Diagnosis of bacterial diseases
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Transcript of Diagnosis of bacterial diseases
IDENTIFICATION OF BACTERIAL PATHOGENS
Infecti ous diseases
Infectious diseases are disorders caused by organisms — such as bacteria, viruses, fungi or parasites. Many organisms live in and on our bodies. They're normally harmless or even helpful, but some organisms under certain conditions may cause disease. Some infectious
diseases can be passed from. Types of causative agents (bacteria , virus , fungi, parasite).
Bacteria There are prokaryotes (a group of organisms whose cells lack a membrane-bound nucleus).
Many of these bacteria are saphrophytic and live by causing decay and putrification of organic material. Some eubacteria are parasitic and responsible for disease in plant, animals, and humans
Size:Size of bactreia measured by micro
The bacteria of medical importance 0.2-1.5 micron in diameter and 3-5 micron in length.Different Shapes of bacteriaCocci=spherical bacteriaBacilli=rod shaped bacteriaSpirochetes = spiral twisted bacteriaActinomycetes=branching filamentous bacteriaMycoplsma without cell memberane pleomorphic.
Structure of bacterial cell
1-cell wall2-cytoplasmic memberane
3-cytoplasm with some cytoplasmic organelles4-single circular or douple stranded DNA.
5-Some specific structurs as capsule, flagella, spores
Arrangement of bacteria :Single .
Diploid =in pairs.Streptococcus or streptobacilli = presenti n chains.Stphylococcus = present in clusters.Size:Size of bactreia measured by micro The bacteria of medical importance
0.2-1.5 micron in diameter and 3-5 micron in length.
Different Shapes of bacteriaCocci=spherical bacteriaBacilli=rod shaped bacteriaSpirochetes = spiral twisted bacteriaActinomycetes=branching
filamentous bacteriaMycoplsma without cell memberane pleomorphic.
better animal care usage appropriate
antibiotic sparing of expenses
Control of the disease preventive measures can
be initiatedAll for decrease the losses from the disease
Why We must make a specific diagnosis
♥Using the proper aseptic techniques.♥Correctly obtaining the specimen.♥Correctly handling the specimen
♥Quickly transporting the specimen to the lab.♥Once the specimen reaches the lab it is
cultured and identified
The successful identification of microbe depends on:
•Successful identification depends on how the specimen is collected, handled and stored.
•It is important that general aseptic procedures be used including sterile sample containers and sampling methods to prevent contamination of the specimen.
•What other precautions must be taken when collecting specimens?
•After collection the specimen must be taken promptly to the lab and stored appropriately (e.g. refrigeration).
Specimen Collection
•Microbiologists use 5 basic techniques to grow, examine and characterize microorganisms in the lab.
•They are called the 5 ‘I’s: inoculation, incubation, isolation, inspection and identification.
•Inoculation: to culture microorganisms a tiny sample (inoculum) is introduced into medium (inoculation).
•Isolation involves the separating one species from another.
•Incubation: once the media is inoculated it is incubated which means putting the culture in a controlled environment (incubation) to allow for multiplication.
•After incubation the organisms are inspected and identified phenotypically, immunologically or genetically.
Phenotypic Methods of Identification
1-Direct microscopical method
Microscopic Morphology include a combination of cell shape, size, Gram stain special structures e.g. endospores, granule and capsule can be used to give an initial identification.
Magnification –enhancement of size using ocular and
objective lenses.•Ocular: eyepiece (10X)
•Objective: 4X – 100X –allows for visualization of bacteria.
Gram negative
Gram positive
Ziehl Nelsen stain
2-Culture and isolation of bacteria
A bacteriological culture is a method of multiplying the bacterial cell by letting them reproduce in predetermined culture media under controlled laboratory conditions.
2-Culture and isolation of bacteria
Media classifications and functions
Enrichment•used to enhance growth of specific organisms
Supportive•support growth of most non-fastidious organisms
Selective•contains agents that inhibit the growth of all agents except that
being sought (dyes, bile salts, alcohols, acids, antibiotics)Differential
•contains factor(s) that allow certain organisms to exhibit different metabolic characteristics
1-temperature2-moisture
3-pH4-gaseous requirement
5-light
Growth requirements
Blood agar
Enriched Media
Liquid nutritive broth
Enriched Media
Mannitol salt agar
Selective media
Differential media
MacConkey’s agar
Colony characteristics
–colony form: pinpoint, circular, filamentous, irregular
–colony elevation: flat, raised ,convex
–colony margin: smooth, irregular
Biochemical tests
Many bacteria secrete enzymes as lipases , proteinases and other hydrolytic enzymes .
The microbe is cultured in a media with a special substrate and tested for an end product.
Common Tests To identify Bacterial isolates
1-Indole2-Methyl Red/ Voges Proskauer
3-Citrate4-H2S production5-Urea hydrolysis
6-Motility7-Lactose fermentation8-Sucrose fermentation
9-Glucose fermentation and gas production
Serology Serology is the scientific study of serum. In practice, the term usually refers to the diagnostic identification of antibodies in the serum. Such antibodies are typically formed in response to an infection.
Types of Antigen and Antibody reactions
1.Agglutination tests 2.Double diffusion precipitation tests
3.Immunoelectrophoresis 4.Complement fixation tests
5.Immunofluorescence testing 6.Immunoassays
•Genotypic methods involve examining the genetic material of the organisms and has revolutionized
bacterial identification and classification .•Genotypic methods include PCR (RT-PCR, RAPD-
PCR),use of nucleic acid probes, RFLP and plasmid fingerprinting .
•Increasingly genotypic techniques are becoming the sole means of identifying many
microorganisms because of its speed and accuracy.
Genotypic Methods
The responsibility of the microbiology laboratory includes not only microbial detection and isolation but also the determination of microbial susceptibility to antimicrobial agents.