Bacilli

 

Bacilli 

( sing-Bacillus)--- Rod shaped organism

          Gram positive bacillus  

                    ➡Anaerobic (Growth in absence of oxygen)

                        eg Clostridium.tetani(Cause Tetanus)

                             Cl.botulinum                                   

                   ➡ Aerobic (growth in presence of oxygen)

                         eg.Bacillus.anthracis 

                              B.subtilis,  

         Gram negative bacillus 

                            eg.Escherichia, Shigella, Salmonella

          Acid fast bacillus 

                eg.Mycobacterium.tuberculosis

 

                          Gram +ve bacillus

Classifications:-

( A)Non spore forming bacillus

    (1) Aerobic —Corynebacterium diphtheriae,

Listeria,Erysipelothrix,Nocardia                                            

    (2) Anaerobic —Actinomyces.

(B)Spore forming bacillus

      (1)   Aerobic —Bacillus

           Pathogenic —B.anthracis, B.cereus

           Non pathogenic —B.subtilis,B.stearothermophilus.

       (2) Anaerobic —Clostridium— Cl.tetani,Cl.perfringens,Cl.botulinum,  Cl.difficile.

 

Corynebacterium diphtheriae(KLB)

➡Morphology & staining character :-It is gram+ve slender,straight 

       or slightly curved rod with expanded ends.They are markedly 

        pleomorphic(varatiion in size and shape).

        They lie in cluster,parallel to one another or at various angle 

          resembling letters V or H or combination of both which 

          compares to Chinese letters.

       They are non sporing and non motile.

       It contain granules called Metachromatic granules.

Metachromatic granules(Volutine granule )—These granules are 

         present at poles or throughout cytoplasm.These granules are 

         used to identify  the organism.Seen by albert’s stain.

➡Cultural character :-Growth needs enriched media.

                                   Temp. is 37 0 C,pH 7.2,Aerobic.Media are 

        Loeffler’s serum media—Organism grows rapidly in 6 hrs.    

            Metachromatic granules formation is marked in this media .

       Tellurite agar media—Colonies are black.

➡Biochemical reaction —Ferment glucose and maltose to produce acid .

➡Toxin production :-Produce exotoxin.

➡Pathoginicity :-Produce Diphtheria which is manifested by 

     `White patch ’.Diphtheria bacillus localises to tonsil.             

            From tonsil may spread to pharynx,larynx and trachea.

           The organism multiply on epithelial cell and produce

            acute inflammation which form grayish pseudomembrane 

            called White patch.

            But damaging effect is due to powerful exotoxin.

           Toxin has effect on heart muscle,Nerve and skeletal muscle.

➡Source —Patient & carrier

➡Mode of transmission-Respiratory droplet by coughing & sneezing

➡Route of entry —Inhalation.

  ➡Laboratory Diagnosis:--

(A)Collection of material —Material is collected from white patch 

         with sterile swab stick.

(B)M/E —A smear is made on slide.Stained with albert’s stain.               

Metachromatic granules are seen.The granules look bluish while rest of 

          cytoplasm looks green.

(C ) Cultural character—Materials is placed on tellurite agar media 

                         .Colonies look black.

( D)Toxigenicity –studied in vivo and in vitro.

                              In vivo —Test is done on Gueneapig.

                              In vitro-(Elek test)-Done on media.The test depends on 

                              flocculating precipitate on media.

 

                                  Bacillus anthracis

➡Morphology & staining character :-They are spore bearing,gram+ve 

           rods,arranged in chain.Aerobic,non motile.Capsulated when in living  

           tissue.No capsule when it is outside the  body.Spore is oval and 

           central in position and formed when it is outside the body.

          In body tissue no spore is formed.Capsule contain polypeptide.

➡Cultural character :-Aerobe and facultative anaerobe.Temp-37 0 C.It grows 

                in ordinary media like Nutrient agar .In culture media bacilli have 

                spores but no capsule.

      In blood agar media—Colony looks “Medusa head” appearance

              ie.Large circular colony with wavy margin.

      In Nutrient broth —Floccular deposit and thick pellicle.

      In gelatin stab—Inverted fir tree growth due to liquefaction of gelatin.

➡Toxin production :-Virulence factor (1)Exotoxin (2)Capsular polypeptide.

➡Pathogenicity: -It causes Anthrax.

➡Source of infection:- Sheep,Cattle,Goat and Pig.

           Bacilli are excreted in Faeces,Urine and Saliva.

On basis of Mode of transmission & Route of entry Anthrax is of 3 types.

(1)Cutaneous anthrax,Malignant pustule or hideporters disease-Inocculation 

                  occur from skin,hair of infected animal.

(2)Pulmonary anthrax or wool sorter’sdisease-Caused by inhalation of  spore

(3)Intestinal (enteric) anthrax-It is rare and caused by ingestion of infected 

                  meat.

➡Laboratory Diagnosis:-

(A)Collection of material —Pus,Sputum,Blood.

 (B)M/E :-Smears prepared and stained by gram stain.Seen under oil 

               immersion lens.Gram+ve rod arranged in chain.

 (C)Cultural character —Materials is cultured on blood agar media.Non 

               haemolytic colony which looks Medusa head appearance.

Ascoli ’s thermoprecipitin test—Extract of infected tissue is placed on  antiserum in a test tube. A ring of precipitate at junction indicates   positive test.It is useful for suspected caracasses.

➡Animal inoculation —The materials injected subcutaneously in guineapig or   mice.Animal dies in 2 days.Large no.of B.anthracis are present on  blood,spleen and local site. 

 

                                        Clostridium tetani

➡Morphology & staining character :-Gram+ve spore bearing motile rod.Spore is spherical and terminal.

  Looks like `drum stick’appearance.

➡Cultural character :-It grows in ordinary media.

    Temp. 37 0 C,anaerobic.

         In Robertson’s cooked meat media—There is gas formation with  digestion and blackening of meat.

         In Nutrient agar or blood agar media —     

               Irregularly round colony with 

              branching projection and granular surface.

          In Agar stab culture —Fir tree growth.

➡Biochemical reaction —No carbohydrate is fermented

➡Antigenic character —On basis of flagellar antigen 10 types are identified. 

➡Toxin production –Cl.tetani produce very powerful exotoxin called Tetanospasmin

➡Pathogenicity: --It causes Tetanus.

     ➡ Source of infection -Soil,Manure and stool of animal   

                                particularly horse.

➡Mode of transmission & Route of entry —Spores are 

    introduced in injury like wound,burn,umbilical stump 

    surgical suture.

   The infection localized in the area.

   Spore is germinated to vegetative form in anaerobic 

   condition which is due to     

      (1)Necrosis of tissue

      (2)Associated aerobic organism utilizes oxygen.

      (3)Calcium salt.

    Vegetative organism produce exotoxin which reach CNS.

Toxin interferes inhibitory action of upper motor neurone 

over lower motor neuron.

 

➡S/S-- Trismus & lock jaw due to tonic contraction of voluntary muscle of jaw.

Tonic spasm of other voluntary muscles occur.

       Death rate is very high due to respiratory failure.

➡Laboratory Diagnosis:-

(A)Collection of material —Piece of necrosed tissue from local lesion

(B)M/E —Smear is made & gram stain is done.

 

(C )Culture —Material is cultured in Robertson’scooked meat media.

There is gas formation with slight digestion & blackening of meat.

            

    Clostridium botulinum

➡Morphology & staining character :- Gram+ve spore bearing motile rod with oval terminal spore. 

➡Culture —Grows on ordinary media. Obligatory anaerobe.Temp.- 20-30 0 C

➡Toxin production- Cl.botulinum produce exotoxin.

     Toxin production is under control of viral gene.

 Cl.botulinum divided into 8 types on antigenically distinct toxin(A-H)

  Type A,B&E are associated with human disease.

➡Pathogenicity:- Cl.botulinum causes disease called        

                 Botulism(Food poisoning).

  ➡Source of infection- Soil,ocationally animal stool.

 ➡ Mode of transmission- Smoked,Spiced or canned food.

  ➡Route of entry-By ingestion of preformed toxin in smoked or  canned food.

             In food spores of Cl.botulinum germinate under anaerobic  condition into vegetative cell,multiply & produce toxin. Botulism is due to intoxication.

Exotoxin blocks release of acetylcholine at neuromuscular    junction  and synapses.Flaccid paralysis results.

➡S/S —        In 18-20 hrs.there is Double vision,

                  Incoordination of eye muscle, 

            Inability to swallow,Speech difficulty,Bulbar paralysis & 

              death from respiratory paralysis or cardiac arrest.

                           

                                  Infant botulism

Spores are probably in baby’s food(eg Honey),Produce toxin in gut.It occur in 1 st month of life leading to poor feeding.Weakness & signs of paralysis(Floppy baby) The organism and toxin are found in faeces but not in serum.

➡Laboratory Diagnosis:-

   1.  Collection of materials:--food

2.M/E- Smear on slide and gram stain done.Gram+ve rod with terminal spore.                 

3.Culture- Food is heated at 80 0 C for half an hour to kill vegetative forms.

               It is then cultured in cooked meat media.

4.Animal inoculation —Filtrate from culture is inoculated in 2 gueneapigs 

                      The test animal shows characteristic change.

                      The control animal (Previously given antitoxin)survives.  

 

                                       Gram--ve bacillus 

(A)Enterobacteriacae(Coliform bacteria)(B)Other gram –ve rod.

 

Characteristics of enterobacteriacae

(1)They are gram-ve,non spore forming bacillus

(2)Some are motile & some are non motile

(3)They live in large intestine of man and animal

(4)All of them ferment glucose (5)They reduce nitrate to nitrite.

(6)They are oxidase negative

(7)They are facultative anaerobe

 

Enterobacteriacae(Coliform bacteria) include many genera.They are differentiated into lactose fermenter & non lactose fermenter.

     Lactose fermenter                                   Non lactose fermenter

      (1)Escherichia                                                (1)Salmonella

      (2)Klebsiella                                                   (2)Shigella      (3)Enterobacter                                               (3)Proteus

     (4)Serratia                                                        (4) Morganella

     (5)Citrobacter                                                   (5)Providencia

       (6)Arizona                                                      (6)Hafnia

Other gram –ve rods

(1)Vibrio cholerae(2)Campylobacter jejunae(3)Helicobacter pylori (4)Pseudomona

                      

                           Salmonella

Salmonella of medical importance are

(1)Salmonella typhi —Produce typhoid fever

(2)Salmonella paratyphi A,B,C —Produce paratyphoid fever.

(3)S.typhi murium,S.cholerasuis,S.enteritidis —Produce food poisoning and  enterocolitis.

➡Morphology & staining character:-

           Gram –ve, non spore forming motile rod.Have flagella.

➡Cultural character —Grows on ordinary media.Temp.-37 0 C. pH-7.2-7.4.

          In nutrient agar media- Colonies are moderately large,circular,moist.

         In Mc Conkey’s media—Pale colourless colony.

➡Biochemical reaction —Ferment glucose but do not ferment lactose. ( Non lactose fermenter) 

 

➡Antigenic character —Have somatic O antigen & flagellar H 

                            Antigen. Fresh S.typhi produce Vi antigen.

Phage typing -33 phage types.Depends on action of bacteriophage on Vi antigen.Done in epidemiological study.

➡Toxin productiion –Produce endotoxin 

➡Pathogenicity -Cause (1)Enteric fever (2)Food poisoning. (3)Bacteraemia(S.cholerasuis)- Osteomyelitis,Pneumonia,Meningitis

 

➡Source -Patient and carrier.(Gall bladar,Billiary tree)

➡Mode of transmission -Contaminated water,Food,Drink.

➡Route of entry -oral route. 

➡Lab Diag of enteric fever:-

               Enteric fever include Typhoid and para typhoid fever.

( A)Routine blood exam-Leucopenia with lymphocytosis.

( B)Bacteriological exam-

         (1) Collection of materials- blood,stool and urine 

        (2) Culture-In McConkey’s media-Produce pale colony.

        (3) Biochemical-Ferment glucose but do not ferment lactose.

        (4) Antigenic character- Done by Serological test-Widal test                

 

                             Shigella

➡Morphology & staining character:- Gram –ve, non motile rod.No flagella.

➡Cultural character —Aerobes and facultative anaerobe.

                      Temp-37 0 C.pH-7.2-7.4.Grows on Mc Conkey’s media.

                      Colony is pale and colourless due to non lactose fermenter.

➡Biochemical reaction —They ferment glucose but do not ferment lactose.   (Non lactose fermenter)

➡Antigenic character —Shigella posseses somatic O antigen.

On basis of O antigen it is classified into 4 groups.

(1)Group A- Shigella dysenterae 

(2) Group B-Shigella flexneri.

(3) Group C-Shigella boydii.

(4) Shigella sonnei.

➡Pathogenicity:- They cause bacillary dysentery,

                       food  poisoning,summer diarrhoea.

➡Source of infection -Patient and carrier(strictly human source)

➡Mode of transmission -Four F-Food,Finger,Flies,Faeces.

➡Route of entry -Ingestion

 

➡Diagnosis of bacillary dysentery- Done by stool exam.

                             Bacteria is not present in blood or urine

(1)Naked eye exam- Mucopurulent stool mixed with blood.

       In severe cases it may consists of pure blood with little mucus.

(2)M/E- Pus cell –Plenty,RBC—Plenty.

(3) Culture-Stool collected in a sterile pot and cultured in

          Mc Conkey’s media.Morphology,Biochemical reaction and 

            antigenic character are studied.  

Escherichia

Escherichia of medial importance is E.coli.

➡Morphology & staining character:- Gram –ve, motile rod.Have flagella   Some are capsulated. 

➡Cultural character-- Aerobes and facultative anaerobe.

    Temp-37 0 C.pH-7.2-7.4.Grows on ordinary media   & M c Conkey’s media.

       In nutrient agar-Colonies are moderately large,circular and moist.

       In Mc Conkey’s media –Colonies are rose pink due to lactose fermenter

➡Biochemical reaction- Ferment lactose and produce acid and gas.

➡Antigenic character -Main antigen somatic O antigen and flagellar H  antigen.Some strain have capsular or K antigen . 

➡Toxin production- Produce Endotoxin and Exotoxin.

➡Pathoginicity:- Produce

(A)Disease of intestinal tract —Watery diarrhea,Bloody 

                       diarrhea,Dysentary,Travellar’s dairrhoea.

(B)Disease outside intestinal tract-

     (1)Urinary tract infection

     (2)Neonatal meningitis

     (3)Neonatal sepsis.(4)Other pyogenic infection like Wound infection  Abscess,Cholecystitis,Peritonitis.

➡Source -Normal flora of large intestine

➡Mode of transmission -(1)Contaminated food and drinks

(2)Through birth passage(Neonatal meningitis) (3)Direct contact(UTI)

➡Route of entry- Ingestion,birth passage,direct contact.

➡Lab Diag-

(1)Collection of materials -

       (A) Lesion outside  intestinal tract — Urine,Pus,CSF,Blood                                                                     

       (B)Lesion inside intestinal tract-Stool                                                               

(2) M/E- Materials are taken on slide. smear is prepared & gram  

                stain done.Gram –ve rod are seen.

(3)Culture- Material is cultured on McConkey’s media,Incubated  aerobically at temp . 37 0 C.pH-7.2-7.4.over night.

 Colonies look rose pink colour.