Written Old Flashcards
Enteric fever patients may give negative Widal test results.
False negative results;
Performance of the test during the first week of illness (before appearance of antibodies)
Early antibiotic treatment
Serologic diagnosis of HIV in neonates born to HIV-T positive mothers is not useful in diagnosis.
Newborns of infected mothers due to presence of passively acquired maternal lgG->(commercial tests for HIV-specific IgM are not yet available)->in such cases, other diagnostic methods should be applied
Endemic relapsing fever is considered a zoonotic disease whereas epidemic relapsing fever is not a zoonotic disease
Tick-borne (endemic) relapsing fever, which is caused by variety of Borrelia species
-> Rodents & small animals are the main reservoir from which they are transmitted to man (zoonotic disease).
Louse-borne (epidemic) relapsing fever, which is caused by B. recurrenitis
-> transmitted from man to man by human body louse (not zoonotic disease).
Disease(s) and associated disease(s) caused by Epstein-Barr virus.
Infectious mononucleosis
Burkitt’s lymphoma.
T-cell lymphoma
Mention the causative organism of each disease /clinical condition:
a. Herpangina
b. Transmissible spongiform encephalopathy
c. Lockjaw
d. inclusion conjunctivitis
a. coxsackieviruses A
b. Prions
c. Clostridium tetani
d. Chlamydia trachomatis
Rabies infection can be aborted by using post-exposure preventive measures
Rabies infection can be aborted by using preventive measures —-> long I.P. gives anti-rabies vaccines administered after bite sufficient time to induce protective immunity
Pathogenic Neisseria can survive inside macrophages
@ Anti-phagocytic factors:
Capsule -> prevents phagocytes from attachment to bacteria
© Cell wall proteins of Gram-positive cocci -> such as:
® M protein
@ Protein A
© Coagulase -> accelerates formation of fibrin clot from fibrinogen -> this clot can protect bacteria from phagocytosis
Salk polio vaccine has many advantages over the Sabin polio vaccine
Being killed, it has the following advantages
over Sabin vaccine
O Safe to be given in pregnancy & immunosuppressed individuals
© Does not require refrigeration
© Does not revert to wild type
Prevention of transmission of prion infections by the usual infection control procedures is ineffective
Prevention of transmission of prion infections by usual infection control procedures is ineffective -> due to extreme resistance of prions to heat, disinfectants & irradiation
Prophylactic immunization is the only effective way to control tetanus
because spores of C. tetani are so widely disseminated in nature and cannot be avoided
In post-exposure prophylaxis, human rabies immune globulin and rabies vaccine should be given at different sites.
to prevent neutralization of virus in vaccine by antibody in HRIG
Prions are transmitted by:
O Ingestion of diseased brain & other CNS tissues or eye balls
© Corneal transplant & use of brain electrodes
Listeria monocytogenes is transmitted to
humans by:
O Contact with domestic farm animals or
their faeces
© By milk or by contaminated vegetables
© Vertical transmission can also occur transplacentally or during delivery
Mention the causative organism, mode of transmission of the following
1) Actinomycosis
2) Malignant pustule
3) Acute gengivomatitis
4) Warts
1) Actinomycosis Israeli endogenous following local trauma
2) B. Anthracis; contact of infected animals
3) Acute gengivomatitis HSV 1: contact with saliva
4) Warts: HPV sexual contact
Measles infection give live long immunity
Measles virus has only 1 stable antigenic type
© There is stage of viraemia -> allowing circulating Abs (IgM and IgG) to neutralize virus
Acute glomerulonephritis (AGN) after streptococcal infection
Deposition of antigen-antibody complexes in glomeruli
Lepromin test is of prognostic value
It is positive in tuberculoid & negative in lepromatous leprosy.
Mention the causative organism(s) & mode(s) of transmission of the following diseases:
1) Gas gangrene
3) Chicken pox
4) Tinea capitis
1) Cl. perfrenges; spores enter traumatized tissue
3) Varicella zoster virus; respiratory drop
4) Dermatophytes infection by direct contact
Staphylococcus aureus pyogenic infections are usually localized.
© Coaqulase: most important factor
The clumping factor -> attachment of organism to traumatized tissue & blood clot
Few acid-fast bacilli are present in the tissues in tuberculoid leprosy.
CMI response mediated by Th1 cells predominate & forms granulomas -> resulting in destruction of most of mycobacteria
-> So only few AFB remain in tissues
M protein is the most important virulence factor for Streptococcus pyogenes
Surface protein -> enables bacteria to colonize skin & to escape phagocytosis
divides S. pyogenes into about 80 M serotype
Mention the causative organism(s) & mode(s) of transmission of the following diseases:
- Eumycotic mycetoma
- Benign skin warts
- German measles
- Madurella; mycetomatis
- Molluscum contagiosum virus,; sexual contact
- Rubella, droplets
Erythema infectiosum caused by parvovirus B19 is associated with rash
is due to infection of endothelial cells as well as deposition of immune complexes
Necrotizing fasciitis caused by streptococcal pyrogenic exotoxin B particularly is associated with severe tissue destruction
Acts as protease contributes to pathogenesis of necrotizing faciitis
Clostridial wound infections are usually polymicrobic.
Organism & its spores are found in soil & in human & animal faeces therefore, clostridial wound infections are usually polymicrobic
Smallpox is the only disease that has been eradicated
- Global use of highly effective vaccine by WHO -> vaccine contains vaccinia virus which is naturally attenuated for man
- Smallpox virus has single, stable serotype
- There is no animal reservoir -> & humans are the only host
- Disease is easily recognized clinically
- There is no carrier state or subclinical infection
Scarlet fever is associated with red rash and strawberry tongue
Erythrogenic toxin -> responsible for red rash characteristic of scarlet fever
Definition of significant bacteriuria
Count of 105 organisms/ml
Although Neisseria gonorrhoeae is frequently resistant to tetracyelines, this antibiotic or azithromycin should be given while treating gonorrhoe
because chlamydia is usually comes with gonorrhoeae
Urinary tract infection caused by Proteus encourages the formation of stones
Urease hydrolyses urea in urine to form ammonia which raises pH encouraging formation of stones
Sterile pyuria
Means absence of growth on ordinary culture media despite presence of pus cells in urine
Mention TWO predisposing factors for urinary tract infection
- Short female urethra
- Sexual intercourse
Why repeated gonococcai infections may occur despite antibody production
O High Ag variations of gonococcal pili
© Superficial nature of infection
© Production of IgA protease
TWO causes of sterile pyuria.
- Recent antimicrobial chemotherapy
- Female genital tract infections
TWO virulence factors of uropathogenic E. coli
Fimbrial adhesins -> bind to specific receptors on urinary tract epithelium
Capsular (K) antigens -> interfere with phagocytosis -» thereby enhancing organism’s ability to cause pyelonephritis
Coxiella is not classified as Rickettsia. (2 reasons)
It is not transmitted to humans by arthropods
It is extremely resistant to heat, drying & sunlight, hence can persist outside the host for long period
Some people show natural resistance to HIV infection
by binding to chemokine receptor on cell
surface
Most infections caused by Haemophilus influenzae occur in children between the age of 6 months and 6 years. (2 reasons)
This is attributed to decline of maternal IgG
together with inability of child to generate antibodies against polysaccharide capsular (Tl) antigen
A person can have repeated attacks of common cold during the same season. (2 reasons)
Superficial nature of infection
Unavailability
Yersinia pestis is considered an agent of bioterrorism.
the organism may be delivered by aerosol to cause pneumonic plague by using infected fleas to cause bubonic plague
Children older than 6 years of age should not receive the killed whole cell pertussis vaccine.
In a very small number of cases, severe or irreversible brain damage (encephalopathy)
may occur especially if given after 6 years of age.
Three characteristics of atypical pneumonia
-Low-grade fever
- Dry cough with scanty sputum
- Failure to demonstrate the causative organism by Gram stain or its isolation on ordinary culture media
TWO predisposing factors for Candida infection
Broad-spectrum antibiotic treatment
Immunosuppression
TWO modes of transmission of Leptospira interrogans infection
Contact with contaminated water where
the organism enters through small skin abrasions
Consumption of contaminated food or drink
Chloramphenicol may be added to Sabouraud’s dextrose agar (SDA) to grow fungi from clinical specimens
To become selective
Helicobacter pylori can survive the gastric acidic pH
Urease cleaves urea producing “ammonium cloud”, which permits H. pylori to survive in an acidic environment
Forest wood-cutters may be infected with yellow fever.
Primarily disease of monkeys
Disease is transmitted from monkey to monkey by mosquito in Africa.
Mention ONE mode of transmission for the following microorganisms:
- Mumps virus
- Norwalk virus
Droplets
Faeco-oral
Breastfeeding decrease diseases of rota virus
gives baby protective IgA
Campylobacter enteritis cause guilian parret disease
it is attributed to antibodies against C. jejuni
that cross react with antigens on neurons
H pylori is transmitted from person to person
There is clustering of infection within families
