Pneumococci: Meaning, Characteristics and Feature

In this article you will learn about Pneumococci:- 1. Meaning of Pneumococci 2. Morphology and Staining 3. Cultural Characteristics 4. Biochemical Reaction 5. Bile Solubility 6. Optochin Sensitivity 7. Antigenic Structure 8. Pathogenicity and Clinical Features 9. Laboratory Diagnosis 10. Treatment.

Contents:

1. Meaning of Pneumococci
2. Morphology and Staining of Pneumococci
3. Cultural Characteristics of Pneumococci
4. Biochemical Reaction of Pneumococci
5. Bile Solubility
6. Optochin Sensitivity
7. Antigenic Structure of Pneumococci
8. Pathogenicity and Clinical Features of Pneumococci
9. Laboratory Diagnosis of Pneumococci
10. Treatment of Pneumococci

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1. Meaning of Pneumococci:

The pneumococci are Gram-positive diplococci, often lancet shaped, cause lobar pneumonia, sinusitis, otitis, bronchitis, bacteriaemia, meningitis.

2. Morphology and Staining of Pneumococci:

They are Gram-positive lancet shaped diplococci, often seen in young cultures. Also in sputum, pus, single cocci or chains. With age, the organisms become Gram-negative and tend to lyse spontaneously.

3. Cultural Characteristics of Pneumococci:

They are aerobic and facultative anaerobic. They grow best in enriched media at 37°C. Growth is improved by 5-10% CO₂. On blood agar, after incubation for 18 hours, the colonies are small (0.5-1 mm) dome shaped and glistening with an area of alpha haemolysis which causes confusion with Str. viridans.

The colonies are at first plateau shaped, later develop elevated margins and concentric ridges—draughtsman colony. Green pigmentation is more obvious when the organism is growing on heated blood agar.

4. Biochemical Reaction of Pneumococci:

They ferment various sugars, differ from Str. viridans by frequently fermenting inulin. They are catalase and oxidase-negative.

5. Bile Solubility:

Pneumococci are soluble in bile. The test consists of adding 1 part of sterilised 10% solution of sodium taurocholate in normal saline to 10 parts of broth culture and incubating at 37°C. Pneumococci are lysed within 15 minutes.

6. Optochin Sensitivity:

Pneumococci are sensitive to optochin (hydrocuprein hydrochloride). They are tested by making radial stock cultures on a blood agar plate and by placing in the centre of the plate a sterile disk of filter paper impregnated in optochin. Pneumococci are inhibited in a zone of at least 5 mm from the circumference of the disk.

7. Antigenic Structure of Pneumococci:

At least 80 specific serotypes have been recognised by “capsular swelling reaction or Quelling reaction.” In this technique a loopful of broth culture is mixed with a loopful of diagnostic antiserum and the mixture is covered with a coverslip and examined under oil immersion lens, the sub stage condenser is lowered and diaphragm partially closed.

The capsule swells markedly and the sharpness of the capsule is more significant.

8. Pathogenicity and Clinical Features of Pneumococci:

Pneumococci produce no toxin and the disease onsets through its ability to multiply in the tissues. Their virulence is a function of its capsule. The onset of pneumococcal pneumonia is usually sudden with fever, chill and sharp pleural pain. The sputum is bloody or rusty. Empyema (pus in the pleural cavity) is a significant complication.

Lactobacillus Acidophilus Bacillus Acidophilus Odontolyticeus:

Dental caries this destructive condition is noted in earlier stages of discolouration of the enamel of the tooth and loss of translucency, cavity formation follows and, at the dentinoenamel junction, there is always lateral extension of the process with progressive softening of the dentine.

For many years, there have been differing opinions on the part played by bacteria, particularly lactobacillin providing caries.

Their role has been confused with that of cariogenic food; even with such a diet, caries does not apparently occur in the absence of bacteria. Thus germ free rats do not develop caries with a cariogenic diet unless streptococci, lactobacilli are added to the diet, then caries develops rapidly in the molar teeth.

Lactobacilli Count:

It is known that there is quantitative difference in the number of lactobacilli in the mouths of those prone to caries in comparison with those who are apparently immune. The estimation of lactobacilli is of increasing importance in dentistry.

The saliva flow is activated by the person chewing a small piece of paraffin wax for ten minutes, saliva is collected in a sterile container as it is produced and the volume is made up to 10 ml. with sterile saline.

Then Lactobacilli count is the numbers of lactobacilli present in 1 ml. of this standard specimen of the sample which is serially diluted in broth of peptone water and distributed in 0.1 ml. quantities on a selective medium for lactobacilli, e.g.. in Kulp’s tomato peptone agar plates.

After three or four days incubation at 37°C counts of more than 10⁵ lactobacilli per ml of saliva are often taken as indicative of caries activity. In the same individual, significant reductions in this count are noted when a non-carcinogenic diet is taken.

9. Laboratory Diagnosis of Pneumococci:

Blood is drawn for culture and sputum collection for demonstration of pneumococci by smear and culture. Serum antibody tests are impracticable.

The sputum’s may be examined in several ways:

(1) Stained Smears:

A Gram stained film of rusty red sputum shows typical organism.

(2) Capsule Swelling Test:

Fresh emulsified sputum mixed with anti-serum gives capsule swelling reaction for identification of Pneumococci.

(3) Culture:

Sputum cultures on blood agar and incubated in CO₂ or candle jar. Blood culture is also done.

(4) Animal (Mouse) Inoculation:

Sputum is injected intra-peritoneally into the mouse. Animal dies in 18-48 hours. Heart blood gives pure culture of pneumococci.

(5) Pneumolysin Polymerase Chain Reaction:

(PCR) is sensitive; it is a specific new method to study pneumococcal acute otitis media.

(6) Pneumococcal Meningitis:

It is diagnosed by prompt examination and cultures of CSF.

10. Treatment of Pneumococci:

Pneumococci are sensitive to many antimicrobial drugs. Penicillin is the drug of choice.