Anaerobiospirillum succiniciproducens y Desulfovibrio desulfuricans en 2 casos de bacteriemias insidiosas / Anaerobiospirillum succiniciproducens and Desulfovibrio desulfuricans in 2 cases of insidious bacteremia

Se presentan 2 casos de bacteriemias insidiosas por bacilos gram negativos anaerobios curvos, espiralados, móviles e infrecuentes en pacientes atendidos en un hospital de la ciudad de Buenos Aires. Estas bacteriemias, asociadas al aislamiento de Anaerobiospirillum y Desulfovibrio, fueron de origen poco claro y afectaron a pacientes inmunocomprometidos, con patologías simultáneas. Pruebas claves en la identificación del género Anaerobiospirillum fueron el estudio de la micromorfología, su carácter de anaerobio estricto, el resultado negativo en la prueba de catalasa, el patrón de discos de interés taxonómico, la fermentación de glucosa y la producción de β-N-acetilglucosaminidasa. El género Desulfovibrio se diferenció por el perfil presentado en las pruebas con discos, por ser asacarolítico, sin actividad de enzimas glucosídicas, y por producir desulfoviridina y H2S. Se alerta sobre la resistencia o sensibilidad intermedia de Anaerobiospirillum succiniciproducens (especie a la que correspondió el aislado de Anaerobiospirillum) a algunos de los antimicrobianos de primera línea frente a bacilos gram negativos anaerobios, como el metronidazol; fueron activas las combinaciones de aminopenicilinas con inhibidores de β-lactamasas y el imipenem. Desulfovibrio desulfuricans (especie a la que correspondió el aislado de Desulfovibrio) fue productora de β-lactamasas y resistente a las cefalosporinas; en cambio, fueron activos el metronidazol, el imipenem y la levofloxacina. La identificación confiable de estos microorganismos orienta hacia el mejor esquema terapéutico.

Two cases of insidious bacteremia by uncommon curve and spiral-shaped, motile anaerobic gram-negative rods are presented. Both of them were of an unclear origin and occurred in immunosuppressed patients with simultaneous diseases. The key tests for the identification of Anaerobiospirillum were its micromorphology, a strictly anaerobic condition, negative catalase activity, the special-potency disk profile, glucose fermentation, and β-NAG production. Desulfovibrio species was identified by all the above preliminary tests but with a different disk profile, as well as for being asaccharolytic and desulfoviridin and H2S producer. We here alert about the resistance or intermediate susceptibility of Anaerobiospirillum succiniciproducens against antimicrobial agents, such as metronidazole, one of the first-line drugs used for the treatment of anaerobic gram-negative infections. Aminopenicillins with β-lactamase-inhibitor combinations and imipenem were active for this agent. Desulfovibrio desulfuricans was β-lactamase producer and resistant to cephalosporins, while metronidazole, imipenem and levofloxacin were active. A reliable identification of these microorganisms is important for establishing the best therapeutic scheme.

[Anaerobiospirillum succiniciproducens and Desulfovibrio desulfuricans in 2 cases of insidious bacteremia]. / Anaerobiospirillum succiniciproducens y Desulfovibrio desulfuricans en 2 casos de bacteriemias insidiosas.

Two cases of insidious bacteremia by uncommon curve and spiral-shaped, motile anaerobic gram-negative rods are presented. Both of them were of an unclear origin and occurred in immunosuppressed patients with simultaneous diseases. The key tests for the identification of Anaerobiospirillum were its micromorphology, a strictly anaerobic condition, negative catalase activity, the special-potency disk profile, glucose fermentation, and ß-NAG production. Desulfovibrio species was identified by all the above preliminary tests but with a different disk profile, as well as for being asaccharolytic and desulfoviridin and H2S producer. We here alert about the resistance or intermediate susceptibility of Anaerobiospirillum succiniciproducens against antimicrobial agents, such as metronidazole, one of the first-line drugs used for the treatment of anaerobic gram-negative infections. Aminopenicillins with ß-lactamase-inhibitor combinations and imipenem were active for this agent. Desulfovibrio desulfuricans was ß-lactamase producer and resistant to cephalosporins, while metronidazole, imipenem and levofloxacin were active. A reliable identification of these microorganisms is important for establishing the best therapeutic scheme.

[Anaerobiospirillum thomasii bacteremia with fatal outcome]. / Bacteriemia por Anaerobiospirillum thomasii con desenlace fatal.

Anaerobiospirillum thomasii has been reported as a causative agent of diarrhea in humans; however no bacteremia associated with this pathogen has been described so far. We present here the first case of fatal A. thomasii bacteremia in an alcoholic patient.

Bacteriemia por Anaerobiospirillum thomasii con desenlace fatal / Anaerobiopirillum thomasii bacteremia with gatal outcome

Anaerobiospirillum thomasii ha sido descrito como causante de diarrea en humanos, pero no se han informado bacteriemias asociadas a este organismo. En esta comunicación describimos el primer aislamiento de A. thomasii como causa de bacteriemia fatal en una paciente alcohólica

Anaerobiospirillum thomasii has been reported as a causative agent of diarrhea in humans; however no bacteremia associated with this pathogen has been described so far. We present here the first case of fatal A. thomasii bacteremia in an alcoholic patient

Stereochemistry of the carboxylation reaction catalyzed by the ATP-dependent phosphoenolpyruvate carboxykinases from Saccharomyces cerevisiae and Anaerobiospirillum succiniciproducens.

The stereochemistry of CO(2) addition to phosphoenolpyruvate (PEP) to yield oxaloacetate catalyzed by ATP-dependent Saccharomyces cerevisiae and Anaerobiospirillum succiniciproducens PEP carboxykinases was determined using (Z)-3-fluorophosphoenolpyruvate ((Z)-F-PEP) as a substrate analog. A. succiniciproducens and S. cerevisiae PEP carboxykinases utilized (Z)-F-PEP with 1/14 and 1/47 the respective K(m) values for PEP. On the other hand, in the bacterial and yeast enzymes k(cat) was reduced to 1/67 and 1/48 the value with PEP, respectively. The binding affinity of pyridoxylphosphate-labeled S. cerevisiae and A. succiniciproducens PEP carboxykinases for PEP and (Z)-F-PEP was checked and found to be of similar magnitude for both substrates, suggesting that the lowered K(m) values for the fluorine-containing PEP analog are due to kinetic effects. The lowered k(cat) values when using (Z)-F-PEP as substrate suggest that the electron withdrawing effect of fluorine affects the nucleophilic attack of the double bond of (Z)-F-PEP to CO(2). For the stereochemical analyses, the carboxylation of (Z)-F-PEP was coupled to malate dehydrogenase to yield 3-fluoromalate, which was analyzed by (19)F NMR. The fluoromalate obtained was identified as (2R, 3R)-3-fluoromalate for both the A. succiniciproducens and S. cerevisiae PEP carboxykinases, thus indicating that CO(2) addition to (Z)-F-PEP, and hence PEP, takes place through the 2-si face of the double bond. These results, together with previously published data [Rose, I.A. et al. J. Biol. Chem. 244 (1969) 6130-6133; Hwang, S.H. and Nowak, T. Biochemistry 25 (1986) 5590-5595] indicate that PEP carboxykinases, no matter their nucleotide specificity, catalyze the carboxylation of PEP from the 2-si face of the double bond.

Comparative kinetic effects of Mn (II), Mg (II) and the ATP/ADP ratio on phosphoenolpyruvate carboxykinases from Anaerobiospirillum succiniciproducens and Saccharomyces cerevisiae.

The kinetic affinity for CO(2) of phosphoenolpyruvate PEP(5) carboxykinase from Anaerobiospirillum succiniciproducens, an obligate anaerobe which PEP carboxykinase catalyzes the carboxylation of PEP in one of the final steps of succinate production from glucose, is compared with that of the PEP carboxykinase from Saccharomyces cerevisiae, which catalyzes the decarboxylation of oxaloacetate in one of the first steps in the biosynthesis of glucose. For the A. succiniciproducens enzyme, at physiological concentrations of Mn(2+) and Mg(2+), the affinity for CO(2) increases as the ATP/ADP ratio is increased in the assay medium, while the opposite effect is seen for the S. cerevisiae enzyme. The results show that a high ATP/ADP ratio favors CO(2) fixation by the PEP carboxykinase from A. succiniciproducens but not for the S. cerevisiae enzyme. These findings are in agreement with the proposed physiological roles of S. cerevisiae and A. succiniciproducens PEP carboxykinases, and expand recent observations performed with the enzyme isolated from Panicum maximum (Chen et al. (2002) Plant Physiology 128: 160-164).

Fatal bacteremia due to Anaerobiospirillum succiniciproducens: first description in Brazil.

Anaerobiospirillum succiniciproducens is an anaerobic, Gram-negative, spiral shaped bacteria, which is motile by means of bipolar tuffs of flagella. This organism appears to be a rare cause of bacteremia in humans, and it usually affects patients submitted to immunosuppressive therapy. Anaerobiospirillum succiniciproducens resembles Campylobacter spp. in Gram-stained preparations, however, it is considered resistant to most antimicrobial drugs that are used to treat Campylobacter infections. We observed Gram-negative, spiral shaped bacteria in Gram-stained preparations from blood culture flasks. Growth occurred only under anaerobic incubation, and identification to the species level was achieved by PCR amplification of the 16S rRNA gene, followed by direct sequencing and a GenBank homology search. To the best of our knowledge, this is the first reported Brazilian case of Anaerobiospirillum succiniciproducens bacteremia.

Fatal bacteremia due to Anaerobiospirillum succiniciproducens: first description in Brazil

Anaerobiospirillum succiniciproducens is an anaerobic, Gram-negative, spiral shaped bacteria, which is motile by means of bipolar tuffs of flagella. This organism appears to be a rare cause of bacteremia in humans, and it usually affects patients submitted to immunosuppressive therapy. Anaerobiospirillum succiniciproducens resembles Campylobacter spp. in Gram-stained preparations, however, it is considered resistant to most antimicrobial drugs that are used to treat Campylobacter infections. We observed Gram-negative, spiral shaped bacteria in Gram-stained preparations from blood culture flasks. Growth occurred only under anaerobic incubation, and identification to the species level was achieved by PCR amplification of the 16S rRNA gene, followed by direct sequencing and a GenBank homology search. To the best of our knowledge, this is the first reported Brazilian case of Anaerobiospirillum succiniciproducens bacteremia.

Anaerobiospirillum succiniciproducens phosphoenolpyruvate carboxykinase. Mutagenesis at metal site 1.

Anaerobiospirillum succiniciproducens phosphoenolpyruvate (PEP) carboxykinase catalyses the reversible metal-dependent formation of oxaloacetate (OAA) and ATP from PEP, ADP and CO(2). Mutations of PEP carboxykinase have been constructed where the residues His(225) and Asp(263), two residues of the enzyme's putative Mn(2+) binding site, were altered. Kinetic studies of the His225Glu, and Asp263Glu PEP carboxykinases show 600- and 16,800-fold reductions in V(max) relative to the wild-type enzyme, respectively, with minor alterations in K(m) for Mn(2+). Molecular modeling of wild-type and mutant enzymes suggests that the lower catalytic efficiency of the Asp263Glu enzyme could be explained by a movement of the lateral chain of Lys(248), a critical catalytic residue, away from the reaction center. The effect on catalysis of introducing a negatively charged oxygen atom in place of N(epsilon-2) at position 225 is discussed in terms of altered binding energy of the intermediate enolpyruvate.