Friday, 23 September 2016

BORDETELLA SPECIES





(Bordetella species) Mode of transmission,mechanisms by which microorganisms cause disease and diagnosis



 Define Bordetella  
A Gram negative coccobacili
List the species of medical importance 
  • Bordetella pertussis
  • Bordetella parapertussis
  • Bordetella bronchiseptica
Mention the species of medical importance
  • Bordetella pertussis

Describe the normal habitat
  • Pseudomonas species can be found in water, soil sewage and vegetation. They can also be found in the intestinal tract.
  • Pseudomonas aeruginosa is frequently present in hospital environments especially in moist places such as sinks, bowls, drains, cleaning buckets and humidifiers. It can also be found growing in eye drops, ointments and weak antiseptic solutions
  • Pseudomonas pseudomalleiis naturally found in rice paddy fields, the mud of riverbanks and surface stagnant water. The organism can infect cattle, pigs and other animals.




Describe the morphology Pseudomonas aeruginosa
·         .Bordetella pertussis is a small non- motile, capsulated Gram negative coccobacillus. It may occur singly or in chains and may show bipolar staining.
·         Bordetella parapertussis is a non- motile gram-negative rod.
·         Bordetella brochiseptica is similar to Bordetella pertussis but is motile

Describe the mode of transmission and pathogenicity of Pseudomonas aeruginosa 
TRANSMISSION
·         By inhalation droplets from infected person.


PATHOGENICITY-
·         Bordetella pertussis causes whooping cough an infection of the mucosa of the upper respiratory tract. Toxin from the organisms causes the secretion; of mucus which leads to irritation and the spasms of coughing associated with the disease. There is a marked Leucocytosis with an absolute Lymphocytosis.
·         Complications of infection include lung damage with emphysema, secondary infection leading to bronchopneumonia, bronchiectasis, convulsions and occasionally brain damage.
·         Bordetella parartussis causes a milder form of whooping cough.
  • Bordetella bronchiseptica is mainly animal pathogen. It may however cause a whooping cough like illness in humans and occasionally infection of wounds.




 Describe the laboratory diagnosis Salmonella 
1.SPECIMENS
·         Nasopharyngal secretions are required.
·         These are collected using a pernasal swab or by aspiration

2.CULTURE CHARACTERISTICS
·         Bordetella species are strict aerobes. Specimen for the isolation of Bordetella pertussis must be cultured as soon as possible after they are collected.
·         As selective and enrichment medium such as charcoal cephalexin blood agar (CCBA) or Bordet – Gengou penicillin medium is required for the primary isolation of Bordetella pertussis. Blood agar can be used for subculturing the organism.
·         When incubated for 2 – 6 days at 35 – 370c in a most aerobic atmosphere Bordetella pertussis produces small, raised shiny (mercury – like) colonies on CCBA or Bordet – Gengou medium. The colonise are usually mucoid
·         Bordetella parapertussis grows more rapidly and forms larger colonies than Bordetella pertussis. It produces a pigment in the medium and is able to grow aerobically on blood agar and nutrient agar.
·         Bordetella bronchiseptica grows well on blood agar and nutrient agar. On blood agar, it produces glistening beta- haemolytic colonies, usually after 24 – 48 hours incubation at 35 – 370c



3.BIOCHEMICAL TESTS
.
      Species
Motility
Urea
Oxidase test
Catalase
  Bordetella pertussis
     -
    -
        +
    +
  Bordetella parapertussis
     -
   +
After 24 hrs
         -
     +
   Bordetella bronchiseptica
       +
    +
After 4 hrs
         +             
      +
All three species ferment glucose and lactose with acid production.

4.PREVENTION AND CONTROL
·         By giving prophylactic vaccination. Erythromycin can be given to contacts.

·         Treatment of infected persons.


PSEUDOMONAS SPECIES





(pseudomonas species) Mode of transmission,mechanisms by which microorganisms cause disease and diagnosis



Define pseudomonas
  
A Gram negative rod.Its an enterobactericeae
 List the species of medical importance 
  • Pseudomonas pseudomallei
  • Pseudomonas aeruginosa
  • Pseudomonas mutlophilia
 Mention the species of medical importance
Pseudomonas aeruginosa

Describe the normal habitat
  • Pseudomonas species can be found in water, soil sewage and vegetation. They can also be found in the intestinal tract.
  • Pseudomonas aeruginosa is frequently present in hospital environments especially in moist places such as sinks, bowls, drains, cleaning buckets and humidifiers. It can also be found growing in eye drops, ointments and weak antiseptic solutions
  • Pseudomonas pseudomalleiis naturally found in rice paddy fields, the mud of riverbanks and surface stagnant water. The organism can infect cattle, pigs and other animals.


Describe the morphology Pseudomonas aeruginosa
  • Gram negative rods
  • Are motile by polar flagellum
  • Non-capsulated
 Describe the mode of transmission and pathogenicity of Pseudomonas aeruginosa
TRANSMISSION

Contact the opening with contaminated object or penetration through injuries.

PATHOGENICITY-
Pseudomonas aeruginosa causes:-
1.      Skin infections especially at burn sites wounds pressure sores and ulcers, often as a secondary invader.
2.      Urinary infection, usually following catheterization or associated with chronic urinary infections.
3.      Respiratory infections especially in-patients with cystic fibrosis or conditions that cause immunosuppression.
4.      External ear infections (otitis external).
5.      Eye infections usually (hospital – acquired).
6.      Septicaemia especially in persons already in poor health



Pseudomonas pseudomallei
·         Prendomonas prseundomallei; causes melioidosis (pneumoenteritis) in humans and animals the bacteria enter open wounds but can also be inhaled.
·         In melioidosis, pus filled nodules and abscesses form in these lungs, spleen, lever, joints, skin or subcutaneous tissues
·         Severe diarrhoea and vomiting may occur and occasionally septicaemia. Fever and a rash are usually present laboratory diagnosis.
·         Specimens; Depending on the site of infection, specimens include pus, urine, sputum and effusions for microscopy and culture, and occasionally blood for culture.
·         Specimens; that may contain prseudomonas pseudomallei must be marked HIGH RISK and; handled with great care. This specie is highly infections

Describe the laboratory diagnosis Salmonella 



1.SPECIMENS
Depending on the site of infection, these include urine, pus and sputum

2.CULTURE CHARACTERISTICS
·         Pseudomonas aeruginosa is an obligatory aerobe and is usually recognized by the blue – green pyocyanin pigment it produces.
·         Usually produces large, flat; haemolytic colonies on blood agar
·         Also it grows well on nutrient agar, Macconkey agar and other media containing bile salts and also on centrimide agar.
·         When grown on Kligler iron agar, it produces a characteristic pink – red slope and butt.
·         Pseudomonas pseudomallei produces non – haemolytic, small ringed, and striated colonies on blood agar after overnight aerobic incubation. On Macconkey agar colonies have a rough annd corrugated appearance. Cultures give off an ammoniacal smell. A pellicle (skin) is formed on broth cultures.
·         Preudomonas species grow well at room temperature Pseudomonas aeniginosa is also able to grow at 41 – 42 oc
Clinical features.
·         Severe diarrhoea and vomiting
·         Otitis external
·         Infected wounds and ulcers on the skin
·         Fever and rash.

3.BIOCHEMICAL TESTS
·         .All strains are strongly oxidase positive
·         Pseudomonas species are catalase positive
·         Pseudomonas species are indole negative
·         mostly are citrate positive
·         Preudomonads produce acid from carbohydrate media by oxidation not by fermentation. Glucose is oxidised and also maltose by most species except Proteus aeruginosa

PREVENTION AND CONTROL:
  • Eliminating the source of infection, particularly by control of carriers.
  • Treating the infected cases
·         Avoid contaminating the open areas with contaminated microbial

·         Sanitation in the hospital to avoid nasocomial infections


Thursday, 22 September 2016

PROTEUS SPECIES




(proteus species) Mode of transmission,mechanisms by which microorganisms cause disease and diagnosis



Define proteus
A Gram negative rod.Its an enterobactericeae
 List the species of proteus 
·         Proteus mirabilis
·         Proteus vulgaris
 Mention the species of medical importance
·         Proteus mirabilis
·         Proteus vugaris

Describe the normal habitat
  • Proteus species are found in the intestines of humans and animals in soil sewage and water. They are frequent contaminants of cultures
Describe the morphology Proteus 
  • Proteus species are
  •  actively motile,
  • Non-capsulated Gram negative
  • pleomorphic rods (wide rage in shape and size) vary from an almost coccal form to very long filaments (proteus a Greek god who often changed his shape).
.

 Describe the mode of transmission and pathogenicity of Salmonella species

TRANSMISSION
  •  Through contact to the urethra or wound
PATHOGENICITY-
Proteus mirabilis causes:-
1.      Urinary infections, especially following catheterisation or cystoscopy. Infections are also associated with the presence of stones. Proteus infected urine has an alkaline reaction.
2.      Abdominal and wound infections. Proteus is often a secondary invader of ulcers, pressure sore burns and damaged tissues.
3.      Septicaemia and occasionally meningitis and chest infections
Proteus vulgaris occasionally isolated from urine pus and other specimens

 Describe the laboratory diagnosis Salmonella 
1.SPECIMENS
Depending on the site of infection, these include urine, pus and sputum
2.CULTURE CHARACTERISTICS
Media for growth are;-
  • Blood agar-swarming is seen
  • DCA-    Swarming inhibited
  • SSA--    Swarming inhibited
  • Macconkey agar--       Swarming inhibited

·         When cultured aerobically, most proteus strains produce a characteristic swarming growth over the surface of blood agar and several other culture  Media.
·         Swarming however, is inhibited on media containing bile salts such as Mac Conkey agar, DCA, XLD agar and SS agar.
·         On these media individual non – lactose-fermenting colonies are produced after overnight incubation at 35 – 37 0c.
·          proteus cultures has a distinctive smell.

Culture on various enrichment and selective media.The media include:-
  • Selenite F
  • XLD agar
  • DCA
  • SS agar
  • Blood agar(sub culture)
3.BIOCHEMICAL TESTS
·         Proteus mirabilis can be differentiated from proteus vulgaris by the indole test.
·          Proteus mirabilis is indole negative.
·         Proteus Vulgaris are indole positive
·         Proteus rapidly hydrolyzes urea (with 4 hours) this is an important early screening test in differentiating enteric pathogens from proteus.  Serology
·         Motility is positive in MIU
·         Methyl red positive
·         Citrate pisitive

·         Some of the antigen of proteus strains (OX19,) OXK and OX2) agglutinate with sera from patients with rickettsial disease . These reactions form the basis of the Weil – Felix test .
·         NB:It produces an enzyme known as Beta lactamase



PREVENTION AND CONTROL:
  • Eliminating the source of infection, particularly by control of carriers.
  • When sanitary control of the environment is difficult, active immunization with typhoid vaccine.
  • Treating the infected cases


Key Points 
Define proteus
A Gram negative rod in the Genus enterobactericiae
·          Proteus mirabilis
·         Proteus vulgaris
Mention the species of medical importance(5 minutes)
·         Proteus mirabilis
·         Proteus vugaris

:Describe the normal habitat
  • Proteus species are found in the intestines of humans and animals in soil sewage and water. They are frequent contaminants of cultures


Evaluation

  • List 2species of proteus
  • Mention 3 Biochemical tests
  • Mention the appearance of colonies on blood Agar
  • Mention on how to prevent swarming

Wednesday, 21 September 2016

SALMONELLA SPECIES





(Salmonella species) Mode of transmission,mechanisms by which microorganisms cause disease and diagnosis
                                           one of symptoms of salmonella                  



 Define Salmonella 
A Gram negative rod. Its an enterobactericiae.
 List the species of Salmonella 
·         Salmonella typhi
·         Salmonella paratyphi A
·         Salmonella paratyphi B
·         Salmonella paratyphi C
·         Salmonella typhimurium

 Mention the species of medical importance
·         Salmonella typhi
·         Salmonella paratyphi A
·         Salmonella paratyphi B
·         Salmonella paratyphi C
·         Salmonella typhimurium

Describe the normal habitat
  • Most salmonellae are found in the intestines of animals especially of pigs, cows, goats, sheep, rodents, hens, ducks and other poultry.
  • Salmonella typhi and paratyphi are usually found only in humans. Also are excreted in the faeces and urine of infected patients and are present in the gall bladders of long-term carriers.



Describe the morphology Salmonella 
  • Salmonellae are gram negative rods.
  • All salmonellae are actively motile.
  • Non-capsulated
  • Non-sporing.

Describe the mode of transmission and pathogenicity of Salmonella species

TRANSMISSION
  •  Infection is by ingesting the organisms in contaminated food or water or from contaminated hands.
  • Salmonella typhi is spread mainly by water and salmonella paratyphi A and B by food.
  • In schistosomiasis endemic areas there is a high incidence of chronic Salmonella typhi and Salmonella paratyphi A infections and carriers. The salmonellae adhere to adult schistosome flukes.
PATHOGENICITY-
Salmonella typhi causes:
1.      Typhoid (enteric) fever.
  • The bacteria pass from the small intestine into the blood by way of the lymphatic system. The reticuloendothelial system becomes infected and also the gall bladder and kidneys. From the gall bladder, the organisms invade the intestine causing inflammation and ulceration.
  • Symptoms of infection include fever with low pulsate, headache, toxaemia, and enlargement of the spleen and a path or mental confusion.
  • Epistasis, intestinal haemorrhage and perforation may also occur.
  • In uncomplicated typhoid the total white cell count is low with a relative lymphocytosis. There may also be anaemia.
2.      Neurotyphoid is those with urinary schistosomiasis. The condition is an immune complex disorder of the kidneys and is characterized by fever, oedema, marked albuminuria and haematuria.
3.      Osteomyelitis (inflammation of the bone marrow), especially in children with sickle cell disease and Thallassaemia.
-       Typhoid nodules can be found in the bone marrow.
-       Inflammation of the joints (typhoid arthritis) may also occur.
4.      Abscesses of the spleen and elsewhere
5.      Meningitis and rarely pneumonia and endocarditis.

 Explain the antigens of Salmonella 
Salmonellae are based on identifying the O (somatic) and H (flagella) antigen by the different serovars.
  • O. Antigens: these are cell wall, heat – stable antigens. Their O antigens group salmonellae.
  • H antigens: These are flagella, heat – labile antigens. Their H antigens serotype salmonellae
  • Vi Antigens

Step 9: Describe the laboratory diagnosis Salmonella (30 minutes)
1.SPECIMENS
·         For the diagnosis of enteric fever, specimens include blood, faeces and urine for culture.

2.CULTURE CHARACTERISTICS
They are aerobes and facultative anaerobes.They grow between 15-450c with  optimal temperature of 370c.

Culture on various enrichment and selective media.The media include:-
  • Selenite F
  • XLD agar
  • DCA
  • SS agar
  • Blood agar(sub culture)
Salmonellae produce non-lactose fermenting colonies
(i)XLD AGAR(xylose Lysine Deoxycholate)
Hydrogen sulphide gas is produced and colonies are pink-red,3-5 mm in diameter with black centre.
(ii)DCA AGAR(Deoxycholate Citrate Agar)
Pale colonies are seen(NLF).The colonies are small with black centre and are non-late Non Lactose Fermentor(Non-lactose fermentor).

3.BIOCHEMICAL TESTS
·         The differentiation of suspect’s salmonella colonies using motility indole urea (MIU) media and kligler iron agar (KIA) or the API2 screening test are used.
·         KIA culture salmonellae and Shigellae produce a pink – red slope and yellow butt indicating the fermentation of glucose but not lactose. Much salmonella also produce blackening due to hydrogen sulphide production and cracks in the medium due to gas production from glucose fermentation.
·         MIU medium salmonellae are motile so show the turbidity throughout the medium.
·         Urease is negative
·         Indole is negative
·         Lactose is negative.
·         Motility is positive
·         Citrate is positive
·         Methyl red is positive
·         Voskuer voges is negative
4.SEROLOGY:
  • Salmonellae are based on identifying the O (somatic) and H (flagella) antigen by the different serovars.
  • O. Antigens: these are cell wall, heat – stable antigens. Their O antigens group salmonellae.
  • H antigens: These are flagella, heat – labile antigens. Their H antigens serotype salmonellae.
5.WIDAL TEST:
  • The patient’s serum is tested for O and H antibodies against antigen suspension (usually stained suspensions). Salmonella typhi 09,12 and Salmonella typhi H suspension.
  • It is reported by giving the titre for both O and H antibodies. The antibody titre is taken as the highest dilution of serum in which agglutination occurs.
  • If no agglutination occurs the test should reported as:
·         Salmonella typhi) titre less than 1cm 20
·         Salmonella typhi H titre less 1 in 20.
  • In typhoid endemic areas in developing countries, active typhoid is suggested if the titres of H or O or both agglutinins are significantly raised (i.e. titres greater than 1 in 180 or 1 in 200 depending on the titres found in local healthily people.)
  • Causes of raised O or H titre other than active typhoid:
  • Chronic salmonellosis associated with schistosomal infection.
  • Vaccination with TAB or typhoid vaccine
  • Infection with other salmonella species
  • Chronic liver disease
  • Immunological disorders such as rheumatoid arthritis, rheumatic fever, multiplemyeloma, neuphrotic syndrome and ulcerative colitis.

SUMMARY OF BIOCHEMICAL TESTS REACTION
I-indole=  -VE
M-methyred= +VE
V-voges prousker= -VE
C-Citrate= +VE
U-urease= -VE
4.PREVENTION
  • Seek medical treatment
  • Hygiene
  • Isolation of the infected
  • Screening before admission
  • Proper cooking and storage of food

Key Points 
Define Escherichia
A Gram negative rod in the Genus enterobactericiae
 List the species of Shigella
  • Shigella dysenteriae-sero group A
  • Shigella flexineri-sero group B
  • Shigella boydii-sero group C
  • Shigella sonnei-sero group D
BIOCHEMICAL TESTS
FOR  Shigella:-Perform Biochemical tests to identify the organisms
Perform the following tests for Shigella:-
  • Lactose –ve                
  • H2s –ve                                               
  • Oxidase –ve
  • Citrate –ve
  • TSI-R(slope)/Y(butt) ,No gas, No H2s
  • MR +ve
  • Nitrate reductase      +ve
  • indole     -/+ve(varies)
  • Urease –ve

Evaluation 
  • List 3 species of Shigella
  • Mention 3 Biochemical tests
  • Mention the appearance of colonies on blood Agar and Macconkey

Salmonella  paratyphi A and B
  • These salmonellae cause paratyphoid (enteric) fever.
  • The disease is generally milder than typhoid with s. paratyphoid A and B being less invasive than Salmonella typhi.
  • There is usually diarrhoea and vomiting and the entire intestinal tract may be flamed especially in Salmonella paratyphoid B infections.
  • Paratyphoid is more commonly caused by Salmonella paratyphi A than Salmonella paratyphi B.
Salmonella  paratyphi C.
  • This serovar causes mainly septicaemia, complications of Salmonella paratyphi C. infections include the formation of abscesses, arthritis and inflammation of the gall bladder.

Other salmonellae

  • Several thousands salmonella serovars are capable of causing food – poisoning (enterocolitis)
  • Symptoms of salmonella food – poisoning occur within 10 – 30 hours of ingesting the contaminated food.
  • Food – poisoning strains can also cause bacteraemia, inflammation of the gall bladder, osteitis (inflammation of bone) especially in children with sickle cell disease and occasionally abscesses.
Laboratory diagnosis:
  • Specimens: For the diagnosis of enteric fever, specimens include blood, faeces and urine for culture.
  • Blood: Organisms can usually be detected in 75 – 90% of patients during the first ten days of infection and in about 30% of patients during the third week.
  • Faeces: Organism can be isolated from 40 – 50% of patients during the second week of infection and from about 80% of patients during the third week.
  • For the diagnosis of salmonella food – poisoning, faeces are required for culture and blood during times of fever.
  • Pus or joint fluid is required for culture if an abscess or arthritis is suspected.
Culture on various enrichment and selective media e.g. Selenite F, XLD agar, DCA and SS agar.


Salmonellae produce non-lactose fermenting:
  • Biochemical reactions:
  • The differentiation of suspect’s salmonella colonies using motility indole urea (MIU) media and kliglar iron agar (KIA) or the API2 screening test are used.
  • KIA culture salmonellae and Shigellae produce a pink – red slope and yellow butt indicating the fermentation of glucose but not lactose. Much salmonella also produce blackening due to hydrogen sulphide production and cracks in the medium due to gas production from glucose fermentation.
  • MIU medium salmonellae are motile so show the turbidity throughout the medium.
Serology:
  • Salmonellae are based on identifying the O (somatic) and H (flagella) antigen by the different serovars.
  • O. Antigens: these are cell wall, heat – stable antigens. Their O antigens group salmonellae.
  • H antigens: These are flagella, heat – labile antigens. Their H antigens serotype salmonellae.
Widal Test:
  • The patient’s serum is tested for O and H antibodies against antigen suspension (usually stained suspensions). Salmonella typhi 09,12 and Salmonella typhi H suspension.
  • It is reported by giving the titre for both O and H antibodies. The antibody titre is taken as the highest dilution of serum in which agglutination occurs.
  • If no agglutination occurs the test should reported as:
·         Salmonella typhi) titre less than 1cm 20
·         Salmonella typhi H titre less 1 in 20.
  • In typhoid endemic areas in developing countries, active typhoid is suggested if the titres of H or O or both agglutinins are significantly raised (i.e. titres greater than 1 in 180 or 1 in 200 depending on the titres found in local healthily people.)
  • Causes of raised O or H titre other than active typhoid:
  • Chronic salmonellosis associated with schistosomal infection.
  • Vaccination with TAB or typhoid vaccine
  • Infection with other salmonella species
  • Chronic liver disease
  • Immunological disorders such as rheumatoid arthritis, rheumatic fever, multiplemyeloma, neuphrotic syndrome and ulcerative colitis.
Prevention and Control:
  • Eliminating the source of infection, particularly by control of carriers.
  • Preventing the spread if infection by public health measures e.g. milk, hygienic preparation of food.
  • When sanitary control of the environment is difficult, active immunization with typhoid vaccine.



REFERENCES
·         Ivan M. Roitt & Peter J.Delves ROITTS ESSENTIAL IMMUNOLOGY, 10th Edition, (2004) Replika press  Pvt.ltd ,india
·         Monica Cheesbrough – MEDICAL LABORATORY MANUAL FOR TROPICAl Countries, part 2, Edition (2003) Cambridge University press,international sales department.
·         Monica Cheesbrough – MEDICAL LABORATORY MANUAL FOR TROPICAL COUNTRIES, volume 2, Microbiology, Edition (1984) Cambridge University press.
·         Warren Levinson. MD,PHD– Medical Microbiology & Immunology edition (2004) Mc Graw –HillCompanies

·         Satish Gupte THE SHORT TEXT BOOK FOR MEDICAL MICROBIOLOGY(including parasitology) 10th Edition, (2004) Replika press  Pvt.ltd ,india