Aeromonas-associated gastroenteritis in Egypt

Aeromonas spp. including A. hydrophila, A. sobria, and A. caviae, were recovered from the feces of 88% of diarrheic Egyptian children. In contrast, only 45% of nondiarrheic children contained Aeromonas spp. A probable source of Aeromonas spp. is from drinking water inasmuch as nine out of ten samples analysed from the district of Cairo in which the children resided tested positive for Aeromonas spp. Enterotoxigenicity of the isolates from various sources was tested. 33% of the diarrheic samples produced enterotoxin whereas 47% of the nondiarrheic and 56% of the tap water strains produced enterotoxin.     

Aeromonas popoffii sp. nov., a mesophilic bacterium isolated from drinking water production plants and reservoirs

We examined the taxonomic position of seven Aeromonas isolates, recovered from Flemish and Scottish drinking water production plants and reservoirs, which were previously recognized by numerical analysis of genomic AFLP fingerprints as members of an unknown Aeromonas taxon that most closely resembled the species Aeromonas bestiarum (DNA hybridization group [HG] 2). The new phenotypic and DNA-DNA hybridization data obtained in this study show that the A. bestiarum-like strains constitute a separate Aeromonas species, for which the name Aeromonas popoffii sp. nov. is being proposed. The new species exhibited an internal DNA relatedness ranging from 79 to 100% and was 22 to 63% related to the type or reference strains of other Aeromonas spp. The highest DNA binding values were determined with A. bestiarum (51 to 63%), followed by Aeromonas hydrophila sensu stricto (HG1; 50 to 60%) and Aeromonas salmonicida (HG3; 39 to 55%). Although fingerprints generated by ribotyping and cellular fatty acid analysis often were highly similar, minor differences between the respective fingerprints were of significance for the differentiation of A. popoffii from its closest taxonomic neighbors, HG1, HG2, and HG3. Phenotypically, all seven strains of A. popoffii were positive for acid and gas production from D-glucose and glycerol, growth in KCN broth, arginine dihydrolase, DNase, Voges-Proskauer reaction, and resistance to vibriostatic agent O/129 and ampicillin but displayed negative reactions for production of urease, tryptophan deaminase, ornithine decarboxylase, and lysine decarboxylase (LDC). None of the strains displayed strong hemolytic activity. The lack of D-sucrose fermentation and LDC production and the ability to utilize DL-lactate as the sole energy and carbon source were useful characteristics for the biochemical separation of A. popoffii from A. bestiarum. Other Aeromonas spp. could be differentiated phenotypically from the new species by at least two features. The chromosomal G+C content of A. popoffii ranges from 57.7 to 59.6 mol%. Strain LMG 17541 is proposed as the type strain.     

Population dynamics of Aeromonas spp. in an urban river watershed

Density of Aeromonas spp. at one site in the Buffalo River and at four sites on its upstream tributaries was followed from June 1992-June 1993. Membrane filtration counts of Aeromonas during the summer ranged between 18 and 4000 ml-1, which were one to two logs higher than faecal coliform and faecal streptococci densities. Aeromonas spp. in the Buffalo River, and faecal coliforms, faecal streptococci, and the heterotrophic plate count throughout the watershed, increased by approximately one log during summer rainstorms. However, Aeromonas spp. increased only by a factor of two during rainstorms at the upstream sites. Aeromonas spp. showed a strong positive correlation with both indicator bacteria and total suspended solids at the upstream sites during the summer but not the winter. Correlations between Aeromonas and indicator bacteria remained strong in the Buffalo River during the winter, signifying that different conditions exist in the Buffalo River and its upstream tributaries. The strong correlation between Aeromonas spp. and indicator bacteria in the Buffalo River suggest that, in the absence of media capable of the quantitative recovery of potentially pathogenic aeromonads, standard faecal coliform analyses may adequately assess public health risks from Aeromonas spp. in an urban river used for recreational purposes.     

Studies on the bacterial flora of fish which are potential pathogens for human. Virulence factors of potential human pathogen isolated

Tests for various virulence factors, such as production of haemolysin on sheep blood agar plate, cytotoxin on HeLa cell line and enterotoxin in GM-1 ELISA and suckling mouse assay model, were done among the various strains of Aeromonas spp., Vibrio spp., Plesiomonas shigelloides and Esch. coli isolated from fresh water fish samples. Invasive properties of the isolates were also seen by using Sereny test. Haemolysin production was observed in 85.7% of Aeromonas, all (100%) of Vibrios, 13.3% of Esch. coli and none (0%) of P. shigelloides strains. Cytotoxin production was demonstrated in 60.8% of Aeromonas, 38.4% of Vibrios and none (0%) of P. shigelloides and Esch. coli strains. About 8% of Vibrio spp., were found positive for LT in GM-1 ELISA method whereas, none of the Aeromonas spp., Plesiomonas and Esch. coli. strains were found positive for LT and ST in GM-1 ELISA. By suckling mouse assay model 43.4% strains of Aeromonas were found positive for enterotoxin production whereas, strains of Vibrio spp., Plesiomonas and Esch. coli yielded negative results. Sereny test for invasive property was found negative in all the strains tested. The isolates from fish possess various virulence factors which contributes for pathogenicity in order to cause various diseases to susceptible individual.     

Isolation and identification of Aeromonas species from human stools

One thousand and three diarrhoeal stool samples were processed in our laboratory during the period 1996/1997 for the presence of enteric pathogens especially Aeromonas spp., which has emerged as a new agent causing diarrhoea. Ampicillin sheep blood agar was found to be the best medium for the isolation of Aeromonas spp. from stool specimens. Enteric pathogens were found in 200 (20%) stools, of which Aeromonas spp. was the second commonest pathogen isolated amounting to 21% of isolates. This study clearly indicates that Aeromonas spp. must be looked for in every diarrhoeal stool samples, specially in children below 10 years of age. Isolation and identification is cost effective and easy, if the given protocol is observed.     

Resistance to antibiotic and heavy metals of motile aeromonads from Chilean freshwater

In this work the resistance of 172 motile Aeromonas isolates recovered from raw drinking water supplies (56), irrigation waters (60) and runoff waters receiving sewage (56), to some antibiotics and heavy metals was investigated by agar diffusion and agar dilution methods. A high proportion of isolates from all water sources showed resistance to carbenicillin, erythromycin, streptomycin, cephradine and cadmium, and susceptibility to chloramphenicol, kanamycin, gentamicin, tetracycline, nalidixic acid, trimethoprim-sulphametoxazole and chromium. No amikacin-resistant Aeromonas were recovered. No relationship was found between antimicrobial resistance and Aeromonas species, with the exception of cephradine, that exhibited a significantly higher activity against the A. sobria isolates than the other Aeromonas species (P < 0.05). Moderately polluted waters showed lower antibiotic multiresistance and metal susceptibility than unpolluted and highly polluted ones. Although significant differences (P < 0.05), between resistance frequencies to erythromycin, carbenicillin, streptomycin and cephradine were found among isolates from different sources, the antimicrobial resistance patterns of aeromonads could not be related to the level of faecal pollution. These results indicate that aeromonads resistant to antibiotics and heavy metals are easily recovered from water sources in Chile, posing a potential public health risk.     

Private business: the uptake of confidential HIV testing in remote aboriginal communities on the Anangu Pitjantjatjara Lands

Bacterial populations associated with three sample types from the neck region of poultry carcasses in the dirty area of an abattoir were characterized. Sample types before and after scalding were skin only, feathers only, and a skin and feather combination. The neck skin of carcasses after the defeathering processing stage was also sampled. Bacterial populations associated with water from the scald tank, rubber fingers at the exit of the defeathering machine, and air in the dirty area were also characterized. Bacterial colonies (751) were randomly isolated from yeast extract-supplemented tryptone soya agar plates exhibiting 30 to 300 colonies. Micrococcus spp. were isolated in the highest proportion from pre-and postscalded carcass samples (63.5 to 86.1% of isolates), regardless of the sample type. Conversely, Enterobacteriaceae (40.3%), Acinetobacter (19.4%), and Aeromonas/Vibrio (12.5%) species predominated on neck skin samples taken from mechanically defeathered carcasses. Isolates from the rubber fingers were, however, predominantly Micrococcus spp. (94.4%). Bacterial groups isolated in the highest proportion from scald tank water samples were Micrococcus spp. (38.3%), species of Enterobacteriaceae (29.1%), and lactic acid bacteria (17.0%). Corynebacterium spp., species of Enterobacteriaceae, and Micrococcus spp. were dominant on air settle plates.     

Evaluation of glaucoma patients referred to a university clinic during one year

Infections by Aeromonas spp. are a rare cause of systemic infection in normal and immunocompromised hosts. We report the cases of two patients with acute non-lymphoblastic leukemia who developed septic shock by Aeromonas species with unusual soft-tissue complications. One patient who was undergoing consolidation chemotherapy developed septic shock by Aeromonas hydrophila with rhabdomyolysis and subsequent soft-tissue destruction consistent with myonecrosis. She recovered with combination antibiotic therapy and supportive care. The second patient developed neutropenia due to ganciclovir treatment for post-allogeneic transplant cytomegalovirus antigenemia. He developed a rapidly progressive septic shock due to Aeromonas sobria with rhabdomyolysis, multi-organ failure and bilateral lower limb myonecrosis, and died within 48 hours. The portal of entry was not identified in either case. These cases confirm the potentially aggressive nature of these bacteria in neutropenic cancer patients with an unusual tendency to produce muscular and soft-tissue destruction.     

Characterization of the bacterial flora isolated from a pilot-scale lagoon processing swine manure

The bacterial flora of an experimental plant that processes liquid swine manure by an aerated compartmented (multistage) lagoon system has been studied. The total flora is characterized by a larger number of oligotrophic bacteria than eutrophic ones. Each compartment displays a specific flora, different from the flora in the manure, and consisting of a complex assembly of Gram-negative and Gram-positive ubiquitous species, such as Aeromonas spp. and Pseudomonas spp., and specialized species, such as Sphingobacterium spp. and Corynebacterium spp. The fecal indicator microorganisms have been shown to disappear in the course of the processing. A significant population of nitrifying bacteria has been observed at levels up to 10(4) bacteria.mL-1.     

Medical mummies: the history of the Burns Collection

Of the 43 Aeromonas spp. isolated from various clinical samples 94% isolates were Beta-lactamase producers. The isolates were tested for sensitivity by disc diffusion method which is commonly used in Pakistan. MIC was determined by using Epsilometer test (E-test) method. More than 80% isolates were sensitive to cephalosporins and quinolones. However, resistance to commonly used antibiotics was very high, 94% isolates were resistant to ampicillin which corresponds to the betalactamase production. More than 60% of the isolates were resistant to cotrimoxazole and 40% to chloramphenicol, hence quinolones and cephalosporins appear to be the drugs of choice for treating serious Aeromonas infections. The MIC range of Aeromonas was best for cefotaxime < 0.06 - 1.0 ug/ml. MIC 90 for cefotaxime was 0.50 ug/ml, for imipenem 0.25 ug/ml and for ciprofloxacin 2.0 ug/ml.     

Prophylactic activity of tetracycline against Brugia pahangi infection in jirds (Meriones unguiculatus)

The ability of oral tetracycline to inhibit the development of third-stage infective larvae (L3) of Brugia pahangi to adult worms in jirds was studied using 2 experimental protocols. Jirds treated with 1.4% tetracycline in drinking water for a period beginning 30 days before inoculation of L3 until 30 days post-inoculation (DPI) had 97% reduction in adult worm recovery compared to untreated controls. Jirds that received 1.2% tetracycline in drinking water beginning 1 day before until either 12 or 26 DPI had adult worm recoveries of 11% and < 1%, respectively. Untreated jirds and those given tetracycline beginning at or later than 13 DPI had similar adult worm recovery (27-29%). Prepatent periods were prolonged, and circulating microfilariae were reduced in jirds given tetracycline from 27 to 54 DPI compared to controls. These data indicate that tetracycline administered to jirds in drinking water inhibits B. pahangi development from L3 to adult worms and suggest that this effect occurs during early larval development. Tetracycline administered to infected jirds prior to and continuing through the onset of patency can also affect development of microfilaremia.     

Identification of Aeromonas hydrophila hybridization group 1 by PCR assays

Synthetic oligonucleotide primers of 24 and 23 bases were used in a PCR assay to amplify a sequence of the lip gene, which encodes a thermostable extracellular lipase of Aeromonas hydrophila. A DNA fragment of approximately 760 bp was amplified from both sources, i.e., lysed A. hydrophila cells and isolated DNA. The amplified sequence was detected in ethidium bromide-stained agarose gels or by Southern blot analysis with an internal HindIII-BamHI 356-bp fragment as a hybridization probe. With A. hydrophila cells, the sensitivity of the PCR assay was < 10 CFU, and with the isolated target, the lower detection limit was 0.89 pg of DNA. Primer specificity for A. hydrophila was determined by the PCR assay with cells of 50 strains of bacteria, including most of the 14 currently recognized DNA hybridization groups of Aeromonas spp. as well as other human and environmental Aeromonas isolates. Detection of A. hydrophila by PCR amplification of DNA has great potential for rapid identification of this bacterium because it has proved to be highly specific.     

Blast colony forming cells in umbilical cord blood: frequency and correlation to other haemopoietic progenitors

Streptomycin-treated adult mice were investigated as a possible model for studying the enteropathogenicity of Aeromonas species. C57BL mice pre-treated with streptomycin (5.0 g/L drinking water, 48 hours) received a single intragastric dose (10(10) bacteria /10.5 mL) of one of six well-characterized, toxin-producing, human diarrhoeal isolates of A. veronii biovar sobria (n = 3) or A. hydrophila (n = 3). Their faeces were examined for Aeromonas for 10 days post-challenge. All strains colonized the antibiotic-treated mice. Colonization did not occur in mice which did not receive streptomycin. Strains of A. hydrophila were recovered in greater numbers than strains of A. veronii biovar sobria, and colonized ( > or = 10(3) cfu/g of faeces) a greater proportion of mice at day 10. Strains of the latter species, however, were more adherent in cell line assays used as models of intestinal adhesion. A. hydrophila strains localized in the large intestine and appeared not to be cell associated. This study, therefore, points to species-related differences in intestinal colonization mechanisms. The streptomycin-treated adult mouse model may prove useful for further investigation of some of these mechanisms. Diarrhoeal symptoms were, however, not produced in this model.     

Development of antibiotic-resistant strains for the enumeration of foodborne pathogenic bacteria in stored foods

Strains of Aeromonas spp., Salmonella enteritidis phage type 4, Salmonella typhimurium, verotoxigenic Escherichia coli O157:H7 (VTEC) and Yersinia enterocolitica resistant to streptomycin, nalidixic acid and a combination of both antibiotics were selected. When compared with the parent strains, most of the antibiotic-resistant strains had slightly slower growth rates at their optimum incubation temperature but the difference was reduced progressively when the temperature was lowered. Some antibiotic-resistant strains had considerably slower growth rates in the presence of the relevant antibiotic and these were not used further. Several agar and impedance media with added streptomycin and nalidixic acid were assessed for the enumeration of the antibiotic-resistant strains in artificially contaminated stored foods. Differential/selective media were required to enumerate low numbers of antibiotic-resistant strains in certain foods. The following agar and impedance media were selected: Aeromonas Agar (Ryan) for Aeromonas spp., Xylose Lysine Agar and Lysine Iron Cysteine Neutral Red Medium for Salmonella, Eosin Methylene Blue Agar and Coliform Medium for VTEC, and Yersinia Selective Agar without selective agents for Yersinia enterocolitica. The agar and impedance media have been used successfully to enumerate antibiotic-resistant strains inoculated into foods and stored at different temperatures.     

Epilepsy associated with low-grade brain glial neoplasms

Ozone and chlorine are agents that disinfect by destroying, neutralizing or inhibiting the growth of pathogenic microorganisms. The treatment of drinking water with ozone has shown to be more efficient against spores of Bacillus subtilis. It was observed that the ozone already in dose of 0.35 mg/l produced the reduction of at least 5 log in populations of approximately 1 x 10(6) cells/ml of Escherichia coli, Vibrio cholerae, Salmonella typhi, Yersinia enterocolitica, Pseudomonas aeruginosa, Aeromonas hydrophila, Listeria monocytogenes and Staphylococcus aureus. With a dose of 0.50 mg/l of chlorine, the reduction was much smaller for the tested microorganisms (except Vibrio cholerae), while the effect of 2 mg/l of chlorine was similar to the ozone treatment. For spores of Bacillus subtilis, the reduction observed with ozone concentrations of 0.35 and 0.70 mg/l was of almost 3 log, while no considerable effect was obtained with chlorine in the tested conditions. Our results have shown that both disinfectans were consumed during the treatment period, probably because of the own water demand and the added bacterial mass.     

Evaluation of universal preenrichment broth for the recovery of foodborne pathogens from milk and cheese

The use of universal preenrichment broth for the recovery of verotoxigenic Escherichia coli, Salmonella spp., and Listeria monocytogenes from milk and cheese was examined. Universal preenrichment broth supported the growth of low inoculum levels (10 cfu/ml) of these organisms in pure cultures and in mixed cultures containing higher levels of other pathogens or bacterial flora from raw milk. This medium also supported the recovery and growth of heat-injured Salmonella spp., L. monocytogenes, and verotoxigenic E. coli at inoculum levels of 10(2) cfu/ml to yield cell levels of 10(8) cfu/ml in pure cultures and at least 10(5) cfu/ml in the presence of high levels of known competitive pathogens or microflora of cheese samples after 24 h of incubation. Universal preenrichment broth performed better than Listeria enrichment broth in supporting the recovery and growth of heat-injured L. monocytogenes and equally as well as buffered peptone water or trypticase soy broth in supporting the growth of uninjured L. monocytogenes, Salmonella spp., and verotoxigenic E. coli. Coenrichment of these pathogens in universal preenrichment broth reduced the quantity of milk or cheese samples that were required for analysis and also reduced the cost and labor involved in preparing and processing separate preenrichment media.     

ETA receptor blockade prevents hypertension associated with exogenous endothelin-1 but not renal mass reduction in the rat

The purpose of this study was to determine the effect of chronic ETA receptor blockade, using the orally active antagonist A-127722 in rats with reduced renal mass. The initial series of experiments was designed to characterize the effects of the ETA-selective antagonist A-127722 on arterial pressure and renal function when administered via drinking water over a 4-wk period. Male Sprague-Dawley rats were acclimated to metabolism cages, and baseline 24-h urine collections were obtained. A-127722 was placed in the drinking water at concentrations that delivered doses of 1 to 10 mg/kg per d. The compound had no effect on any of the variables measured, including arterial pressure, food and water intake, urine volume, and sodium and potassium excretion. In a separate group of rats, ETA receptor blockade was verified after 3 d of drinking water containing A-127722. Rats were anesthetized, a jugular vein catheter was inserted for infusions, and a femoral artery catheter was used for monitoring arterial pressure. The pressor response to intravenous injection of Big endothelin-1 (1 nmol/kg, intravenously) was inhibited by > 50% in rats given A-127722 at 10 mg/kg per d, which confirms the efficacy of A-127722 in blocking ETA-mediated responses when placed in drinking water. In an additional series of experiments, rats were anesthetized, the right kidney was removed, and two of three major branches of the left renal artery were ligated. After recovery, rats were returned to their cages and given A-127722 in the drinking water to deliver 1 or 10 mg/kg per d. Control rats underwent the same surgical procedures but were given tap water to drink. After 4 wk, rats that were treated with A-127722 developed similar increases in arterial pressure and urinary protein excretion as rats that received tap water. Therefore, although the ETA receptor antagonist A-127722 can inhibit ETA-mediated hypertension, it has no effect on hypertension produced by a reduction in renal mass. It is concluded that ETA receptor activation does not play a significant role in the functional derangements associated with renal mass reduction in the rat.     

The naming impairment of living and nonliving items in Alzheimer''s disease

The role of the renin-angiotensin system (RAS) in the control of blood pressure and drinking was investigated in fresh water (FW)- and seawater (SW)-adapted eels, Anguilla anguilla, by comparing the effects of pharmacological manipulation through the use of papaverine (stimulator) and captopril (inhibitor) on the endogenous system. In SW eels basal blood pressure levels were lower (23.3 +/- 0.8 mm Hg) with correspondingly higher basal drinking rates (0.51 +/- 0.07 ml/kg/hr) and plasma AII concentrations (32.89 +/- 4.19 fmol/ml) compared to FW eels (33.8 +/- 1.3 mm Hg, 0.06 +/- 0.02 ml/kg/hr, 9.72 +/- 0.60 fmol/ml, respectively). In FW eels papaverine caused immediate hypotension with full recovery, decrease in plasma osmolality, and increase in drinking rate and plasma AII concentration, but in SW eels, hypotension with full recovery and an increase in plasma osmolality, drinking rate, and plasma AII concentration occurred. In FW eels captopril had no effect on the parameters measured, but in SW eels it caused a sustained decrease in blood pressure and a decline in the basal drinking rate and plasma AII concentration. Papaverine was also administered 15 min after captopril. In FW eels this manipulation caused hypotension only after the papaverine injection, followed by a partial recovery. Osmolality was unaffected, the previously observed papaverine-induced dipsogenic response was blocked, and the rise in plasma AII concentrations was smaller than with papaverine only. In SW eels there was an immediate hypotension after captopril administration with full recovery.(ABSTRACT TRUNCATED AT 250 WORDS)     

Comparison of BGB-MUG and LSTB-MUG in microbiological surveillance of recreational waters

Recreational water surveillance is an important tool to prevent health hazards for the population. Therefore distinct guide and imperative values for fecal indicators are listed in the EC directive about water quality control. The detection methods, however, give laboratories some room to choose their own method, which has led to difficulties in the comparability of results. In 1989 an ad-hoc working group of the coastal countries of Germany established detection methods, which by now are obligatory for these countries. Fecal and total coliforms (FC and TC) are detected by a triplicate mpn-procedure using brilliant green-bile-lactose broth supplemented with tryptophane and 4-methylumbelliferyl-beta-D-glucuronide (BGB-MUG) as selective medium. Gas-, fluorescence- and indole-positive cultures are considered fecal coliform-positive. In the last years rises in TC but not in FC counts were observed in fresh waters. A study was carried out to evaluate the official method in another bathing season, to determine bacterial species leading to false-positive TC cultures and to compare BGB-MUG with laurylsulphate-tryptophane-MUG (LSTB-MUG). Water samples of different salinities and nutrient input were collected in weekly intervals from April to October. FC and TC concentrations were determined and all TC-positive cultures were differentiated further. The FC counts obtained by enrichment in BGB-MUG or LSTB-MUG were nearly identical, the rate of fluorescence-positive, indole-negative tubes being approximately 0.6%. Differentiation of FC-negative cultures showed a false-negative rate of 2.87% for BGB-MUG and of 8% for LSTB-MUG. During the summer months TC counts in BGB-MUG exceeded FC counts by far at most of the sampling sites. This effect was much less pronounced in LSTB-MUG; the difference between both enrichment media being significant. Differentiation of presumptive TC from BGB-MUG resulted in a high percentage of Aeromonas spp. in fresh waters. LSTB-MUG was clearly more selective for TC than BGB-MUG, but still with an average of 10% of the test tubes being false TC-positive (BGB-MUG 46%). The sensitivity of BGB-MUG was below 60% (LSTB-MUG 89%). LSTB-MUG should be preferred as enrichment medium in mpn-examination of recreational water, if no further differentiation is carried out. The selectivity for TC is better than in BGB-MUG and the only slight inhibitory effects can be tolerated.     

Effect of oxytetracycline-medicated feed on antibiotic resistance of gram-negative bacteria in catfish ponds

The effect of oxytetracycline-medicated feeds on antibiotic resistance in gram-negative bacteria from fish intestines and water in catfish ponds was investigated. In experiments in the fall and spring, using ponds with no previous history of antibiotic usage, percentages of tetracycline-resistant bacteria in catfish intestines obtained from medicated ponds increased significantly after 10 days of treatment. In the fall, resistance of the intestinal and aquatic bacteria returned to pretreatment levels within 21 days after treatment. In the spring, resistance declined after treatment but remained higher than pretreatment levels for at least 21 days in intestinal bacteria and for 5 months in aquatic bacteria. Plesiomonas shigelloides, Aeromonas hydrophila, and Citrobacter freundii were isolated frequently in both spring and fall; Escherichia coli, Klebsiella pneumoniae, Edwardsiella tarda, and Enterobacter spp. were isolated primarily in the spring. Oxytetracycline treatment did not affect the distribution of bacterial species in the fall but may have accelerated a shift toward greater prevalence of members of the family Enterobacteriaceae in the spring. Multiple antibiotic resistance did not appear to be elicited by oxytetracycline treatment.