- Host transcriptomic responses to pneumonic plague reveal that Yersinia pestis inhibits both the initial adaptive and innate immune responses in mice. [Journal Article]
- IJInt J Med Microbiol 2016 Nov 14
- Pneumonic plague is the most deadly form of infection caused by Yersinia pestis and can progress extremely fast. However, our understanding on the host transcriptomic response to pneumonic plague is ...
Pneumonic plague is the most deadly form of infection caused by Yersinia pestis and can progress extremely fast. However, our understanding on the host transcriptomic response to pneumonic plague is insufficient. Here, we used RNA-sequencing technology to analyze transcriptomic responses in mice infected with fully virulent strain 201 or EV76, a live attenuated vaccine strain lacking the pigmentation locus. Approximately 600 differentially expressed genes (DEGs) were detected in lungs from both 201- and EV76-infected mice at 12h post-infection (hpi). DEGs in lungs of 201-infected mice exceeded 2000 at 48hpi, accompanied by sustained large numbers of DEGs in the liver and spleen; however, limited numbers of DEGs were detected in those organs of EV-infected mice. Remarkably, DEGs in lungs were significantly enriched in critical immune responses pathways in EV76-infected but not 201-infected mice, including antigen processing and presentation, T cell receptor signaling among others. Pathological and bacterial load analyses confirmed the rapid systemic dissemination of 201-infection and the confined EV76-infection in lungs. Our results suggest that fully virulent Y. pestis inhibits both the innate and adaptive immune responses that are substantially stimulated in a self-limited infection, which update our holistic views on the transcriptomic response to pneumonic plague.
- Pathogenic features of clinically significant coagulase-negative staphylococci in hospital and community infections in Benin. [Journal Article]
- IJInt J Med Microbiol 2016 Nov 10
- In West Africa, very little consideration has been given to coagulase negative Staphylococci (CNS). Herein, we describe the features contributing to the pathogenicity of 99 clinically-significant ind...
In West Africa, very little consideration has been given to coagulase negative Staphylococci (CNS). Herein, we describe the features contributing to the pathogenicity of 99 clinically-significant independent CNS isolates associated with infections encountered at the National Teaching Hospital Center of Cotonou (Benin). The pathogenic potentials of nosocomial strains were compared with community strains. S. haemolyticus (44%), S. epidermidis (22%) and S. hominis (7%) were the most frequently isolated while bacteremia (66.7%) and urinary tract infections (24.2%) were the most commonly encountered infections. Most strains were resistant to multiple antibiotics, including penicillin (92%), fosfomycin (81%), methicillin (74%) and trimethoprim-sulfamethoxazole (72%). The most frequently isolated species were also the most frequently resistant to methicillin: S. hominis (100%), S. haemolyticus (93%) and S. epidermidis (67%). Screening of toxic functions or toxin presence revealed hemolytic potential in 25% of strains in over 50% of human erythrocytes in 1h. Twenty-six percent of strains exhibited protease activity with low (5%), moderate (10%) and high activity (11%), while 25% of strains displayed esterase activity. Three percent of strain supernatants were able to lyse 100% of human polymorphonuclear cells after 30min. Polymerase chain reaction and latex agglutination methods revealed staphylococcal enterotoxin C gene expression in 9% of S. epidermidis. A majority of hospital-associated CNS strains (68%) had at least one important virulence feature, compared with only 32% for community-acquired strains. The present investigation confirms that these microorganisms can be virulent, at least in some individual cases, possibly through genetic transfer from S. aureus.
- Key role of an ADP - ribose - dependent transcriptional regulator of NAD metabolism for fitness and virulence of Pseudomonas aeruginosa. [Journal Article]
- IJInt J Med Microbiol 2016 Nov 05
- NAD is an essential co-factor of redox reactions and metabolic conversions of NAD-dependent enzymes. NAD biosynthesis in the opportunistic pathogen Pseudomonas aeruginosa has yet not been experimenta...
NAD is an essential co-factor of redox reactions and metabolic conversions of NAD-dependent enzymes. NAD biosynthesis in the opportunistic pathogen Pseudomonas aeruginosa has yet not been experimentally explored. The in silico search for orthologs in the P. aeruginosa PAO1 genome identified the operon pncA - pncB1-nadE (PA4918-PA4920) to encode the nicotinamidase, nicotinate phosporibosyltransferase and Nad synthase of salvage pathway I. The functional role of the preceding genes PA4917 and PA4916 was resolved by the characterization of recombinant protein. PA4917 turned out to encode the nicotinate mononucleotide adenylyltransferase NadD2 and PA4916 was determined to encode the transcriptional repressor NrtR that binds to an intergenic sequence between nadD2 and pncA. Complex formation between the catalytically inactive Nudix protein NrtR and its DNA binding site was suppressed by the antirepressor ADP-ribose. NrtR plasposon mutagenesis abrogated virulence of P. aeruginosa TBCF10839 in a murine acute airway infection model and constrained its metabolite profile. When grown together with other isogenic plasposon mutants, the nrtR knock-out was most compromised in competitive fitness to persist in nutrient-rich medium in vitro or murine airways in vivo. This example demonstrates how tightly metabolism and virulence can be intertwined by key elements of metabolic control.
- Adaptation of Escherichia coli traversing from the faecal environment to the urinary tract. [Journal Article]
- IJInt J Med Microbiol 2016 Nov 04
- The majority of extraintestinal pathogenic Escherichia coli (ExPEC) causing urinary tract infections (UTI) are found in the patient's own gut flora, but only limited knowledge is available on the pot...
The majority of extraintestinal pathogenic Escherichia coli (ExPEC) causing urinary tract infections (UTI) are found in the patient's own gut flora, but only limited knowledge is available on the potential adaptation that may occur in the bacteria in order to traverse the perineum and successfully infect the urinary tract. Here, matching pairs of faecal and UTI isolates from 42 patients were compared pairwise using in-depth whole-genome sequencing to investigate whether genetic changes were evident for successful colonization in these two different environments. The identified non-synonymous mutations (0-12 substitutions in each pair) were primarily associated to genes encoding virulence factors and nutrient metabolism; and indications of parallel evolution were observed in genes encoding the major phase-variable protein antigen 43, a toxin/antitoxin locus and haemolysin B. No differences in virulence potential were observed in a mouse UTI model for five matching faecal and UTI isolates with or without mutations in antigen 43 and haemolysin B. Variations in plasmid content were observed in only four of the 42 pairs. Although, we observed mutations in known UTI virulence genes for a few pairs, the majority showed no detectable differences with respect to mutations or mobilome when compared to their faecal counterpart. The results show that UPECs are successful in colonizing both the bladder and gut without adaptation.
- Molecular characterisation of Czech Clostridium difficile isolates collected in 2013-2015. [Journal Article]
- IJInt J Med Microbiol 2016; 306(7):479-485
- Clostridium difficile is a leading nosocomial pathogen and molecular typing is a crucial part of monitoring its occurrence and spread. Over a three-year period (2013-2015), clinical C. difficile isol...
Clostridium difficile is a leading nosocomial pathogen and molecular typing is a crucial part of monitoring its occurrence and spread. Over a three-year period (2013-2015), clinical C. difficile isolates from 32 Czech hospitals were collected for molecular characterisation. Of 2201 C. difficile isolates, 177 (8%) were non-toxigenic, 2024 (92%) were toxigenic (tcdA and tcdB) and of these, 677 (33.5%) carried genes for binary toxin production (cdtA, cdtB). Capillary-electrophoresis (CE) ribotyping of the 2201 isolates yielded 166 different CE-ribotyping profiles, of which 53 were represented by at least two isolates for each profile. Of these, 29 CE-ribotyping patterns were common to the Leeds-Leiden C. difficile reference strain library and the WEBRIBO database (83.7% isolates), and 24 patterns were recognized only by the WEBRIBO database (11.2% isolates). Isolates belonging to these 53 CE-ribotyping profiles comprised 94.9% of all isolates. The ten most frequent CE-ribotyping profiles were 176 (n=588, 26.7%), 001 (n=456, 20.7%), 014 (n=176, 8%), 012 (n=127, 5.8%), 017 (n=85, 3.9%), 020 (n=68, 3.1%), 596 (n=55, 2.5%), 002-like (n=45, 2.1%), 010 (n=35, 1.6%) and 078 (n=34, 1.6%). Multi-locus sequence typing (MLST) of seven housekeeping genes performed in one isolate of each of 53 different CE-ribotyping profiles revealed 40 different sequence types (STs). We conclude that molecular characterisation of Czech C. difficile isolates revealed a high diversity of CE-ribotyping profiles; the prevailing RTs were 001 (20.7%) and 176 (027-like, 26.7%).
- Colicins U and Y inhibit growth of Escherichia coli strains via recognition of conserved OmpA extracellular loop 1. [Journal Article]
- IJInt J Med Microbiol 2016; 306(7):486-494
- Interactions of colicins U and Y with the OmpA (Outer membrane protein A) receptor molecule were studied using site-directed mutagenesis and colicin binding assay. A systematic mutagenesis of the col...
Interactions of colicins U and Y with the OmpA (Outer membrane protein A) receptor molecule were studied using site-directed mutagenesis and colicin binding assay. A systematic mutagenesis of the colicin-susceptible OmpA sequence from Escherichia coli (OmpAEC) to the colicin-resistant OmpA sequence from Serratia marcescens (OmpASM) was performed in regions corresponding to extracellular OmpA loops 1-4. Susceptibility to colicins U and Y was significantly affected by the OmpA mutation in loop 1. As with functional analysis, a decrease in binding capacity of His-tagged colicin U was found for recombinant OmpA with a mutated segment in loop 1 compared to control OmpAEC. To verify the importance of the identified amino acid residues in OmpA loop 1, we introduced loop 1 from OmpAEC into OmpASM, which resulted in the substantial increase of susceptibility to colicins U and Y. In addition, colicins U and Y were tested against a panel of 118 bacteriocin non-producing strains of four Escherichia species, including E. coli (39 strains), E. fergusonii (10 strains), E. hermannii (42 strains), and E. vulneris (27 strains). A majority (82%) of E. coli strains was susceptible to colicins U and Y. Interestingly, colicins U and Y also inhibited all of the 30 tested multidrug-resistant E. coli O25b-ST131 isolates. These findings, together with the fact that OmpA loop 1 is important for bacterial virulence and is evolutionary conserved, offer the potential of using colicins U and Y as specific anti-OmpA loop 1 directed antibacterial proteins.
- A hypervariable genomic island identified in clinical and environmental Mycobacterium avium subsp. hominissuis isolates from Germany. [Journal Article]
- IJInt J Med Microbiol 2016; 306(7):495-503
- Mycobacterium avium subsp. hominissuis (MAH) is an opportunistic human pathogen widespread in the environment. Genomic islands (GI)s represent a part of the accessory genome of bacteria and influence...
Mycobacterium avium subsp. hominissuis (MAH) is an opportunistic human pathogen widespread in the environment. Genomic islands (GI)s represent a part of the accessory genome of bacteria and influence virulence, drug-resistance or fitness and trigger bacterial evolution. We previously identified a novel GI in four MAH genomes. Here, we further explored this GI in a larger collection of MAH isolates from Germany (n=41), including 20 clinical and 21 environmental isolates. Based on comparative whole genome analysis, we detected this GI in 39/41 (95.1%) isolates. Although all these GIs integrated in the same insertion hotspot, there is high variability in the genetic structure of this GI: eight different types of GI have been identified, designated A-H (sized 6.2-73.3kb). These GIs were arranged as single GI (23/41, 56.1%), combination of two different GIs (14/41, 34.1%) or combination of three different GIs (2/41, 4.9%) in the insertion hotspot. Moreover, two GI types shared more than 80% sequence identity with sequences of M. canettii, responsible for Tuberculosis. A total of 253 different genes were identified in all GIs, among which the previously documented virulence-related genes mmpL10 and mce. The diversity of the GI and the sequence similarity with other mycobacteria suggests cross-species transfer, involving also highly pathogenic species. Shuffling of potential virulence genes such as mmpL10 via this GI may create new pathogens that can cause future outbreaks.
- Heterologous Pseudomonas aeruginosa O-antigen delivery using a Salmonella enterica serovar Typhimurium wecA mutant strain. [Journal Article]
- IJInt J Med Microbiol 2016; 306(7):529-540
- There is a broad interest in adapting live vaccine strains (LVS) for use as recombinant vaccines that can deliver heterologous antigens. The Salmonella enterica serovar Typhimurium SL1344 ΔwecA LVS c...
There is a broad interest in adapting live vaccine strains (LVS) for use as recombinant vaccines that can deliver heterologous antigens. The Salmonella enterica serovar Typhimurium SL1344 ΔwecA LVS contains a mutation in wecA that abrogates production of Enterobacterial common antigen. This ΔwecA strain is attenuated in vivo, persistently colonizes the host, and protects against both wild type and cross-Salmonella serovar lethal challenge in a murine model of salmonellosis. Given these characteristics, we hypothesized that the SL1344 ΔwecA strain could be used as a carrier for heterologous antigen expression. To test this hypothesis, SL1344 ΔwecA was engineered to express the Pseudomonas aeruginosa O11 O-antigen gene cluster. Intraperitoneal (IP) but not oral immunization of BALB/c mice with the heterologous expression strain protected against lethal P. aeruginosa intranasal (IN) challenge. Furthermore, IP immunization resulted in P. aeruginosa O11-specific Ig and IgG antibody production. Functional analysis of sera collected from the IP immunized mice showed antibody-mediated agglutination and opsonophagocytic activity against P. aeruginosa. En masse, these results indicate that the S. Typhimurium SL1344 ΔwecA strain expressing the P. aeruginosa O11 O-antigen gene cluster is able to induce a humoral immune response and to protect against lethal P. aeruginosa challenge. As such, the S. Typhimurium SL1344 ΔwecA LVS can likely serve as a vehicle for expression of a wide variety of heterologous antigens as a means to create recombinant vaccines.
- Propionibacterium acnes inhibits FOXM1 and induces cell cycle alterations in human primary prostate cells. [Journal Article]
- IJInt J Med Microbiol 2016; 306(7):517-528
- Propionibacterium acnes has been detected in diseased human prostate tissue, and cell culture experiments suggest that the bacterium can establish a low-grade inflammation. Here, we investigated its ...
Propionibacterium acnes has been detected in diseased human prostate tissue, and cell culture experiments suggest that the bacterium can establish a low-grade inflammation. Here, we investigated its impact on human primary prostate epithelial cells. Microarray analysis confirmed the inflammation-inducing capability of P. acnes but also showed deregulation of genes involved in the cell cycle. qPCR experiments showed that viable P. acnes downregulates a master regulator of cell cycle progression, FOXM1. Flow cytometry experiments revealed that P. acnes increases the number of cells in S-phase. We tested the hypothesis that a P. acnes-produced berninamycin-like thiopeptide is responsible for this effect, since it is related to the FOXM1 inhibitor siomycin. The thiopeptide biosynthesis gene cluster was strongly expressed; it is present in subtype IB of P. acnes, but absent from type IA, which is most abundant on human skin. A knock-out mutant lacking the gene encoding the berninamycin-like peptide precursor was unable to downregulate FOXM1 and to halt the cell cycle. Our study reveals a novel host cell-interacting activity of P. acnes.
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- Differential compartmentalization of Streptococcus pyogenes virulence factors and host protein binding properties as a mechanism for host adaptation. [Journal Article]
- IJInt J Med Microbiol 2016; 306(7):504-516
- Streptococcus pyogenes is an important human pathogen responsible for substantial morbidity and mortality worldwide. Although S. pyogenes is a strictly human pathogen with no other known animal reser...
Streptococcus pyogenes is an important human pathogen responsible for substantial morbidity and mortality worldwide. Although S. pyogenes is a strictly human pathogen with no other known animal reservoir, several murine infection models exist to explore different aspects of the bacterial pathogenesis. Inoculating mice with wild-type S. pyogenes strains can result in the generation of new bacterial phenotypes that are hypervirulent compared to the original inoculum. In this study, we used a serial mass spectrometry based proteomics strategy to investigate if these hypervirulent strains have an altered distribution of virulence proteins across the intracellular, surface associated and secreted bacterial compartments and if any change in compartmentalization can alter the protein-protein interaction network between bacteria and host proteins. Quantitative analysis of the S. pyogenes surface and secreted proteomes revealed that animal passaged strains are associated with significantly higher amount of virulence factors on the bacterial surface and in the media. This altered virulence factor compartmentalization results in increased binding of several mouse plasma proteins to the bacterial surface, a trend that was consistent for mouse plasma from several different mouse strains. In general, both the wild-type strain and animal passaged strain were capable of binding high amounts of human plasma proteins. However, compared to the non-passaged strains, the animal passaged strains displayed an increased ability to bind mouse plasma proteins, in particular for M protein binders, indicating that the increased affinity for mouse blood plasma proteins is a consequence of host adaptation of this pathogen to a new host. In conclusion, plotting the total amount of virulence factors against the total amount of plasma proteins associated to the bacterial surface could clearly separate out animal passaged strains from wild type strains indicating a virulence model that could predict the virulence of a S. pyogenes strain in mice and which could be used to identify key aspects of this bacteria's pathogenesis.