Growth Of Aeromonas Research Articles

Effects of Chelators (Deferoxamine, Deferiprone and Deferasirox) on the Growth of Klebsiella Pneumoniae and Aeromonas Hydrophila Isolated from Transfusion-Dependent Thalassemia Patients

Infections are among the leading causes of death for thalassemia major patients. The known predisposing factors of infection include prior splenectomy, iron overload and use of iron chelator such as deferoxamine (DFO). While encapsulated organisms frequently found in splenectomized patients were readily controlled by prophylactic vaccination and vigilant antibiotic treatment, ferrophilic organisms such as Yersinia and Klebsiella remain common pathogens in thalassemic patients. Yersinia infections are more prevalent in temperate regions and Klebsiella infections are commonly found in tropical and subtropical areas. While the use of DFO further aggravates the risk of Yersinia infection, oral chelators such as deferiprone (L1) do not enhance the growth of Yersinia in vitro or in vivo. We found that the growth of Klebsiella was marginally enhanced by DFO in vitro when compared to Yersinia. Such an unfavorable effect was not found in either L1 or deferasirox (DFRA) in vitro. The growth of Aeromonas was not affected by the presence of all three forms of chelators. Therefore, we suggest that factors other than DFO may account for the increased prevalence of Klebsiella and Aeromonas infection in Asian thalassemic patients.

Effect of packaging atmosphere on the microbial attributes of pearlspot ( Etroplus suratensis Bloch) stored at 0–2 °C

Effect of packaging atmosphere (air and under different modified atmospheres (MAs), 40% CO 2/60% O 2, 50%/50% O 2, 60% CO 2/40% O 2, 70% CO 2/30% O 2 and 40% CO 2/30% O 2/30% N 2) on the microbial and biochemical attributes of fresh pearlspot ( Etroplus suratensis Bloch) stored at 0–2 °C was investigated. Trimethylamine nitrogen (TMA-N) and thiobarbituric acid (TBA) values remained lower than the proposed acceptability limits throughout the storage period. Results demonstrated that storage of pearlspot under air and MA 40% CO 2/30% O 2/30% N 2 resulted in growth of Enterobacteriaceae, Aeromonas and H 2S-producing bacteria including Shewanella putrefaciens, while all other packaging atmospheres did not allow multiplication of Enterobacteriaceae and Aeromonas within 3 weeks. Aeromonas spp. identified were Aeromonas hydrophila, Aeromonas veronii biovar sobria and A. veronii biovar veronii. Significant reduction ( p<0.01) was noticed in Aeromonas population of pearlspot stored under MA 60% CO 2/40% O 2 and 70% CO 2/30% O 2. A delay of growth of Pseudomonas below 5.0 log 10 cfu g −1 was observed during the 15th day of storage at 0–2 °C under modified atmosphere packaging (MAP) conditions. Growth of faecal streptococci was significantly inhibited in all the packaging atmospheres at 0–2 °C during the entire storage period. Survival of coagulase positive Staphylococci (<50 cfu g −1) in low numbers was noticed during storage in all the packaging atmospheres. Clostridium botulinum toxin was not detected. All the packaging atmospheres did not allow multiplication of sulphite-reducing clostridia at 0–2 °C during the entire storage period. Packaging in MA 60% CO 2/40% O 2 resulted in the inhibition of growth of Aeromonas and Enterobacteriaceae, and the slowest growth of psychrotrophic bacteria, H 2S-producing bacteria, including Shewanella putrefaciens and Pseudomonas and extended microbiological shelf life to 9–10 days. This study confirms the survival of potentially pathogenic A. hydrophila, A. veronii biovar sobria and A. veronii biovar veronii capable of growth at low temperature in pearlspot stored under MA.

Aeromonas–Acanthamoeba interaction and early shift to a viable but nonculturable state of Aeromonas by Acanthamoeba

To investigate the hypothesis that amoeba may comprise a significant environmental reservoir for Aeromonas, Acanthamoeba-Aeromonas interaction experiments were performed. Acanthamoeba were grown in monoculture and co-cultures with three different species of Aeromonas. Survival, invasion and viable but nonculturable state experiments were performed. We showed that at a low initial bacterial cell density, growth of Aeromonas spp. was inhibited by Acanthamoeba castellanii, while A. castellanii growth was unaffected. In contrast, a high initial bacterial cell density, Aeromonas hydrophila AEW44 and Aeromonas veronii biovar sobria AEW104 suppressed the growth of A. castellanii. Fluorescent and phase-contrast microscopic observations of GFP tagged Aer. hydrophila AEW44 demonstrated that the bacterial cells aggregated on A. castellanii cells after 15 min of incubation and internalized. Aeromonas hydrophila AEW44 cells were found to be actively moving. Interestingly, Aer. hydrophila AEW44 cells shifted more rapidly to a viable but nonculturable form when co-cultured with A. castellanii than in monoculture. We demonstrated that Aeromonas spp. are able to interact with and to infect the protozoan A. castellanii under laboratory conditions. Free-living amoeba might play a role as reservoir for Aeromonas, and thus may increase the transmission of Aeromonas by acting as a vehicle.

Kinetic aspects of biofilm formation on surfaces exposed to drinking water

Biofilm formation in drinking water distribution systems should be limited to prevent the multiplication of undesirable bacteria and other organisms. Certain types of drinking water with an AOC concentration below 10 μg of acetate-C eq/l can support the growth of Aeromonas. Therefore, the effect of acetate at a concentration of 10 μg of C/l on the biofilm formation rate (BFR) of drinking water with a low AOC concentration (3.2 μg C/l) was determined. Drinking water without acetate had a BFR of 3.9 pg ATP/cm2.day, whereas a BFR value of 362 pg ATP/cm2.day was found with acetate added. These data indicate that a low acetate concentration strongly affects biofilm formation, and that only a small fraction of AOC is available for biofilm formation. Aeromonads did not multiply in the biofilm despite their ability to grow at a concentration of 10 μg of acetate-C/l. Further investigations are needed to elucidate the relationship between substrate concentration and biofilm formation in drinking water distribution systems and the growth of undesirable bacteria in these biofilms.

Kinetic aspects of biofilm formation on surfaces exposed to drinking water

Biofilm formation in drinking water distribution systems should be limited to prevent the multiplication of undesirable bacteria and other organisms. Certain types of drinking waler with an AOC concentration below 10 μg of acetate-C eq/1 can support the growth of Aeromonas. Therefore, the effect of acetate at a concentration of (3.2 μg of C/1) on the biofilm formation rate (BFR) of drinking water with a low AOC concentration (3.2 μg C/1) was determined. Drinking water without acetate had a BFR of 3.9 pg ATP/cm2, day whereas a BFR value of 362 pg ATP/cm2 was found with acetate added. These data indicate that a low acetate concentration stmngly affects biofilm formation, and that Only a small fraction of AOC is available for biofilm formation. Aeromonads did not multiply in the biofilm despite their ability to grow at a concentration of 10 μg of acetate-C/1. Further investigations are needed to elucidate the relationship between substrate concentration and biofilm formation in drinking water distribution systems and the growth of undesirable bacteria in these biofilms.

Proteolytic activity of Aeromonas caviae.

Aeromonas strains produce a variety of virulence factors including proteases. Studies on the kinetics of growth of Aeromonas caviae NRRL B-966 and its proteases suggest that the proteolytic activities are produced throughout the growth phase, with peak level occurring at stationary phase. A. caviae synthesize both intracellular and extracellular proteases with the latter account for major portion of the total activity. Optimum pH for the A. caviae proteolytic activity is at 7.0. A. caviae produces a thermoresistant protease, whose activity is dependent on Mg++ and Ca++ ions. Inhibition of proteolytic activity by phenyl methyl sulfonyl fluoride suggest the presence of a serine protease in A. caviae. Nitrogenous compounds enhance the proteolytic activity while carbohydrates tested in this study inhibit the activity.

Growth of Aeromonas spp. at 4°C and related toxin production

Over the last few years Aeromonas spp. have been considered to be potential intestinal pathogens (Altwegg & Geiss 1989). Recently, detailed evidence has linked a strain from contaminated shrimp with a clinical isolate from a patient with diarrhoea and found them to be the same (Altwegg et al. 1991). It is now known that Aeromonas spp. are present in many foods, especially those of animal origin (Palumbo et al. 1989). Furthermore, previous studies have shown that these organisms are quite capable of growing at refrigeration temperatures. For example, Palumbo et al. (1985) found that seven out of 14 strains showed significant growth within 14 d at 5°C. However, most studies have only examined a relatively small number of strains, which were not speciated and were simply called A. hydrophila. In this paper we examine the growth of 36 strains of aeromonas (divided into A. hydrophila, A. sobria and A. caviae) at 4°C, and their ability to produce cyotoxins at 4°C, 30°C and 37°C.

Spontaneous Bacterial Peritonitis due to Aeromonas Hydrophila

Spontaneous Bacterial Peritonitis due to Aeromonas Hydrophila

Growth of Aeromonas spp. on Butzler Campylobacter selective agar and evaluation of the agar for the primary isolation of Aeromonas spp. from clinical specimens.

The fortuitous finding that Aeromonas spp. grew well on Butzler Campylobacter selective medium (BCSA) in a microaerobic atmosphere at 42 degrees C prompted us to evaluate the performance of BCSA for selective isolation of aeromonads in comparison with ampicillin (30 micrograms/ml) sheep blood agar (ASBA30). Overall recovery rates of aeromonads from 563 stool samples from patients with acute diarrhea were higher on ASBA30 (70.4%) than on BCSA (56.3%); however, 21 (29.5%) grew only on BCSA. The three human-associated Aeromonas spp. could be recovered on BCSA and ASBA30. We recommend the use of BCSA to laboratories reluctant to include a specific selective medium for aeromonads.

Isolation of Aeromonas hydrophila from a metropolitan water supply: seasonal correlation with clinical isolates.

The occurrence of Aeromonas spp. in the metropolitan water supply of Perth, Western Australia, Australia, was monitored at several sampling points during a period of 1 year. Water within the distribution system conformed to international standards for drinking water but contained Aeromonas spp. in numbers comparable to those in raw surface water, although this water was free of Escherichia coli. Coliforms and E. coli were found in raw surface waters, and Aeromonas spp. were found in raw water from surface and underground sources. Chemical treatment, followed by chlorination at service reservoirs, resulted in water free of E. coli and a decrease in the number of Aeromonas spp. Aeromonas spp. were found in the greatest numbers in summer. Multiple regression analysis showed that growth of Aeromonas spp. in chlorinated water was related to water temperature, residual chlorine, and interaction between these variables. The incidence of Aeromonas-associated gastroenteritis, determined from isolates referred to us for enterotoxin testing, paralleled the pattern of isolation of Aeromonas spp. in water within the distribution systems. We suggest that the presence of Aeromonas spp. in drinking water needs public health appraisal and that further work should be undertaken to permit reevaluation of standards for the quality of drinking water.