The first person to observe bacteria – Anton von leuwen hock

The earliest discovery of pathogenic micro organism was probably made by – Augustino Bassi

The development of bacteriology as a scientific discipline date from Louis Pasteur

The kingdom Protista has been divided into two groups – prokaryotes and Eukaryotes

Bacteria and blue green algae are Prokaryotes while fungi, algae, slime moulds and protozoa are Eukaryotes.

The types of staining that may be toxic and that which kills bacteria is called supravital staining.

Bacteria have an affinity to basic dyes due to acidic nature of protoplasm.

Acid fast staining discovered by Ehrlich and modified by Zeil and Neelssen.

According to shape bacteria are classified into

1.     Cocci -  spherical shaped bacteria

2.     Bacilli -  rod shaped cells

3.     Vibrio -  comma shaped cells

4.     Spirilla- rigid spiral forms

5.     Spirochetes- flexuous spiral forms

6.     Actinimycetes -  branching filamentous form.

7.     Mycoplasma – lacks cell wall. Hence do not possess stable morphology.

Cultural media may be a complex medic if ingredients are added for special purpose of growth.

IMMUNITY

            Refers to resistance exhibited by host towards injury caused by microorganisms and their products.

Innate immunity is inborn.

Acquired immunity may passive and active immunity.

Active immunity developed by an individual due to antigenic stimulus . once developed it is long lasting.

In PASSIVE immunity no antigenic stimulus; preformed ontibodies are administered.

An antigen has been defined as any substance when introduced parenterally into the body stimulates the production of antibodies. The smallest unit of antigenicity is called an epitope

Antibodies are immunoglobulins

IgG :- this is major serum immunoglobulin. Its level is raised in chronic malaria, kala azar, or myeloma. IgG is only maternal immunoglobulin that is normally transported across the placenta and provides natural passive immunity in newborn.

IgA:-it is the second most abundant class of immunoglobulin seen in body fluids such as colostrums, saliva and tears.

IgM:- is called ‘millionaire” molecule. It is not transported across the placenta hence presence of IgM in the foetus or newborn indicates diagnosis of congenital infection such as syphilis, rubella, HIV and toxoplasmosis.

IgM antibodies are short lived, hence their presence in serum indicates recent infection.

IgE:- greatly elevated in atopic (Type I allergy) conditions such as asthma, hay fever, eczema, and also in children having high load of intestinal parasites.

In general

            IgM – protects body fluids

            IgA – protects body surfaces

            IgM – protects blood stream

            IgE -  mediates reagenic hypersensitivity

Bence jones proteins are abnormal light chain immunoglobulins seen in multiple myeloma.

Coomb’s test – antiglobulin test- dirct commb’s test is positive in haemolytic disease of newborn due to Rh incompatibility

            Indirect commb’s test is positive in Brucellosis

Wasserman reaction (Serodiagnosis of syphilis) is a complement fixation test

The term hypersensitivity means injurious consequence in sensitized host following contact with specific antigens. Mainly classified into

Immediate – B-cell or antibody mediated and Delayed – t cell mediated

-          In anaphylactoid reactions there is no immunological basis.

-          Shwartzan reaction is not an immune reaction but reaction resembles immune inflammation.

-          Auto immunity is a condition in which structural or functional damage is produced by action of immunologically competent cells or antibodies against normal components of body.

-          Rose water test is used for the detection of rheumatic fever.

STAPHYLOCOCCUS

      Gram positive

Occurs in ‘grape like clusters’

Enzyme coagulase present

It causes LOCALISED SUPPURATIVE LESIONS

Common culture media is nutrient ogar and organization shows ‘oil –paint’ appearance in medica. Main exotoxins of S.aureus are cytolytic toxin, enterotoxin and exfoliative toxins. Entero toxin causes staphylococcal food poisoning (milk and milk products are responsible for common food items)

Exfoliative toxins causes TSS (toxic shock syndrome)

And SSSS  - Staphylococcal scalded skin syndrome- seen in infants – Ritter’s disease

PATHOGENESIS

-          Localized skin lesions including furuncles, styes, boils, abscesses, carbuncles, impetigo.

-          Sepsis in burns and wounds

-          Acute osteomyelitis

-          Tonsillitis, pharyngitis, pneumonia, especially bronchopneumonia secondary to some respiratory infections

-          Breast abscess in lactating mothers

-          Tropical myositis- in young adults of tropics multiple abscess in voluntary muscles.

-          In staphylococcal food poisoning diarrhea and vomiting starts with in 6 hours of taking contaminated food

-          Exfoliative diseases such as impetigo, pemphigus neonatorum, Ritter’s disease, toxic epidermal necrolysis.

-          Non pathogenetic staphylococci- staphylococcus epidermitidis

STREPTOCOCCI

            Gram positive

It causes SPREADING PYOGENIC INFECTIONS  and non suppurative lesions sucj as rheumatic fever and glomerulonephritis

3 types

Alpha haemolytic s.cocci

Beta haemolytic s.cocci

Gamma haemolytic s.cocci (non haemolytic)

Streptococci form several exotoins and ensumes. The two haemolysins are haemolysin ‘O’ and ‘S’.

Streptolysin ‘O’ is oxygen labile. Streptolysin regularly appear in sera following streptococcal infection -  ASO tite

Strepto lysine S is not antigenic

Erythrogenic toxin is also called Dick , scarlatinal or pyrogenic toxin.

DICK TEST:- this test is used to identify children susceptible to scarlet fever (scarlet fever is a type of acute pharyngitis with extensive rash caused by str.pyogens

SCHULRZ CHARTON reaction:- blanching of rash on localinfection convalescent serum. This is used as a diagnostic test in scarlet fever.

The enzyme sternodornase present in the str.cocci helps to liquefy pus and hence responsible for serous character of pus.

PATHOGENESIS

-          Respiratory infection including sore throat, tonsillitis, pharyngitis

-          Extension of infection from  throat to surrounding tissues causes ASOM, mastoiditis , quinsy, Ludwig’s angina, suppurative adenitis

-          Skin and subcutaneous infection -  Variety of suppurative infection including infection of wounds or burns.

-          2 typical streptococcus infections are Erysipelas and impetigo (impetigo are vesicular pin head like infection with exfoliation.)

-          Streptococcal subcutaneous infection range from cellulites to necrotizing fascitis.

-          Genital infection including puerperial sepsis and abscess in internal organs such as brain, kidneys etc.

-          Non suppurative leisions such as rheumatic fever and acute glomerualonephritis.

-          In rheumatic fever, a connective tissue degeneration of heart valve and inflammatory myocardial leisions causes Aschoff nodules

-          Str. Viridans normally residing in mouth and upper respiratory tract

PNEUMOCOCCI

            It is gram positive

Single most prevalent bacterial genera in pneumonia, otitis media, acute sinusitis, meningitis, and other infectious processes

Cultural characters :- on blood agar draughtsman or carom coin appearance. It exhibits capsule swelling reaction called quelling reaction.

The toxins are oxygen labile haemolysin and a leucosidin

PATHOGENESIS

-Lobar pneumonia

- Bronchopneumonia following viral infections

- Acute exacerbation of chronic bronchitis (haemophilus influenza also causes this)

- Empyema, pericarditis, ASOM, otitis media, sinusitis, conjunctivitis, suppurative arthritis

NEISSERIA

Gram negative cocci

N.meningitidis

            Causes meningococcal meningitis or cerebrospinal fever

Oval or spherical in shape

Grows only on enriched media such as blood agar, chocolate agar

Modified  Thayer-Martin media is a useful selective media

PATHOGENESIS

Cerebrospinal meningitis

Meningococcal septicemia

In meningococcal septicemia there occurs adrenal haemorrhage and shock. This is Water house – Frederickson syndrome

N. gonorrhoea

            Causes veneral disease gonorrhoea. Here also Thayer – Martin media is used.

PATHOGENESIS

            Gonorrhoea is acquired by sexual contact. c/c urethritis lead to stricture formation. The may spread to periurethral tissue causing abscess and multiple discharging sinuses. (Water can perineum)

-          In women causes Bartholinitis and salpingitis

-          Proctitis, conjunctivitis, arthritis, ulcerative endocarditis and meningitis

-          Non veneral infection is gonococcal ophthalmia in newborn

NON GONOCOCCAL URETHRITIS (NGU)

Causative organisms are

a.     Chlamydia trachomatis

b.     Ureaplasma urealyticum

c.     Mycoplasma hominis

CORYNE BACTERIA

            Gram positive

Non acid fast, non motile rods

C.diphtheria :- syn. (Loffler’s bacillus)

Having Chinese letter of cuneiform arrangement

Usual media -  Loeffler’s serum slope and tellurate blood agar

3 types –

            Gravis – most fatal infections

            Intermediate

            Mitis

Universally used strain is Park william’s strain

PATHOGENESIS

Site of infection

1.     Faucial

2.     Laryngeal

3.     Nasal

4.     Otitic

5.     Conjunctival

6.     Genital

7.     Cutaneous

-Faucial diphtheria is the commonest type. Classified into malignant or hyper toxic diphtheria in which there is sever toxaemia with marked adenitis – bull neck. Death occurs due to circulatory failure.

-Septic- which leads to ulceration, cellulitis, gangrene

- Haemorrhagic – characterized by bleeding from edge of membranes

Common complication – asphyxia, acute circulatory failure, post diphtheritic paralysis

SHICK TEST- susceptibility test for diphtheria  

BACILLUS

            Rod shaped bacteria

2 types

Aerobic bacilli and anaerobic bacillus

Gram positive

B.anthracis :- first pathogenic bacteria observed under microscope and it is the first bacillus to be isolated in pure culture and first bacterium used for preparation of attenuated vaccine.

M-Fayden’s reaction:- used for presumptive diagnosis of anthrax in animals

Culture media:- on agar media frosted glass appearance with locks of matted hair called medusa head appearance, on gelatin slab having ‘inverted fir tree’ appearance when grown on solid media ‘ strings of pearl reaction’.

ANTRAX is a zoonosis

3 types

1. Cutaneous 2. Pulmonary 3. Intestinal

All types leads to fatal septicemia.

Cutaneous anthrax

Follows infection through skin. Leisions are called ‘malignant pustule’ or black eschar

Disease is common in dock workers carrying loads of hides and skins on bare back. Hence called hide porter’s disease.- 

PULMONARY ANTHRAX:-

Wool sorter’s disease due to inhalation of dust from infected wool. There is haemorrhagic pneumonia. Haemorrhagic meningitis is a complication.

Intestinal anthrax is rare. Occurs mainly in primitive communities which uses undercooked meat.

Lab diagnosis is by immunofluoroscence

Bacillus cereus – causes food borne disease characterized by diarrhea and abdominal pain associated with consumption of cooked rice, usually fried rice from Chinese restaurant.

CLOSTRIDIUM

Gram positive

Anaerobic sphere forming bacilli

Genus responsible for  3 major diseases

1.     Gas gangrene. 2. Food poisoning 3. Tetanus

Spores may be central or equatorial.  Eg. Cl. Bifermingens

                  Oval or terminal   Tennis racket  eg. Cl. Tertian

                  Spherical and terminal – drum stick appearance eg. Cl. Tetani

Useful media

      Robertson’s cooked meat broth

cl. perfingens -  Gas gangrene (malignant oedema)

                              Wound contamination

                              Septic abortion

                              Anaerobic myositis

                              Food poisoning and

                              Necrotizing enteritis

In litmus reaction fermentation of lactose causes stormy fermentation

cl. perfingens show ‘Nagler reaction’ due to specific lecithinase effect

Food poisoning starts between 8-24 hours – self limiting illness

cl.noviji (cl.oedematiens)

Also causes gangrene characterized by high mortality and large amount of oedema fluid with little or no observable gas.

Clostridium tetani

      Drumstick appearance

Media: robertson’s cooked meat broth

2 toxins: tetanolysin which is haemolysin and tetanospasmin which is a powerful  neurotoxin

Tetanus toxins block synaptic inhibitors in spinal cord. While  strychnine acts post synaptically.

Abolition of spinal inhibition causes uncontrolled spread of impulses initiated any where in CNS. This results in muscle rigidity and spasm.

Sometimes tetanus may be due to local suppuration called otogenic tetanus.

Clostridium botulinum

      Causes food poisoning – exotoxin is responsible for pathogenicity. It acts by blocking acetylcholine at synapse and neuromuscular junction. Hence onset marked by diplopia, dysphagia and dysarthria

Botulinum – 3 type

1.     Food borne botulism

2.     Wound botulism

3.     Infantile botulism

Food borne botulism- 12- 36 hours after ingestion

            Vomiting, thirst, constipation, ocular paresis, difficulty in swallowing, speaking, breathing, coma or delirium

Death is due to respiratory failure.

Wound botulism – Rare. Symptoms similar to food borne botulism except GIT symptoms

Infant botulism -  Infants less than 6 months are affected. Manifestations are constipation, poor feeding, lethargy, weakness, pooled oral secretion, weak or altered cry, loss of head control.

NON SPORING ANAEROBS

 Enterobacteria – proteus

Mc conkeney’s medium

E coli- pathogenesis

            Neonatal meningitis

            Septicemia

Clinical features:

1.     UTI

2.     Pylonephritis and hypertension in pregnant women

For diagnosis -  Mid stream urinalysis

3.     Diarrhea – traveller’s diarrhea

4.     Enterohaemorrhagic colitis – frank dysentery

5.     Pyogenic infection and septicemia

KLEBSIELLA (fried –landler’s bacillus)

            -Pneumonia, UTI, septicemia and rarely diarrhea

ENTEROBACTERIA

            Shigella causes bbacillary dysentery

            Short incubation period – 1-7 days; usually 48 hours

Enterobacteria  - Salmonella

Salmonella typhi:- causes typhoid fever.

Enteric fever :- typhoid and paratyphoid fever- salmonella paratyphi A,B,C

Widal reacton

Leucopenia

Diazo test of urine

Slamonella gastroenteritis

Poultry, meat, milk, cream and eggs

Short incubation period – less than 24 hours

VIBRIO

            Gram negative; comma shaped

Described by Koch as ‘fish in stream’ vibrio colonies are identified by ‘string test’

Biochemical reaction- cholera rod reaction

In cholera – watery diarrhea, vomiting with hypovolumic shock and death in less than 2 hours

Stool has fishy odour and it is described as ‘rice watery’ stool.

PSEUDOMONAS

            Bacillus pyocyanius

Gram negative

Pyocyanis forms blue pus ; self limiting illness -  shanghai fever

YERSINIA, PASTEURELLA, FRANCISCILLA

Yersinia safety pin appearance

On nutrient agar -  stalactile growth

Yersinia causes plague

            Pandemic plague causes black death due to extensice cutaneous haemorrhage and gangrene.

3 forms

            Bubonic, pneumonic and septicemic

Vector is rat flea – xenophilla cheopis

HAEMOPHILUS INFLUENZAE

Gram negative bacillus

Cultural media is blood agar and shows Satelletism in media

Pathogenesis

Meningitis

Otitis media

Pneumonia

Arthritis

Endocarditis, pericarditis

Bronchitis

Haemophilus ducreyi

Cause chancroid or soft sore. Veneral disease. Bacilli are arranged in groups called school of fish or rail road track appearance

BORDETELLA PERTUSIS ( bordet- gengou glycerine –potatoe blood agar

‘Bisected pearls’ or mercury drops’ with ‘aluminium paint’ appearance

Pathogenesis: Pertusis  or whooping cough.

BRUCELLA

Acute brucellosis ; undulant fever

                        Malta fever

                        Relapsing fever

Caused by B. melitensis – Brucellosis is primarily a disease of reticuloendothelial system

Lab investigation:- castinada method of blood culture.

MYCOBACTERIUM TUBERCULOSIS

Gram positive

Acid fast bacillus

In children it causes primary complex.

Ghon’s focus :- subpleural focus of tuberculous pneumonia in lung parenchyma

Adult type TB is due to reactivation of primary infection.

In mantoux test 0.1 ml. purified protein derivative is injected intracutaneously on flexor aspect of forearm. Site is examined after 48-72 hours

If induration of diameter 10mm or more – positive mantoux test

If induration is 5 mm. or less than 5mm. – negative

If induration is between 6-9 mm it is doubtful case.

LEPROSY

            Caused by gram positive mycobacterium leprae. Organism is arranged in parallel rows are having ‘cigar bundle’ appearance. Masses of bacilli are called globi. The globi appear in virchow’s lepra cell or foamy cell

Leprosy is a chronic granulomatous disease.

4 types

            1. Lepromatous

            2. Tuberuloid

            3. Dimorphous

            4. Indeterminate

Lepromatous variety is most infectious type. Lepromin test is negative in lepromatous leprosy due to deficient cell mediated immunity.

In Tuberculoid leprosy patient is having high resistance. Good prognosis. Lepromin test is positive. Few skin lesions but neurological symptoms are more and deformity occurs early.

The term borderline or dimorphous refers to lesions possessing characteristic of both tuberculoid and lepromatous type.

The indeterminate type is early unstable tissue response to the microorganism. Lesions undergo spontaneous healing.

Classification according to Reiding & jopteng scale of classification

Lepromin test is described by metsuda

Biphasic events

First phase -  early reaction -  Fernandes reaction. Ie. Erythema and induration developing in 24-48 hours.

Late phase -  Mitsuda reaction -  starting 1 or 2 weeks later. It consists of indurated skin nodule which may ulcerate.

Lepromin test is positive in Tuberculoid leprosy

Lepromin test is negative in lepromatous leprosy

Lepromin test is variable in dimorphous and indeterminate varieties

SPIROCHAETES

            Treponema pallidum causing syphilis

            Treponema pertenue  causes yaws

            Treponema carateum  causes pinta

Staining reaction is silver impregnation method

Syphilis is a veneral disease

Primary lesion is chancre

Lymph nodes are characteristically rubbery in consistency

Secondary syphilis starts after 2-6 weeks, characterized by roseolar skin rashes

After secondary syphilis there is a stage of latent syphilis. During this period diagnosis is possible by serological test. There occurs cardiovascular lesions including aneurysm.

Tertiary syphilis – delayed hypersensitivity reaction mainly tabes dorsalis and general paralysis of insane.

Serological test for diagnosing syphilis

A.    Reagin test

B.    Kahn test (floaculation test)

C.    VDRL test (veneral disease research laboratory test)

D.    Rapid plasma regain test is the first modified VDRL

First reagen test is Wasserman reaction

BORELLIA

            Causes relapsing fever

2 types

            Louse borne relapsing fever

            Tick borne relapsing fever

Louse borne relapsing fever is caused by Borellia recurrentis

Borellia vincenti causes ulcerative gingivostomatitis or oropharyngitis called – vincent’s angina or cancre oris

Borellia burgdorferi causes lyme disease

Rat bite fever caused by spirillum minus or streptobacillus moniliformis

LEPTOSPIRA

Leptospira icterohaemorrhagica causes Weil’s disease which causes hepatorenal damage.

Antibodies appear in serum towards the end of first week of disease and increase till 4^th week. Caonicola fever is caused by leptospira canicola.

MYCOPLASMA

 Smallest free living microorganism. Organism in colony have ‘fried egg’ appearance.

Mycoplasma causes pneumonia and genital infection especially of children and adolescents.

ACTINOMYCETES

             Gram positive. Between bacteria and fungi

It causes ‘lumpy jaw’ in cattle.

Actinomycosis is a chrnic granulomatous infection characterized by development of indurated swelling mainly in connective tissue with suppuration and discharge of sulphur granules. Actinomycosis in human being is an endogenous infection. Actinomycetes Israeli is the causative organism.

3 forms

1. Cervico fascial

2. Thoracic

3. Abdominal

            Pelvic actinomycosis is associated with the use of IUCD (intra uterine contraceptive device)

Actinomycetes mycetoma( Madura mycosis)

            It is a localized chronic granulomatous involvement of subcuteneous and deeper tissue affecting foot and less commonly hands and presenting as a tumour with multiple discharging sinuses.

Helicobacter pylori associated with antral gastritis and peptic ulcer disease.

Legionella pneumonia is caused by Legionella pneumophilia. Human infection is typically caused by inhalation of aerosols produced by airconditioners and shower heads.

RICKETTSIAE

            Gram negative organism

Weil – Felix raction used for diagnosis of rickettsial infection.

Scrub typhus

            Rickettsiae tsu tsu gambusti

Epidemic typhus

            Rickettsiae prowazekii (vector is louse or pediculus humanis)

Recrudescent typhus is activated latent infection called Brill- Zeinsser disease

Rocky mountain spotted fever  - Rickettsia rickettsi

Endemic typhus is caused by rickettsiae typhi  ( r. mooseri)

Transmitted by xenopsyla cheopis or rat flea

Trench fever  is caused by Rickettsiae Quintana

Transmitted by body louse

Q fever is caused by coxellia burnetti

CHLAMYDIAE

            Main pathogenitic varieties are

            Chlamydiae psittaci

            Chlamydiae pneumoniae

trachomatis causes

1.Trachoma which is a chronic keratoconjunctivitis  (lab diagnosis by Hp bodies)

2. Inclusion benorrhoea (neonatal form of inclusion conjunctivitis)

3. Pool conjunctivitis

4. Lymphogranuloma venerum

Chlamydia psittaci

             Causes psittacosis – consumption of infected poultry products leads to this disease

VIROLOGY

             Interferon – antiviral substances, it is a family of host coded proteins produced by cells on induction by viral or non viral substances

Pox virus:- small pox- last detected case of small pox – sarban devi , a bengladeshi woman on 24^th may 1975.

HERPES VIRUS

            Herpes simplex virus  type I causes oral and cutaneous lesions spreading by direct contact

Herpes simplex type II causes genital tract infection transmitted venerally.

Occupational variety of cuteneous lesion is herpetic whitlow seen in doctors, nurses and dentists.

Eczema herpeticum

            Generalized eruption occurs in children suffering from eczema

Crops of vesicles appear around the ulcer;clinically indistinguishable from vaccinia virus infections . both designated as Kaposi’s varicella form eruptions.

In chicken pox eruptions are centrifugal in distribution. (small pox rashes are centripetal in distribution)

In chicken pox patients , secondary bacterial infection due to streptococci or staphylococci occurs. This is called Reyes syndrome. Clinically characterized by acute hepatic failure, encephalopathy and hypoglycemia.

Herpes zoster (syn; shingles, zona)

            Occurs in patients affected with chicken pox years later.

Ramsay hunt syndrome:- rare form of zoster affecting facial nerve with eruption on areas of tympanic membrane and external auditory canal with facial palsy.  

Epstein – Barr virus

Causes IMN (infectious mono nucleosis)

Associated with

-          Burkitt’s lymphoma

-          Immunodeficiencies

-          Naso pharyngeal carcinoma

IMN (glandular fever) – acute self limited illness seen in non immune adults following primary infection with EB virus. Incubation period is 4- 8 weeks . standard diagnostic test is Paul -  Bunnel test

Adenovirus causes respiratory infection , usually picorno virus includes

-          enterovirus -  coxachie virus and polio virus

poliomyelitis is mainly 3 types

1.     Minor illness :- called abortive polio with head ache, sore throat, and malaise

2.     Non paralytic illness:- it does not progress beyond asceptic meningitis

3.     5-10% causes paralytic polio

Vaccine:- 2 types

a.     Salk’s killed polio vaccine

b.     Live polio vaccine is oral polio vaccine

Orthomyxovirus causes influenza.

Paramyxovirus  Eg. Mumps virus

Measles (Rubiola) – genus morbiliform virus

Multinucleated giant cells called Warthin – Finkelclay cells are found in lymphoid tissue of patients.

Koplik’s spots developon buccal mucosa two or three days before the appearance of rash.

FLAVI VIRUS

             Causes

1.     Japanese encephalitis (vector- culex tritaneorynchus)

2.     Yello fever – Vector – Aedes aegypti

3.     Dengue fever -  Vector  - Aedes aegypti

Tick borne encephalitis eg. KFD (Kyansur forest disease)

RHABDO VIRUS

             Eg. Rabies virus  causes hydrophobia

Diagnosis is confirmed by negri bodies (inclusion bodies) in brain in post mortem examination mostly in hippocampus and cerebellum

PAPOVA virus include papilloma virus group and polyoma virus group.

The common human disease produced by papova virus is papilloma or wart. (verruca vulgaris)

A special type of wart is condylom accuminatum or genital wart found on external genitalia. This may be transmitted venerally and may occasionally turn malignant.

Parvo virus cause erythema infectiosum –‘the fifth disease’ a contagious disease of children characterized by erythematous rash first appearing on cheeks. – slapped cheek appearance.

RUBELLA OR GERMAN MEASLES

             Caused by genus rubivirus of family toga viridae

-          Koplik’s spot absent

-          Rash is discrete and coalesce and disappear on 3^rd day

-           Non tender enlargement of post cervical glands is characteristic

-          If Rubella occurs in early pregnancy, the foetus may die

-          Congenital malformations are common during first trimester.

-          Infected babies constitute an important source of infection for about 6 months (virus may persist for years in tissues such as cataractous lenses)

-          Diagnosis of Rubella in early pregnancy is an indication for therapeutic abortion.

-          Cruzfelt – Jacob disease is sub acute encephalopathy with progressive incoordination and dementia caused by group b prion virus.

Haemorrhagic fever with renal syndrome(HFRS)- also known as epidemic haemorrhagic nephrosonephritis is caused by Huntaan virus of family Bunya viridae.

HIV – human immunodeficiency virus – retro virus now called Human T cell lymphotrophic virus

- RNA virus attacks CD4 cells.

A. Envelops antigens – 1. spicks antigen, 2. transmembrane

B. Shell antigen

C. Core antigen

D. Polymerase antigen

            Incubation period varies from 2-6 weeks to 15 years.

Features characaterising AIDS

1.     Lymphopenia

2.     Selective T cell deficiency – reduction in numbers of T4 (CD4) cells, inversion of T4: T8 ratio

3.     Decreased delayed hypersensitivityon skin testing

4.     Hypergammaglobulinaemia – predominantly IgG and Ig A; also IgM in children.

5.     Polyclonal activation of B cells an dincreased spontaneous spontaneous secretion Ig.

Common malignancies associated with HIV infection is Kaposi’s sarcoma and lymphoma- hodgkin’s and Non hodgkin’s types.

HIV- Elisa for detection

            Western blot for confirmation

Ergotoxicosis (ergotism) is due to claviceps purpura growing on fruiting heads of rye.

HEPATITIS

            Hepatitis A – incubation period  -   2- 6 weeks

            Hepatitis B  - I P                                     4 – 8 weeks

            Hepatitis C  -      I P                                2 – 22 weeks

            Hepatitis D         I p                                4 – 8 weeks

            Hepatitis E          I P                               2 – 9 weeks

Hepatitis B – DNA virus ; all others are RNA virus

Spreads by faeco oral route -  hepatitis A and E

Spreads by percutaneous route -  Hepatitis B,C and D

Hepatitis B also spread by vertical and sexual route

-          Oncogenicity present in Hepatitis B especially after neonatal infection.

-          Carrier state present in Hepatitis B only

-          Hepatitis B virus may present in blood and other body fluids and excretions such as saliva, breast milk,semen, vaginal secretions, urine , bile etc.

-          Feces not known to be infectious

-          HBs Ag is the first viral marker to appear in blood after infection; it remains in circulation throughout icteric course of disease. In a typical case it disappear within roughly 2 months but may last for 6 months.

-          HBsAg is not demonstrable in circulation but antibody, antiHBe appear in serum a week or two after appearance of HbSAg

-          So anti-HbeAg is the antibody marker to be seen in blood.

-          HBeAg (HB envelop antigen) appears in blood concurrently with HBsAg. HbeAg is an indicator of intrahepatic viral replication and its presence in blood indicates high infectivity.

-          For diagnosis of HBV infection, simultaneous presence of IgM, HBC indicates recent infection and presence of IgG ;anti H-Be indicates remote infection.

Type E hepatitis : enterically transmitted.

Non A – non B hepatitis caused by Hep. C virus

Inclusion body inviruses

a.     Intracytoplasmic

Guarnieri body -  Varicella, Vaccinia

Negri body – Rabies

Henderson – Paterson body -  Molluscum contagium

b.     Intranuclear

a.     Lipschutz bodies -  herpes fibrilis, herpes zoster, varicella

b.     Councilmann’s bodies -  yellow fever, virus B encephalitis

c.     Nicolau’s bodies – herpes fibrilis, herpes zoster , polio, Rift valley fever

Association of virus with human cancer

Viral infections associated with associated with maculopapular rash

1.     Adenovirus infection

2.     Arbovirus infection

3.     Measles

4.     Cytomegalovirus infections

5.     Enterovirus

6.     Hep-B virus

7.     IMN (kissing disease)

8.     Rubella

-          Haemolytic uraemic syndrome caused by virotoxin producing e-coli

-          Brazilian purpuric fever caused by Haemphilus aegypticus

-          Cryptospridum causes diarrhea

-          Cat scratch disease is caused by cat scratch bacillus

FUNGAL INFECTIONS

            Superficial mycosis(cutaneous ) or dematophytis

1.     Microsporum -  attacks skin and hair ; not nail

2.     Tricophyton attacks skin , hair and nails. Most important human parasites are T. rubrum and T. tonsuran

3.     Epidermophyton  - e.floccosum attacks skin and nails but not hair.

Dermatophytes:

-          Tinea capitis – ring worm of scalp

-          Tinea circinata – ringworm of glabrous skin

-          Tinea barbae -  ringworm of beard

-          Tinea pedis – Athletes foot

-          Tinea cruris – Dhobi itch or Jock itch

-          Tinea unguum  - ring worm of nails

Systemic mycosis

            Candid albicans – yeast like fungi

            Histoplasma capsulatum -  Darling’s disease

            Cryptococcus neoformans – yeast

            Aspergillus  -  fungus ball

            Cocciodes immitis – desert rheumatism