Key Pathogens Flashcards
(11 cards)
What is Cellulitis?
Definition - Severe inflammation of dermal and subcutaneous layers of skin.
No growth seen in blood culture means that organism is not found in the circulating blood but still can be found in tissue.
Most commonly streptococcus and staphylococcus, enter through a crack or break in your skin.
Treated with flucloxacillin.
What is Neisseria meningitidis septicaemia?
Neisseria meningitidis septicaemia is commonly referred to as meningococcal septicaemia.
Rates of meningococcal disease are highest for young children and increase again for adolescents and young adults.
Neisseria meningitidis causes both meningitis and septicaemia. They can occur together or separately.
Septicaemia relates to the bacteria in the blood. Neisseria meningitidis in the blood triggers an intense host immune response.
• Fever: The patient will have a fever.
• Sepsis: The patient will have the features of ‘sepsis’ as outlined in the lecture and sepsis notes. Typical features will include reduced level of consciousness, tachycardia, low blood pressure, poor peripheral circulation, reduced urine output.
• Disseminated Intravascular Coagulation (DIC)
• Rash: Do all patients have a rash? This is present in many but not all patients (30 – 75%)
How is the rash described? The rash can take different forms as the illness develops. Petechiae: Initially it is discrete lesions 1 to 2 mm in diameter, most frequently on the trunk and lower portions of the body but also on mucosal membranes and sclera. These lesions are described as petechial. A petechial rash is commonly associated with a low platelet count and is a tiny bleed into the skin. Petechiae of meningococcaemia are usually larger and bluer than pinpoint petechiae caused by thrombocytopenia – reflecting the complex pathophysiology of DIC and meningococcal sepsis. Tumbler test: The rash does not blanch when pressure is applied. This is the basis of the tumbler test. This is the case for all petechial rashes.
Ecchymoses: The petechial lesions can coalesce and form larger lesions that appear ecchymotic. Ecchymoses (diameter >10 mm) are mainly noted in patients with severe DIC. These lesions are secondary to subcutaneous haemorrhage.
Necrosis: Necrosis is the death of tissue. In meningococcal sepsis, necrosis can occur affecting digits or limbs and may require amputation. Necrosis is due to the combination of vascular damage, lack of blood and oxygen (i.e. perfusion) to skin and the periphery, clots in small vessels and haemorrhage.
Management of Neisseria meningitidis septicaemia The management was covered in the lecture and follows the principles of sepsis management:
• Early recognition
• Early administration of antibiotics. The recommendation if Neisseria meningitidis is suspected is to give intravenous CEFTRIAXONE
• Urgent investigation
• Supportive care, often in an intensive care unit to manage organ dysfunction and DIC.
• Notify Public Health
• Prevention
What is meningitis?
Meningitis relates to the bacteria in the cerebrospinal fluid that surrounds the brain and spine. The bacteria attach to the meningeal lining and cause intense inflammation. This is responsible for the symptoms of meningitis that include headache, photophobia (difficulty looking at bright lights) and vomiting. Caused by Neisseria meningitidis or Gram negative diplococcus (both types of meningococcus) .
It is a commensal of the nasopharynx, gram-negative, an example of one of its virulence factors is lipopolysaccharide. Spread by aerosol. The recommendation if Neisseria meningitidis is suspected is to give intravenous CEFTRIAXONE. Can be vaccinated against and prophylaxis used for close contacts.
Give information on Streptococcus mutans
Gram-positive bacteria, normally found in mouth and nasopharynx. Can enter blood and colonise causing endocarditis.
Give information of Escherichia coli
Common in UTIs, peritonitis, neonatal meningitis.
It’s a commensal of the colon.
Gram negative rods.
Give Trimethoprim for UTI.
Produces shiga (a toxin) which causes symptoms.
Give information on Strep pyogenes
gram positive cocci chains.
group A, beta haemolytic.
common cause of pharyngitis/tonsillitis.
Virulence factors:
Hyaluronic acid capsule makes it poor immunogen and seem like self.
M-protein (hijacks respiratory burst mechanism of neutrophils).
Streptokinase (breaks down blood clots.)
Treat with penicillin V
Give information on Strep pneumoniae
gram positive bacteria found normally in respiratory tract and in the mucosal layer of the pharynx. transmitted by respiratory droplets. can cause infection by attaching to surface adhesions of epithelial cells. Pneumococcal pneumonia is the most common clinical presentation of pneumococcal disease among adults. Pneumonia without bacteraemia or empyema is not considered to be “invasive” disease. The incubation period of pneumococcal pneumonia is short, about 1 to 3 days. Symptoms generally include an abrupt onset of fever and chills or rigors. Typically, there is a single rigor, and repeated shaking chills are uncommon. Other common symptoms include Pleuritic chest pain Cough productive of mucopurulent Rusty sputum Dyspnoea Tachypnoea or tachycardia Hypoxia Malaise or weakness Nausea, vomiting, and headaches occur less frequently.
Give information on Cadida albicans
Gram positive bacteria normally found in the mouth, intestines and skin but can overgrow and cause genital yeast infection. Can cause vaginal thrush when patient’s normal flora is depleted by antibiotic treatment. Can also cause thrush in back of mouth which can be an aids defining illness. Opportunistic infection.
Give information on the adeno virus
Adenoviruses are nonenveloped, icosahedral viruses containing double-stranded linear DNA . They commonly cause diseases such as respiratory tract infections, gastroenteritis, and conjunctivitis.
No antiviral agents available.
Generally causes symptoms in the ae of transmission e.g. if inhaled causes respiratory infection.
most adenoviruses also replicate efficiently and asymptomatically in the intestine, and can be isolated from stool well after respiratory disease symptoms have ended as well as from the stools of healthy persons.
Adenoviruses all replicate well in epithelial cells. The observed disease symptoms are related primarily to the killing of these cells, and systemic infections are rare.
Give information on Staphylococcus aureus
Gram positive cocci that form clusters. Can cause cellulitis.
Virulence factors:
protein A is a major component of the staph aureus cell wall. It binds to IgG exerting an anti-opsonin and therefore an antiphagocytic effect.
Normal commensal of the skin. Can form skin abscesses, Treated with vancomycin for MRSA or flucloxacillin for cellulitis.
What is Staph Epidermis
Most common bacteria found on the skin.
Can cause cellulitis and so treat with flucloxacillin.
gram positive cocci that form in clusters
very difficult to remove as it creates biofilms.
exhibits quorum sensing and forms slime
can cause infections with prosthetic devices and must be removed as a result.
