Molecular identification of Capnocytophaga spp. via 16S rRNA PCR-restriction fragment length polymorphism analysis

A Novel 16S rRNA PCR-Restriction Fragment Length Polymorphism Assay to Accurately Distinguish Zoonotic Capnocytophaga canimorsus and C. cynodegmi

The zoonotic bacteria Capnocytophaga canimorsus and C. cynodegmi, the predominant Capnocytophaga species in the canine oral biota, can cause human local wound infections or lethal sepsis, usually transmitted through dog bites. Molecular surveying of these Capnocytophaga species using conventional 16S rRNA-based PCR is not always accurate due to their high genetic homogeneity. In this study, we isolated Capnocytophaga spp. from the canine oral cavity and identified them using 16S rRNA and phylogenetic analysis. A novel 16S rRNA PCR-restriction fragment length polymorphism (RFLP) method was designed based on our isolates and validated using published C. canimorsus and C. cynodegmi 16S rRNA sequences. The results showed that 51% of dogs carried Capnocytophaga spp. Among these, C. cynodegmi (47/98, 48%) was the predominant isolated species along with one strain of C. canimorsus (1/98, 1%). Alignment analysis of 16S rRNA sequences revealed specific site nucleotide diversity in 23% (11/47) of the C. cynodegmi isolates, which were misidentified as C. canimorsus using previously reported species-specific PCR. Four RFLP types could be classified from all the isolated Capnocytophaga strains. The proposed method demonstrates superior resolution in distinguishing C. cynodegmi (with site-specific polymorphism) from C. canimorsus and especially in distinguishing C. canimorsus from other Capnocytophaga species. After in silico validation, this method was revealed to have an overall detection accuracy of 84%; notably, accuracy reached 100% in C. canimorsus strains isolated from human patients. Overall, the proposed method is a useful molecular tool for the epidemiological study of Capnocytophaga in small animals and for the rapid diagnosis of human C. canimorsus infections. IMPORTANCE With the increased number of small animal breeding populations, zoonotic infections associated with small animals need to be taken more seriously. Capnocytophaga canimorsus and C. cynodegmi are part of common biota in the mouths of small animals and can cause human infections through bites or scratches. In this study, C. cynodegmi with site-specific 16S rRNA sequence polymorphisms was erroneously identified as C. canimorsus during the investigation of canine Capnocytophaga by conventional PCR. Consequently, the prevalence of C. canimorsus is incorrectly overestimated in epidemiological studies in small animals. We designed a new 16S rRNA PCR-RFLP method to accurately distinguish zoonotic C. canimorsus from C. cynodegmi. After validation against published Capnocytophaga strains, this novel molecular method had high accuracy and could detect 100% of C. canimorsus-strain infections in humans. This novel method can be used for epidemiological studies and the diagnosis of human Capnocytophaga infection following exposure to small animals.

Comparison of culture and polymerase chain reaction-restriction fragment length polymorphism for identification of various Capnocytophaga species from subgingival plaque samples of healthy and periodontally diseased individuals

Introduction

Capnocytophaga are facultative anaerobic Gram-negative bacilli and recognized as opportunistic pathogens of various extraoral infections. Only a few studies attempted to identify all the seven species of Capnocytophaga phenotypically and genotypically in healthy individuals and patients with chronic periodontitis. Studies to determine the prevalence of Capnocytophaga in subgingival plaque samples from healthy individuals, chronic gingivitis and periodontitis among Indian population are lacking.

Aim

The aim of this study was to identify and compare the presence of Capnocytophaga species phenotypically through microbial culture and biochemical tests and genotypically through polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in subgingival plaque of healthy individuals and patients with chronic gingivitis and chronic periodontitis.

Materials and Methods

A total of 300 subjects, 100 each with gingivitis, periodontitis and periodontally healthy gingiva subjected, were included. Subgingival plaque was collected and was cultured for phenotypic identification (microbial culture and biochemical test), and for genotypic identification, DNA extraction was done and PCR-RFLP analysis was performed to identify the genus Capnocytophaga and also to identify different species of Capnocytophaga.

Results

Of 300 individuals, Capnocytophaga species were identified from 237 (79%) individuals by PCR and 82 (27.33%) by culture. The prevalence of Capnocytophaga ochracea was found to be higher with both the methods followed by Capnocytophaga gingivalis and Capnocytophaga granulosa. Capnocytophaga genospecies, Capnocytophaga leadbetteri and Capnocytophaga Sputigena were isolated only by culture with very low prevalence that is 1.33%, 1.33% and 0.66%, respectively. We could not get any isolate of Capnocytophaga haemolytica by any of the two methods.

Conclusion

Capnocytophaga species could be found in gingival sulci as well as periodontal pockets and can be detected by culture and PCR-RFLP. However, higher prevalence of these species in healthy compared to disease requires further analysis to determine their role in healthy and diseased periodontium.

Double valve infective endocarditis due to Capnocytophaga canimorsus

Infective endocarditis caused by Capnocytophaga canimorsus, a commensal organism commonly found in dog saliva, is uncommon. We describe a case of a 76-year-old male with native aortic and mitral valve endocarditis with ventricular-atrial fistulization due to Capnocytophaga canimorsus. He was successfully treated with intravenous antimicrobials and surgery. Capnocytophaga canimorsus should be considered as a cause of infective endocarditis in patients with negative blood cultures, in asplenic patients, and in those with appropriate exposures.

Haemophilus parasuis (Glaesserella parasuis) as a Potential Driver of Molecular Mimicry and Inflammation in Rheumatoid Arthritis

Background:Haemophilus parasuis (Hps; now Glaesserella parasuis) is an infectious agent that causes severe arthritis in swines and shares sequence similarity with residues 261–273 of collagen type 2 (Coll_261−273), a possible autoantigen in rheumatoid arthritis (RA).

Objectives/methods: We tested the presence of Hps sequencing 16S ribosomal RNA in crevicular fluid, synovial fluids, and tissues in patients with arthritis (RA and other peripheral arthritides) and in healthy controls. Moreover, we examined the cross-recognition of Hps by Coll_261−273-specific T cells in HLA-DRB1^*04^pos RA patients, by T-cell receptor (TCR) beta chain spectratyping and T-cell phenotyping.

Results:Hps DNA was present in 57.4% of the tooth crevicular fluids of RA patients and in 31.6% of controls. Anti-Hps IgM and IgG titers were detectable and correlated with disease duration and the age of the patients. Peripheral blood mononuclear cells (PBMCs) were stimulated with Hps virulence-associated trimeric autotransporter peptide (VtaA10_755−766), homologous to human Coll_261−273 or co-cultured with live Hps. In both conditions, the expanded TCR repertoire overlapped with Coll_261−273 and led to the production of IL-17.

Discussion: We show that the DNA of an infectious agent (Hps), not previously described as pathogen in humans, is present in most patients with RA and that an Hps peptide is able to activate T cells specific for Coll_261−273, likely inducing or maintaining a molecular mimicry mechanism.

Conclusion: The cross-reactivity between VtaA10_755−766 of a non-human infectious agent and human Coll_261−273 suggests an involvement in the pathogenesis of RA. This mechanism appears emphasized in predisposed individuals, such as patients with shared epitope.

Performance and Application of 16S rRNA Gene Cycle Sequencing for Routine Identification of Bacteria in the Clinical Microbiology Laboratory

This review provides a state-of-the-art description of the performance of Sanger cycle sequencing of the 16S rRNA gene for routine identification of bacteria in the clinical microbiology laboratory. A detailed description of the technology and current methodology is outlined with a major focus on proper data analyses and interpretation of sequences. The remainder of the article is focused on a comprehensive evaluation of the application of this method for identification of bacterial pathogens based on analyses of 16S multialignment sequences. In particular, the existing limitations of similarity within 16S for genus- and species-level differentiation of clinically relevant pathogens and the lack of sequence data currently available in public databases is highlighted. A multiyear experience is described of a large regional clinical microbiology service with direct 16S broad-range PCR followed by cycle sequencing for direct detection of pathogens in appropriate clinical samples. The ability of proteomics (matrix-assisted desorption ionization-time of flight) versus 16S sequencing for bacterial identification and genotyping is compared. Finally, the potential for whole-genome analysis by next-generation sequencing (NGS) to replace 16S sequencing for routine diagnostic use is presented for several applications, including the barriers that must be overcome to fully implement newer genomic methods in clinical microbiology. A future challenge for large clinical, reference, and research laboratories, as well as for industry, will be the translation of vast amounts of accrued NGS microbial data into convenient algorithm testing schemes for various applications (i.e., microbial identification, genotyping, and metagenomics and microbiome analyses) so that clinically relevant information can be reported to physicians in a format that is understood and actionable. These challenges will not be faced by clinical microbiologists alone but by every scientist involved in a domain where natural diversity of genes and gene sequences plays a critical role in disease, health, pathogenicity, epidemiology, and other aspects of life-forms. Overcoming these challenges will require global multidisciplinary efforts across fields that do not normally interact with the clinical arena to make vast amounts of sequencing data clinically interpretable and actionable at the bedside.

Molecular identification of Capnocytophaga species from the oral cavity of patients with chronic periodontitis and healthy individuals

Introduction:

Capnocytophaga species are recognized as part of human oral microbiota and implicated as periodontal pathogens associated with various periodontal diseases. The three original Capnocytophaga species - Capnocytophaga ochracea, Capnocytophaga sputigena and Capnocytophaga gingivalis were initially isolated from periodontitis in adults, but subsequent studies demonstrated their presence also at periodontally healthy sites in both children and adults. Their association with periodontal disease is a matter of controversy. Considering the differing virulence features of the respective isolate, it is crucial to identify these isolates to species level.

Aims:

The aim of this study is to investigate the prevalence of Capnocytophaga species by polymerase chain reaction (PCR) through restriction fragment length polymorphism in healthy individuals and patients with periodontal disease.

Material and Methods:

The study included a total of 300 individuals, 100 each with Gingivitis, Chronic periodontitis, and Healthy individuals. The plaque samples were collected using sterile curette in reduced transport fluid. DNA extraction was carried out for PCR analysis.

Results:

Of 300 individuals, Capnocytophaga species were identified from 237 (79%) participants in all groups. The prevalence was statistically analyzed using Chi-square test. The prevalence was more in males in gingivitis and healthy individuals (42% and 49% respectively), and females in periodontitis (40%). C. ochracea was observed in a higher proportion (36.33%), followed by C. granulosa (32.66%) and C. gingivalis (10%). They were identified more in the age group of 30–40 years in gingivitis and periodontitis, (30 and 21 individuals, respectively) and 39 individuals in 18–29 years in healthy individuals. They were present in 87% in healthy individuals, 77% in gingivitis and 73% in periodontitis.

Conclusion:

Capnocytophaga species are commonly present in healthy individuals and may be associated with periodontal disease. There is a need for further study to know the prevalence of other species of Capnocytophaga in health and disease.

Cat Rearing: A Potential Risk of Fulminant Sepsis Caused by <b><i>Capnocytophaga canimorsus</i></b> in a Hemodialysis Patient

Capnocytophaga canimorsus is a commensal organism colonized in oral flora of dogs and cats and causes severe sepsis through bite wound in immunocompromised patients. To date, hemodialysis has not been reported as a risk of C. canimorsus infection. A 75-year-old woman with end-stage renal disease secondary to hypertension suddenly developed septic shock. She reared 6 cats in her home, but no bite or scratch wound was found on her body. She was empirically treated with piperacillin-tazobactam and temporally received continuous hemodiafiltration. On the fifth day after sampling, blood culture revealed C. canimorsus as the cause of sepsis. After 4 weeks of antibiotic therapy targeting this organism, she recovered from the sepsis and was discharged on the 109th hospitalization day. Hemodialysis patients may be vulnerable to invasion into the blood stream by C. canimorsus due to the presence of punctures in their skin and the impaired immune function associated with uremia. Physicians should consider this organism as a cause of sepsis in hemodialysis patients who rear dogs or cats even in the absence of apparent bite wounds.

Double Native Valve Infective Endocarditis due to Capnocytophaga canimorsus: First Reported Case Caused by a Lion Bite

Capnocytophaga canimorsus is a Gram-negative bacilli that is part of the normal oral flora of dogs and some cats; it is well known to cause septicemia and endocarditis after their bite. This is the first reported case of infective endocarditis affecting both native mitral and aortic valves after a lion bite in a patient with heavy ethanol consumption, who ultimately died after valve replacements.

On the mechanism of biological activation by tritium

The mechanism of biological activation by beta-emitting radionuclide tritium was studied. Luminous marine bacteria were used as a bioassay to monitor the biological effect of tritium with luminescence intensity as the physiological parameter tested. Two different types of tritium sources were used: HTO molecules distributed regularly in the surrounding aqueous medium, and a solid source with tritium atoms fixed on its surface (tritium-labeled films, 0.11, 0.28, 0.91, and 2.36 MBq/cm(2)). When using the tritium-labeled films, tritium penetration into the cells was prevented. The both types of tritium sources revealed similar changes in the bacterial luminescence kinetics: a delay period followed by bioluminescence activation. No monotonic dependences of bioluminescence activation efficiency on specific radioactivities of the films were found. A 15-day exposure to tritiated water (100 MBq/L) did not reveal mutations in bacterial DNA. The results obtained give preference to a "non-genomic" mechanism of bioluminescence activation by tritium. An activation of the intracellular bioluminescence process develops without penetration of tritium atoms into the cells and can be caused by intensification of trans-membrane cellular processes stimulated by ionization and radiolysis of aqueous media.

Capnocytophaga ochracea-related Bacterium Bacteremia in a Hypertrophic Cardiomyopathy Patient without Neutropenia

Gram-negative fusiform rods were detected in a blood culture obtained from a 63-year-old man who had been hospitalized for a long duration for severe heart failure. Although the organism could not be identified using a conventional method, it was finally identified as a bacterium of the Capnocytophaga ochracea group based on the results of biochemical testing, 16S rRNA sequencing and a matrix-assisted laser desorption ionization time-of-flight mass spectrometry analysis. Although neutropenic patients with poor oral hygiene are exclusively vulnerable to Capnocytophaga bacteremia, this case was unique because such predisposing conditions were not noted. A multi-centered investigation is warranted for a better understanding of this clinically rare, but potentially pathogenic organism.

Intra-Genomic Heterogeneity in 16S rRNA Genes in Strictly Anaerobic Clinical Isolates from Periodontal Abscesses

BACKGROUND

Members of the genera Prevotella, Veillonella and Fusobacterium are the predominant culturable obligate anaerobic bacteria isolated from periodontal abscesses. When determining the cumulative number of clinical anaerobic isolates from periodontal abscesses, ambiguous or overlapping signals were frequently encountered in 16S rRNA gene sequencing chromatograms, resulting in ambiguous identifications. With the exception of the genus Veillonella, the high intra-chromosomal heterogeneity of rrs genes has not been reported.

METHODS

The 16S rRNA genes of 138 clinical, strictly anaerobic isolates and one reference strain were directly sequenced, and the chromatograms were carefully examined. Gene cloning was performed for 22 typical isolates with doublet sequencing signals for the 16S rRNA genes, and four copies of the rrs-ITS genes of 9 Prevotella intermedia isolates were separately amplified by PCR, sequenced and compared. Five conserved housekeeping genes, hsp60, recA, dnaJ, gyrB1 and rpoB from 89 clinical isolates of Prevotella were also amplified by PCR and sequenced for identification and phylogenetic analysis along with 18 Prevotella reference strains.

RESULTS

Heterogeneity of 16S rRNA genes was apparent in clinical, strictly anaerobic oral bacteria, particularly in the genera Prevotella and Veillonella. One hundred out of 138 anaerobic strains (72%) had intragenomic nucleotide polymorphisms (SNPs) in multiple locations, and 13 strains (9.4%) had intragenomic insertions or deletions in the 16S rRNA gene. In the genera Prevotella and Veillonella, 75% (67/89) and 100% (19/19) of the strains had SNPs in the 16S rRNA gene, respectively. Gene cloning and separate amplifications of four copies of the rrs-ITS genes confirmed that 2 to 4 heterogeneous 16S rRNA copies existed.

CONCLUSION

Sequence alignment of five housekeeping genes revealed that intra-species nucleotide similarities were very high in the genera Prevotella, ranging from 94.3-100%. However, the inter-species similarities were relatively low, ranging from 68.7-97.9%. The housekeeping genes rpoB and gyrB1 were demonstrated to be alternative classification markers to the species level based on intra- and inter-species comparisons, whereas based on phylogenetic tree rpoB proved to be reliable phylogenetic marker for the genus Prevotella.

'Bobo-Newton syndrome': An unwanted gift from man's best friend

Capnocytophaga canimorsus is a facultative Gram-negative bacillus that is typically a constituent of the oral flora of dogs and cats. It was first isolated by Bobo and Newton in 1976 from a man presenting with meningitis following a dog bite. Transmission to humans follows various animal-related injuries, which may be gross or subtle. C canimorsus can cause a spectrum of syndromes ranging from skin and soft tissue infection to invasive disease such as meningitis or endocarditis. The present article reports a case of C canimorsus meningitis in a patient with the classic risk factor of alcoholic liver cirrhosis. Clinical suspicion was confirmed by culture and genetic identification of the blood isolate. The present article reviews the Capnocytophaga genus, the clinical syndromes most commonly associated with this zoonotic organism, its laboratory identification and treatment.

Capnocytophaga spp. involvement in bone infections: a review

Capnocytophaga are commensal gliding bacteria that are isolated from human and animal oral flora and are responsible for infections both in immunocompromised and immunocompetent hosts. Accumulation of microbial plaque, loss of collagen attachment, and alveolar bone resorption around the tooth can lead to local Capnocytophaga spp. bone infections. These capnophilic bacteria, from oral sources or following domestic animal bites, are also causative agents of bacteraemia and systemic infections as well as osteomyelitis, septic arthritis, and infections on implants and devices. The present literature review describes the main aetiologies of bone infections due to Capnocytophaga spp., the cellular mechanisms involved, methods used for diagnosis, antimicrobial susceptibility, and effective treatments.

Fluorescent In Situ hybridization: a new tool for the direct identification and detection of F. psychrophilum

F. psychrophilum is the causative agent of Bacterial Cold Water Disease (BCW) and Rainbow Trout Fry Syndrome (RTFS). To date, diagnosis relies mainly on direct microscopy or cultural methods. Direct microscopy is fast but not very reliable, whereas cultural methods are reliable but time-consuming and labor-intensive. So far fluorescent in situ hybridization (FISH) has not been used in the diagnosis of flavobacteriosis but it has the potential to rapidly and specifically detect F. psychrophilum in infected tissues. Outbreaks in fish farms, caused by pathogenic strains of Flavobacterium species, are increasingly frequent and there is a need for reliable and cost-effective techniques to rapidly diagnose flavobacterioses. This study is aimed at developing a FISH that could be used for the diagnosis of F. psychrophilum infections in fish. We constructed a generic probe for the genus Flavobacterium (“Pan-Flavo”) and two specific probes targeting F. psychrophilum based on 16S rRNA gene sequences. We tested their specificity and sensitivity on pure cultures of different Flavobacterium and other aquatic bacterial species. After assessing their sensitivity and specificity, we established their limit of detection and tested the probes on infected fresh tissues (spleen and skin) and on paraffin-embedded tissues. The results showed high sensitivity and specificity of the probes (100% and 91% for the Pan-Flavo probe and 100% and 97% for the F. psychrophilum probe, respectively). FISH was able to detect F. psychrophilum in infected fish tissues, thus the findings from this study indicate this technique is suitable as a fast and reliable method for the detection of Flavobacterium spp. and F. psychrophilum.

Presence of the oral bacterium Capnocytophaga canimorsus in the tooth plaque of canines

Capnocytophaga canimorsus is a potentially pathogenic microorganism when transmitted to humans from the oral cavity of canines. Although there is some knowledge about the frequency of occurrence in canines, it is uncertain whether there is a correlation between its occurrence and lifestyle, health, or breed of dog. Samples of tooth plaque from a total of 131 canines were collected, cultured on selective media, and tested using physiological and molecular analyses to help discern the presence of C. canimorsus. Phylogenetic analyses determined that 49.2% of canines sampled carried a species of Capnocytophaga and 21.7% of the canines sampled in this study carried C. canimorsus. Statistical analyses found that male dogs and those that are neutered and spayed are more likely to host Capnocytophaga species. The data also suggested that breed was a statistically significant predictor of C. canimorsus, with the smaller breeds more likely to carry the potential pathogen. In addition, three "human" species of Capnocytophaga; C. ochracea, C. haemolytica, and one isolate of either C. gingivalis or C. granulosa were cultured from five canines. Sixteen canines sampled carried an unidentified Capnocytophaga species, with the sequences from all isolates forming a well-defined phylogenetic clade with 100% bootstrap support that may well represent a new species of Capnocytophaga.

Molecular characterization of Capnocytophaga canimorsus and other canine Capnocytophaga spp. and assessment by PCR of their frequencies in dogs

Capnocytophaga canimorsus can be a virulent pathogen, whereas C. cynodegmi is of low virulence. Heterogeneity within these species, their frequency in dogs, and pathogenicity factors are largely unknown. Strains from blood cultures from patients presumptively identified as C. canimorsus (n = 25) and as C. cynodegmi by rrs analysis (n = 4), blood cultures from dogs (n = 8), blood cultures from cats (n = 2), and cultures from swabs from dog mouths (n = 53) were analyzed. PCR-restriction fragment length polymorphism (PCR-RFLP), a species-specific PCR on rpoB, and rrs sequencing were used. All 29 strains from human blood cultures could be grouped into three PCR-RFLP types. One included the C. canimorsus type strain, and the other types were closely related. Two canine strains were C. canimorsus and grouped into the least common RLFP pattern group. Five were C. cynodegmi and clustered with the reference strain. One canine and both feline strains were distinct. Four human strains that presumptively had been identified as C. cynodegmi by RNA gene sequence analysis clustered with the C. canimorsus strains by both PCR-RFLP and the sequence-specific PCR of the rpoB gene. C. canimorsus DNA was present in 73% (range, 61 to 85%) of dogs' mouths, and C. cynodegmi DNA was present in 96% (range, 94 to 100%) of dogs' mouths. As defined by rpoB PCR-RFLP and by PCRs using specific primers, all strains from human blood were C. canimorsus. The sequencing of rrs genes suggested the presence of different gene copies in a few strains, indicating that the method is less appropriate for species identification. Both species are present in the majority of dogs. Additional Capnocytophaga species occur in dogs' and cats' mouths.

Prevalence of Capnocytophaga canimorsus in dogs and occurrence of potential virulence factors

Capnocytophaga canimorsus is a Gram-negative commensal of dog's mouth causing severe human infections. A strain isolated from a human fatal infection was recently shown to have a sialidase, to inhibit the bactericidal activity of macrophages and to block the release of nitric oxide by LPS-stimulated macrophages. The present study aimed at determining the prevalence of C. canimorsus in dogs and the occurrence of these hypothetical virulence factors. C. canimorsus could be retrieved from the saliva of 61 dogs out of 106 sampled. Like in clinical isolates, all dog strains had a sialidase and 60% blocked the killing of phagocytosed Escherichia coli by macrophages. In contrast, only 6.5% of dog strains blocked the release of nitric oxide by LPS-challenged macrophages, suggesting that this property might contribute to virulence. The comparative analysis of 69 16S rDNA sequences revealed the existence of C. canimorsus strains that could be misdiagnosed.

A patient with bacteraemia and possible endocarditis caused by a recently-discovered genomospecies of Capnocytophaga: Capnocytophaga genomospecies AHN8471: a case report

INTRODUCTION

Capnocytophaga are a genus of bacteria that have been found to be the causative organisms in a range of infections, including serious conditions such as bacteraemia, endocarditis and meningitis. This has been especially true amongst those with serious comorbidities and the immunocompromised populations. Although several species are known to cause human disease, historically, laboratories have often not identified isolates to species level due to the unreliable, laborious techniques needed. With the advent of Polymerase Chain Reaction-Restriction Fragment Length Polymorphism Analysis, identification to species level is now frequently possible and desirable, as it may provide clues as to the source of infection and its treatment.

CASE PRESENTATION

Here we describe a case of bacteraemia and possible endocarditis in a 64-year-old white British man caused by a newly identified genomospecies of Capnocytophaga in a patient subsequently diagnosed with metastatic adenocarcinoma of the oesophagus. The source of the bacteraemia was presumed to be from the patient's own oral flora.

CONCLUSION

Our case further confirms the potential for Capnocytophaga to cause systemic infections, highlights the availability and need for identification of isolates to species level and re-emphasises the difficulty in diagnosing Capnocytophaga infections due to their slow growth in the laboratory.

[Capnocytophaga sputigena pleuropneumonitis: a case report]

Community-acquired pneumonia is complicated by purulent pleural effusion in approximately 28% of affected children. Its incidence has increased over the last decade. Streptococcus pneumoniae is the most frequent causal microorganism, encountered in roughly 80% of cases. We report the case of an immunocompetent 13-year-old teenager wearing orthodontic braces who suffered from pleuropneumonia due to Capnocytophaga sputigena. To date, this Gram-negative bacillus, a commensal of the buccal cavity, had never been reported to be responsible for pleural or lung infection. The clinical presentation is similar to that observed with usual bacteria, while bacterial sensitivity to betalactam antibiotics is excellent.

Comparative microbiota of Rickettsia felis-uninfected and -infected colonized cat fleas, Ctenocephalides felis

Fleas serve as arthropod vectors for several emerging and re-emerging infectious disease causing agents including, Rickettsia felis. Although the prevalence of R. felis infection in colonies of fleas has been examined, the influence of the R. felis infection on flea microbiota has not been investigated. We identified three colonies of cat fleas, Ctenocephalides felis, with varying prevalence of R. felis infection (Louisiana State University (LSU), 93.8%; Professional Laboratory and Research Services Inc. (PLRS), 16.4%; Elward II (EL), 0%) and subsequently utilized polymerase chain reaction amplification, restriction fragment length polymorphism analysis and sequencing of the 1.4-kb portions of 16S rRNA genes to examine the diversity of bacteria in the flea populations. A total of 17 different bacterial 16S rRNA gene sequences were identified among the C. felis colonies. The prevalence of two Wolbachia species that were identified in each flea colony differed between colonies and R. felis-uninfected and -infected fleas. Species richness was unchanged among the R. felis-uninfected (LSU, PLRS and EL colonies) and -infected (LSU and PLRS colonies) fleas; however, between R. felis-uninfected and -infected fleas within both the LSU and PLRS colonies, R. felis-uninfected fleas have greater species richness. Diversity indices did not identify a difference in diversity between any of the flea samples. The interaction of endosymbionts within arthropods can widely impact the dissemination of vertically transmitted pathogenic bacteria; and the reciprocal may be true. These results suggest that carriage of R. felis has an impact on the richness of flea microbiota.

Meningitis caused by Capnocytophaga canimorsus: When to expect the unexpected

In this article we review the available data concerning meningitis caused by Capnocytophaga canimorsus. The clinical presentation of this rare condition is described with the emphasis on associated conditions and management issues. Two additional cases, illustrating the difficulties in recognizing this rare disease, are presented. Reviewing a total of 28 reported cases, a preceding bite-incident by a cat or dog, or close contact with these animals, was described in the majority of cases (89%). Patients had a median age of 58 years; splenectomy and alcohol abuse were noted in, respectively, 18% and 25% of patients. Only in one case immune suppressive drug use was reported. The diagnosis C. canimorsus meningitis should be considered in healthy and immunocompromised adults, especially after splenectomy, who present with symptoms attributable to meningitis and a history of recent exposure to dogs or cats. The possibility of this condition has implications for both the diagnostic work-up and the treatment of the patient.

Antimicrobial treatment of Capnocytophaga infections

Capnocytophaga spp. are normal inhabitants of the oropharyngeal flora. They are also involved in periodontal diseases or animal bites, complicated by septicaemia with dissemination to a great variety of sites, both in immunocompetent and immunocompromised hosts. This review will focus on their pathogenesis, spectrum of clinical infections and susceptibility to disinfectants and antibiotics. The spread of beta-lactamase-producing strains limits the use of beta-lactams as first-line treatments, underlying the necessity to test the in vitro susceptibility of clinical strains. Many antimicrobial treatments have been used, despite an absence of randomised studies and guidelines regarding the duration of treatment according to infected sites. Imipenem/cilastatin, clindamycin or beta-lactamase inhibitor combinations are always effective and their use can be recommended in all infections.

Brain abscess associated with multidrug-resistant Capnocytophaga ochracea infection

Brain abscesses are occasionally associated with a dental source of infection. An unusual case of frontal lobe abscess in a nonimmunocompromised child infected with multidrug-resistant Capnocytophaga ochracea is described and confirms the pathogenic potential of this organism to cause human disease in the central nervous system.

Meningitis due to Capnocytophaga canimorsus: contribution of 16S RNA ribosomal sequencing for species identification

We report a case of Capnocytophaga canimorsus meningitis, which is distinguishable from previous reports by the use of 16S rRNA sequencing for species identification. Our case report highlights the interest of molecular new tools for bacteriological diagnosis of human infections.