Capnocytophaga ochracea infection: two cases and a review of the published work

Recombinant Prevotella melaninogenica α-1,3 glucanase and Capnocytophaga ochracea α-1,6 glucanase as enzymatic tools for in vitro degradation of S. mutans biofilms

Dental biofilms represent a serious oral health problem playing a key role in the development of caries and other oral diseases. In the present work, we cloned and expressed in E. coli two glucanases, Prevotella melaninogenica mutanase (PmGH87) and Capnocytophaga ochracea dextranase (CoGH66), and characterized them biochemically and biophysically. Their three-dimensional structures were elucidated and discussed. Furthermore, we tested the capacity of the enzymes to hydrolyze mutan and dextran to prevent formation of Streptococcus mutans biofilms, as well as to degrade pre- formed biofilms in low and abundant sugar conditions. The percentage of residual biofilm was calculated for each treatment group in relation to the control, as well as the degree of synergism. Our results suggest that both PmGH87 and CoGH66 are capable of inhibiting biofilm formation grown under limited or abundant sucrose conditions. Degradation of pre-formed biofilms experiments reveal a time-dependent effect for the treatment with each enzyme alone. In addition, a synergistic and dose-dependent effects of the combined enzymatic treatment with the enzymes were observed. For instance, the highest biomass degradation was 95.5% after 30 min treatment for the biofilm grown in low sucrose concentration, and 93.8% after 2 h treatment for the biofilm grown in sugar abundant condition. Strong synergistic effects were observed, with calculated degree of synergism of 5.54 and 3.18, respectively and their structural basis was discussed. Jointly, these data can pave the ground for the development of biomedical applications of the enzymes for controlling growth and promoting degradation of established oral biofilms.

Oral and fecal microbiome of confiscated Bengal slow lorises in response to confinement duration

Slow lorises are small arboreal and nocturnal primates. Due to the illegal trade, a large number of slow lorises were confiscated into wildlife sanctuaries or rescue centers. The re-release has been considered a preferable approach for alleviating the captive pressure, but inappropriate and long-term confinement make it difficult to achieve this goal. In this study, we investigated and compared the fecal and oral microbiome of Bengal slow lorises (Nycticebus bengalensis) under long-term captivity (LC) and short-term captivity (SC) groups based on 16s rRNA high-throughput gene sequencing. The oral microbiome displayed higher Chao1 richness but lower Shannon and Simpson indices than the fecal microbiome. The Bengal slow lorises under long-term captivity had abundant pathogenic genera in both gut and oral microbiomes, such as Desulfovibrio, Actinomyces, Capnocytophaga, Neisseria, and Fusobacterium, while some specific bacterial taxa associated with intestinal balance were more enriched in the SC group. Due to the plant gum scarcity in the diet, both groups had a low abundance of Bifidobacterium. Function profile prediction indicated that the LC group was enriched with genetic information processing and metabolism pathways due to the stable food intake. The increased membrane transport and xenobiotic metabolism and degradation functions in the SC group could be explained by the function of the host microbiome in facilitating adaptation to changing environments and diets. The results demonstrated that the oral microbiome had the potential to be used as a regular surveillance tool. Also, current captive management should be improved to ensure reintroduction success.

Identification and Characterization of the Biosynthetic Pathway of the Sulfonolipid Capnine

Capnine (2-amino-3-hydroxy-15-methylhexadecane-1-sulfonate) and capnoids (N-fatty acylated capnine derivatives) are sulfonolipids present in the outer membrane of gliding bacteria in the phylum Bacteroidetes and play a role in their unique gliding motility. They are structurally similar to sphingolipids and are thought to be biosynthesized via a similar pathway. Here we report the identification and biochemical characterization of the capnine biosynthetic enzymes cysteate synthase (CapA) and cysteate-C-fatty acyltransferase (CapB) from the pathogenic gliding bacterium Capnocytophaga ochracea and NAD(P)H-dependent dehydrocapnine reductase CapC from the avian pathogen Ornithobacterium rhinotracheale. CapA catalyzes the formation of cysteate from O-phospho-l-serine and sulfite, and CapB catalyzes the formation of dehydrocapnine from cysteate and 13-methyl-myristoyl-CoA, followed by reduction by CapC. CapA is closely related to cystathionine-β-synthase but distantly related to the archaeal cysteate synthase. Close homologues of CapA, CapB, and the CapA isozyme archaeal cysteate synthase are present in many Bacteroidetes bacteria, including environmental, pathogenic, and human oral and intestinal microbiome bacteria, suggesting the widespread ability of these bacteria to biosynthesize capnine and related sulfonolipids.

Multidrug-resistant oral Capnocytophaga gingivalis responsible for an acute exacerbation of chronic obstructive pulmonary disease: Case report and literature review

INTRODUCTION

Capnocytophaga genus was recently known to highly contribute to the beta-lactam (BL) and macrolide-lincosamide-streptogramin (MLS) resistance gene reservoir in the oral microbiota (BL: bla_CSP-1 and bla_CfxA; MLS: erm(F) and erm(C)). But fluoroquinolone (FQ) resistance remains uncommon in literature, without available data on resistance mechanisms.

CASE REPORT

For the first time, a case of acute exacerbation of chronic obstructive pulmonary disease (COPD) was described in a 78-year-old immunocompetent patient due to a multidrug-resistant Capnocytophaga gingivalis isolate with significant microbiological finding. C.gingivalis acquired resistance to third generation cephalosporins (bla_CfxA3 gene), MLS (erm(F) gene), and fluoroquinolones. Genetics of the resistance, unknown as regards fluoroquinolone, was investigated and a substitution in QRDR of GyrA was described (Gly80Asn substitution) for the first time in the Capnocytophaga genus.

LITERATURE REVIEW

A comprehensive literature review of Capnocytophaga spp. extra-oral infection was conducted. Including the present report, on 43 cases, 7 isolates were BL-resistant (17%), 4 isolates were MLS-resistant (9.5%) and 4 isolates were FQ-resistant (9.5%). The studied clinical isolate of C.gingivalis was the only one to combine resistance to the three groups of antibiotics BL, MLS and FQ. Four cases of Capnocytophaga lung infection were reported, including three infections involving C. gingivalis (two FQ resistant) and one involving C. sputigena.

CONCLUSION

This multidrug-resistant C. gingivalis isolate illustrated the role of oral flora as a reservoir of antibiotic resistance and its contribution to the limitation of effective antibiotics in severe respiratory infections.

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.

Capnocytophaga spp. DF-1 pneumonia in an immune-competent 56-year old man post-CABG

We report a case of a nosocomial Capnocytophaga spp. DF-1 pneumonia in an intubated 56-year-old man following coronary artery bypass grafting. We review Capnocytophaga spp., including the infections they produce and antibiotic susceptibilities.

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.

Capnocytophaga ochracea causing severe sepsis and purpura fulminans in an immunocompetent patient

Capnocytophaga ochracea (C. ochracea), a known human microflora, has been reported to cause sepsis in immunocompromised patients and less severe infections such as intrauterine infections, endocarditis, peritonitis and septic arthritis in the immunocompetent patient. We present the first described case of C. ochracea causing severe sepsis and purpura fulminans in an immunocompetent host.

Recovery of uncommon bacteria from blood: association with neoplastic disease

Table 6 is a summary of the organisms discussed with a listing of the environmental source, the endogenous source, the predisposing factors including neoplasms, and the postulated mechanisms by which the organism can gain access to the circulation. The evidence considered indicates that the entrance of one of these microorganisms into the bloodstream of a human being depends on the presence of multiplicity of predisposing factors. In the majority of cases of bacteremia due to one of these unusual organisms, two or more predisposing factors are present. Certain predisposing factors, such as cancer chemotherapy or intravenous catheterization, often provide a barrier break, while others, such as liver disease, may render the host immune system less capable of clearing organisms from the circulation. For organisms such as Campy-lobacter, Listeria, and Salmonella spp., attributes that allow the invasion of a healthy host are present and seem to be enhanced by the simultaneous presence of a predisposing condition, such as liver disease, in the host. Although somewhat fragmentary, a number of individual case reports describe bacteremia due to one of these organisms occurring weeks to years after surgery and after other therapeutic measures had effected a supposed cure of a cancer. It may be speculated that cancer patients, even after a cure, are still susceptible to bloodstream invasion by one of the aforementioned organisms by virtue of the presence of one or more predisposing metabolic, physiologic, or immunologic factors, even though these factors may be cryptic. The predominance of hematologic malignancies among cases of bacteremia due to these unusual organisms is also apparent. Although, as pointed out by Keusch (169), the reduction in the performance of immune function in hematologic malignancies compared with solid tumors is likely to be responsible, other associations of certain organisms with specific neoplasms warrant further examination. The frequency of bloodstream infections of Salmonella typhimurium and Capno-cytophaga canimorsus in Hodgkin's disease patients seems likely due to a particular mechanism which infection by these species is favored. The specific nature of these mechanisms remains to be determined. The recovery of any unusual bacterium from blood should warrant a careful consideration of the possibility of underlying disease, especially cancer. Microbiologists should advise clinicians of the unusual nature of the identified organism and provide the counsel that certain neoplastic processes, often accompanied by neutropenia, render the human host susceptible to invasion by almost any bacterium. The recovery of such organisms as C. septicum or S. bovis should prompt the clinician to aggressively seek to identify an occult neoplasm if one has not yet been diagnosed.

Restriction fragment length polymorphism analysis of PCR-amplified 16S ribosomal DNA of human Capnocytophaga

The confusion in the taxonomic status of the genus Capnocytophaga has made identification of strains and studies on the role of this genus in infectious diseases equivocal. In this study 33 strains of Capnocytophaga including reference strains and various clinical isolates, were studied using RFLP analysis of 16S ribosomal RNA genes. The 16S ribosomal RNA (rRNA) gene sequences from whole cell suspensions and isolated genomic DNA samples were amplified by the polymerase chain reaction (PCR) using eubacterial specific primers. PCR products were purified and characterized by single digestions with 12 restriction endonucleases. Five of these, BanI, CfoI, HaeIII, HphI and RsaII were found to discriminate reproducibly between strains, and restriction patterns (ribotypes) produced by these were analysed to clarify the classification of Capnocytophaga strains. Dendrograms inferring similarities were derived from these data by the UPGMA method. This analysis produced three major clusters of strains, each of which was associated with a previously proposed species type strain: C. gingivalis, C. sputigena and C. ochracea. The results support the division of Capnocytophaga into three species and demonstrate that, despite the heterogeneity of this genus, the modified ribotyping method provides a simple, rapid and reproducible way to identify Capnocytophaga strains.

Capnocytophaga keratitis. A clinicopathologic study of three patients, including electron microscopic observations

BACKGROUND

Histopathologic studies of this unusual keratitis caused by Capnocytophaga species have not been reported previously.

METHODS

The authors report the light microscopic and ultrastructural findings of three patients with a distinctive necrotizing keratitis caused by an anaerobic gram-negative bacillus. In three patients, ages 19, 81, and 91 years, a necrotizing stromal keratitis developed; two of these patients had a previous penetrating keratoplasty for pseudophakic bullous keratopathy. The first patient did not have ocular surgery previously and was treated initially for presumed Acanthamoeba keratitis.

RESULTS

By light microscopy, all three keratectomy specimens were strikingly similar and showed a necrotizing and/or suppurative stromal keratitis displaying myriad slender, fusiform, gram-negative bacilli located anterior to Descemet's membrane and extending into the deep corneal stroma, assuming a "picket fence" appearance. Cultures of the cornea in case 1 grew Capnocytophaga ochracea. For the remaining two patients, a diagnosis presumptively was made based on characteristic histopathologic features. Results of electron microscopic examination showed numerous bacilli that were mostly extracellular; occasional organisms were phagocytosed by macrophages.

CONCLUSION

The histopathologic features of Capnocytophaga keratitis are unique; therefore, a presumptive diagnosis can be made based on the morphology and location of the bacilli in the keratectomy specimens. To the authors' knowledge, this is the first study describing the typical histopathologic and electron microscopic findings of Capnocytophaga keratitis.

Spontaneous ulcerative keratitis in immunocompromised patients

We studied the occurrence of ulcerative keratitis in five eyes of four patients who were examined at the University of Maryland Hospital ophthalmology clinic over a 12-month period. All were young women who were intravenous drug abusers, with no known predisposing factors for ulcerative keratitis. Two patients had acquired immunodeficiency syndrome (AIDS), one was human immunodeficiency virus (HIV)-positive, and the fourth refused HIV testing. One had a corneoscleral limbus to corneoscleral limbus keratitis; three had inferiorly located corneal ulcers (bilateral in one patient with AIDS). Corneal cultures disclosed Capnocytophaga species in the corneoscleral limbus to corneoscleral limbus keratitis. The remaining ulcers were polymicrobial; cultures of three grew Candida albicans, cultures of two grew alpha-hemolytic streptococci, cultures of two grew Staphylococcus aureus, and culture of one grew Pseudomonas aeruginosa. Treatment with topical fortified antibiotics and antifungal agents resulted in complete healing in all four inferiorly located ulcers. The corneal ulcer became perforated and the eye was eviscerated. Histopathologic analysis of the eviscerated specimen disclosed acute keratitis with necrosis and no microorganisms.

Inguinal lymphadenitis associated with Capnocytophaga bacilli

Capnocytophaga organisms are capnophilic, gram-negative bacilli that have been associated with infections deriving from the flora of the oropharynx. We report a case of inguinal adenitis caused by Capnocytophaga species that probably represents sexual transmission of the pathogen.

Novel beta-lactamase from Capnocytophaga sp

A novel beta-lactamase activity which confers resistance to expanded-spectrum cephalosporins and penicillins has been found in strain IC 5/21 of Capnocytophaga spp. Enzyme activity migrated at a molecular size of 38,000 daltons and at an isoelectric point of 3.6, with a minor band at 4.1. Kinetic studies suggested that it belonged to Richmond and Sykes beta-lactamase class 1c. Isoelectric focusing could be achieved only if a nonionic detergent was added to the gel, suggesting the presence of a hydrophobic enzyme akin to a membrane-bound beta-lactamase of gram-positive bacteria. The location of the gene coding for this beta-lactamase is not yet known.

Susceptibility testing of Danish isolates of Capnocytophaga and CDC group DF-2 bacteria

Twelve Capnocytophaga and seven DF-2 strains were tested for their susceptibility to 14 antimicrobial agents using an agar dilution and an agar diffusion method. Twenty-three other antibiotics were evaluated using the diffusion test only. All strains were fully susceptible to penicillin, ampicillin, cefuroxime, cefotaxime, erythromycin, clindamycin, chloramphenicol, doxycycline, rifamycin and ofloxacin using both methods. Clindamycin, rifamycin and cefotaxime were most active. Using agar dilution some strains were susceptible to gentamicin, but agar diffusion showed total resistance. One Capnocytophaga strain was susceptible and another moderately susceptible to metronidazole, other strains were resistant. The agar diffusion test showed that both Capnocytophaga and DF-2 were resistant to most other aminoglycosides, to fosfomycin, polymyxin and trimethoprim. All strains of both taxa were fully susceptible to piperacillin, cefoxitin, imipenem and fusidic acid and showed different susceptibilities to the other agents. Susceptibility testing by means of agar diffusion using an enriched chocolate agar and 5% CO2 atmosphere could be used to test Capnocytophaga and DF-2 strains and gives sufficient accuracy for routine use, when revised inhibition zone breakpoints are employed.

Necrotizing keratitis caused by Capnocytophaga ochracea

We studied three cases of Capnocytophaga keratitis that demonstrated stromal necrosis and a ring infiltrate. In all cases, the keratitis occurred in a previously diseased or traumatized cornea. One patient was treated with chronic antiamoebic therapy for presumed Acanthamoeba keratitis. Two cases resulted in corneal perforation. Laboratory isolation was difficult because of slow, fastidious growth. Capnocytophaga is not uniformly sensitive to commonly used topical antibiotics such as the cephalosporins and aminoglycosides, but may respond to treatment with topical clindamycin.

Capnocytophaga

Capnocytophaga has been found to cause disease in the normal and the immunocompromised patient. Most often this organism is an opportunist that is difficult to isolate but easy to identify and a unique reminder that uncommon infection may respond to common antibiotics.

In vitro susceptibility of Capnocytophaga species to antimicrobial agents

A total of 33 clinical isolates of Capnocytophaga spp. were susceptible to 4-quinolone antimicrobial agents. The antipseudomonal penicillins tested were equally active against all isolates, as were cefuroxime, ceftriaxone, ceftizoxime, cefotaxime, latamoxef, and ceftazidime. Most isolates were resistant to trimethoprim, and some were resistant to aztreonam. Most regimens for the empirical treatment of septic episodes in immunocompromised patients are suitable for the treatment of Capnocytophaga spp. infections.

Capnocytophaga in the amniotic fluid of a woman in preterm labor with intact membranes

Chorioamnionitis is thought to be uncommon with intact fetal membranes. A case is reported of a woman in preterm labor with intact membranes from whose amniotic fluid, placenta, and infant's gastric aspirate an unusual organism, Capnocytophaga, was identified. The findings are discussed.