Identifying Causative Organisms and Transmission Modes in Microbiology

Microbiology 204 (Final) Q : Mention the causative organism of the following diseases: Q :Mention the mode of transmission and diseases caused by : Q : Mention the disease caused and mode of transmission of : Disease MOT Causative organism Neonatal sepsis Acquired at time of birth Streptococcus agalactiae Otitis media Pneumonia Meningitis Mostly Endogenous Exogenous by respiratory droplets Streptococcus pneumoniae Epidemic cerebrospinal meningitis By droplets from carriers and cases Neisseria meningitis Abortion Neonatal meningitis Septicemia Food poisoning - Contact with domestic farm animals or their faeces - Food-borne - Vertical transmission during delivery Listeria monocytogenes Tetanus: - Lock jaw (trismus) - Arching of the back (opisthotonos) Germenatation of spores Retrograde transmission within the axon or hematogenous Clostridium tetani Classic botulism Ingestion of preformed toxin Clostridium botulinum Floppy baby syndrome (infant botulism) Germination of spores in the GIT - Pink eye (Acute mucopurulent conjunctivitis) - Brazilian purpuric fever Haemophiles aegyptius

Disease MOT Causative organism Rabies (Acute fatal encephalomyelitis): - Paresthesia - Encephalitis - Hydrophobia Zoonotic disease (Bite or salivary contamination) Rabies virus Jungle yellow fever (Disease of monkeys) Aedes africanus bite (MOT for monkeys) Man is infected accidentally Yellow fever virus (Flavivirus) Urban yellow fever Man to man transmission by Aedes egypti bite Classic dengue (Breakbone fever) Aedes mosquito bite Dengue fever virus (Flavivirus) Dengue hemorrhagic fever Zika virus Microcephaly (infection during pregnancy) Aedes ae gypti bite Sexual Blood-borne Zika fever virus (Flavivirus) West Nile encephalitis Mosquito bite West Nile encephalitis virus (Flavivirus) Rift valley fever - Contact of infected animals - Mosquito bite Rift valley fever virus (Bunyaviridae) Poliomyelitis Faeco-oral poliovirus Spongiform encephalopathy Ingestion of diseased brain and other CNS tissues or eyeballs Porin protein scrapie Aspergillosis Inhalation of spores Aspergillus fumigatus Cryptococcosis Inhalation Cryptococcus neoformans Interstitial pneumonia Pneumocystis jiroveci

Give reason Q1-ampicillin is given intra partum to mothers colonized with strept agalactiae A: to reduce neonatal sepsis Q2-the pnemococcal capsular polysaccharide vaccine is not effective in children less than 2 years of age A: they respond poorly to polysaccharide (thymus independent) Ag Q3-conjugated pneumococcal vaccine is administered to children below 2 years of age : A: makes vaccine more effective in children less than 2 years of age Q4-discrimination must be done between s.pneumonia and viridans streptococci

A: Q5- the capsular polysaccharide of N.meningitides group B is poorly immunogenic in humans A: due to anti-phagocytic properties Q6- during meningococcaemia there is skin rash A: due to endotoxin action of LPS Q7-children under the age of 2-3 years are particularly susceptible most of epidemic cerebrospinal meningitis A: because they fail to make antibody against antiphagocytic capsule (TI antegin ) test s.pneumonia Viridans strept Growth inhibition by optochin + - Solubility of colonies in bile + - Capsular Ag detection (latex agglutination) + - Quellung test + -

Q8-the quadrivalent meningococcal vaccine does not include the capsular polysaccharide of group B A: it is poorly immunogenic because of its similarity to sialic acid found in human tissues Q9-protein conjugate meningococcal vaccine are recommended to children less than 2 years old A: they respond poorly to polysaccharide (thymus independent) Ag Q10-listeria can cause outbreaks of food poisoning A: it resist freezing , drying and heat Q11- L.monocytogenes can survive in the phagocytic cell A: due to its ability to produce membrane damaging toxin called listeriolysin – O Q12- L.monocytogenes can escape the immune defensive mechanisms A: by passage directly to neighbouring cell

Q13- tetanospasmin causes generalized muscle spasm A : tetanospasmin spreads by retrograde transport within axon and probably Q14- successful treatment of tetanus depends on early diagnosis A: before lethal amount of toxin become fixed to neural tissue Q15- prophylactic immunization is the only way to control tetanus A: because spores of C.tetani are so widely disseminated in nature and cannot be avoided Q16- antibiotics are given for the treatment of infant botulism not for classic botulism A: Classic botulism is infected by the toxin only, but infant botulism is infected by sporting bacteria so there is no reason to give antibiotics in classic botulism

Q17- boiling or intense heating of contaminated food can prevent botulism A: because toxin is heat labile boiling for 10 minutes or intense heating ( cooking ) of contaminated food will inactive the toxin Q18-botulinum toxin cause flaccid paralysis A: toxin binds to neuron , prevent release of Ach across synaptic cleft , thus it produce paralysis of the motor system Q19- tetanus toxoid is recommended during pregnancy A: to prevent tetanus neonatorum Q20-pseudomonus aeruginosa is considered non enterobacteriaceae A: because enterobacteriaceae have 4 characters :

1- Facultative anaerobe 2- Ferment glucose 3- Oxidase negative 4- ( nitrate reductase enzyme ) which change nitrate to nitrite Q21- E.coli produce rose pink colonies on MaCconkey agar A: due to lactose fermentation Q22-chocolate agar is suitable medium for haemophilus species A: (heat used in preparing chocolate agar ) 1- Provides v factor and extra x factor from RBCs into medium 2- Inactivates non specific inhibitors (eg: NADase) Q23- most H.influenzae infections occur between the age of 6 months and 6 years

A: this is attributed to decline of maternal IgG together with inability of child to generate antibodies against polysaccharide capsular (TI) antigen Q24- chlamydia are considered as bacteria not virus A: their cell wall structure resembles that of gram - negative bacteria Q25- chlamydia are obligate intracellular organism A: they lack ability to produce sufficient energy to grow independently , they only grow inside host cell Q26- chlamydia are not sensitive to B lactam antibiotics A : due to lack of typical peptidoglycan layer Q27- IP of rabies is long and variable ( 2 weeks – 3 months )

A: long IP gives anti rabies vaccine administered after bite sufficient time to induce protective immunity Q28- RIG should not be administered in the same syringe with rabies vaccine A: to prevent neutralization of virus in vaccine by antibody in HRIG Q29-crude rabies vaccine are not recommended for post or pre exposure prophlaxis A: 1- less immunogenic 2- require 23 injec ons 3- cause allergic encephalomyelitis

Mention the causative organism of the following diseases: (4 marks) - Herpangina ………………………………………………........ - Inclusion conjunctivitis ………………………………………………… - Spongy form encephalopathy ………………………………………………….. - Tetanus ………………………………………………… Total marks : 6 4 MCQs for 2 marks 4 questions for 4 marks