Symbiosis of Aeromonas veronii biovar sobria and Hirudo medicinalis, the medicinal leech: a novel model for digestive tract associations - PubMed (original) (raw)

Symbiosis of Aeromonas veronii biovar sobria and Hirudo medicinalis, the medicinal leech: a novel model for digestive tract associations

J Graf. Infect Immun. 1999 Jan.

Abstract

Hirudo medicinalis, the medicinal leech, is applied postoperatively in modern medicine. Infections by Aeromonas occur in up to 20% of patients unless a preemptive antibiotic treatment is administered. The associated infections demonstrate the need for a better understanding of the digestive tract flora of H. medicinalis. Early studies reported the presence of a single bacterial species in the digestive tract and suggested that these bacteria were endosymbionts contributing to the digestion of blood. In this study, we cultivated bacteria from the digestive tract and characterized them biochemically. The biochemical test results identified the isolates as Aeromonas veronii biovar sobria. This species identification was supported by sequence comparison of a variable region of the genes coding for 16S rRNA. In a colonization assay, a rifampin-resistant derivative of a symbiotic isolate was fed in a blood meal to H. medicinalis. The strain colonized the digestive tract rapidly and reached a concentration similar to that of the native bacterial flora. For the first 12 h, the in vivo doubling time was 1.2 h at 23 degreesC. After 12 h, at a density of 5 x 10(7) CFU/ml, the increase in viable counts ceased, suggesting a dramatic reduction in the bacterial growth rate. Two human fecal isolates, identified as Aeromonas hydrophila and A. veronii biovar sobria, were also able to colonize the digestive tract. These data demonstrate that the main culturable bacterium in the crop of H. medicinalis is A. veronii biovar sobria and that the medicinal leech can be used as a model for digestive tract association of Aeromonas species.

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Figures

FIG. 1

Drawing of a ventrally dissected H. medicinalis. The digestive tract of an adult is shown. The jaws (J), pharnyx (P), crop (C), lateral cecae (LC), posterior cecae (PC), intestine (I), and posterior sucker (PS) are shown and labeled. Bar, 0.5 cm.

FIG. 2

Colonization kinetics of a symbiotic strain. The Rfr test strain was fed to H. medicinalis in a blood meal. The blood was warmed to 37°C, and the bacteria were added (2 × 104 CFU/ml). The bacteria recovered from the intraluminal fluid of the digestive tract (A) and those associated with digestive tract tissue (B) are shown. Culturable bacteria (native bacterial flora and test strain) were recovered on blood agar plates (■), and the test strain was recovered on LB-RIF plates (▴) at the indicated times as described in Materials and Methods. Each error bar depicts 1 standard deviation.

FIG. 3

Ability of Aeromonas species to colonize H. medicinalis. The abilities of Rfr derivatives from A. hydrophila, A. veronii biovar sobria, and the symbiotic isolate were determined. The animals were fed blood containing 2 × 104 CFU of the test strain per ml. The strains were compared at 6 and 18 h after feeding. Bacteria recovered from the intraluminal fluid of the digestive tract and associated with the digestive tract tissue are shown. Recovery of all bacteria (native bacterial flora and test strain) (black bars) and the introduced test strain (shaded bars) is shown. Each error bar depicts 1 standard deviation.

References

1. Abbott S L, Cheung W K W, Kroske-Bystrom S, Malekzadeh T, Janda J M. Identification of Aeromonas strains to the genospecies level in the clinical laboratory. J Clin Microbiol. 1992;30:1262–1266. - PMC - PubMed
1. Abrutyn E. Hospital-associated infections from leeches. Ann Int Med. 1988;109:356–358. - PubMed
1. Büsing K-H. Pseudomonas hirudinis, ein bakterieller Darmsymbiont des Blutegels (Hirudo officinalis) Zentralbl Bakteriol. 1951;157:478–485. - PubMed
1. Büsing K-H, Döll W, Freytag K. Die Bakterienflora der medizinischen Blutegel. Arch Mikrobiol. 1953;19:52–86. - PubMed
1. de Chalain T M. Exploring the use of the medicinal leech: a clinical risk-benefit analysis. J Reconstr Microsurg. 1996;12:165–172. - PubMed

Symbiosis of Aeromonas veronii biovar sobria and Hirudo medicinalis, the medicinal leech: a novel model for digestive tract associations - PubMed (original) (raw)