Clostridium perfringes

  They are gram positive, rod shaped, and non capsulated and anaerobic spore forming bacteria. It causes Gas gangrene and food poisoning.

Toxins:

·         The toxin causes gas gangrene.

v   No immunization is available against clostridium perfringes.

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Clostridium Tetani

  It is gram positive, rod shaped, non capsulated anaerobic bacteria. This tetanus bacilli is present in dust, garbage and horse dung

Toxins:

Tetanospasmin:

·         It is a toxin produced by tetanus bacilli in an infected wound.

·         The toxin diffuses along nerves, causing paralysis (spastic) and may reach the spinal cord and brain when it causes violent muscular spasm (tetanus) and the condition of lockjaw.

·         It inhibits Ach release at NMJ and also inhibits the synthesis and release of GABA in rest of the nervous system. All these causes spastic paralysis, exaggerated reflexes and scissors or fits.

Immunization is available both Active (Anti – Tetanus Serum) and Passive (Tetanus Toxoids).

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Clostridium Botulinum

   It is anaerobic, rod shaped, non capsulated gram positive bacterium. It grows freely in badly preserved canned food and improper cooked food, producing a toxin causing serious food poisoning (botulism).

Toxins:

Botulinum toxin:

                It strongly inhibits the Ach release at NMJ causing Flaccid paralysis. Sometime used for muscle spasm.

·         No immunization is available against clostridium botulinum.

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Escherichia Coli (E – coli)

  They are gram negative, rod shaped, capsulated and facultative anaerobe ( prefer oxygen rich condition for production of energy)

Antigens:

·         O – Antigen (somatic antigen):

                                Present in body

·         K – Antigen (capsular antigen):

                                Present in capsule

·         H – Antigen (flagellar antigen):

                                Present in flagella

Toxins:

·         Endotoxin: Present inside the body

·         Exotoxin: Present in capsule

·         Adhesion factor: Helps E – coli in adhesion

·         Enterotoxin: Cause problems in intestine

Habitat:

                Part of normal flora present in intestine, contaminated food and water

Mode of transmission:

·         Orofaecal route

·         Urethra called as retrograde infection may ascend up to the kidney urethritis cystic and polynephritis. This whole is called UTIs.

·         Mother to baby during child birth

Pathologies:

·         UTI

·         Traveler’s diarrhea (acquire during travel due to food poisoning)

·         Dysentery (blood in faeces)

·         Meningitis

                No immunity for E – coli infection (no vaccine)

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Neisseria Gonorrhea (gonococcus)

   They are gram negative, diplococci and non capsulated aerobic bacteria. They are present in pus cells of urethral and vaginal discharge.

Common sites:

                Human genital tract both male and female, eye, joints, throat, rectum and prostate

v  It cause epididymitis, prostitis, urethritis, epididymo – orchitis, vaginitis, proctitis, uveitis and arthritis.

v  Gonococcal infection has history of unsafe sexual interaction, children after birth and adult after honeymoon.

v  Gonococcal ophthalmia neonatorum: eye infection in children due to passing of infant through infected birth canal.

No immunization is available.

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Neisseria meningitides (Meningococci)

They are gram negative, diplococci and capsulated.

Pathologies:

·         Meningitis

v   Immunization is available against some of the types.

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Salmonella

It is gram negative, rod shaped, capsulated and aerobic bacterium.

Habitat:

v  Normal flora of cattle

v  Contaminated food and water

Mode of transmission:

§  Some may act as a carrier (Human carriers)

§  Orofaecal transmission

Subtypes:

Salmonella – Typhi

Salmonella – Paratyphi

                Both the above types cause enteric fever (typhoid fever).

Antigens:

ü  Somatic antigen (O):

ü  Flagellar antigen (H):

ü  Capsular antigen (Vi Antigen):

Toxins:

o   Endotoxin

Pathology:

·         Enteric fever (typhoid fever)

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Shigella

They are gram negative, rod shaped, facultative anaerobe and non capsulated bacteria.

Habitat:

Contaminated water and food

Mode of transmission:

Orofaecal route

Antigen:

Somatic antigen

Toxins:

·        Shigella dysentrae toxin:

                                This toxin causes bacillary dysentery.

·        Exotoxin

·        Endotoxin

Disease:

·         Shigellosis: An infestation of the digestive system by bacteria of genus shigella

·         Bacillary dysentery

No immunization after infection and no vaccine.

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Treponema pallidum

·         These are atypical spiral bacteria.

·         They can be detected by special procedure called as Dark Field Illumination.

·         These are microaerophillic organism because they can live in oxygen concentration 4 – 5 %.

Habitat:

§  Human genital tract

Transmission:

ü  Sexual contact

Disease:

Ø  Syphilis: STD cause by T Pallidum.

v  No immunity

v  No vaccine

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Vibrio cholera

They are gram negative, non capsulated, rod shaped and aerobic bacteria.

Antigen:

·         – Antigen (somatic):

Toxin:

Vibrio cholera Enterotoxin (Choleragen):

                It causes severe watery diarrhea.

v  No immunity available for their infection and no vaccine.

Disease:

·         Cholera

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Staphylococci

Group of gram positive non-motile aerobes cocci spherical in shape arranged in grape like clusters.

Subgroups:

According to the coogulase enzymes presence or absence the staphylococci is divided into two groups.

         i.            Coogulase positive: coogulase enzyme is present e.g. Staphylococcus Aureaus

       ii.            Coogulase negative: coogulase enzyme is absent e.g. Staphylococcus Epidermitis

Habitat:

Staph epidermitis is present in normal flora is Skin, GIT and Respiratory Tract. Staph areaus is never present in normal flora.

Transmission:

·         Direct contact (touching, handling etc)

·         Contaminated ingestion (food, air, drinking etc)

Antigen present in Staph Areaus:

Antigen is any substance which stimulate complement system.

        i.            Peptidoglycan:

                       Produce antibody for own destruction. Antibodies can be detected. It acts as chemotactic factor (neutrophils etc are attracted). It also activates the complement system.

      ii.            Protein A:

                       It causes cooglutination (clumping of bacteria together). The antibodies can be detected in the serum.

Enzymes present in staphylococci:

a.      Catalase:

                       The enzyme present in staphylococci which convert hydrogen per oxide into water and oxygen. Oxygen is released in the form of bubbles which shows the differentiation between the staphylococci and streptococci (catalaseis not present in streptococcus).

b.      Coogulase:

                       The enzyme which convert fibrinogen to fibrin. It causes the coogulation disorders due to clumping of platelets and RBCs.

c.       Hyaluronidase:

                       It causes regradation of connective tissue which causes quick and easy spread of infection. It increases the permeability of connective tissue.

d.      β – lactamase:

                       β – lactamase is enzyme which convert pencillin into pencillinoic acid. The pencillinoic acid has no antibacterial feature.

Toxins:

                       The toxins produced by the staph cocci are the following.

        i.            Exotoxins:

                       A highly potent poison that is produced by a bacterial cell wall causes the breakdown of RBCs and Platelets.

      ii.            Leuocidin:

                       A bacterial toxin that selectively destroys WBCs (leucocytes).

    iii.            Exfoliation:

                       The exfoliation (rupturing) of upper layers of the skin.

     iv.            Toxic shock syndrome Toxins:

                       The toxin which causes the toxic shock syndrome

       v.            Entero-toxin:

                       The toxin which causes food poisoning.

Pathologies:

Local infections:

ü  Abscess

ü  Furuncle (hair follicle involvement)

ü  Acne, Pimple (small inflamed swelling on skin that contains pus)

Systemic infection:

Ø  Osteomyelitis

Ø  Meningitis endocarditis

Ø  Pylonephritis

Ø  Pneumonia

Ø  Scalded skin syndrome:

                       It is due exfoliation of skin. It is eruption of small swellings, upper layer of skin is gone (post Burn skin)

Ø  Toxic shock syndrome:

                       Due to toxic shock syndrome toxin characterized by fever, septicemic shock and multiple organ failure.

Diagnostic lab tests:

                       The specimen can be blood serum, urine, stool, and swab (eyes, skin, vagina, anus, CSF)

v  Microscopy

v  Gram Stainy

v  Culture and sensitivity

v  Serological tests:

                       Antibodies titre from serum

v  Immunization:

                There is no passive immunization (vaccination) for staphylococci.

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Normal flora

Microorganisms which are present naturally in human body is called normal flora. The most common microorganism is bacteria which are present in eye, intestine, skin and vagina etc. Protozoan, viruses, and fungi are not included in normal flora. The bacteria and human body have symbiotic relationship with each other in which both are getting benefit without harming each other e.g. bacteria in small intestine produce fat soluble vitamins which helps in digestion and absorption of food while human body give shelter to it. Bacteria cause pathology:

v  When Overpopulated

v  In Immunocompromised patients

v  At Other site

Sterilization:

Removal of the entire microorganism from any substance is called sterilization. Autoclaving is the sterilization procedure for which the Gold Standard is 121°C heated steam at 15 lb/in² for 15 min exposure of thing. Pasteurization is the sterilization of milk.

Disinfection:

Removal of almost all the microorganism from any substance is called disinfection. It may be by chemical agents such as alcohol (methyl e alcohol, ethanol), hydrogen per oxide, ethylene, aldehydes, detergents, chlorine, iodine etc or may be due to physical agents such as filtration, radiation and heat.

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Bacteriology:

The bacteriology is further classified into basic and clinical bacteriology.

Prokaryotes:

Ø  Prokaryotes are organisms  containing prokaryotic cells

Ø  No well defined nucleus

Ø  Genetic material DNA and RNA are present

Ø  Membrane bounded structures such as mitochondria, endoplasmic reticulum, chloroplast and Golgi bodies are absent

Ø  Contain small sized ribosome of 70S

Ø  Cell division occur by fission mitosis is absent

Ø  Examples are bacteria, blue green algae

Bacteria:

§  Bacteria are the prokaryote found in every part of the world where life can exist.

§  Largest size is 7µm and average size is 0.2µm - 5µm

§  The inner half of bacterial cell wall is made up of peptidoglycan while the outer half vary (made up of polysaccharides)

§  Bacteria show growth by exponential division during suitable conditions

Bacteria are found in three different forms (shapes)

                    i.            Cocci:

They are spherical or rounded in shape.

                  ii.            Bacilli:

They are rod in shape.

                iii.            Spirilla:

They are spiral or twisted in shape.

Classification:

 According to arrangement are:

a.      Pair:

Diplococci

b.      Chain:

Streptococci

c.       Cluster:

Staphylococci

A.     Gram positive bacteria:

These bacteria on treatment with crystal violet dye take the color of the dye and retain it if treated with ethanol. The outer covering is thick as compared to gram negative.

B.     Gram negative bacteria:

These bacteria on treatment with crystal violet dye do not take the color of the dye.

Both the gram positive and negative may or may not have capsule. The capsule act as endotoxin which causes low BP, increased Temperature, peripheral dilatation and decreased cardiac output.

The type of antigen present on the capsule performs the following functions:

v  Identify the type of bacteria

v  Adherence to the tissue of host

v  Determine virulence of bacteria

Classification:

According to availability or absent are the following.

a)      Obligate aerobes:

The bacteria which grow in oxygen suitable condition

Bacteria are obligate aerobes on our skeletal muscles when we are at rest.

b)      Obligate anaerobes:

The bacteria which grow in oxygen deficient condition

c)       Facultative aerobes:

Those bacteria prefer aerobic conditions but can also avail anaerobic conditions. Bacteria are facultative aerobes on our skeletal muscles when we are at exertion.

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