NRE Step 1: Microbiology Made Simple – Pass with Precision

Microbiology is the study of tiny living things called microorganisms and the diseases they cause.

These microorganisms include:

• Viruses
• Bacteria
• Fungus
• Parasites

Viruses

• Virology is the study of viruses.
• All DNA viruses have double-stranded DNA (dsDNA), except for parvovirus, which has single-stranded DNA (ssDNA).
• Most DNA viruses are shaped like a line, except for Hepa DNA Virus (Hepatitis B virus or HBV), which is circular.
• All RNA viruses have single-stranded RNA (ssRNA), except for Reovirus, which has double-stranded RNA (dsRNA).
• Herpesviruses get their outer coat (envelope) from the cell’s nucleus, while other viruses get it from the cell membrane.

Types of DNA Viruses

• Herpesviruses contain DNA as their genetic material and are enveloped.
  • HSV-1 (Herpes Simplex Virus type 1)
    • Spreads through breathing in germs or saliva.
    • Can cause mouth sores (gingivostomatitis) and eye infections (keratoconjunctivitis).
    • Stays hidden in nerve cells in the face (trigeminal ganglia).
  • HSV-2 (Herpes Simplex Virus type 2)
    • Spreads through sex or from a mother to baby during birth.
    • Causes painful sores.
    • Stays hidden in nerve cells in the lower back (sacral ganglia).
  • HHV-3 (Varicella-Zoster Virus)
    • Spreads through breathing in germs.
    • Causes a rash known as chickenpox.
    • If it affects the eye, it’s called herpes zoster ophthalmicus.
  • HHV-4 (Epstein-Barr Virus)
    • Spreads through breathing in germs or saliva.
    • Can cause a sore throat, swollen spleen, and infectious mononucleosis.
    • Can be linked to certain cancers like Burkitt’s Lymphoma and nasopharyngeal cancer.
    • Infects B lymphocytes.
  • HHV-5 (Cytomegalovirus)
    • Spreads through saliva, during birth, through the placenta, or through sex.
    • Can cause infections in people who have received organ transplants or eye problems (retinitis) in people with HIV.
    • Treated with Ganciclovir.
  • HHV-8
    • Seen in people with AIDS.
    • Causes Kaposi’s sarcoma, a cancer of the blood vessel lining.
• Parvovirus
  • Has single-stranded DNA and is linear in shape.
  • Can cause aplastic crisis (a problem where the body stops making enough new blood cells) in people with conditions like thalassemia, hereditary spherocytosis, or sickle cell disease.
• Papillomavirus (HPV)
  • Has circular DNA.
  • HPV types 16 and 18 are linked to cervical cancer.
  • HPV types 6 and 11 cause warts.
• Adenovirus
  • Has linear DNA.
  • Can cause sore throats, bladder bleeding (acute hemorrhagic cystitis), pneumonia, and eye infections (conjunctivitis).
  • Sometimes treated with Cyclophosphamide, with Mesna as an antidote.

Types of RNA Viruses

• Reoviruses
  • Are non-enveloped and have double-stranded RNA.
  • Rotavirus is a type of Reovirus that causes severe diarrhea in children and can be deadly.
• Picornaviruses
  • Are non-enveloped and have single-stranded RNA.
  • Include:
    • Poliovirus (causes polio, preventable by Sabin/Salk vaccine).
    • Echovirus.
    • Rhinovirus (causes the common cold).
    • Coxsackievirus.
    • HAV (Hepatitis A virus, causes acute hepatitis).
• Flaviviruses
  • Include:
    • Hepatitis C virus (can cause cirrhosis and liver cancer).
    • Dengue virus (causes dengue fever).
• Togaviruses
  • Rubella is a Togavirus.
    • In adults, it causes swollen lymph nodes behind the ear, rashes, and fever.
    • If a baby gets it before birth, it can cause cataracts, hearing loss, and heart problems.
• Retrovirus
  • HIV (Human Immunodeficiency Virus) causes AIDS.
• Paramyxoviruses
  • Include Measles and Mumps viruses.
  • RSV (Respiratory Syncytial Virus) causes bronchiolitis in children.
  • Parainfluenza virus causes croup.
• Rhabdoviruses
  • Rabies virus is bullet-shaped.
  • It has a 100% death rate.
  • Doctors look for Negri bodies in brain tissue after death to diagnose it.
• Delta virus
  • Hepatitis D virus is a “defective” virus.

Antiviral Drugs

• Acyclovir is used for HSV-1, EBV, and CMV.
• Ganciclovir is used for CMV.

Influenza

• Influenza viruses can change in two ways:
  • Antigenic drift: Minor, gradual changes in antigens, leading to epidemics.
  • Antigenic shift: Major, sudden changes in antigens, leading to pandemics.
• Oseltamivir is a drug that works by targeting neuraminidase, a protein on the virus.

Genital Ulcers

• Painless sores (chancre) can be caused by Syphilis (Treponema pallidum).
• Painful sores can be caused by HSV-2 (Herpes simplex virus type 2).
• Chancroid is caused by Haemophilus ducreyi and results in deep sores.