Microbial Diseases and Host Pathogen Interaction

DPT consists of inactivated diphtheria toxin known as toxoid, destroys whooping cough microbes and inactivated tetanus toxin known as toxoid. Each of these is obtainable individually or tetanus diphtheria immunisation may be mixed up without whooping cough, then it is known as DT (double toxoid).  Usually DPT is applied in 3 doses at the interval of every month starting at the age of  6 weeks.

Trichosporon beigelii or T. captitatum are responsible for rare but growing infections in immune deficit patients. These agents can be insulated from the healthy skin and other sites like food, air, etc.
Trichosporonosis frequently causes death in patients having haematologic malignance. Early symptoms involve fever, pneumonia, positive blood cultures and lung or eye infections. Trichosporon sp are vulnerable to Amphotericin B, miconazole but in maximum cases patients with disseminated infections die.

Adenovirus causes many airborne infections in respiratory tract and eyes. In adults, Acute Respiratory Disease (ARD) and acute follicular conjunctivitis may develop. In children and infants, acute febrile pharyngitis often develops. Adenovirus is icosahedral virus made up of double stranded DNA and does not possess lipid layer. Human adenovirus is classified into 4 groups on the basis of their capability to agglutinate blood cells of monkey or rats.

Toxic Shock Syndrome (TSS) is the rare Straphylococcal infection that mainly occurs in young women during menstrual period. Sometimes, the disease is developed in males as well. Symptoms are caused may be due to exotoxin C which involves fever, diarrhoea, vomiting, shock and skin rashes. If the disease is not treated, it may be fatal.

Trehalose dimycolate (cord factor) inactivates mitochondrial membrane of phagocytes and other normal cells. Diphtheria bacillus is the slender rod has the tendency of forming chains. Bacilli are pleomorphic, non-spore producing, non-capsulated and non-motile. Polymetaphosphate are present in the cells and these are highly stained with Gram stains.

Streptococcus pyogenes is mainly the causative agent for the diseases Sore throat (Streptococcal pharyngitis) and scarlet fever. In complicated situations, the infections results in several disturbances like inflammation in middle ear, mastoid bones, sinuses, lung infections and rheumatic fever.

Clostridium perfringens is the causative agent of gas gangrene disease where gas is produced within tissue in the gangrene. It may even be fatal that requires medical emergency. Gas gangrene may cause myonecrosis, i.e. death of tissue, production of gas and sometimes, development of toxemia and shock becomes very fast. This microbe is opportunistic and usually enters into the body through significant skin damages.

Measles vaccine gives protection against red measles only but not against Rubella measles. During vaccination, gamma globulin injection is provided in opposite arms. Usually mild or high fever and rashes are developed specially in children after the vaccination. But all such instances are mild than the measles. Due to the usage of gamma globulin, measles vaccine is more expensive than any other immunisation.

Treponema pallidum cannot be cultivated in laboratory. It can be developed in tissue cultures. Plain serologic screening tests like VDRL test (Venereal Disease Research Laboratory test) or RPR (Rapid plasma Reagin test) are usually used for diagnosis of syphilis. Cardiolipin, a nontreponemal antigen is used for the test.

Cryptococcosis is the sporadic widely spread infection caused by the microbes often encountered in soil and in the avian feces like pigeon droppings that apparently gives the organism’s reservior. AIDS patients are highly vulnerable to cryptococcosis. Maximum AIDS patients with cryptococcal meningitis have severely high antigen titers in both the spinal fluid and serum. Microscopic test of spinal fluid disclose huge number of yeast cells.

Pneumococcal pneumonia is different from the pneumonia caused by Klebsiella. The disease is characterised by extreme mucoid inflammatory exudates including one or more lung lobes. Necrosis and abscess production are more frequent than in case of Pneumococcal pneumonia. Maximum Klebsiella pneumoniae’s stains are resistant to antibiotics which makes the treatment more difficult.

Sabin vaccine is administered one type at a time starting at 6 weeks of the age at the interval of each month. It is provided as sweet, cherry-flavoured syrup. Booster dose of trivalent oral vaccine is administered at 1 year of age.

Cellular immunity helps in protecting our bodies i. by activating antigen specific cytotoxic T-lymphocytes which are capable of inducing apoptosis within the body cells showing foreign antigen’s epitopes on their surface like virus-infected cells, cells having intracellular bacteria and cancer cells showing tumor antigens. ii. By activating macrophages and other normal killer cells causing them to kill pathogens and the stimulating cells for secreting number of cytokines which trigger other cells’ function associated in adaptive and innate immune response.

Historically immune system was differentiated into two groups: humoral immunity where protective purpose of immunisation could be present in humor (cell free serum) and cellular immunity where protective purpose of immunisation was correlated with cells. CD4 cells or helper T cells protects against several pathogens. Due to death of cytotoxic T cells by apoptosis without the use of cytokines in the cell mediated immunity, presence of cytokines is optional.

Polysaccharide capsule is the major virulence factor of Streptococcus pneumoniae (Diplococcus pneumoniae). Unlike other streptococci, S.pneumoniae’s cells appear in form of diploccocci. Polysaccharide capsule prevents phagocytosis. In lungs, pneumococci begin an inflammatory response. Fluid of neighboring blood capillaries start to affect air sacs causing the affected region of lung becomes tough and solid. Encapsulated pneumococci are extremely resistant to phagocytosis.

The other name used earlier for the same virus was HTLV-3 (Human T-cell Leukemia Virus-3). There are two different strains: HIV-1 and HIV-2. HIV is characterised with viral Capsid such as “soccer ball” consisting of 12 pentagones and 20 hexagones attached together to form a sphere.

Complement system is the biochemical cascade of innate immunity system which helps plain pathogens from the organism. It is inherited from several tiny plasma proteins which work together for interrupting plasma membrane of target cells resulting in cytolysis of cells. Complement system is made up of 35 soluble cell bound proteins, 12 of which are associated directly in complement pathways. Major part of these proteins move on as zymogens that are dormant until proteolytic cleavage.
Complement system is associated with the activation of both innate and acquired immunity.

During IFA, patient's serum is combined with HIV infected cell fixed to glass slide. If HIV antibodies are found in serum, they will attach to HIV antibodies exhibited on cellular surface. Antihuman antibodies sample having fluorescent complex like fluorescein isothiocyanate is included to the cells. Antihuman antibodies mix with HIV antibody on cell surface causing fluorescein tag to grow. When it is observed under fluorescent microscope, then cells will fluorescence with the green glow. If fluorescence is not there, then fluorescent complex has not accumulated on cell surface and HIV antibodies are not found in the sample.

Incomplete blood transfusion results in a transfusion reaction that is done by humoral immune response. This form of reaction is known as acute haemolytic reaction that causes fast destruction (haemolysis) of donor red blood cells by the host antibodies. The reason is normally a clerical error (i.e. the faulty blood unit being provided to wrong patient). Symptoms include fever, chills, back pain and red urine (haemoglobinuria). Main complication is the release of haemoglobin due to red blood cells’ destruction causing acute renal failure.

1C, 2E, 3D, 4B, 5A
Yersinia pestis is a facultative anaerobic gram-negative bacterium responsible for causing plague which is transferred through the infected rats. Plague bacillus is usually infective to rodents and it spreads among them by rat fleas. After the death of rats, these fleas leave carcass that bite human causing bubonic plague. HSV-2 causes herpes in genital tract and it is a sexually communicated disorder. It is extremely contagious while blisters are found and transmitted through straight sexual contact. Neisseria gonorrhoeae is an aerobic gram-negative bacterium causing venereal disorder gonorrhoea. The disease is accomplished by sexual contact. In males, it begins as subtle urethritis and in females, urethra and cervix become infected. Bordetella pertussis causes whooping cough. Children get more affected by this infection than adults. The disease is characterised by paroxysmal cough which results with inspiratory crowing sound or “whoop”. Shigellae are categorised into 4 species. Shigellae are mainly responsible for causing bacillary dysentery. Infection takes place by ingestion and some cells are sufficient to begin the disease.