Streptococcus Pneumonia

Streptococcus pneumoniapneumococcus

This bacterium G +ve ,diplococci gived alpha hemolytic on blood agar, which caused lobar pneumonia but it may also cause otitis media, sinusitis , meningitis and endocarditis

Pneumonia due to Str.pneumonia

Streptococcus pneumonia

Pneumococci

Streptococcus pneumonia, mucoid colonies

Way of infection

By the droplet
Clinical picture of lobar pneumonia:
1- sudden onset of fever.
2- sharp pleural pain.
3- sputum is exudative and rusty.
4- in untreated cases consolidation of the lung will occur.

Virulence factor

The virulence of the organism is a function of its capsule which prevent or delays ingestion of pneumococcus by phagocytes,

Predisposing factor of pneumococcus

1- Viral and other respiratory infection that damage surface cells.
2- Alcohol drinking.
3- Pulmonary congestion
4- Malnutrition
5- Heavy smoking


Antigenic structure
1- Peptidoglycan
2- Teichoic acid
3- Polysaccharide capsule, so the pneumococcus can be serologically classified into more than 90 types
4- M-protein

Diagnosis

Blood is drawn for culture and sputum is collected for demonstration of pneumococci by smear and culture.
The sputum is examined by:
1- direct smear stained by gram stain, show G+ve diplococci lancet –shaped, there is unstained halo around the organism which represent its capsule

Diagnosis

2- Culture on blood agar: the colonies r alpha haemolytic and similar to Strep. Viridinas
3- Biochemical reaction its bile solubility , sensitive to optochin, and ferement inulin to produce acid only.
4- Intraperitoneal injection of the sputum into white mouse , will lead to severe fatal septicaemia in the inoculated animal, and pneumococcus can be isolated and demonstrated in blood smear.

Right (optochin +) left (optochin negative)

Diagnosis

5- Serological typing: fresh emulsified sputum mixed with antiserum gives capsule swelling this reaction called quellung reaction.

Treatment

Pneumococcus is sensitive to many antimicrobial drugs, early treatment usually results in rapid recovery.
Penicillin G is the drug of choice, other beta lactam drugs like cephalosporin generations
Also pnumococcus susceptible to vancomycin.

Neisseria

The genus Neisseria includes large number of Gram-negative cocci . many of these are commensals in the respiratory tract which is called N. pharyngis . In this genus , there are two pathogenic members called : N. gonorrhoeae ( gonococcus ) & N. meningitides ( meningococcus ) .

Neisseria gram stain

Neisseria gonorrhoeae

This species can cause 2 types of infections include :-
A – Venereal infection : gonorrhoea which is transmitted by sexual contact .
B - Non-venereal infection : Ophthalmia neonatorum is transmitted by contamination of infant's eye during labour through the birth canal of a gonorrhoeal mother and vulvo-vaginitis in small girls through contaminated toilet seats & contaminated towels .

Gram stain of N.gonno

Antigenic structures of Neisseria:

1-Outer membrane protein (omp): which antigenic and antiphagostic factor
2-Lipopolysaccharide which act as endotoxine
3-Pili which help neisseria to attach with epithelial host cells

Clinical manifestations

In the male , there is cause urithritis with yellow creamy pus & painful urination , the process may extend to prostate & epididymis .
In female the infection may extend to the cervix to cause mucopurulent discharge , it may be then progress to the fallopian tube causing pelvic inflammation , fibrosis & obliteration of tubes with consequent sterility , chronic gonorrhoea is often asymptomatic .

Salpinitis

Diagnosis of gonorrhoea :-

Acute gonorrhoea can be detect by :
a – Microscopical examination : direct smear from the discharge stained with Gram's stain to show the kidney shape G-ve diplococci present intracellular & extracellularily , non-spore forming .

b – Culture : this perform on blood agar or chocolate agar or Thayer-Martin medium incubated in 5% CO2 . the colonies are non haemolytic , non-pigmented or gray in color , smooth , circular , small & convex .
While in case of chronic gonorrhoea , in male , the morning drop of discharge or prostatic secretion after massage can be examined as before . In female , cervical swab may give positive results .

c – Serology : in this tests can be use serum & genital fluid that contain IgG and IgA antibodies against gonococcal pili , outer membrane proteins and lipopolysaccharide .

Treatment :-

Gonococci is treat by penicillin , but sensitivity test is indicated because gonococcal resistance to pencillin has gradually increased, therefore used new drugs like Ciprax single dose, .

Neisseria meningitidis

This bacterium mainly cause cerebrospinal meningitis but it also can cause pharyngitis , adrenal haemorrhages & rarely myocarditis , the infection transmitted from the patient or carrier by droplets of nasopharyngeal secretions .

N.meningitidis

Clinical manifestation of cerebrospinal meningitis :

This infection causes sudden onest of fever , vomiting , stiff neck , haemorrhage , skin rash and coma within a few hours .

Diagnosis :

1 – C.S.F. examination :
Lumber puncture is done under complet aseptic conditions , the CSF appear turbid ( it's clear colourless in normal case ) .


a – Direct smear : stained by Gram's stain , the bacteria appear as G-ve diplococci mainly intracellularly usually coffee bean in shape , non-spore forming .
b – Culture : this bacteria no growth in ordinary media , but grow on blood & chocolate agar in the presence of 5% CO2 , the colonies on blood agar are non-haemolytic , moist , devated , smooth , translucent , round & convex . Thayer-Martin medium containing antibiotic can also be used .

2 – Blood culture is perform in case of septicemia .

3 – Nasopharyngeal swab for culture is perform .
4 – Biochemical reaction tests : this include fermentation of glucose & maltose with acid only . catalase & oxidase tests are positive





5– Serological test : Antigenically , meningococci are divided into several groups are A,B,C,w- 135&y , group A found in a most countries , while group c and w-135 associated with the epidemiology . specific anti-meningococcal antibiody in serum to detect colony by agglutination test , meningococcal antigen can be detect in C.S.F. of patient with active disease .

Treatment :

Penicillin G has become the drug of choice , also 80-90 % of strains are sensitive to sulfonamide that is diffuse readly into C.S.F. chloramphenicol or third generation cephalosporin is used in patient with allergy to penicillin .