staphylococci and micrococci - ksu...
TRANSCRIPT
![Page 1: Staphylococci and Micrococci - KSU Facultyfac.ksu.edu.sa/sites/default/files/lec_3_staphylococci_and_micrococci.pdf · •Gram stain observation •Inoculation of media Culture •Pure](https://reader033.vdocuments.mx/reader033/viewer/2022041622/5e3f78171462786c7610e26a/html5/thumbnails/1.jpg)
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Micrococci
• Micrococcus genus
• Gram positive cocci
• Related diseases: – Pulmonary infections
– recurrent bacteremia
– septic shock
– septic arthritis
– Endocarditis
– Meningitis
– pneumonia
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Steps in laboratory diagnosis of bacterial infection
Specimen processing
• Macroscopic examination
• Gram stain observation
• Inoculation of media
Culture
• Pure culture of the suspected pathogen
Biochemical tests
• Perform tests necessary to identify suspected pathogen
Antibacterial susceptibility
tests
• Examine the related antibacterial drugs
Report
• Report findings to clinician
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Identification of Micrococci:
• Gram Stain 1. Gram positive cocci
2. Characteristically in tetrads
• Colony morphology 1. Micrococcus luteus= yellow pigment
2. Micrococcus roseus= pink pigment
• Biochemical tests 1. Catalase positive
2. Oxidase positive
• Susceptibility tests 1. Bacitracin sensitive
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Introduction
• Staphylococcus genus
• Groups:
A. Coagulase-positive
B. Coagulase-negative
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The structure
• Gram positive cocci
• Cell division occurs in different planes
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The physiology
• Salt-tolerant:
• Tolerate to desiccation:
• A major human pathogen
– 60% intermittently colonised
– 20% persistent
– 20% Never
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A. Staphylococcus aureus
• Reservoir –
• Carriage sites –
• Colonizers
– MRSA
– MSSA
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Modes of transmission
• Endogenous
• Exogenous
• Sources of infection
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Factors predisposing to S. aureus infections
Host factors Pathogen factors
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Virulence factors and pathogenesis
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The diseases and the clinical presentation
Pyogenic infections Toxin-mediated infections
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Pyogenic infections
A. Skin lesions
B. Deep abscesses
C. Systemic infections – With obvious focus
– No obvious focus
– Assoc. with predisposing factors
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Toxin-mediated infections
A. Staphylococcal food poisoning
B. Scalded skin syndrome (SSS)
C. Toxic shock syndrome (TSS)
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Laboratory diagnosis
1. Specimen
2. Processing of specimens:
3. Identification of S. aureus:
– Gram stain
– Catalase test
– Coagulase test
– DNAse test
– Oxidase test
4. Rapid identification:
5. Susceptibility tests
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Laboratory diagnosis
Microdase (Modified Oxidase) Test
1. Staphylococcus species
2. Micrococcus species
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Staphylococcus aureus Resistant Sensitive
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Treatment
• Drain infected area
• Antibiotic treatment
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Antibiotic resistance
• Mechanisms
• Historical progression of antibiotic resistance of S. aureus
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MRSA
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Prevention and control
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Coagulase-negative Stapylococci
Staphylococcus epidermidis
Staphylococcus saprophyticus
• Opportunistic pathogens