R. Ruimy

Roseobacter algicola sp. nov., a new marine bacterium isolated from the phycosphere of the toxin-producing dinoflagellate Prorocentrum lima

We describe a new species on the basis of phenotypic characteristics and the results of an analysis of small-subunit rRNA sequences. Three strains of this organism were isolated from a culture of the toxin-producing dinoflagellate Prorocentrum lima. These bacteria are gram-negative, strictly aerobic, ovoid organisms that are motile by means of one or two subpolar flagella. They grow at temperatures ranging from 10 to 37 degrees C and in the presence of NaCl concentrations ranging from 0.1 to 2 M and have an absolute requirement for sodium ions. They are strictly aerobic with a nonfermentative type of metabolism and are not able to grow anaerobically in presence or absence of nitrate. They do not denitrify. They exhibit oxidase, catalase, gelatinase, esculinase, beta-galactosidase, and (to a lesser extent) amylase activities. The three strains which we examined require thiamine and biotin for growth. They grow only when glucose, trehalose, saccharose, fructose, maltose, pyruvate, malate, citrate, esculin, 2-ketoglutarate, 5-ketogluconate, glutamate, or shikimate is present as a sole carbon source. The three strains have identical small-subunit rRNA sequences. A phylogenetic analysis of these sequences revealed that these bacteria belong to the alpha subdivision of the Proteobacteria and that they form a distinct and robust monophyletic group with Roseobacter denitrificans and Roseobacter litoralis. This result and the general phenotypic characteristics of the organisms place them in the genus Roseobacter, although they do not produce bacteriochlorophyll a, in contrast to previously described Roseobacter species.(ABSTRACT TRUNCATED AT 250 WORDS)

Small-Subunit rRNA Sequences and Whole DNA Relatedness Concur for the Reassignment of Pasteurella piscicida (Snieszko et al.) Janssen and Surgalla to the Genus Photobacterium as Photobacterium damsela subsp. piscicida comb. nov.

The taxonomic status of Pasteurella piscicida (strain NCIMB 2058T [T = type strain] and a strain isolated from the environment) was investigated by performing phylogenetic analyses of small-subunit rRNA sequences, DNA-DNA hybridization analyses, and biochemical characterization analyses. The results of the phylogenetic analyses and the levels of DNA-DNA complementarity demonstrated conclusively that Pasteurella piscicida is extremely closely related to Photobacterium damsela ATCC 33539T. Since the two taxa exhibited a level of DNA-DNA relatedness of 80%, they are members of the same species. The high level of DNA relatedness and the presence of specific morphological and biochemical characteristics support the hypothesis that two subspecies should be recognized. On the basis of its phylogenetic position, we concluded that Pasteurella piscicida should be renamed Photobacterium damsela subsp. piscicida comb. nov.

Species identities and antimicrobial susceptibilities of corynebacteria Isolated from various clinical sources

Over a 14-month period, 415 clinical isolates of coryneform gram-positive rods were recovered from various sources and identified to the species level according to recent identification schemes.Corynebacterium urealyticum, Corynebacterium striatum, Corynebacterium amycolatum, andCorynebacterium jeikeium predominated, accounting for 63% of all isolates.Corynebacterium accolens, Corynebacterium striatum, Corynebacterium argentoratense, Corynebacterium propinquum andCorynebacterium pseudodiphtheriticum were mostly recovered from the respiratory tract, whereasCorynebacterium afermentans, CDC group G, andCorynebacterium jeikeium were mainly isolated from blood. None of the isolates was identified asCorynebacterium diphtheriae orCorynebacterium xerosis. Ampicillin resistance was detected inCorynebacterium jeikeium (96%) andCorynebacterium urealyticum (99%) and varied amongCorynebacterium amycolatum (56%) and CDC group G (26%). These data emphasize the need for an accurate identification of coryneform organisms at the species level and for antimicrobial susceptibility testing of these organisms.

Genomic diversity and phylogenetic relationships among lipid-requiring diphtheroids from humans and characterization of Corynebacterium macginleyi sp. nov.

DNA relatedness experiments were performed with 38 clinical isolates and 13 reference strains of coryneform taxa exhibiting a lipid requirement for optimal growth. Forty-five of these strains split into five genomic groups at the species level, whereas six other strains remained unclustered. Genomospecies II fits Corynebacterium accolens, but the other genomospecies were not genetically related to any of the defined Corynebacterium species. Phylogenetic analyses of genes coding for small-subunit rRNA sequences revealed that two genomospecies (I and III) and C. accolens form a tight cluster within the robust branch that groups all Corynebacterium species presently sequenced. Reference strains of biotypes C-1, C-2, and C-3 of Corynebacterium pseudogenitalium were found to fall into genomospecies I, as well as Corynebacterium tuberculostearicum, Centers for Disease Control and Prevention (CDC) coryneform group G-1, and CDC coryneform group G-2 reference strains. Biochemical tests allowed differentiation between genomospecies except between genomospecies IV and V and between six unclustered strains and genomospecies I. We propose a new classification for these lipid-requiring diphtheroids within the genus Corynebacterium with the delineation of some CDC coryneform group G-1 strains (genomospecies III) as a new species for which the name Corynebacterium macginleyi is proposed. The type strain is strain JCL-2 (CIP 104099), isolated from a human corneal ulcer.

Corynebacterium argentoratense sp. nov., from the human throat

A new Corynebacterium species, Corynebacterium argentoratense was isolated from the throats of four human patients. It is characterized by the presence of chemotype IV, a cell wall, corynomycolic acids, and a G+C content ranging from 60 to 61 mol%. Strains belonging to this species exhibit high levels of DNA relatedness as determined by DNA-DNA hybridization experiments (S1 nuclease procedure) but no close DNA relatedness with related Corynebacterium species. Phylogenies based on comparative analyses of nearly complete small-subunit rDNA sequences confirmed the inclusion of this new species within the genus Corynebacterium and grouped it in a cluster with C. diphtheriae, C. ulcerans, C. pseudotuberculosis, and C. kutscheri. PCR experiments revealed an absence of the gene coding for diphtheria toxin. This new species can be identified by its mycolic acid pattern, fermentation of sugars, and enzymatic activities. Strain IBS B10697 (CIP 104296) is the type strain of C. argentoratense.

Bartonella quintana Coinfection in Staphylococcus aureus Endocarditis: Usefulness of Screening in High-Risk Patients?

To the Editor—A 43-year-old homeless man was admitted to a Parisian hospital in February 2008 with acute onset of fever, chills, and altered general status. No significant signs were found at initial examination. Usual blood test results were normal except for hyperleukocytosis (16,000 neutrophils/mm) and an elevated C-reactive protein level (298 mg/L). Three blood cultures were obtained, and treatment with amoxicillin-clavulanate (3 g/ day) was empirically started. On day 1, all blood cultures grew methicillin-susceptible Staphylococcus aureus. Transesophageal echocardiography showed large vegetations on the aortic valve, with grade III regurgitation, but no evidence of preexisting valvulopathy. A diagnosis of S. aureus endocarditis was made, and treatment with amoxicillin-clavulanate was switched to oxacillin plus gentamicin (200 mg/kg/ day and 4 mg/kg/day, respectively). On day 5, rapid worsening of the aortic regurgitation resulted in severe pulmonary edema and the patient was referred to the Bichat-Claude-Bernard Hospital for urgent surgery, consisting of aortic valve replacement with a bioprosthesis. Findings obtained during the surgical procedure ruled out concomitant mitral involvement. As expected, direct smears of the resected native valve showed clustered grampositive cocci, but cultures remained negative after 48 h, probably because of previous antibiotherapy. Broad-range eubacterial 16S ribosomal DNA gene PCR was routinely performed on valvular samples. Surprisingly, the resulting sequence was identical to that of Bartonella quintana (GenBank accession number M11927). However, on the sixth day after the operation, cultures of valve samples grew methicillin-susceptible S. aureus. Serologic test results for Bartonella species were negative, but Western blot with cross-adsorption identified antibodies to B. quintana [1]. Because of these conflicting data, the presence of S. aureus and B. quintana DNA in the valve tissue was confirmed by specific PCR [2, 3]. Subsequent WarthinStarry and Giemsa costaining on vegetations revealed both small bacilli and clustered cocci (figure 1). The diagnosis of coinfective endocarditis due to B. quintana and methicillin-susceptible S. aureus was confirmed. A 6-week course of doxycycline (400 mg/day) was added to the previous antibiotherapy regimen to target B. quintana; the patient received oxacillin for 6 weeks and gentamicin for a total duration of 2 weeks (gentamicin acts effectively against both pathogens). The patient was lost to follow-up 3 months after surgery, with no clinical or echocardiographic evidence of relapse. Acute superinfection by S. aureus of chronic B. quintana endocarditis is the most likely cause of illness for this patient. Dual-pathogen endocarditis is rare [4], and to our knowledge, this is the first case report of coinfective native valve endocarditis due to S. aureus plus B. quintana. S. aureus endocarditis accounts for 30%– 40% of all infective endocarditis [5], whereas B. quintana, a fastidious gramnegative bacterium, has been increasingly reported in culture-negative endocarditis over the past decade because of the development of specific serological and molecular diagnostic tools [6]. B. quintana is transmitted by Pediculus humanus var. corporis, the human body louse. Homelessness and other conditions associated with pediculosis thus constitute the leading risk factors for B. quintana infection, which usually involves chronic bacteremia [6, 7]. However, the link between chronic bacteremia and endocarditis remains unclear, because most patients, including ours, do not have preexisting valvulopathy. In polymicrobial specimens, sequences from broad-range eubacterial 16S ribosomal DNA PCR products may be mixed and unreadable. In our case, the fortuitous discovery of B. quintana by amplification and sequencing, in spite of the coexistence of S. aureus in the valvular tissue, was probably favored by the high ratio of B. quintana to S. aureus. This case underlines the usefulness of a systematic search for B. quintana coinfection with use of specific diagnostic tools in homeless patients with endocarditis caused by fast-growing bacterial species, enabling the choice of appropriate antibiotherapy, and undoubtedly leading to improved outcomes.