Your SlideShare is downloading. ×
0
Aeromonas
Aeromonas
Aeromonas
Aeromonas
Aeromonas
Aeromonas
Aeromonas
Aeromonas
Aeromonas
Aeromonas
Aeromonas
Aeromonas
Aeromonas
Aeromonas
Upcoming SlideShare
Loading in...5
×

Thanks for flagging this SlideShare!

Oops! An error has occurred.

×
Saving this for later? Get the SlideShare app to save on your phone or tablet. Read anywhere, anytime – even offline.
Text the download link to your phone
Standard text messaging rates apply
0 Comments
3 Likes
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total Views
3,005
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
Downloads
98
Comments
0
Likes
3
Embeds 0
No embeds

Report content
Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

Cancel
No notes for slide

Transcript

  • 1. AEROMONAS A Presentation By Isaac U.M. Associate Professor & Head, Department of Microbiology, College of Medicine, International Medical & Technological University, Tanzania.
  • 2. INTRODUCTION
    • Aeromonas is a gram negative facultative anaerobic rod that morphologically resembles members of the family Enterobacteriaceae.
    • As with Vibrio , extensive reorganization of the taxonomy of these bacteria has occurred.
    • Fourteen species of Aeromonas have neen described most of which are associated with human disease.
    • The most important pathogenes are Aeromonas hydrophila, Aeromonas caviae, and Aeromonas veroni bivar sobria.
    • The organisms are ubiquitous in fresh and brackish water.
    • The two major diseases associated with Aeromonas are gastroenteritis and wound infections (with or without bacteremia).
  • 3. HISTORY
    • In the 1950s Aeromonas sp. were reported to be associated with children diarrhea.
    • Because the reports were in German language, it was not until early 1980s that the organisms were recognized as significant causes of gastroenteritis in children by Australian researchers.
    • Studies in volunteers in 1985 found no association between aeromonads and diarrhea in healthy adult volunteers.
    • However, the Aeromonas strains used in the study lack certain important virulence factors, adherence properties for example.
    • Although no more volunteer studies were carried out since then, there is strong epidemiological evidence that Aeromonas sp. are responsible for diarrhea in humans (including travelers’ diarrhea).
  • 4. HABITAT
    • Aeromonas species are indigenous to aquatic environment worldwide.
    • Aeromonads have been isolated from fresh water, chlorinated water, polluted water and occasionally marine environment and their numbers are highest at warm months.
    • Aeromonas species have also been isolated from store produce and meats and from environmental and seafood sources.
    • The organisms are associated with a wide variety of diseases in warm- and cold-blooded vertebrates, including frogs, fish, reptiles snakes, and birds.
  • 5. TAXONOMY
    • The genus Aeromonas consists of at least 14 species and 13 DNA hybridization groups (HG) or genospecies (Table 1). Aeromonas species can be grouped into two subdivisions:
    • 1. Psychrophilic group: A. salmonicida . The only species in this group. It is a fish pathogen, nonmotile and do not grow at 37 o C. A. salmonicida have not been isolated from humans and, therefore, is not important in clinical microbiology.
    • 2. Mesophilic group: A. hydrophila group. The organisms are motile and grow at 37 o C. It can be divided into 3 principal phenotypic groups (Phenons) which are equivalent to the species A. hydrophila , A. caviae and A. sobria (Table 1).
  • 6.
    • Table 1.
    • Phenotypic grouping of species and
    • DNA hybridization groups in the genus Aeromonas
    • ____________________________________________________________________________
    • DNA Hypbridization Phynotypic Group Named Species
    • Group (Genospecies)
    • ____________________________________________________________________________
    • 1 A. hydrophila A. hydrophila
    • 2 Unnamed
    • 3 A. salmonicida
    • -------------------------------------------------------------------------------------------------------------------------------
    • 4 A. cavaie A. caviae
    • 5A A. media
    • 5B A. media
    • 6 A. eucrenophila
    • -------------------------------------------------------------------------------------------------------------------------------
    • 7 A. sobria A. sobria
    • 8/10* A. veronii biotype sobria
    • 9 A. Jandaei
    • 10/8* A. veronii biotype veronii
    • 11 A. veronii-like
    • 12 A. schubertii
    • 13 Aeromonas group 501
    • ------------------------------------------------------------------------------------------------------------------------------
    • 14 A. trota
    • ____________________________________________________________________________
    • *DNA groups 8 and 10 have been shown to be identical
  • 7.
    • A number of putative virulence factors have been implicated in the patho-genesis of Aeromonas species. Genes that code for such factors have been described. These virulence markers are important to distinguish between potentially pathogenic and non-pathogenic strains. Aeromonas virulence factors include:
      • Toxins:
        • Hemolysins.
        • Cytotoxins.
        • Enterotoxins.
      • Invasiveness.
      • Adherence.
      • Motility and lateral (polar) flagella:
        • Recent studies have shown that lateral flagella production by Aeromonas is a pathogenic feature due to its enhancement of cell adherence, invasion and biofilm formation.
    VIRULENCE FACTORS
  • 8.
      • Others:
        • Proteases.
        • Outer membrane proteins.
    • Recently genes for putative type III secretion system (TTSS) were identified in Aeromonas .
    • As shown in other pathogenic Gram-negative bacteria, the TTSS plays an essential role in pathogenicity as it facilitates the delivery of toxins to host cells.
    VIRULENCE FACTORS
  • 9. CLINICAL INFECTION
    • Septicaemia: Mainly in immunocompromised individuals (e.g. patients with hepatobiliary disease).
    • Cellulitis and wound infections: Infections associated with exposure to contaminated water or after alligator bite. The infection usually results in gangrene-like syndrome. Also, in patients who went treatment with medicinal leech.
    • Diarrhoea: Most commonly watery in consistency and sometimes cholera-like of short duration. Occur in all ages but mainly in children less than 3 years. Several reports associated Aeromonas species with travelers’ and chronic diarrhoea.
    • Food poisoning: A number of food poisoning outbreaks have been reported.
    • Others: A wide range of infections that include: meningeal, sore throat, urinary tract, ear, endocarditis, septicemia, etc..
  • 10. LABORATORY DIAGNOSIS
    • Media used:
      • Blood agar (BA),
      • Ampicillin BA (ABA, 15mg/L) and
      • Alkaline peptone water (APW) for enrichment.
      • A wide range of other media are available commercially.
    • Isolation:
      • From stool:
        • A loopful of liquid stool specimen is added to 10 ml APW and incubated at 37 ° C. After overnight incubation a loopful from APW is plated onto BA and another loopful onto ABA and incubated at 37 ° C overnight.
  • 11.
    • 2. From blood:
        • 10 ml of blood is inoculated into blood bottles and incubated at 37 ° C for up to 2 weeks. When growth is observed a loopful of culture is plated on BA and incubated at 37 ° C overnight.
      • From wounds:
        • A wound swab is plated directly on blood agar and on ampicillin blood agar (15mg/L) and the swab is then placed in APW. After incubation overnight a loopful from APW is plated on BA and another loopful onto ABA. Plates are incubated overnight at 37 ° C.
    LABORATORY DIAGNOSIS
  • 12.
    • Identification:
        • Suspected colonies are tested for oxidase. Oxidase-positive colonies are then identified using the Aerokey II identification scheme or other schemes
        • A number of PCR techniques are also available for identification of Aeromonas species.
    LABORATORY DIAGNOSIS
  • 13. TREATMENT
    • Aeromonas species are inherently resistant to  -lactams (chromosomally mediated).
    • Aeromonas species are usually susceptible to other antibiotics.
    • Drugs of choice include:
      • Fluoroquinolones: Ciprofloxaxin, Norfloxacin
      • 3 rd generation cephalosporins: Ceftriaxone, Cefuroxime
      • Trimehtoprim-sulfamethoxazole (TMP-SMZ)
      • Tetracyclines (TE)
    • Due to emergence of resistance to TMP-SMZ and TE, antibiotic susceptibility should be performed for such drugs particularly in developing countries.
  • 14. THANK YOU

×