01_bakteri Yang Penting Dlm Medis

7/28/2019 01_bakteri Yang Penting Dlm Medis

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Bacteria of Medical

Importance

Foundation Course

Prof V. O. Rotimi


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Objectives

At the end of this lecture the students should

be able to:

Recall the characteristics of a bacteriumGrasp the basis of classification of

bacteria of medical importance

Name important bacteria of clinicalimportance

Give examples of the infection they cause

Understand the basis of lab investigation


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General characteristics

Single cell prokaryotes

DNA forms a long circular molecule, notcontained in a defined nucleus

May or may not be motile or encapsulatedContains a complex cell wall

Reproduce by binary fission

Wide range of metabolic patterns, aerobic andanaerobic

Uses phenotypic and genotypic data forclassification


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Classification

Distinguished by morphology and staining

reaction

Gram stain separates most bacteria into 2

great divisions:

Gram-positive bacteria

Gram-negative bacteria


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Classification

Main structural component of cell wall is

PEPTIDOGLYCAN(mucopeptide or murein)

Gram-positive

Peptidoglycan is a thick layer external to the cellmembrane

Gram-negative

Peptidoglycan is thin and covered by an outer

membrane (OM)

Molecules of OM lipopolysaccharide & lipoprotein


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True bacteria

Classified on the basis of shape:

Cocci spherical

Bacilli relatively straight, rod-shaped

Vibrios curved rods

Spirochaetes - twisted filamentous rod-shaped


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Gram-stained bacteria

Gram-positive cocci Clusters

Chains

Pairs

Gram-positive bacilli (rods) Short, long, branched, twisted

Gram-negative cocci

Gram-negative bacilli


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Metabolic classification

Aerobes

Utilizes oxygen for respiration

Facultative aerobes

Survives with or without O2

Anaerobes

Cannot survive in the presence of O2


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Aerobic Gram-positive cocci

S. pneumoniae

Viridans streptococci

Pneumonia, meningitis,

septicemia, septic shock,

acute otitis media

Infective endocarditis

(IE), abscesses, dental

caries


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Gram-positive cocciAnaerobic

Peptostreptococcus

(anaerobic cocci)

Peptococcus

Lower respiratory

tract infections

Female genitaltract infections

Post-operative

wound infections

Brain abscess


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Aerobic Gram-positive bacilli

Listeria

L. monocytogenes

Mycobacterium M. tuberculosis

MOTT

Neonatal sepsis,meningitis

Tuberculosis (atypicalpneumonia), spinalosteomyelitis, brainabscess

Atypical pneumonia inimmunocompromized pts


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Aerobic Gram-negative bacilli

Enterobacteriaceae

E. coli

Klebsiella spp.

Enterobacter/Citrobacter spp

UTI, septicemia/septicshock, meningitis,

wound infection,diarrhea

UTI, pneumonia,

septic shockUTI, septicemia/septicshock


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Brucella spp.

B. melitensis

B. abortus

Neisseria spp.

N. gonorrheae

N. meningitidis

Brucellosis Goats milk & cheese

Cows milk & cheese

Gonorrhoea

Meningitis


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Helicobacter

H. pylori

Campylobacter spp

C. jejuni

C. coli

Non-dyspesia

gastritis, duodenal

and gastric ulcers,cancer

Gastroenteritis


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Vibrios

V. cholerae

V. parahemolyticus

Legionella spp

L. pneumophila

Cholera

Food-poisoning

Legionnaires disease

(atypical pneumonia)


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Other Gram-negative bacteria -

Spirochetes

Treponema spp T. pallidum

T. pertenue

Borrelia spp. B. recurrentis

B. duttoni

B. burgdorferi

Leptospira spp.

Syphilis

Yaws

Epidemic relapsing fever

Endemic relapsing fever

Lyme disease

Leptospirosis


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Anaerobes

Cannot tolerate molecular oxygen

Lack superoxide dismutase

Requires low redox potential (Eh)

Measured in mV (-75 to -450 mV)

Resistant to aminoglycosides

Majority are sensitive to metronidazole


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Anaerobic Gram-positive bacilli

Spore-forming:

Clostridium tetani

Cl. perfringens

Cl. difficile

Cl. botulinum

Tetanus

Food-poisoning, gas

gangrene, septic abortionCDAD: Antibiotic-

associated diarrhoea,

Antibiotic-associated

colitis,

Pseudomembranous

colitis

Botulism food-poisoning


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Anaerobic Gram-positive bacilli

Non-sporing:

Actinomyces

A. israelii

Propionibacterium

P. acnes

Actinomycosis: cervico-

facial, thoracic,

abdominal, cutaneous.

Acute/chronic prosthesesinfection, prostatitis, acne


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Laboratory diagnosis

Specimens

Collection

Transportation

Processing Gram-stain, ZN stain

Culture non-selective and selective media

Non-cultural techniques

Serology EIA, ELISA, Immunofluorescence

Molecular, e.g. PCR


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