Medical Microbiology Flashcards
Sero groups of N meningitidis
A, B, C, W135
Morphology of N meningitidis
Gram negative diplococci
Up to half N meningitidis membrane made up of
Lipo-oligosaccharide (containing endotoxin Lipid A)
Predisposing factors for N meningitidis
Asplenia ( anatomical or functional) Complement deficiency (C8/C9)
Most common sporadic serogroup for N meningitidis in WP
Serogroup B
What does the lipo-oligosaccharide do in N meningitidis
Activates macrophages - TNF released = shock mediator in septicaemia
Alters permeability of BBB = CNS invasion
Who gets chemoprophyaxis in N meningitidis
Direct contacts
Mouth to mouth resus
What drugs are used as chemoprophyaxis in N meningitidis
Ceftriaxone
Ciprofloxacin
Rifampicin
What is factor X and where is it found
Haemin
Found in whole blood
What is factor V and where is it found
NAD
Found inside RBC
How is factor V created in petridish
Blood is heated = chocolate blood agar
Or
Organisms added to blood eg. Staphylococci. H influenzae grows on edges of colonies = satellitism
What is the typical pathogenesis of untypeable H influenzae
Contiguous spread from nasopharynx
- conjunctivitis
- otitis media
- sinusitis
- acute exacerbations of chronic bronchitis
What is pathogenesis of type b H influenzae
Spread beyond resp tract -> bacteraemia -> metastatic infection
- acute meningitis
- acute epiglottitis
- pneumonia
- septic arthritis
- cellulitis
Rx of H influenzae
3rd gen cephalosporin
If non invasive = oral co-amoxiclav
Lab diagnosis of H influenzae
MC&S
Latex agglutination - PRP Ag
Vaccine type given to those under 2 years for h influenza
Conjugate vaccine
What stain doesH influenzae have
Gram negative coccobacilli
What is the morphology of strep pneumonia
Gram positive lanceolate diplococci
Alpha haemolysis
What are the predisposing factors for strep pneumonia
Asplenia Overcrowding Viral URTI Diabetes Fluid in alveoli eg CCF, aspiration
What is the lab diagnosis of s pneumonia
Gram stain tissue
NB culture in pneumonia as bacteraemia is common
Rx of s pneumonia
IV penicillin except in meningitis must give third gen cephalosporin
Type of vaccine for s pneumonia
Protein conjugate (polyvalent) pneumococcal vaccine
Who gets s pneumonia vaccine
Splenectomy
? Those with predisposing factors
Do you isolate s pneumonia pts and why
No. Infection is most often endogenous
Complication of pneumonia in s pneumonia infection
Pleural effusion
Pericarditis = rare
Pathologies caused by s pneumonia
Pneumonia, meningitis, otitis media, sinusitis, endocarditis, arthritis, peritonitis
Gram stain of E. coli
Gram negative bacilli
Types of surface Ag on E. coli
O - LPS
K - polysaccharide capsule
H - flagella
Gram stain of listeria monocytogenes
Small gram positive bacilli
What is the appearance on culture of l monocytogenes
Translucent grey/white colonies
B haemolysis on blood agar
L monocytogenes grows in presence of what..and what does it hydrolyse
Bile
Aesculin
Who is at risk for l monocytogenes infection
Pregnant
Neonate
Elderly
Immunocomprimsed
Treatment of l monocytogenes
High dose ampicillin or penicillin
NOTE resistant to cephalosporins
Gram stain of strep agalactiae
Gram positive cocci
Haemolysis seen on culture for s agalactiae
Beta haemolysis (less than group A strep)
What determines s agalactiae serotype
Capsular polysaccharide
Surface protein
Rx of s agalactiae
Penicillin
When is s agalactiae most commonly transmitted
During birth
Days following birth
Rx of s agalactiae
Penicillin
Predisposing factors for cryptococcus neoformans
Immunocomprimsed pts
Where is c neoformans found
Soil mixed w pigeon faeces
Lab diagnosis of c neoformans
CSF analysis
Microscopy - India ink
Culture
Latex agglutination
Rx of c neoformans
Amphotericin B followed by fluconazole
NB no cure in AIDS
Common sites of spread of c neoformans in immunocomprimsed pts
CNS
Bone
Skin
Orgs that can cause genial ulcer and Rx
Treponema pallidum - penicillin
Chlmydia trachomatis - tetracycline
HSV - acyclovir
Haemophilus ducreyi - ceftriaxone
Effect of antibiotics of CSF findings
- negative cultures
- glucose normalizes
- gram stain negative
- white cell count decreases
- protein decreases
CSF test that shouldn’t be done routinely (no effect on management)
- bacterial latex antigen test
- lactate
- chloride
- adenosine deaminase
Which parasite causes primary amoebic meningoenceohalitis?
Naegleria fowleri
Possible reasons for candida infection
- immune system is compromised
- normal flora disturbed by antibiotics
- trauma
Opportunistic organisms
- cryptococcus neoformans
- pneumocystis jiroveci
- cryptosporidium
- Isospora
- herpes simplex
Complications of acute bacterial meningitis in infants
- focal neurological deficit
- hearing loss
- blindness
- intellectual disability
- seizures
- hydrocephalus
Antibiotics used as prophylaxis in meningococcal meningitis
- ceftriaxone
- ciprofloxacin
- rifampicin
Organisms causing vaginal discharge
- neisseria gonorrhoea
- chlamydia trachomatis
- trichomonas vaginalis
- Candida albicans
Anaerobes causing infection in diabetic foo
Bacteroides fragilis
Where can anaerobes be found as normal flora?
- colon
- oral cavity
- naso pharynx
- lower urogenital tract
Predisposing factors for anaerobes infection
- breach in mucosal or cutaneous barrier
- reduced oxygen tension in tissue
Antibiotics to treat anaerobic infection
- metronidazole
- clindamycin
- penicillin
4 infections commonly caused by anaerobes
- peritonsillar abscess
- tubo-ovarian abscess
- dental infections
- peritonitis
- perirectal abscess
- lung abscess
- aspiration pneumonia
Fungal infections to Which diabetics are prone
- candidiasis
- mucormycosis (nasal sinuses)
