Quick Review on Veterinary Microbiology

Vetnepal Review Note 2019-03-15

TERMINOLOGY

  • A disinfectant: It is used to destroy micro-organisms off of any surface usually used in living tissue
  • Aero tolerant anaerobes:  Ignore oxygen, grow equally well with or without
  • An antiseptic: It is used to destroy micro-organisms off of the skin usually used on non-living things which are also much stronger and are too toxic to be used on living tissue
  • Facultative anaerobes: grow with or without oxygen, grow better in oxygen (respire)
  • Hygiene: Any regulation or remedy which is intended to produce beneficial effects by gradual operation
  • Mesophyllic: optimum from 20-450C minimum around 15-200C (Most pathogenic)
  • Microaerophiles: won't grow at normal atmospheric oxygen (20%), require some oxygen for growth (2-10%)
  • Obligate aerobes: grow only when oxygen is present
  • Obligate anaerobes: die in presence of oxygen
  • Psychrophiles: optimum temperature typically 150C or lower.
  • Sanitation: the study and use of practical measures for the preservation of public health
  • Thermophiles: optimum 550C or higher. Some (hyperthermophiles) have optima of 80 deg or higher (mostly Archaea in this group).
  • Thermoduric: Bacteria which can not destroyed by pasteurization temperature

DISCOVERED BY/IN

  1. Anthrax bacilli:- Claire,                   ARV vaccine:- L. Pasteur in 1871
  2. Avian sarcoma:- Budding,               Electron Microscope:- Knoll & Rusna
  3. FMD virus:- Loefler & Frosch,       MD virus:- Marek’s in 1907
  4. Microscope:- Leuwan Hook,          The term “Allergy”:- Von Pirquet in 1906
  5. ND:- England in 1926                      The term “Complement”:- Bordet in 1895

GENERAL CHARACTERISTICS OF BACTERIA

  • Bacteria are single-celled microorganisms found in nearly all natural environments.
  • Gram-negative bacteria are those bacteria that don't retain crystal violet dye in Gram staining.
  • Flagella  which aid for mobility
  • fimbriae which aid in attachment
  • Membranous inclusions for regulating life processes

The first antibody produced against any antigen is IgM

Bacteria reproduce by the asexual process of binary fission.

  • First phase, called the lag phase,
  • Logarithmic phase, or log phase or exponential phase
  • Stationary phase (accumulation of waste products)
  • Decline or death phase

SHAPE OF THE BACTERIA

  • Streptococci:- Chains                  Staphylococci:- Bunch like grapes
  • Diplococci: - Attach in pairs      Sarcinae:- Cuboidal
  • Cocci:- Spherical shape              Bacilli:- Rectangular shape
  • Spirilla:- Spiral                            Vibrio:- Comma shape

CLOSTRIDIAL INFECTION

  1. Clostridium nouyi - Black disease,                 
  2. Clostridium botulism - Botulism,                        
  3. Clostridium haemilyticum - BBH
  4. Clostridium chauvoei - Black Quarter (BQ),      
  5. Clostridium septicum - ME, Braxy
  6. Clostridium perfringes have five types
  • Type A: Gas gangrene        Type B: Calf dysentery
  • Type C: Struck                     Type D: Pulpy kidney disease
  • Type E: Enterotoximia

GENERAL CHARACTERISTICS OF VIRUS

  • They are obligate intracellular parasites.
  • Viruses that infect bacteria are called bacteriophages
  • Outside the cell, they consist of particles called virions
  • The virion consists of an outer shell, the capsid, made of protein.
  • The genome; either DNA or RNA. They encode those proteins needed for viral reproduction that the host cell will not supply.
  • Except poxviridae, all the  DNa virus have dsDNA
  • Except Reoviridae and Birnaviriodae, all other RNA virus have ssRNA
  • VN test is only used in live virus
  • Virus protein is normally synthesized by cytoplasm
  • Rabies virus has bullet shaped where as Pox virus has bricked shaped

INCLUSION BODIES PRODUCED BY VIRUS

  • CD and RP virus: - Both IC and IN inclusion bodies
  • Adino, herpes, Parvo virus: - Intra nuclear inclusion bodies (IN)
  • Pox, Reo, Rabies, Paramyxo virus: - Intra cytoplsmic inclusion bodies (IC)
  • Viriol virus: - Guarnieri Bodies
  • Small Pox : -  Paschen Bodies, Elementary bodies
  • Ring Sore viorus: -  Milker’s Bodies
  • Rinderpest virus: -  Intra cytoplsmic in bovine kidney cell
  • Rabies virus: -  Negri bodies (Intra cytoplasmic in brain cell)
  • MD virus: - Intranuclear in chiken kidney cell and fibroblast in skin
  • ILT virus: - Intranuclear in trachea of birds
  • ICH virus: -  Intranuclear in kidney and testes of dog cell culture
  • IBR virus: -  Intranuclear inclusion in calf kidney and testes cell
  • Herpes virus, ALT virus: - Cowdry Bodies
  • Fowl pox: -  Bollinger bodies (In cytoplasmic of infected cells)

CLASSIFICATION OF VIRUS 

DNA virus

  • Papovaviridae:- Papiloma
  • Adenoviridae:- ICH, EDS
  • Iridiviridae:- African Swine fever
  • Poxviridae (largest virus):- Cow pox, Avian pox, Ring sore in cows
  • Herpes viridae:- IBR, MCF, MD, ILT, Red nose in cattle, Pink eye in cattle, Duck plague, Mad itch in Swine

RNA virus

  • Retroviridae:- EIA, Bovine leukemia                     Picornaviridae:- AE
  • Aptho virus:- FMD                                                     Pesti virus/Toga:- BVD, Hog cholera, Eiphemeral fever    
  • Paramyxoviridae:- ND, CD                                       Morvilli virus:- RP (Cattle Plague)    
  • Coronaviridae:- IB                                                      Rhabdoviridae:- Rabies
  • Birnaviridae:- IBD                                                      Reoviridae/Orbi:- BT
  • Buniyaviridae:- Rift valley fever

MODE OF TRANSMISSION OF ANIMAL VIRUS

  • Airborn droplet - Influenza, Rhino virus, Apthos virus, Entroviruses
  • Arthropod vectors - Fowl pox, Rabbit Myxoma
  • Genito urinary Tract - Herpes viruses
  • Intimate contact - Pox virus, Herpes Virus, Papova virus
  • Oral Transmission - Corona virus, Adenoviruses, Rota viruses
  • Transplacental - Hog cholera, Blue tongue

Sterilizing Agents

A. Heat

  1. Boiling. 1000C, Endospore formers, hepatitis virus can resist
  2. Autoclaving. 15 min @ 1210C. Longer times for larger volume
  3. Dry Heat. Used for dry products. Typically 170-2000C overnight
  4. Pasteurization. 63-670C for 30 minutes, or 71 0C for 15 seconds

B. Membrane Filters: 0.45 um filters retard bacteria. Good for heat-labile materials.

C. Chemicals: Ethylene Oxide = alkylating agent, usually carried out for 1-10 hours at 600C.

D. Radiation

  1. UV light. Reacts with DNA, causes DNA damage -- death. Cannot penetrate glass.
  2. Ionizing radiation. Gamma rays produce free radicals, destroy all kinds of chemicals. e. g. OH-

Disinfectants and Antiseptics Action

  1. Heavy metals (Mercury, Silver, Arsenic)- cause protein denaturation
  2. Halogens (Chlorine, Iodine, Hypochlorite)- oxidizing agents
  3. Phenols and cresols- dissolve membranes, denature proteins
  4. Alcohols- denature proteins, dissolve membranes.
  5. Detergents- dissolve membranes

Disinfectants are classified into 3 groups:

  1. High level: effective against all life, including endospores. e.g. ethylene oxide, 2% glutaraldehyde. May require 10 hours to kill all population of endospore-forming bacteria
  2. Intermediate level: defined as tuberculocidal (kill Mycobacterium tuberculosis), as well as more resistant viruses (hepatitis, rhinovirus). Not effective against endospores.
  3. Low level: not effective against tuberculosis or endospores, or viruses without membranes. But do kill vegetative bacteria and fungi, used extensively. Economical, not overly toxic to humans. e.g. Lysol, detergents, mercurials.