Identification And Characterization Of Hafnia Alvei From Seafood

The Hafnia alvei is generally considered to be a conditional pathogen with a wide range of survival and can be isolated from the intestines of humans and animals.Hafnia can be detected in rivers,oceans and soils in the natural environment.It is more common in foods,and there are a large number of H.alvei in the frozen milk,meat products and fish.Studies have shown that H.alvei bacteria can produce hydrogen sulfide,an acidic smell,which is also the cause of food spoilage.Hafenia in the hive can grow in a low temperature environment,so for low temperature refrigerated foods,H.alvei has a greater hazard.Therefore,the main purpose of this paper is to identify H.alvei bacterium and to explore some biological characteristics of the bacterium,so as to provide a theoretical basis for the clear understanding and research of H.alvei.The test strain used in this article,H.alvei,is isolated by screening with LB medium.Five H.alvei(G1,G2,G3,G4 and G5)were isolated from the shrimp broth in the same LB medium;one H4 was isolated from sea cucumber;one was isolated from sea bass.H.alvei L1;a H.alvei Y1 was isolated from fish sauce,and the 8 strains were identified by studying the morphological characteristics,physiological and biochemical characteristics and 16S rDNA molecular sequence of the strain.The results showed that the 8 strains were straight,smooth,moist,translucent,gray,shiny,and neatly edged;biochemical identification results were consistent,Gram staining was negative;flagella staining was positive;dynamic test was positive;Negative oxidase test;positive gas production by sugar alcohol fermentation;positive for methyl red test;negative for VP test;positive for sputum test;negative for ONPG test,negative for hydrogen sulfide test.With the 16S rDNA molecular sequence analysis,the sequences of the 8 strains are different.The difference in homology can also be seen by establishing the phylogenetic tree,indicating that there are differences in the gene sequence of the eight strains.It provides a basis for studying the differences in biological characteristics of the eight strains.In this paper,the biological characteristics of these eight H.alvei were analyzed by growth curve test,biofilm test,motility test,salt tolerance test and drug sensitivity test.The research shows that the growth characteristics of 8 strains under 7 temperature gradients(4 °C,10 °C,15 °C,20 °C,25 °C,30 °C and 35 °C)were studied in the growth curve test.Previous studies have shown that the optimum growth temperature of H.alvei Haemenia is 30 °C.It can be found from the growth curve test of this paper that the higher the temperature,the faster the growth of H.alvei.Although the H.alvei grows fastest at 35 °C,the decay period will be advanced.Under the condition of 30 °C,although it does not grow faster than 35 °C,the stable period is the longest at these 7 temperatures.Therefore,it is most meaningful to study the H.alvei under the culture condition of 30 °C,and thus the optimum growth temperature of H.alvei habri at 30 °C is obtained,which is also consistent with the previous report.In the biofilm test,it was found that only the G4 strain formed a strong membrane at 144 h;while the L1 film-forming ability was weak in the 8 strains,and the medium-strength biofilm was formed at 144 h and 168 h.The strains are all medium-strength biofilms.Swimming is the movement of H.alvei by virtue of flagella,and flagella is closely related to the formation of biofilm.The main role of flagella is to help bacteria overcome the surface tension of the object to adhere to the contact surface,which is conducive to the formation of infectious diseases and biofilm.In the motility test,these 8 H.alvei strains were all motility and reached a maximum at 48 hours.Then,in the salt tolerance test,five strains of G1,G2,G3,G4 and G5 isolated from the shrimp,and one of the sea cucumbers had a maximum salt tolerance of 5%,while the sea bass One of the L1 and one of the fish sauces has a maximum salt tolerance of 6%.In the drug susceptibility test,the susceptibility test of 17 antibiotics of 8 H.alvei was performed.(chloramphenicol,kanamycin,ampicillin,gentamicin,spectinomycin,clindamycin,tetracycline,erythromycin,streptomycin,ciprofloxacin,sulfadiazine,sulfonamide,Methylpyrimidine,ofloxaci,nitrofurazone,furazolidone,metronidazole and chlortetracycline hydrochloride).Overall,the resistance of each strain to the same antibiotics is similar,but for ampicillin,G1,G2,G3,G4 and G5 can withstand 450 ?g/ml,L1 and Y1 can withstand 500 ?g/ml.H4 can only withstand 100 ?g/ml;the same for gentamicin,G1,G2,G3,G4 and G5 can withstand 600 ?g/ml,while H4,L1 and Y1 can only withstand 100 ?g/ml;Antibiotics,the resistance of 8 strains of Hafni's bacteria were not much different.In addition,two corruption indicators of 8 strains were made: TVB-N(volatile base nitrogen)and biogenic amine test.In the TVB-N test,the 8 strains increased the TVB-N value over time in 6 days.The maximum TVB-N of G1,G2,G3,G4,G5 and H4 does not exceed 30 mg/100 g,but is slightly spoiled;the maximum value of L1 is 37 mg/100 g,and the maximum value of Y1 is 48 mg/100 g.More than 30 mg/100 g,both strains caused the sample to be severely corrupted.In the biogenic amine test,8 strains produced only putrescine and cadaverine in 96 hours.Except for H4 strain,the amount of putrescine and cadaverine produced by other strains increased with time.However,these 8 strains produce a very small amount of histamine,which is much worse than putrescine and cadaverine.In addition,the yield of these 8 strains of biogenic amines,was significantly different from 24 h to 96 h(p < 0.05).