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УДК 619.579 ББК 28.4
THE GENUS AEROMONAS
HAFFARESSAS Y.
Lobachevsky State University of Nizhny Novgorod, Nizhny Novgorod, Russia e-mail: [email protected]
Abstract
Aeromonas species are ubiquitous bacteria in terrestrial and aquatic milieus. The main Aeromonas species responsible for human infections are: A. hydrophila, A. caviae, A. veronii biogroup sobria. Aeromonas are thought to be one of the major causes of gastroenteritis, they are becoming renowned as enteric pathogens of serious public health concern as they acquire a number of virulence determinants that are linked with human diseases, such as gastroenteritis, soft-tissue, muscle infections, septicemia, and skin diseases. Proper sanitary procedures are essential in the prevention of the spread of Aeromonas infections.
Keywords: Aeromonas hydrophila, Aeromonas Gastroenteritis.
Species of Aeromonas are Gram-negative, non-spore-forming, rod-shaped, facultatively anaerobic bacteria that occur ubiquitously and autochthonously in aquatic environments. Although historically the Aeromonas genus has been placed in the family Vibrionaceae [17], there have been proposals to place it in its own family, the Aeromonadaceae [4]. The aeromonads share many biochemical characteristics with members of the Enterobacteriaceae, from which they are primarily differentiated by being oxidase-positive. The genus includes at least 13 genospecies, among which are the mesophilic A. hydrophila, A. caviae, A. sobria, A. veronii, and A. schubertii, and the non-motile, psychrophilic A. salmonicida. A. salmonicida is a fish pathogen and has not been associated with human infection. By contrast, the mesophilic species have been associated with a wide range of infections in humans [9]. Although members of the genus have classically been divided into three biochemically differentiated groups (typified by A. hydrophila, A. caviae, and A. sobria), these contain
caviae,Aeromonas veronii, Aeromonas sobria,
a number of genospecies, to which new species have been added [3]. Currently the genus is made up of 17 DNA hybridization groups representing a range of genospecies and phenospecies (see Table 1). The mesophilic aeromonads have been commonly isolated from patients with gastroenteritis although their role in disease causation remains unclear. They are also associated with sepsis and wounds, and with eye, respiratory tract, and other systemic infections [8, 9, 16]; (see Table 2). Many of the systemic infections arise following contamination of lacerations and fractures with Aeromonas-rich waters. The species principally associated with gastroenteritis are A. caviae, A. hydrophila, and A. veronii biovar sobria [10]; A. caviae is particularly associated with young children (under 3 years of age). The health significance of detecting mesophilic aeromonads in drinking-water supplies is not well understood: no clearly defined point-source outbreak has been documented and establishing epidemiological links is difficult.
DNA hybridization group Reference strain (T = type strain) Genospecies Phenospecies
1 ATCC 7966T A. hydrophila A. hydrophila
2 ATCC 51108T A. bestiarum A. hydrophila
3 ATCC 33658T A. salmonicida A. salmonicida
3 CDC 0434-84 A. salmonicida A. hydrophila
4 ATCC 15468T A. caviae A. caviae
5A CDC 0862-83 A. media A. caviae
5B CDC 0435-84 A. media A. media
6 ATCC 23309T A. eucrenophila A. eucrenophila
7 CIP 7433T A. sobria A. sobria
8 ATCC 9071 A. veronii A. veronii biovar sobria
Table 1
Genospecies and phenospecies of the genus Aeromonasa
9 ATCC 49568T A. jandaei A. jandaei
iG ATCC 35624T A. veronii A. veronii
ii ATCC 35941 Unnamed Aeromonas sp. (ornithinepositive)
12 ATCC 437GGT A. schubertii A. schubertii
13 ATCC 43946 Unnamed Aeromonas Group 5G1
14 ATCC 49657T A. trota A. trota
15 CECT 4199T A. allosaccharophilab A. allosaccharophilab
16 CECT 4342T A. encheleiab A. encheleiab
Примечания: a - Modified from Carnahan & Altwegg, 1996 [3]; b - The taxonomic status of A. allosaccharophila and A. encheleia remains to be confirmed. A further new species, A. popoffi (unassigned DNA hybridization group), has also been proposed.
Table 2
Relative frequency of occurrence of human infections associated with mesophilic Aeromonasa
Type of infection Characteristics Relative frequency13
Diarrhoea Acute watery diarrhoea, vomiting Very common
Secretory Acute diarrhoea with blood and mucus Common
Dysenteric Diarrhoea lasting more than 10 days Common
Chronic "Rice water" stools Rare
Choleraic Inflammation of connective tissue Common
Systemic Haemorrhage, necrosis with/without gas gangrene Rare
Cellulitis Skin lesions with necrotic centre, sepsis Uncommon
Myonecrosis Fever, chills, hypotension, high mortality Fairly common
Erythema Inflammation of peritoneum Uncommon
Gangrenosum Pneumonia with septicaemia, sometimes necrosis Rare
Septicaemia Bone infection following soft-tissue infection Rare
Peritonitis Conjunctivitis, corneal ulcer, endophthalmitis Rare
Pneumonia
Osteomyelitis
Eye infections
Примечания: a - Modified from Janda & Duffey, 1988 [8], and Nichols et al., 1996 [16]; b - Frequency of occurrence relative to all cases of Aeromonas infection.
Aeromonas hydrophila species complex. An
example of the taxonomic complexity of the genus Aeromonas is the difficulty in discriminating between the phenotypically and genetically closely related species belonging to the Aeromonas hydrophila species complex (AHC), which includes: A. hydrophila, composed by three subspecies: A. hydrophila subsp. hydrophila, A. hydrophila subsp. ranae and A. hydrophila subsp. dhakensis, A. bestiarum, A. popoffii and A. salmonicida, divided in five subspecies: A. salmonicida subsp. salmonicida, A. salmonicida subsp. masoucida, A. salmonicida subsp. achromogenes, A. salmonicida subsp. pectinolytica and A. salmonicida subsp. Smithia (Miñana-Galbis et al., 2002; Martin-Carnahan & Joseph, 2005).
Recently, two additional species have been described in this group, A. aquariorum and A. piscicola [2, 13]. Members of the AHC were first described as strains producing the enzymes elastase, lecitinase or stapholysin [1]. They are genetically closely related and share multiple phenotypic characteristics, which makes discrimination among the species included in this group extremely difficult [14]. Several approaches have been used to discriminate among the AHC species: Amplified
Fragment Length Polymorphisms (AFLP) [6], fluorescent AFLP (FAFLP) [7], MLEE, Random Amplified Polymorphic DNA (RAPD) and MALDI-TOF MS analysis [13]. Although the results obtained with these methods have been useful for the taxonomy and phylogeny of the AHC, providing a hypothesis for the genealogy of strains and detailing their patterns of descent and degree of genetic variation accumulated over time, only the MLEE study has been used to elucidate their population genetic structure. Previous studies based on the sequence analysis of several housekeeping genes have demonstrated that the AHC is not monophyletic [11, 19]. Nevertheless, controversially, other studies have shown the monophylia of this group [5]. This conflict could be due to the incongruence of phylogenies derived from distinct gene sequence analysis. In order to establish the population structure and divergence of the species included in this group of Aeromonas we studied a set of strains representative of the AHC, in which we analyzed the nucleotide sequences (total or partial) of 6 housekeeping genes: cpn60 (555 bp), dnaJ (891 bp), gyrB (1089 bp), mdh (936 bp), recA (1065 bp), rpoD (843 bp), giving a total fragment length of 5379 bp.
Treatment techniques
Aeromonads are very widespread in many of water environments. They are therefore present in most water sources used to produce drinking water. The currently used treatment and disinfection methods are effective in minimizing the concentration of aeromonads in ready-to-flow drinking water. It has been demonstrated, for example, that A. hydrophila was generally more sensitive than chlorine and monochloramine coliforms [18]. Chlorine dioxide has also been shown to be effective as a disinfectant [15]. Aeromonas may reappear in the distribution
network. By maintaining a chlorine concentration in a microorganism in biological films. The most effective strategy to control the growth of Aeromonas is to limit the entry of Aeromonas spp. In the distribution network through treatment and maintaining temperatures below 14°C, maintaining residual free chlorine levels above 0.1-0.2 mg / L and limiting concentrations of organic carbon compounds (WHO, 2002). If concentrations of Aeromonas increase significantly in the supply of drinking water, this increase indicates a general deterioration in the bacteriological quality of the water.
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БАКТЕРИИ РОДА AEROMONAS
ХАФФАРЕССАС Я.
Нижегородский государственный университет им. Н.И. Лобачевского, г. Нижний Новгород,
Россия
e-mail: yacinechabani@yandex. ru
Аннотация
Аэромонады являются распространенными бактериями в окружающей среде. Основными видами Aeromonas spp., вызывающими инфекции у человека, являются A. hydrophila, A. caviae, A. veronii biogroup sobria. Считается, что Aeromonas spp. являются одной из этиологических причин гастроэнтерита и заслуживают серьезного внимания, поскольку имеют ряд детерминант вирулентности, способствующих развитию, как гастроэнтерита, так и инфекций мягких тканей, кожных инфекций и сепсиса. Для предотвращения распространения инфекций, вызванных Aeromonas spp., необходима оптимизация менеджмента лечебно-профилактических мероприятий.
Ключевые слова: Aeromonas hydrophila, Aeromonas caviae, Aeromonas veronii, Aeromonas sobria, гастроэнтерит.
