Group B Streptococcus

Group B Streptococcus (GBS; Streptococcus agalactiae) is a leading cause of sepsis in neonates and pregnant mothers worldwide. Whereas the hyper-virulent serogroup III clonal cluster 17 has been associated with neonatal disease and meningitis, serogroup III ST283 was recently implicated in invasive disease among non-pregnant adults in Asia. Here, through comparative genome analyses of invasive and non-invasive ST283 strains, we identified a truncated DNA-binding regulator of a two-component system in a non-invasive strain that was homologous to Bacillus subtilis bceR, encoding the bceRSAB response regulator, which was conserved among GBS strains. Using isogenic knockout and complementation mutants of the ST283 strain, we demonstrated that resistance to bacitracin and the human antimicrobial peptide cathelicidin LL-37 was reduced in the ΔbceR strain with MICs changing from 64 and 256 μg/ml to 0.25 and 64 μg/ml, respectively. Further, the ATP-binding cassette transporter was upregulated by sub-inhibitory concentrations of bacitracin in the wild-type strain. Upregulation of dltA in the wild-type strain was also observed and thought to explain the increased resistance to antimicrobial peptides. DltA, an enzyme involved in D-alanylation during the synthesis of wall teichoic acids, which mediates reduced antimicrobial susceptibility, was previously shown to be regulated by the bceR-type regulator in Staphylococcus aureus. In a murine infection model, we found that the ΔbceR mutation significantly reduced the mortality rate compared to that with the wild-type strain (p < 0.01). Moreover, this mutant was more susceptible to oxidative stress compared to the wild-type strain (p < 0.001) and was associated with reduced biofilm formation (p < 0.0001). Based on 2-DGE and mass spectrometry, we showed that downregulation of alkyl hydroperoxide reductase (AhpC), a Gls24 family stress protein, and alcohol dehydrogenase (Adh) in the ΔbceR strain might explain the attenuated virulence and compromised stress response. Together, we showed for the first time that the bceR regulator in GBS plays an important role in bacitracin and antimicrobial peptide resistance, virulence, survival under oxidative stress, and biofilm formation

Severe Acute Respiratory Syndrome–associated Coronavirus Infection

Whether severe acute respiratory syndrome–associated coronavirus (SARS-CoV) infection can be asymptomatic is unclear. We examined the seroprevalence of SARS-CoV among 674 healthcare workers from a hospital in which a SARS outbreak had occurred. A total of 353 (52%) experienced mild self-limiting illnesses, and 321 (48%) were asymptomatic throughout the course of these observations. None of these healthcare workers had antibody to SARS CoV, indicating that subclinical or mild infection attributable to SARS CoV in adults is rare