1.2 Diseases Flashcards
What types of tissues are affected by bacterial infections in SSTIs?
skin, muscles, and connective tissues such as ligaments and tendons
What percentage of hospitalized patients are affected by SSTIs?
approx 7% to 10%
Why are SSTIs particularly common in the emergency care setting?
rapid onset and potential severity , requiring immediate medical attention
Describe the two-step process involved in the clinical manifestations of SSTIs.
- Invasion of bacteria into the tissues.
- Interaction of the bacteria with the host’s defenses, leading to symptoms and clinical signs.
What is the range of severity for SSTIs?
mild infections to serious life-threatening infections such as necrotising fasciitis
What’s the principle barrier against invasion & a portal of entry for pathogens ?
the skin
What inhibits growth of pathogens in skin ?
low pH, sebum, fatty acids
What deters pathogenic organisms in humans = the own natural….. ?
flora
What is the most common route of infection of the skin ? give 6 examples
break in the barrier of the skin
* skin conditions
* wounds
* burns
* surgery
* needles
* bites
Development of an SSTI depends on 3 steps which are what ?
- bacterial adherence to host cells
- invasion of tissue with evasion of host defences
- elaboration of toxins
Virulence factors such as exotoxins can cause what ?
- pore formation
- enzymatic reactions
- tissue damage
Staphylococcus aureus bacteria features ?
Gram positive & opportunistic
Staphylococcus aureus notorious for causing ?
Skin and soft tissue infections
Examples of skin and soft tissue infections caused by staph A
- cellulitis
- osteomyelitis
- mastitis
- folliculitis
- impetigo
Virulence factors of S. aureus ?
ACE
- Adherence factors (adhesins)
- exotoxins and enxymes
- Coagulase
Adhesins (adherence factors) allows S. aurues to do what ?
attach onto the host cell surface
S. aureus virulence factor Exotoxins and enzymes are ….1…. they can spread the organism during …2..
- cytolytic, exofoliative
- infection and deep invasion
Coagulase as a virulence factor for S. aureus does what ?
prevents phagocytosis from the immune system by forming a clot around the bacteria
Conditions caused by S.aureus list them
- staphylococcal scalded skin syndrome
- staphylococcal toxic shock syndrome
- Osteomylitis
- Mastitis
- Folliculitis
Action of enzymes in staphylococcal scalded skin syndrome ?
protease enzymes break down proteins in the skin
SSSS affects age ?
children under 5 yrs
SSSS presentation
BP LIFE / BE FLIP
Bullae (fluid filled blisters)
Erythema on skin
Fever
Lethargy
Irritability
Positive nikolsky sign (sign of blistering skin , where top layer sheers off)
How can generlaised staphylococcal scalded skin syndrome in immunodefiicent states happen ?
exfoliative toxin in patients with bullous impetigo may disseminate
Rupture of bullae can lead to what ?
rapid desquamation with impairment of thermo-regulation , and fluids and electrolyte balance
Mortality in children with SSSS is 4% despite what ?
- fluids
- correction of electrolyte imbalances
- antibiotics
STSS (staphylococcal toxic shock syndrome) is an …1… illness where toxins produced by …2… activate …3… resulting in …4.. of cytokines and …5… cells
- acute onset
- S. aureus
- T-lymphocytes
- over-activation
- inflammatory
STSS is most often seen in ?
- use of tampons
- post-surgical infections
- burns
- post partum vaginal and caesarean wound infections
Presentation of STSS ?
RM N V RMHH
- Rapid onset fever
- Multi-organ failure
- Nausea
- Vomiting
- Rash
- Myalgia
- Headache
- Hypotension
Multi-organ failure is a presenation of STSS what does this involve ?
- renal impairment
- acute respiratory distress
- soft tissue necrosis
- liver involvement
- coagulopathy
Risk factors for TSS ?
- diabetes mellitus
- alcoholism
- vaginal , caesarean deliveries
- single tampon use for several days of the menses cycle
Management for S.aureus infection in TSS ….1… plus ..2… is recommended ?
- clindamycin
- oxacillin
What is recommended as first-line therapy for patients with complicated soft tissue infections (MRSA identified or penicillin allergy) ?
vancomycin
Apart from antibiotics like clindamycin , oxacillin , vancomycin what else should be considered for the management of S. aureus infections ?
- surgical debridement
- supportive therapy
Difference between S. aureus and other staphylococcal species in what they can be referred to as ?
S.aureus - coagulase positive
others - coagulase negative (grape like cluster, gram positive)
Where are coagulase-negative staphylococci (CoNS) primarily found on ?
- skin and mucous membranes
- scalp
- ears
- axilla
CoNS can form biofilm -
1. which is what ?
2. e.g. where ?
- adherence to medical device
- vascular catheter infection , prosthetic valve endocarditis, device-related bone and joint infection, foreign body related bloodstream infection
Can the presence of Coagulase-negative Staphylococci (CoNS) always indicate an infection?
No,
They can be commensals or contaminants.
Who are more at risk of infections caused by Coagulase-negative Staphylococci (CoNS)?
Immunocompromised individuals and preterm babies
Infective endocarditis is an infection involving what ?
endocardial of the heart
Bacteria causing endocarditis / infective endocarditis ?
- streptococcus viridans (found in mouth causes dental caries)
- S. aureus CoNS
Risk factors of endocarditis ?
- heart disease
- congenital heart defect
- valve replacement or pacemaker
- IV drug use
- vascular access e.g. central venous catheter
Endocarditis presentation ?
My Cat was fat know has fever is SoB and lost weight
Myalgia, Fatigue, Weight loss
Cardia murmur
Fever
Shortness of breath
Explain why the ‘normal’ heart is relatively resistant to infection
- bacteria + fungi don’t easily adhere to the endocardial surface
- constant blood flow helps prevent them from settling on endocardial structures
What 2 factors are typically required for endocarditis ?
- predisposing abnormality of the endocardium
- microorganisms in the bloodstream (bacteraemia)
What cause endocarditis on normal valves ?
massive bacteraemia or particularly virulent microorganisms (e.g. staph A)
How do microorganisms adhere to the endocardial surface?
by attaching to abnormal or damaged endothelium via surface adhesions.
What happens after microorganisms adhere to the endocardial surface?
hey proliferate, leading to the colonization of the endocardial structures
Why should blood cultures be taken before starting empirical antibiotic therapy in suspected endocarditis?
prior antibiotic treatment can lead to culture-negative endocarditis, making it difficult to identify the causative organism.
What is a common cause of culture-negative endocarditis?
antibiotic therapy administered before blood cultures are taken
Why is it important to identify the causative organism in endocarditis?
it guides the selection of appropriate antibiotic therapy, ensuring effective treatment of the infection
How does Staphylococcus aureus endocarditis typically progress
it is often rapidly progressive, meaning it advances quickly and aggressively
What is the mortality rate associated with Staphylococcus aureus endocarditis infections?
greater than 45%
Streptococcys pyogenes :
bacteria staining , usually what ?
gram positive
pathogenic
What aids in identification of S. pyogenes ?
Lancefield group A antigen on it’s surface
Why is streptococcus pyogenes often referred to as Group A streptococcus ?
Presence of Lancefield group A antigen on surface
Examples of conditions caused by streptococcus pyogenes ?
- Cellulitis
- Impetigo
- Toxic Shock syndrome
- Pharyngitis
- Rheumatic fever
Virulence factors of S. pyogenes ?
- Streptolysins & haemolysins
- superantigens
- hyaluonidase
- streptokinases
- M protein
Action of streptolysisns & haemolysis
Action of sueprantigens
Action of hyaluronidase
Action of streptokinases
Action of M protein
Scarlet fever most commonly infects what people and age group ?
children between 5-15 years old
What induces inflammation in scarlet fever and are pyrogenic ?
exotoxins and superantigens
Scarlet fever presentation ?
a FEW Mischevious StrawberriesS
Fever
Enlarged lymph nodes
Widespread rash
malaise
Sore throat
Strawberry tongue
Diagnosis of scarlet fever ?
usually clinically due to rash , fever, sore throat
management of scarlet fever ?
- treating GAS infection to prevent rheumatic fever, sepsis
- typically self-resolving
- oral phenoxymethylpenicillin
- supportive care, analgesics, antipyretics
Impetigo is a ..1.. infection of the …2… caused by either …3…
- bacterial
- superficial skin
- Staph aureus or Strep pyogenes
Risk factors for impetigo ?
- diabetes
- compromised skin barrier e.g. eczema
Impetigo presentation ?
PRY
Pus or fluid
Red, itchy sores
Yellow scabs
Cellulitis is an infection of where ?
deep dermis and subcutaneous tissue
Most causative bacteria of cellulitis are?
Strep pyogenes
Staph aureus
Infections of cellulitis can occur when what happens ?
bacteria breach skin surface, where there is fragile skin or decreased local host defences e.g. diabetes, eczema, oedema, obestiy
Presentation of cellulitis ?
FOAM
Fever
Orange-peel appearance
Acute onset of red, painful, hot , swollen skin
Malaise
Treatment of S. pyogenes infections ?
recommend combination therapy with benzylpenicillin plus clindamycin
In patients who are allergic to penicillin what may be used in place of benzylpenicilln ?
vancomycin
Appart from antibioitcs what is included in treatment of S. pyogenes infections ?
ICU support e.g. fluid resuscitation , surgical debridement
Candida albicans ….
