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Phase 2a > Microbiology > Flashcards

Flashcards in Microbiology Deck (260)
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91

Examples of gram positive bacilli?

actinomyces, bacillus, clostridia, diptheria, listeria monocytogenes

92

Examples of gram negative bacilli?

E coli, campylobacter, pseudomonas, salmonella, shigella, proteus

93

What is the catalase test?

to see if the microbe has catalase which destroys H2O2 and produces O2, if O2 is produced it is positive and is staphlococcus and it has catalase, it no O2 it is negative and streptococcus

94

Purpose of catalase test?

distinguishes between staphylococcus and streptococcus

95

What test is used on gram positive cocci?

catalase test

96

What test is used on staphylococci?

coagulase test

97

What is the coagulase test?

coagulase converts fibrinogen to fibrin and differentiates between staphylococcus aureus and staphylococcus epidemidis (positive is s.aureus and appears cream/yellow, negative is white)

98

How does s.aureus appear?

pigmented clusters, coagulated (solid), had DNAase

99

How does s.aureus cause disease?

high disease potential, pore forming toxin proteases. toxic shock syndrome toxin, spread by aerosal and touch and can colonize skin wounds

100

Treatment of s.aureus?

flucloxacillin (MRSA is resistant to B lactams though so needs vancomycin)

101

How does s.epidemidis appear?

non pigmented clusters, non coagulated, no DNAase

102

How does s.epidimidis causes disease?

low disease potential and s opportunistic and forms persistent biofilms

103

What test is done to distinguish streptococci?

haemolysis on blood agar

104

What are the 3 outcomes of haemolysis on blood agar and how do they appear?

beta haemolytic strep - clearing of agar around colonies due to strepolysin O and S production
alpha haemolytic strep (viridans strep) - greening of agar around the colonies due to H2O2 production
gamma haemolysis - no lysis

105

What test is done on beta haemolytic strep and how does it work?

The Lancefield test - serogroups antigenic gorup, differentiates according to surface antigens and their properties and the non coagulated one is the one to classify properties, producing A, B, C G

106

What is the likely diagnosis of group A Lancefield test?

s.pyogenes - causes tonsillitis, impetigo, scarlet fever, cellulitis

107

What test is done on alpha haemolytic strep?

optochin test

108

What are the results of the optochin test?

Put the disc on the bacteria and if bacteria moves away from the disc then it is sensitive (s.pneumoniae) and if it doesn't it is resistant (s.viridans)

109

What does strep viridans cause and where does it occur?

in oral dental canes and deep organ abscess, caused infective endocarditis

110

Where does strep. pneumoniae act on and what does it cause?

in oropaharynx, it has capsule, inflammatory wall constituents and cytotoxins causing impaired mucus trapping, causes hypomnaglobinaemia and is dependent on antibody to capsule

111

What infections does step. pneumoniae cause?

pneumonia, sinusitis and meningitis

112

Where are the sterile parts of the body?

blood, peritoneal cavity, CSF, joint, pleural fluid, urinary tract, lower resp tract

113

Where can norma flora culture?

mouth, skin, urethra, large intestine, vagina

114

What test is used on gram negative bacillus?

the appearance on MacConkey or CLED or XLD

115

What are the outcomes of appearance on MacConkey agar?

white (non lactose fermenting - shigella, salmonella, pseudomonas, proteus)
pink (lactose fermenting - enterobacteriacae (coliforms)

116

What are the outcomes on XLD agar?

red with black dots (fermenting xylose)
red (non fermenting xylose)
yellow (salmonella)

117

What test is done on non lactose fermenting bacteria?

oxidase test using a redox indicator

118

What are the results of an oxidase test?

blue as produces cytochrome c oxidase from bacterial ECT (positive - pseudomonas aeruginosa)
no colour change (enterobacteriaceae - proteus and shigella)

119

What test is done on oxidase positive pseudomonas sp.?

anti pseudomonal sensitivity test

120

What is the treatment of pseudomonas sp?

beta lactams