S2. Pneumococcus & Enterococcus Flashcards
Is Streptococcus pneumoniae a human pathogen?
Yes, its stricly a human pathogen, doesnt cause diseases in other species.
Streptococcus pneumoniae characteristics?
- gram +ve, non motile, encapsulated, diplococci
- lancet shaped
- produces alpha-haemolysis on blood agar
- autolysis of colonies w/ further incubation
- some produces mucoid colonies ( excessive production of polysacchride)
- capsulated (84 serotypes)
Streptococcus pneumoniae clinical infections?
upper resp tract infections:
- otitis media: most common bacterial causative agent in all ages
- sinusitis: common cause in both children & adults
- conjunctivitis (or pink eye, is the inflammation of the transparent membrane lining the eyelid/ eyeball)
Streptococcus pneumoniae clinical infections?
lower resp tract infections:
- Pneumonia
- s.pneumoniae is the commonest cause of community acquired pneumonia
- a leading cause of death in older adults & immonocomprised patients
- pneumonia is often proceeded by upper respiratory viral infection which predisposes to S.pneumoniae infection of pulmonary paranchyma
Streptococcus pneumoniae clinical infections?
Meningitis
- most common cause of adult bacterial meningitis
- bimodal (has 2 peaks) incidence (children < than 3 yrs & adults > 45 yrs)
- mortality rate ~ 20% even if treated properly
Streptococcus pneumoniae clinical infections?
Arthritis
- infection of the joints
- gram -ve cocci, salmonella can cause arthtitis
Streptococcus pneumoniae clinical infections?
Bacteremia & septicemia
- infections of blood
Streptococcus pneumoniae pathogensis?
- normal oropharyngeal flora (5-70%)
- obligate human pathogen
Streptococcus pneumoniae virulence factors?
- capsular polysaccharides
- certain serotypes are resposnsible for more than 90% of invasive disease ( bacteremia & meningitis)
- antigenic & type specific
- non capsulated strains are avirulent
- demonstration of the polysacchride capsule by capsular swelling test
- pneumolysin
- membrane damaging toxin
- induces features of lobar pneumonia
- contributes to mortility
Optochin sensitivity is a feature of?
Streptococcus pneumoniae
What’s serogrouping?
To know which one of the capsular 84 serotypes causes the infection, esp for vaxxed ppl who still got the infection to know which capsular serotype the vaccine didnt work with, or to know new capsular serotypes that isnt covered by the vaccine causing the infection.
Predisposing factors?
- pre-existing resp diseases e.g. viral infections , COPD ( chronic obstructive pulmonary disease)
- predisposing diseases e.g. DM (diabetes mellitus), IHD( ischemic heart disease), CRF ( chronic renal failure), malignancy & elderly
- immune deficiencies eg, sickle cell anemia, asplenia, multiple myeloma, HIV
Labratory diagnosis of streptococcus pneumoniae?
-Culture of the diff specimens: blood, CSF, sputum, ear pus, sinus fluid - alpha- haemolysis on blood agar - bile soluble - optichin sensitive - mucoid colonies in capsulated strains
Lab diagnosis of streptococcus pneumoniae?
- rapid direct detection methods
- direct microscopy ( CSF, joint fluid, eye swab)
- direct antigen detection in CSF & urine (latex)
S.pneumoniae differentiation from S.Viridans?
S.pneumoniae is Optochin disc (Sensitive)
S.pneumoniae is Bile solubility (Soluble)
S.pneumoniae is Serotyping (latex) (Positive)
-
S.Viridans is Optochin disc (Resistant)
S.Viridans is Bile solubility (Not Soluble)
S.Viridans is Serotyping (latex) (Negative)
Immunoprophylaxis
- killed vaccine —> 2 types
- polysacchraide vaccine >2 yrs
- conjugated vaccine —> children < 2 yrs
- diff serotypes:
7- valent ( 7 valent meants that the vaccine covers 7 serotypes)
10- valent
13- valent
Polysacchirde vaccine?
- funtional or anatomical a splenia
- chronic renal failure
- chronic heart disease
- chronic lung disease
- chronic liver disease
- DM
- HIV
Conjugate pneumococcal vaccine?
- all children < 2 yrs
- adults > 50 yrs
Entrococcus general info:
- GI tract if man & animal is the main habitat
- catalase negative
- member of oropharangeal, intestinal, vaginal & skin flora
Most common species of Entrococcus associated w human diseases are?
E.faecalis —> 80-90%
E.faecium —> 5-10%
Pathogensis of Entrococcus?
- intrinsically resistant to many antibiotics
- ability to adhere to heart valve & renal epithelial cells
Lab diagnosis of Entrococcus?
- non-hemolytic colonies on blood agar
- esculin positive
1) Clinical infections of Entrococcus?
2) what are the risk factors for acquiring nosocomial infections include?
1) Community & nosocomial (in hospitals) Endogenous (from flora) & Exogenous (from outside) 2) - serious underlying disease - length of hospital stay - surgery esp abdominal surgery - presence of catheters - ICU - broad spectrum antibiotics eg cephalosporin
Clinical infections of Entrococcus?
UTI
- most common type
- cystitis (lower UTI) & pyelonephritis (upper UTI)
- nosocomial UTI associated w/ catherization
