Medical Microbiology Flashcards
Give the difference defense mechanisms of the skin.
Mechanical
Chemical
Inflammatory cells
Normal Flora
What constitutes Skin Flora
Bacteria, Eukarya and Viruses
Give the different types of bacteria which are part of the skin flora
Cutibacterium acnes
Corynebacterium species
Streptococcus species
Micrococcus species
Coagulase-negative-staphylococcus
Give the different types of Eukarya
Malassezia species
Dermatophytes
Candida parasilosis
modes of infections?
i)Breach of intact skin
ii)Skin manifestation of systemic infections
iii)Damage of the skin by toxins
Virulence Factors of Staphylococcus aureus
State the different types of virulence factors and specify the factors and give biological activity of the factor.
Structural factors, divided into two
i) has a slime layer on the surface which facilitates adherence to foreign bodies, and inhibits phagocytosis
ii) Fibronectin binding protein- which binds to fibronectin on human cells( It is an adhesin which enables Staphylococcus aureus (S. aureus) to adhere to host cells of another organism, and an invasin facilitating its internalisation into these cells.)
TOXINS
divided into four types:
i) Cytotoxins- Lyses erythrocytes, leukocytes, macrophages, platelets
ii) Exfoliative toxin- Splits intercellular brigdes in epidermis
iii) Enterotoxins- Superantigen produces- Diarrhoea
iiii) Toxic shock syndrome toxin 01- Superantigen- produces toxic shock and multi organ failure
ENZYMES
i) Coagulase: Converts fibrinogen to fibrin
ii) Hydrolyses hyaluronic acid in connective tissue- promotes spread
iii) DNAse- Hydro lysis of DNA
Outline the infection of hair follicles, Sebaceous gland and Sweat Glands
Folliculitis(minor infection of the hair follicles) (S aureus)
Furencle(boil)- Small abscesses that develop in the region of a hair follicle. (S aureus)
Carbuncle(mulltiple boils/furencles) Abscesses involving more than one hair follicle.
Give the names of dermatophyte fungi,
Trichophyton, Microsporum and Epidermophyton species
Diagnosis for infection of keratinized layers
Skin scrapings sent to lab
* KOH preparation
* Hyphae or spores detected
* Culture
* PCR
Treatment for infection of keratinized layers
Oral terbinafine, fluconazole, itraconazole, griseofulvin
* Topical preparations for mild infections(medications applied directly to the skin)
* Oral anti-fungals for more extensive infectio
What is the treatment for impetigo
Topical antibiotic therapy (Mupirocin)
* If complicated, systemic manifestations or part of outbreak – treat with cloxacillin, amoxicillinclavulanate or cefuroxime
- Most common bacterial infection in kids
- Very contagious/ highly infectioius
- S. pyogenes is the main cause, followed by S. aureus
- Secondary skin infections of existing lesions may occur
- Can be bullous or non-bullous
- Diagnosis based on history and clinical findings
What are the treatment for erysipelas
Requires immediate treatment with penicillin or
erythromycin
Rapidly spreading infection of deeper layers of dermis
* Caused by S. pyogenes, sometimes groups B, C, or G
streptococci.
* Clinical – erythema, pain, fever, lymphadenopathy
* Complications – septicaemia or local necrosis of skin
What is the treatment of Cellulitis
Treatment
* Oral antibiotics: penicillin, cefuroxime, erythromycin
* IV antibiotics: penicillin G, flucloxacillin, cefazolin
* Elevate limb
- A diffuse, spreading infection/inflammation of the subcutaneous connective tissue
- Extends deeper than erysipelas
- May have marked constitutional signs and symptoms
- May be fatal if not treated correctly
- Often no history of a wound
- Sometimes an accidental wound or draining lesion is present
- Most commonly caused by S. aureus and S. pyogenes
What is the pathogenesis, Clinincal, Diagnosis and Treatment of Necrotizing Fasciitis
Pathogenesis
* Occlusion of blood vessels results in necrosis
Clinical
* Intense pain, area is red, hot, swollen
* Bullae, crepitus (from soft tissue gas) and gangrene may develop
* Spread to adjacent tissues
* Acutely ill, high fever, tachycardia, confusion, hypertension
* May develop Streptococcal toxic shock syndrome
Diagnosis
* History and clinical exam
* Raised white cell count, increased CRP, soft tissue gas on Xray, positive blood or tissue cultures
Treatment
* Surgical debridement and antibiotics
What is the treatment of F. Pyomyositis
- Treatment: – Surgical drainage – IV anti-staphylococcal antibiotics (cloxacillin, vancomycin)
Localized collection of pus in the muscle tissue – Staphylococcus aureus
* It is characterized by: – Muscle pain, fever, swelling, and “wood-like” induration
* Secondary to transient bacteraemia – Diabetic and immunocompromi
What is the treatment for Clostridial Myonecrosis(gas gangrene)
- Emergency surgical exploration and debridement
- Empirical antibiotic therapy with piperacillin– tazobactam
- Definitive treatment: penicillin and clindamycin.
- Life-threatening rapidly progressive infection of skeletal muscle, due to
Clostridia (primarily C. perfringens). - Develops either contiguously or by haematogenous spread.
- Anaerobic environment
- Initial muscle pain out of proportion to physical findings, tense muscle
swelling, crepitation, overlying skin discoloration, bullae and subsequent
systemic toxicity. - large, gram-variable bacilli at the site of injury.
- Notable absence of
Symptons of Scalded Skin Syndrome(SSSS)?
Fever and Lethargy
What is the treatment of Scalded Skin Syndrome?
antiseptic wound dressing, fluid support, antibiotic therapy
Caused by: Exfoliatin A or B
* Toxin is produced by S.aureus locally, passes through the body and localises at the
level of the stratum granulosum (specific cell membrane ganglioside GM4 – only
present in young children & certain adults) * Toxins act by direct effect on stratum granulosum of the keratinized epidermis * The toxin destroys intercellular connections and separates layers within the
epidermis. In severe cases, the whole skin separates leaving typical scalded
appearance
* Mucosa are never involved
Prognosis in children is good, adults have high mortality
What is the treatment for Toxic Shock Surgery
MANAGEMENT: * Antibiotics therapy narrowly targeting GAS is achieved wih penicillin +
clindamycin. Broader coverage may be warranted until streptococcal
infection has been confirmed. * Mortality: 20% - 45%
- Caused by the production of Staphylococcal exotoxins.
- These include a unique group of exotoxins that are referred to
as superantigens because of their ability to cause widespread
non-antigen specific activation of T-lymphocytes. - The activation produced by these superantigens results in rapid
release of cytokines by lymphocytes and macrophages. - First recognized in women
using highly absorptive
tampons - May be caused by S. aureus
infection from non-genital
sites - Involves multiple organ systems
- Characterized by:
- Fever
- Hypotension
- Diffuse macular
erythematous rash - After the rash there is
desquamation of skin (also
soles and palms) - Streptococcal Toxic Shock Syndrome
- A complication of invasive GAS disease characterized by shock and
multiorgan failure; it occurs because of capillary leak and tissue damage due
to release of inflammatory cytokines induced by streptococcal toxins. * Rash is less pronounced in STSS than TSS. * Blood culture may be positive.
MANAGEMENT: * Antibiotics therapy narrowly targeting GAS is achieved wih penicillin +
clindamycin. Broader coverage may be warranted until streptococcal
infection has been con
Antimicrobial Stewardship
The right antibiotic, for the right patient, at the right time, with the right dose, and the right route, causing the least harm to the patient and future patients.
What are the goals of antimicobial stewardship
Improving patient care
Reducing collateral damage- meaning in the short term there is less toxicity in the intermidiate term(weeks/months) it causes reduced antimicrobial use and in the long term(years) it causes less resistance.
Impacting costs- in the intermidiate term it results in less costs due to less collateral damage and in the long term it leads to antimicrobial savings.
What are the optional bacterial mobile elements of a bacteria.
Plasmids
Bacteriophages
Transposons
Give the three different types of horizontal gene transfer.
Conjugation
Transduction
Transformation
What causes intrinsic resistance
Due to genetic properties inherent in all members of specific species of bacteria
