Applied Microbiology Flashcards
Normal flora
→The population of microorganisms that inhabit skin & mucous membranes of normal human body.
- Resident flora→ organisms regularly present in a particular area & when disturbed it re-establishes itself
- transient flora → both non-pathogenic & potentially pathogenic bacteria that inhibit the body surface or mucous membrane for a limited period.
Normal flora of the skin.
→ staph.epidermidis & diphtheroids → peptococcus → str. viridans → enterococcus → micrococcus → esch.coli → proteus → Candida albicans → pityrosporum orbiculare → propionibacterium acne
Normal flora of the conjunctiva
→ corynebacterium xerosis
→ staph.epidermidis
→ moraxella sp
→ non-haemolytic streptococci
Normal flora of the nose & nasopharynx.
Nose: → Diphtheroids → staphylococci → streptococci → Haemophilus sp Nasopharynx: → pseudomonas aeruginosa → esch.coli → proteus
Normal flora of the mouth.
→ micrococci → gram +ve aerobic spore bearing bacilli → coliforms → proteus → lactobacilli
Normal flora of the URT
→ alpha haemolytic streptococci
→ similar flora of mouth
Normal flora of the GIT
Breast fed infants: → lactobacilli → enterococci → colon bacilli → staphylococci Bottle fed infants: → leptotricha → anaerobic lactobacilli → colon bacilli → aerobic & anaerobic spore bearing organisms. Adult: → lactobacilli → enterococci → bifidobacteria → anaerobic lactobacilli. → Bacteroides sp → anaerobic streptococci → clostridia
Normal flora of the GUT
→ mycobacterium smegmatis → strains of mycoplasma & ureaplasma Penile urethra: → gardnerella vaginalis → Bacteroides sp → alpha haemolytic streptococci. Female urethra: → staph. epidermidis Vagina: →Clostridia → anaerobic streptococci → Bacteroides sp → gardnerella vaginalis → diphtheroids → listeria → Candida albicans.
Normal flora of the external auditory meats.
→ staph.epidermidis
→ Diphtheroids
Usinary tract infections
→A disease caused by microbial invasion of the genitourinary tract that extends from the renal cortex of the kidney to the urethral meatus.
→causative organisms:
A. Gram -ve bacilli
1. Escherichia coli
2. Klebsiella sp
3. Proteus mirabilis
4. Enterobacter
5. Pseudomonas aeruginosa
6. Serratia
B. Gram + ve cocci
1. Enterococci faecalis
2. Staph. saprophyticus
3. Staph. aureus
4. Staph. epidermidis
C. Miscellaneous
1. M. tuberculosis
2. Citrobacter
3. Salmonellae
4. Str. pyogenes
5. Str. agalactiae
6. Gardnerella vaginalis
D. Fungus
1. Candida albicans
→lab diagnosis:
1. Specimen- midstream urine specimen,catheter specimen
2.transport- minimum delay, refrigerate @4°c
3. Microscopy- pus cells, epithelial cells, erythrocytes & bacteria
4. Culture- blood agar & Mac conkey's agar @37°c for 24 hours
5. Other methods
a) dip slides
b) pour plate method
c) Griess nitrite test
d) triphenyltetrazolium chloride test
e) catalase test
f) gram staining
g) glucose test paper
h) polymorphonuclear neutrophils
i) leucocyte esterase
j) defection of lipopolysaccharide
6. Differentiation of UUTI & LUTI → antibody coated bacteria detected by immunofluorescence test indicates UUTI.
7. Antibody susceptibility testing.→ Stokes disc diffusion methodOrganisms causing diarrhoea
A. Bacteria
1. Vibrios
• vibrio cholerae
• V. Parahaemolyticus
• other halophitic vibrios
2. Esch. coli ( ETEC, EPEC)
3.salmonellae
• S. enteritidis
• S. Typhimurium
4. Shigella sp
5. Campylobacter jejuni
6. Yersinia enterocolitica
7. Clostridium perfringens
8.C. difficile
B. Viruses
1. Rotavirus
2. Norwalk virus
3. Adenovirus
4. Astrovirus
5. Calicivirus
C. Protozoa
1. Entamoeba histolytica
2. Giardia lamblia
3. Cryptosporidium parvum
D. Fungus → Candida albicans.Food poisoning.
→ an illness acquired through consumption of food or drink contaminated either with microorganisms, their toxins or chemical poisons.
1. Infective type: 8-24 hours, infected dose of microorganisms ingested with food. Eg. , Salmonella sp, vibrio parahaemolyticus, campylobacter jejuni.
2. Toxic type: 2-6 hours, preformed bacterial toxin ingested with food. Eg.staphylococcus aureus, bacillus cereus, clostridium botulinum.
3. Intermediate type: 6-12 hours, bacteria ingested with food release toxin in gut. Eg. Cl. Perfringens.
→lab diagnosis:
1. Specimen- food, vomitus, faeces,blood.
2. Demonstration of toxin- toxin-antitoxin neutralization test in mice
3. Demonstration of organisms- gram staining, culture on blood agar or cooked meat broth in anaerobic conditions.
Causes of acute pyogenic meningitis
In children & adults:
- Neisseria meningitidis
- Streptococcus pneumoniae
- Haemophilus influenzae
- Staphylococcus aureus.
- Listeria monocytogenes
- Esch. coli
- Proteus sp
- Klebsiella sp
- Citrobacter sp
- Enterobacter sp
- Serratia
In neonates & infants:
- Esch. col
- Group B streptococci
- Staphylococcus aureus
- Haemophilus influenzae
- Listeria monocytogenes
- Streptococcus pneumoniae
- Klebsiella sp
Lab diagnosis -acute pyogenic meningitis.
- Specimen -CSF
- Microscopy- gram staining → plenty of pus cells & few gram + ve / -ve organisms.
- Antigen detection - latex agglutination,countercurrent immunoelectrophoresis.
- Culture:
a) CSF culture- blood agar, chocolate agar & cooked meat broth @ 37°c for 24 hours with 5-10% CO2
b) blood culture- in meningitis due to N.meningitidis, H.influenzae & str. preumoniae - Agglutination
- Demonstration of bacterial endotoxins- limulus lysate test → extract prepared from blood cells of the horse shoe crab is coagulated when mixed with blood containing endotoxins.
Tuberculous meningitis.
→ CSF shows moderate rise in cell count & predominant cells are lymphocytes.
→ moderate rise of total protein & sugar is reduced.
→ lab diagnosis:
1. Specimen- CSF shows cobweb appearance.
2. Microscopy-ZN staining shows lymphocytes with few acid-fast-bacilli.
3. Culture - Lowenstein-Jensen medium @37°c x 6-8 weeks.
