Effects of dietary probiotic supplementations on prevention/treatment of yersiniosis disease

Aims:  To evaluate Enterobacter cloacae and Bacillus mojavensis , isolated from rainbow trout gut in the present study, as a probiotic to control yersiniosis disease.
Methods and Results:  A strain of Ent. cloacae and B. mojavensis , isolated from the digestive tract of rainbow trout had an antagonistic effect to Yersinia ruckeri , which causes yersiniosis. After feeding fish with 1 × 10⁸ cells g⁻¹ probiotic containing feed for 60 days, the fish survival rate increased to 99·2% following challenge with Y. ruckeri compared with controls that had 35% survival rate. Effects of Ent. cloacae and B. mojavensis on weight gains and stimulation of red blood cells, white blood cells, platelets and hemoglobin were also evaluated in separate groups of fish fed probiotic containing feed for 2 months. Probiotic significantly affected white blood cells, hemoglobin and weight gains of the experimental fish.
Conclusions:  Enterobacter cloacae and B. mojavensis , can be used to prevent and control yersiniosis disease.
Significance and Impact of the Study:  In conclusion, concomitant use of Ent. cloacae and B. mojavensis as a feed supplement is beneficial to rainbow trout. Use of these organisms can protect fish from yersiniosis and enhance digestibility and utilization of feed. Use of such probiotics may also limit the use of antibiotics and other chemicals in control and treatment of diseases, and thus contribute to the effort to reduce environmental contamination by residual antibiotics and chemicals .     

Surveillance and genotyping of Enterobacter sakazakii suggest its potential transmission from milk powder into imitation recombined soft cheese

Aims:  To examine the presence of Enterobacter sakazakii in milk and milk-related products produced/distributed under Egyptian conditions and to probe possible transmission routes of the pathogen during the preparation of dairy products.
Methods and Results:  One hundred and thirty-seven samples of milk and milk-related products were randomly collected from Egyptian markets and examined for the presence of Ent. sakazakii . The pathogen could be detected only in skimmed milk powder (SMP) and its related product, imitation recombined soft (IRS) cheese. Enterobacter sakazakii isolates recovered from these products were phenotypically similar and sensitive to all antibiotics examined in this study. They also showed indistinguishable banding patterns when subjected to macro-restriction profiling using pulsed-field gel electrophoresis (mrp-PFGE). One Ent. sakazakii isolate was inoculated into SMP that was used in the preparation of IRS cheese using two cheese making procedures. The pathogen could survive for up to 1 month in the IRS cheese prepared by either procedure.
Conclusions:  The simultaneous presence of Ent. sakazakii in SMP and IRS cheese samples collected within the same local market besides the phenotypic and genotypic similarities of isolates recovered from these samples suggested the possibility of Ent. sakazakii being transmitted from SMP into IRS cheese. This hypothesis was supported by the observation that the pathogen could survive in the IRS cheese prepared from contaminated SMP.
Significance and Impact of the Study:  The study highlights SMP and IRS cheese as potential transmission vehicles of Ent. sakazakii . It also raises concern on the microbiological safety of IRS cheese prepared from SMP.     

Expression of AmpC beta-lactamase in Enterobacter cloacae isolated from retail ground beef, cattle farm and processing facilities

AIMS: To better understand antibiotic resistance of Enterobacter cloacae isolates originated from food animals, the phenotypic and genotypic resistance of Ent. cloacae isolates from retail ground beef, cattle farm, processing facilities and clinical settings were investigated. METHODS AND RESULTS: The ampC, ampD and ampR genes in the isolates were sequenced and analysed. beta-Lactamase activities and beta-lactamase profiles of the isolates were analysed by the enzymatic hydrolysis of nitrocefin and isoelectric focussing, respectively. The ampC gene of the Ent. cloacae isolate was cloned and transformed into Escherichia coli strains. The genomic DNA profiles of Ent. cloacae isolates were analysed by using pulse field gel electrophoresis (PFGE). Mutation at one residue (Val-54-->Ile) in the AmpR amino acid sequence was consistently found in Ent. cloacae isolates that were resistant to a broadspectrum of beta-lactam agents. The enzyme activity in the isolates was induced by cefoxitin. The pI (isoelectric point) of the enzymes produced by the test strains ranged from 8.4 to 8.9. Cloning of ampC gene of the Ent. cloacae isolate conferred the resistance to ampicillin, cephalothin and amoxicillin in recipient E. coli strains. One recipient of E. coli O157:H7 strain additionally acquired resistance to ceftiofur. The genomic analysis of Ent. cloacae isolates by PFGE showed that the isolates from various sources were genetically unrelated. CONCLUSIONS: The spread of diverse clones of AmpC-producing Ent. cloacae occurred in the ecosystem and retail products. SIGNIFICANCE AND IMPACT OF THE STUDY: Our findings suggested that AmpC-producing Ent. cloacae could be a contributor in spreading beta-lactamase genes in farm environments and food processing environments.     

Climate variables and spawning migrations of the striped mullet and white mullet in the north‐western area of the Gulf of Mexico

The 'smoothed'(4253e HT smoother) 6 year time series with a monthly periodicity of catches (where the increases of the catches reflect the spawning migration) of Mugil cephalus and Mugil curema , were correlated (Pearson correlation index) against the 'smoothed' data on rainfall, water temperature, daylight and tide monthly averages. Water temperature and M. curema spawning migrations had a negative correlation ( r  = −0·77), while tide monthly averages and M. cephalus spawning migrations were positively correlated ( r  = 0·84). The two environmental variables that showed highly significant correlations were water temperature and daylight ( r  = 0·85, P  < 0·05). Meteorological tides were used as a reflection of the effect of the north winds from the Gulf of Mexico which produce an average tide rise from September to November. The relationship of these variables with spawning migrations is discussed, and it is suggested, in particular, that meteorological tides, as a reflection of the north winds, are the trigger (zeitgebers) for M. cephalus spawning in the ocean.     

Surfactin reduces the adhesion of food-borne pathogenic bacteria to solid surfaces

Aims:  To investigate the effect of the biosurfactants surfactin and rhamnolipids on the adhesion of the food pathogens Listeria monocytogenes , Enterobacter sakazakii and Salmonella Enteritidis to stainless steel and polypropylene surfaces.
Methods and Results:  Quantification of bacterial adhesion was performed using the crystal violet staining technique. Preconditioning of surfaces with surfactin caused a reduction on the number of adhered cells of Ent. sakazakii and L. monocytogenes on stainless steel. The most significant result was obtained with L. monocytogenes where number of adhered cells was reduced by 10² CFU cm⁻². On polypropylene, surfactin showed a significant decrease on the adhesion of all strains. The adsorption of surfactin on polystyrene also reduces the adhesion of L. monocytogenes and Salm. Enteritidis growing cells. For short contact periods using nongrowing cells or longer contact periods with growing cells, surfactin was able to delay bacterial adhesion.
Conclusions:  The prior adsorption of surfactin to solid surfaces contributes on reducing colonization of the pathogenic bacteria.
Significance and Impact of the Study:  This is the first work investigating the effect of surfactin on the adhesion of the food pathogens L. monocytogenes , Ent. sakazakii and Salm. Enteritidis to polypropylene and stainless steel surfaces.     

Resistance of Enterobacter sakazakii (Cronobacter spp.) to environmental stresses

Aim:  To gain a better understanding of the survival and persistence of Enterobacter sakazakii in severe environments.
Methods and Results:  We evaluated the resistance of Ent. sakazakii to various environmental stresses, including heating, drying, water activity ( a _w), and pH. The resistance of Ent. sakazakii to heat varies widely among strains. Most tested strains of Ent. sakazakii exhibited unusual resistance to dry stress, which depends on drying media. Growth of most strains occurred within 24 h at 37°C when the initial a _w of the medium was adjusted to 0·94 with sucrose or sodium chloride. The minimum pH for growth within 24 h at 37°C was 3·9 or 4·1 for most strains tested. Additionally, there did not appear to be any relationship between resistance to stresses and biofilm-forming ability in Ent. sakazakii planktonic cells.
Conclusions:  These results indicate that Ent. sakazakii is much more resistant than other Enterobacteriaceae to environmental stresses. Moreover, it is likely that Ent. sakazakii has cross-resistance to dry and thermal stresses.
Significance and Impact of the Study:  The findings of this study will contribute to an improved understanding of the survival and behaviour of Ent. sakazakii , which will lead to improved strategies for preventing outbreaks of Ent. sakazakii infection.     

Genotypic characterization of Enterobacter sakazakii isolates by PFGE, BOX-PCR and sequencing of the fliC gene

Aims:  Enterobacter sakazakii is an emerging food-borne pathogen that can cause rare but severe forms of neonatal meningitis, bacteraemia and necrotizing enterocolitis. A rapid typing method at the strain level is needed to determine the monoclonality or polyclonality of the isolates during outbreaks.
Methods and Results:  The BOX-PCR fingerprinting technique, which targets the repetitive BOX sequences, and sequencing of the flagellin gene, fliC , were evaluated against a panel of 27 Ent. sakazakii strains from clinical and environmental sources. The typeability and discriminatory power of the techniques were compared with those of pulsed-field gel electrophoresis (PFGE), the reference genotyping method. BOX-PCR results yielded 92% agreement with PFGE results, whereas fliC gene sequencing was poorly discriminative.
Conclusions:  In our study, BOX-PCR and PFGE were similarly discriminatory to type Ent. sakazakii strains. The weak variability of the Ent. sakazakii fliC gene was related to the absence of the variable central domain present in most fliC genes of Enterobacteriaceae.
Significance and Impact of the Study:  The BOX-PCR typing provides an accurate discrimination and a rapid answer to identify clonal isolates of Ent. sakazakii .     

Age and growth of the striped mullet, Mugil platanus (Actinopterygii, Mugilidae), in a southwestern Atlantic coastal lagoon (37°32'S–57°19'W): a proposal for a life-history model

Species of Mugilidae are an important economic resource supporting several small communities in Argentina and Brazil through fishing. The growth parameters of the von Bertalanffy model, age limit ( t _0.95) and natural mortality ( M ) for the striped mullet ( Mugil platanus ) Günther, 1880, in the Mar Chiquita coastal lagoon (37°32'S–57°19'W) were estimated. These results constitute the first estimated values for the species as: L _∞ (cm) = 563.82; K (years⁻¹) = 0.30; t ₀ (years) = −0.057 (age groups 1–8); t _0.95 = 10.07 years and M  = 0.30. Moreover, a hypothetical model is proposed for the life history of the adult stock of M. platanus from the Mar Chiquita coastal lagoon based on CPUE data, environmental parameters, ovarian maturity stages, gonadosomatic indexes, the allometric growth coefficient b and deposition of hyaline or opaque rings in the otholiths. Mugil platanus is therefore regarded as a species of moderate to rapid growth rate, with a relatively low longevity and a high natural mortality rate, compared to other species of Mugilidae.     

Isolation of Enterobacter cowanii from Eucalyptus showing symptoms of bacterial blight and dieback in Uruguay

Aims:  This study was performed to identify bacterial strains isolated simultaneously with Pantoea species from Eucalyptus trees showing symptoms of bacterial blight and dieback in Uruguay.
Methods and Results:  Several molecular techniques including 16S rRNA and rpoB gene sequencing and DNA–DNA hybridization were used to characterize the Gram-negative, facultatively anaerobic, slime-producing bacterial strains isolated along with Pantoea species from Eucalyptus . Hypersensitivity reactions (HR) and pathogenicity tests were performed on tobacco and Eucalyptus seedlings, respectively. The isolates clustered closely with the type strain of Enterobacter cowanii in both phylogenetic trees constructed. The DNA–DNA similarity between the isolates and the type strain of Ent. cowanii ranged from 88% to 92%. A positive HR was observed on the tobacco seedlings, but no disease symptoms were visible on the inoculated Eucalyptus seedlings.
Conclusions:  Enterobacter cowanii was isolated from trees with symptoms of bacterial blight although strains of this bacterial species do not appear to be the causal agent of the disease.
Significance and Impact of the Study:  This study provides the first report of Ent. cowanii isolated from Eucalyptus . Its presence in Eucalyptus tissue suggests that it is an endophyte in trees showing symptoms of blight.     

Larvae of Contracaecum sp. among inshore fish species of southwestern Australia

Larval nematode infections were investigated in 236 fish from 17 estuarine and near-shore species in southwestern Australia. Larvae of the genus Contracaecum were found in 4 species of fish (Acanthopagrus butcheri, Sillaginodes punctata, Mugil cephalus and Aldrichetta forsteri). The prevalence and intensity of infection was highest in the 2 species of mullet: 81% infected and 9.8 +/- 1.5 larvae fish(-1) for M. cephalus; 100% and 12.7 +/- 3.7 larvae fish(-1) for A. forsteri. There was no evidence of post-mortem migration of worms from the visceral organs to the musculature of the fish.     

Fishery, seasonal abundance and mortality of grey mullets (Pisces: Mugilidae) in Negombo Lagoon, Sri Lanka

The seasonal abundance and instantaneous natural and fishing mortalities of six species of grey mullets, namely Liza subviridis, L. macrolepis, L. tade, Mugil cephalus, Valamugil buchanani and V. cunnesius were studied as a prelude for the management of their fishery in Negombo lagoon (7°10′N and 79°50′E). L. subviridis was the most abundant of the grey mullet species in the commercial catches and accounted for 37% of the total grey mullet catch. M. cephalus was the least abundant and constituted 6%. The annual catch of grey mullets was estimated to be around 23 000 kg (5.67 kg/ha); about 40 % of the total fish landings of the lagoon. The seasonal variation in the catch of different species of grey mullets appear to be related to their breeding seasons and spawning migrations. The highest value for instantaneous natural and fishing mortalities, which were 1.04 and 0.94 respectively were obtained for V. cunnesius. The lowest values for instantaneous natural and fishing mortalities which were 0.51 and 0.19 respectively were obtained for M. cephalus. The exploitation ratios calculated were less than 0.5 for all species other than L. tade which suggest that the grey mullet populations excluding L. tade in this lagoon may presently be underexploited.     

Ketone bodies in fish skin mucus as an indicator of starvation: a preliminary report

The detection of starvation is a major problem in fish husbandry. Too often the discovery of starving animals is not made until pathogenic organisms are about to overcome the weakened animals. A simple test, using a commercial plastic strip with a reagent area that changes colour in the presence of starvation-induced ketones, was applied to this problem in the mullet, Mugil cephalus. The strip identified ketones in the fish skin mucus, and demonstrated its value in detecting starvation in fishes.     

鲻和鲮鳃丝的扫描电镜比较观察

对鲻（Mugil cephalus）和鲮（Cirrhina molitorella）的鳃丝表面结构进行了扫描电镜比较观察,结果表明,鲻鳃丝杆状部比鲮粗．鲻鳃小片高度比鲮低;两者鳃丝表面分泌孔洞口径和密度不同;鲻和鲮细胞外被不同,鲻细胞外被稀疏,鲮的则致密复杂;鳃小片细胞和鳃丝表皮细胞的表面形态存在差异,文章还描述了鳃丝表皮形态特异的细胞。     

Myxobolus goensis n. sp. (Myxozoa, Myxosporea, Myxobolidae), a parasite of the gills of Mugil cephalus (Osteichthyes, Mugilidae) from Goa, India

Two species of Myxobolus are reported from the gills of Mugil cephalus collected at Goa, India: M. goensis n. sp. and M. parvus Shulman, 1962. Myxobolus goensis n. sp. forms digitiform or rounded plasmodia between the gill rakers. Their spores are oval in frontal view, with tapered anterior extremity, and lemon-shaped in lateral view, measuring 9.7 (9.5-10.5) microm in length, 6.6 (6-7.5) microm in width, and 5.2 (5-6) microm in thickness. The polar capsules are pyriform and unequal in size. The larger ones are 5.3 (4.5-6) microm long and 2.4 (2-3) microm wide; the smaller ones are 2.4 (2-3) microm long and 1.8 (1.5-2) microm wide. The polar filament forms five turns aligned perpendicularly to the longitudinal axis of the larger polar capsules. Within the smaller polar capsules the polar filament is difficult to observe and, apparently, forms three coils. The spores are distinctly different from other Myxobolus species infecting M. cephalus and other Mugil spp. Furthermore, the present material is also different from 204 Myxobolus species presenting differently sized polar capsules, representing nearly all the known species with this characteristic. The fact that only the M. cephalus specimens were infected among a sample of 206 fish specimens, comprising 27 different species, strongly suggests that this parasite is specific to M. cephalus.     

Coexistence of Mugil cephalus and M. curema in a coastal lagoon in the Gulf of Mexico

Mugil cephalus and M. curema coexist in Tamiahua Lagoon, with no difference in diet or digestive system, but with a separation of 3 months in reproductive timing.     

Studies on the chemical biology of young grey mullet, Mugil cephalus L.

The chemical composition of tank and pond reared and wild young grey mullet, Mugil cephalus L., ranging in length from 15 to 75 mm was studied. Tank reared mullet had a higher percentage of protein, carbohydrate, total lipid and a lower moisture content than wild fish. These differences are attributed to the artificial diet, available in excess, as well as the relatively inactive life in the confined spaces of the rearing tanks. M. cephalus in general has a high percentage of total lipid and therefore, can be classified as a 'fatty' fish. The highest level of protein in tank reared fish was found in those kept at a salinity of 20‰. Fish reared on an excess diet in fresh water tended to show a close similarity to wild fish in trends of change of chemical constituents with growth.     

Aspects of the biology of grey mullet, Mugil cephalus L., adult populations of a coastal lagoon in Sri Lanka

The biology of grey mullet, Mugil cephalus L., adult populations in a coastal lagoon in Sri Lanka is presented. The percentage of grey mullet catches increased with increasing salinity. The larger fish were found in the deeper areas and the relationship of total length to depth was L = 8.4602e^{0.0058 D} where L = total length and D = depth (cm). The overall female to male ratio was 0.95 : 1.0 and seasonal variation in the sex ratio is considered to be caused by the differential timing in the spawning migrations of the two sexes. Males mature at 34.0 cm and females at 31.5 cm. The main spawning season was between January and May and it is hypothesized that the breeding season is geared to utilize the favourable time period, for growth of fry, in the lagoon. Grey mullet sheds its eggs in batches. Fecundity varied from 0.45 to 4.2 million in fish ranging in length from 32 to 56 cm and in weight from 0.7 to 2.2 kg. Fecundity was significantly correlated to body length and weight and gonad weight.     

Aetiology of 'red spot' disease (vibriosis) with special reference to the ectoparasitic digenean Prototransversotrema steeri (Angel) and the sea mullet, Mugil cephalus (Linnaeus)

The ectoparasitic digenean trematode Prototransversotrema steeri was observed to infect a wide range of estuarine fish species of southern Queensland. The intensity and incidence of trematode infections on Mugil cephalus hosts were recorded and appeared to alter with the estuarine movement of the sea mullet host.
Highest trematode population densities were present on post-spawning M. cephalus which had recently traversed brackish estuarine waters. Similarly, the highest prevalence of external 'red spot' lesions was also recorded from such fish.
The degree of complicity between P. steeri and 'red spot' bacterial pathogens was examined and is discussed. 'Red spot' or 'ulcer disease' is presented as a disease of multiple aetiology. It is suggested that some ectoparasites and a variety of primary and secondary bacterial pathogens may interact with environmental and behavioural factors to determine the prevalence of external lesions within each affected fish species.     

Isolation of infectious pancreatic necrosis virus (serotype Ab) from diverse species of estuarine fish

Two significant fish kills occurred in the Pamlico River estuary (North Carolina, USA), one in December 1981 and January 1982, and the other in June 1982. The first involved only the southern flounder(Paralichthys lethostigma). Histopathologic examination of morbid and moribund flounder revealed extensive sloughing and necrosis of the mucosa of the pyloric caeca and intestine, and inflammation of the submucosa of the pyloric caeca. Brain and internal organ homogenates from morbid and moribund flounder were assayed on CHSE-214 cells, and a virus was isolated. Virus titers ranged from8.4 · 10² to 6.3 · 10⁷ TCID₅₀ per gram of tissue. Cross-plaque neutralization assays indicated that the southern flounder virus was infectious pancreatic necrosis virus serotype Ab. Immersion challenge showed the isolate is only slightly virulent for fry of brook trout(Salvelinus fontinalis). The second fish kill involved the southern flounder and six other species: hogchoker(Trinectes maculatus), Atlantic silverside(Menidia menidia), spot(Leiostomus xanthurus), Atlantic croaker(Micropogon undulatus), silver perch(Bairdiella chrysura), and striped mullet(Mugil cephalus). Virus was isolated from southern founder, hogchoker, Atlantic silverside, and spot. Neutralization assays indicated that the four isolates were nearly identical; however, the diversity of species affected suggests that the virus might not have been the specific cause of mortality.     

Effects of bacteria isolated from a saprophagous rhabditid nematode Caenorhabditis elegans on the mycelial growth of Agaricus bisporus

P. S. GREWAL AND P. HAND. 1992. The effects of 10 species of bacteria isolated from a saprophagous rhabditid nematode Caenorhabditis elegans on mycelial growth of the cultivated mushroom Agaricus bisporus were studied in agar cultures. Bacterial species showed differential effects on the mycelial growth of A. bisporus and the effects also depended upon the mushroom strain (C43, C54 and U3). Bacillus cereus, Bacillus sp. and Enterobacter amnigenus caused significant inhibition in mycelial growth of all three strains of A. bisporus. Pseudomonas aeruginosa, Ps. fluorescens biovar reactans and Ps. maltophilia resulted in a significant increase in mycelial growth of C54 strain. Enterobacter cloacae caused a mean inhibition of about 83% in the linear mycelial extension of the most commonly cultivated mushroom strain U3. Bacillus cereus, Ent. amnigenus and Ent. cloacae produced volatile inhibitory substance(s). This is believed to be the first report about the inhibitory effects of specific bacteria isolated from a saprophagous nematode on the mycelial growth of A. bisporus.