A case of Aeromonas hydrophila infection complicating an open Rolando's fracture of the hand is reported. Only two cases, both complicating open tibial fractures have been reported in the literature previously.' ,2 The organism was resistant to the usual antimicrobial (ampicillin and cloxacillin) used in the management of open fractures at University Hospital, Kuala Lumpur. The severity of the infection is largely dependent on the resistance of the host, and could vary from a locally spreading necrotizing cellulitis without systemic signs to a frank septicaemia with serious consequences. Early diagnosis with adequate debridement of the wound and appropriate antimicrobial to which the organisms are sensitive, are essential for effective control.
Eighty-six clinical isolates of Aeromonas hydrophila were studied for their ability to produce four exotoxins: a haemolysin active against rabbit erythrocytes, cytotoxin and enterotoxin detectable with Vero cell cultures, and the cholera toxin-like factor detected by an enzyme-linked immunosorbent assay. At least one exotoxin was produced by 80% of enteric and 96% of non-enteric isolates. The exotoxin profiles of non-enteric isolates were more restricted than those of enteric isolates, with haemolysin and cytotoxin producers preponderant. Although haemolysin and cytotoxin were produced by isolates from all sources, the enterotoxin and cholera toxin-like factor were more common amongst enteric isolates. The production of haemolysin and cytotoxin were closely related but the association between the enterotoxin and the cholera toxin-like factor was not significant.
The haemolysins produced by Aeromonas species were detected and compared by two assay methods--a modified blood agar plate assay and the rabbit erythrocyte haemolysin method. Both assays showed a high level of agreement (86%). The titres of the rabbit erythrocyte haemolysin assay correlated with the haemolytic zone diameter of the ox blood agar assay. In addition the agar haemolysin assay had simple media requirements, was easy to perform and results were well defined.
Eighteen strains of Aeromonas hydrophila from patients with bacteraemia were investigated for possible virulence factors. Cytotoxin and haemolysin were produced by all strains, whereas cholera toxin-like factor was produced by 33% of strains only. Enterotoxin production was not detected. Haemagglutination of guinea-pig, fowl and rabbit erythrocytes was demonstrated by 83%, 67% and 61% of strains, respectively. Fucose- and mannose-sensitive haemagglutinins were predominant. None of the strains agglutinated sheep erythrocytes. Extrachromosomal DNA was detected in 17 strains, 16 of which had a plasmid (3.6-5.1 MDa), the majority being between 4.6 and 5.1 MDa.
Strains of Aeromonas hydrophila isolates from skin lesions of the common freshwater fish, Telapia mossambica, were screened for the presence of plasmid DNA by agarose gel electrophoresis and tested for susceptibility to 10 antimicrobial agents. Of the 21 fish isolates examined, all were resistant to ampicillin and sensitive to gentamycin. Most isolates were resistant to streptomycin (57%), tetracycline (48%) and erythromycin (43%). While seven of 21 isolates harboured plasmids, with sizes ranging from 3 to 63.4 kilobase pair (kb), it was only possible to associate the presence of a plasmid with antibiotic resistance (ampicillin and tetracycline) in strain AH11. Both the plasmid and the associated antimicrobial resistance could be transferred to an Escherichia coli recipient by single-step conjugation at a frequency of 4.3 x 10(-3) transconjugants per donor cell.
Aeromonas hydrophila strains obtained from diarrhoeal samples of human patients (19 isolates) and freshwater ponds (11 isolates) were analysed for siderophore production. Both clinical and environmental isolates showed significantly increased siderophore production under iron-limiting conditions both at 28 degrees C and at 37 degrees C. Clinical isolates consistently produced higher levels of siderophores than did the environmental isolates. The role of plasmids in moderating siderophore production was studied after curing with acridine orange. Treatment with acridine orange for 24 h removed the larger plasmids but the smaller plasmids (< 5 MDa), more common in the environmental isolates, were resistant to curing. As found in the untreated isolates, the cured clinical isolates produced higher mean levels of siderophores than the cured environmental isolates. Siderophore production in A. hydrophila was significantly influenced by iron-limiting cultural conditions and the source of isolates, but plasmid content and growth temperature at 28 degrees C or 37 degrees C had little effect on production. The basis for the greater production of siderophores in clinical isolates than in environmental isolates needs further study.
Four species of synanthropic flies were trapped in downtown Kuala Lumpur: Chrysomya megacephala, Chrysomya rufifacies, Musca domestica, and Musca sorbens. Burkholderia pseudomallei, the organism causing melioidosis, was the dominant bacteria isolated from Chrysomya megacephala. Klebsiella oxytoca, commonly associated with nosocomial infections, was commonly isolated from Chrysomya megacephala, Musca domestica, and Musca sorbens. Aeromonas hydrophila, the bacteria causing gastroenteritis, was predominantly isolated from Chrysomya megacephala and also from Musca domestica and Musca sorbens. A total of 18 bacterial species was isolated from the synanthropic flies trapped. Burkholderia pseudomallei had been reported for the first time.
This study was to determine the median lethal concentration (LC50) of copper to Javenese carp, Puntius gonionotus (Bleeker), and the immune response after the fish were exposed to sublethal levels of copper and challenged with formalin killed Aeromonas hydrophila. The LC50 of copper on P. gonionotus at 24, 48, 72, 96 and 120 h were estimated as 2.17, 0.91, 0.57, 0.53 and 0.42 mg l(-1), respectively. To determine the effect of copper on the immune system, fish were exposed for 66 days to 0.05, 0.10 and 0.15 mg Cu l(-1). After 56 days of initial exposure to copper, fish were challenged with 0.1 ml of 4.5 x 10(5) cfu ml(-1) formalin killed A. hydrophila and maintained in the same concentration of copper. After the challenge, the immune response was monitored for 2 weeks using haematological and serological assays. During the initial phase of exposure to copper, significant changes were noted in the white blood cell, lysozyme, potential killing activity, total plasma protein, total immunoglobulin and haematocrit levels between the control and treated fish. One week after challenge with A. hydrophila, there was a significant increase in the values of white blood cells, total protein and total immunoglobulin compared to the values before the challenge. However, these values were not significantly different (P>0.05) between the control and the treated fish. In contrast, NBT and lysozyme assays exhibited a significant difference (P<0.05) in fish exposed to 0.10 mg Cu l(-1) (0.525 +/- 0.17; 24.42 +/- 3.35 x 10(2) micromg ml(-1)) and 0.15 mg Cu 1(-1) (0.536 +/- 0.19; 21.78 +/- 1.29 x 10(2) micromg ml(-1)) compared to the control (0.746 +/- 0.31; 30.73 +/- 5.42 x 10(2) micromg ml(-1)) after the bacterial challenge (day 61). There was however no significant difference (P>0.05) in NBT and lysozyme levels in fish exposed to lower level of copper (0.05 mg Cu l(-1)), suggesting the absence of immunosuppressive effects at lower level of exposure.
A total of 87 market fish samples representing five types of fish were evaluated for the presence of Aeromonas spp. Of the samples examined, 69%, 55%, 11.5% and 2.3% harbored Aeromonas spp., A. veronii biovar sobria, A. hydrophila and A. caviae, respectively. The 60 isolated Aeromonas spp. strains were further examined for hemolytic activity, resistance to antimicrobial agents and presence of plasmids. Hemolytic activity varied widely among the isolated strains. Though all the isolates demonstrated resistance to three or more of the antibiotics tested, all were susceptible to ceptazidime. Thirty-four (56.7%) of the sixty isolates harbored plasmids, with sizes ranging from 2.3 to 15.7 kb. These results indicate that hemolytic, multiple antibiotic resistant and genetically diverse aeromonads are easily recovered from fish in this region.
Microbiological analysis of samples collected from cases of white spot disease outbreaks in cultured shrimp in different farms located in three regions along East Coast of India viz. Chidambram (Tamil Nadu), Nellore (Andhra Pradesh) and Balasore (Orissa), revealed presence of Vibrio alginolyticus, Vibrio parahaemolyticus, and Aeromonas spp. but experimental infection trials in Penaeus monodon with these isolates did not induce any acute mortality or formation of white spots on carapace. Infection trials using filtered tissue extracts by oral and injection method induced mortality in healthy P. monodon with all samples and 100% mortality was noted by the end of 7 day post-inoculation. Histopathological analysis demonstrated degenerated cells characterized by hypertrophied nuclei in gills, hepatopancreas and lymphoid organ with presence of intranuclear basophilic or eosino-basophilic bodies in tubular cells and intercellular spaces. Analysis of samples using 3 different primer sets as used by other for detection of white spot syndrome virus (WSSV) generated 643, 1447 and 520bp amplified DNA products in all samples except in one instance. Variable size virions with mean size in the range of 110 x 320 +/- 20 nm were observed under electron microscope. It could be concluded that the viral isolates in India involved with white spot syndrome in cultured shrimp are similar to RV-PJ and SEMBV in Japan, WSBV in Taiwan and WSSV in Malaysia, Indonesia, Thailand, China and Japan.
Palm kernel oil, palm olein, crude palm oil and palm acid oil were used for the synthesis of poly (3-hydroxybutyrate-co-3-hydroxyhexanoate) [P(3HB-co-3HHx)] by a mutant strain of Wautersia eutropha (formerly Ralstonia eutropha) harboring the Aeromonas caviae polyhydroxyalkanoate (PHA) synthase gene. Palm kernel oil was an excellent carbon source for the production of cell biomass and P(3HB-co-3HHx). About 87% (w/w) of the cell dry weight as P(3HB-co-3HHx) was obtained using 5 g palm kernel oil/l. Gravimetric and microscopic analyses further confirmed the high PHA content in the recombinant cells. The molar fraction of 3HHx remained constant at 5 mol % regardless of the type and concentration of palm oil products used. The small amount of 3HHx units was confirmed by 13C NMR analysis. The number average molecular weight (M(n)) of the PHA copolymer produced from the various palm oil products ranged from 27 0000 to 46 0000 Da. The polydispersity was in the range of 2.6-3.9.
Polymerase chain reaction (PCR) technique was used to assay for the detection of specific genes in the genomes of the Aeromonas spp. isolated from environmental and shellfish sources, particularly aero and hlyA genes, responsible for aerolysin and hemolysin toxins production in this genus. The results showed that: (i) the 1500 bp amplicon of the hlyA gene was detected in 20/38 of the Aeromonas hydrophila, 13/38 of the A. caviae and 6/9 of the A. veronii biovar sobria isolates; (ii) the 690 bp amplicon of the aero gene was detected in 20/38 of A. hydrophila, 17/38 of A. caviae and 6/9 of A. veronii biovar sobria isolates; (iii) the nucleotide blast results of aerolysin gene sequences of the representative strains of A. hydrophila, A. caviae and A. veronii biovar sobria revealed a high homology of 94%, 95% and 95% with published sequences, respectively and ; (iv) the protein blast showed 97%, 94% and 96% homology when compared to the published sequences, respectively. The finding of A. hydrophila virulence genes in other members of the genus Aeromonas, may give a new perspective to the significance of these results. The method described here may be a useful detection tool to assist in further investigation of aero and hlyA genes in the genus Aeromonas, especially for food microbiologist.
The objective of this study is to gain a better understanding of the antimicrobial properties of the mucus extract of snakehead fish, Channa striatus against selected human and fish pathogenic microbes.
To evaluate a live recombinant Lactococcus lactis vaccine expressing aerolysin genes D1 (Lac-D1ae) and/or D4 (Lac-D4ae) in protection against Aeromonas hydrophila in tilapia (Oreochromis niloticus).
Four species of bacteria, Acinetobacter lwoffii, Aeromonas hydrophila, Pseudomonas aeruginosa and Pseudomonas putida, were isolated from soil contaminated with hydrocarbons and selected for the determination of growth requirements and the ability to degrade petroleum hydrocarbon. The bacteria were grown in mineral salt medium (MSM) supplemented with two types of crude oil, either Sumandak or South Angsi at 1% (v/v) concentration. The optimum pH for growth of A. hydrophila and P. aeruginosa was 6.5 when grown with Sumandak and South Angsi oil. For A. lwoffii and P. putida the optimum pH for growth with Sumandak and South Angsi oil was 6.5 or 7.0, respectively. The growth of P. aeruginosa was the highest in MSM when supplemented with 1% South Angsi oil and 0.5% tryptone at pH 6.5 while, in Sumandak oil the growth was the highest when yeast extract was added. Gas chromatography analysis showed that the South Angsi crude oil components of C12 to C25 were more extensively degraded by A. lwoffii after 24 h of incubation compared to the other bacteria over the same period.
An experiment was conducted to evaluate the use of Bacillus thuringiensis (Bt) as a probiotic to enhance the cellular innate immune response of the African catfish (Clarias gariepinus) challenged with a bacterial fish pathogen, Aeromonas hydrophila.
Bacterial quorum sensing signal molecules called N-acylhomoserine lactone (AHL) controls the expression of virulence determinants in many Gram-negative bacteria. We determined AHL production in 22 Aeromonas strains isolated from various infected sites from patients (bile, blood, peritoneal fluid, pus, stool and urine). All isolates produced the two principal AHLs, N-butanoylhomoserine lactone (C4-HSL) and N-hexanoyl homoserine lactone (C6-HSL). Ten isolates also produced additional AHLs. This report is the first documentation of Aeromonas sobria producing C6-HSL and two additional AHLs with N-acyl side chain longer than C(6). Our data provides a better understanding of the mechanism(s) of this environmental bacterium emerging as a human pathogen.
Burkholderia sp. synthase has been shown to polymerize 3-hydroxybutyrate (3HB), 3-hydroxyvalerate, and 3-hydroxy-4-pentenoic acid monomers. This study was carried out to evaluate the ability of Burkholderia sp. USM (JCM 15050) and its transformant harboring the polyhydroxyalkanoate (PHA) synthase gene of Aeromonas caviae to incorporate the newly reported 3-hydroxy-4-methylvalerate (3H4MV) monomer. Various culture parameters such as concentrations of nutrient rich medium, fructose and 4-methylvaleric acid as well as harvesting time were manipulated to produce P(3HB-co-3H4MV) with different 3H4MV compositions. The structural properties of PHA containing 3H4MV monomer were investigated by using nuclear magnetic resonance and Fourier transform infrared spectroscopy (FTIR). The relative intensities of the bands at 1,183 and 1,228 cm⁻¹ in the FTIR spectra enabled the rapid detection and differentiation of P(3HB-co-3H4MV) from other types of PHA. In addition, the presence of 3H4MV units in the copolymer was found to considerably lower the melting temperature and enthalpy of fusion values compared with poly(3-hydroxybutyrate) (P(3HB)). The copolymer exhibited higher thermo-degradation temperature but similar molecular weight and polydispersity compared with P(3HB).