16. Infectious Diseases Pathologies Flashcards
Infectious Pathologies
- A possible complication of an infection is sepsis (septicaemia), which occurs when the pathogen has infected the blood. It arises when the body’s response to the infection causes injury to the body’s own organs, potentially leading to multi-organ failure.
- The risk is higher in elderly populations (over 75), the very young (<1), alcoholics, diabetics, chemotherapy patients.
- Symptoms include lethargy, nausea, vomiting, abdominal pain, diarrhoea, coughing, etc.
Systemic Symptoms
•SYSTEMIC SYMPTOMS: –Fever (+ possibly chills). –Fatigue and weakness. –Headache. –Nausea.
Local Signs
–Pain and swelling.
–Redness.
–Warmth.
–Purulent exudate (bacterial).
Diagnostic Testing
- CULTURE / STAINING:
- BLOOD TESTS:
- STOOL TESTS.
- RADIOGRAPHY: (E.g. tuberculosis).
Culture /Staining
- Identification of micro-organisms.
* If required: Drug sensitivity test.
Blood Tests
- Bacterial infection: Often leukocytosis.
- Viral infection: Often leukopenia.
- High ‘erythrocyte sedimentation rate’ (ESR).
Cellulitis and Erysipelas
‘Cellulitis’ is a bacterial skin infection creating inflammation of dermal and subcutaneous layers.
‘Erysipelas’ is a more superficial bacterial skin infection of the dermis and upper subcutaneous layer, producing a well-defined edge.
•Both often co-exist, so it can be difficult to make a distinction between the two.
Cellulitis and Erysipelas: Cause
- Bacterial: Staphylococcus aureus, infections can enter the skin through minor trauma, eczema, IV drug abuse and ulcers.
- Can originate from streptococci bacteria in the subject’s own nasal passages (common in erysipelas — facial involvement).
Cellulitis and Erysipelas: Signs and Symptoms
- Very red, inflamed skin.
- Fever.
- Malaise.
Cellulitis and Erysipelas: Diagnosis
- Microbe analysis — can be difficult to detect.
* Usually diagnosed from clinical presentation.
Cellulitis and Erysipelas: Treatment
Antibiotics
Impetigo
Impetigo is a very contagious bacterial skin infection.
•Common in infants / young adults (poor hygiene / breaks in skin).
•Bacterial: Staphylococcus aureus or haemolytic streptococci.
Impetigo: Transmission
•Very contagious, spread by direct or indirect contact; e.g. towels.
Impetigo: Signs and Symptoms
- Pustules with round oozing patches and golden-yellow crusts that grow larger daily.
- Mostly affects exposed areas (hands and face) or in skin folds (particularly armpits).
Impetigo: Treatment
Antibiotics (e.g. flucloxacillin or erythromycin).
Oral Candidiasis
A superficial fungal yeast infection of mucous tissues.
Oral Candidiasis: Causes
•Mostly Candida albicans (less than 60% have candida in their
flora where it is commensal).
•Often presents after broad spectrum antibiotics or in immune compromised patients (normally skin / mucous membranes provide physical barrier with support of CD4 cells).
Oral Candidiasis: Signs and Symptoms
- White plaques.
* Can cause dysphagia and reduced appetite.
Oral Candidiasis: Complications
Can become systemic in severely immune-compromised patients (deposited on organs) ‘systemic candidiasis’.
Oral Candidiasis: Treatment
Antifungals (e.g. clotrimazole — topical or oral). These can significantly impact liver function and also damage the local skin or mucous membranes
Genital Candidiasis
A very common fungal infection (mycosis) of the genitals.
Genital Candidiasis: Triggers
- Not sex-related.
* Immune compromise, antibiotic treatment, diabetes mellitus, pregnancy, immune system disorders.
Genital Candidiasis: Signs and Symptoms
- Vaginal / genital itch, discomfort or irritation.
* Thick, clumpy discharge (‘cottage cheese’).
Genital Candidiasis: Yeast Infection
- Physical examination, fungal culture and analysis.
* Treatment as for oral candidiasis.
Lyme Disease
Lyme disease is caused by a bacterium called ‘borrelia’ which is often transmitted by tick bites.
•Different bacterial strains cause different clinical manifestations (hence differences between Europe and USA).
Lyme Disease: Signs and Symptoms
- A circular pink or red rash at the site of tick attachment that radiates from the bite, usually over 5 cm diameter.
- Flu-like symptoms. Can lead to neurological disease, cardiovascular disease and arthritis especially if untreated.
Lyme Disease: Treatment
Antibiotics
Diptheria
A highly contagious upper respiratory tract infection affecting primarily the nose and throat.
Diptheria: Cause
Bacterial: Corynebacterium diphtheriae (gram-positive), transmitted by droplets.
Diptheria: Signs and Symptoms
- Sore throat and fever.
- Grey membrane (necrosis) grows across the tonsils / pharynx or nose (impairs breathing).
- Enlarged cervical lymph nodes.
Diptheria: Diagnosis
Throat culture
Diptheria: Complications
•Exotoxins cause endothelial necrosis by inhibiting protein synthesis. Can cause myocarditis and paralyse diaphragm. The membrane can block the airways.
Diptheria: Treatment
• Medical emergency: Anti-toxins and antibiotics may be required; respirator.
• DPT vaccine introduced in 1941 (diphtheria /
tetanus / whooping cough / polio).
Scarlet Fever
An infectious disease resulting from exotoxins released by Streptococci pyogenes bacteria.
• Bacteria secrete haemolytic enzymes and exotoxins (damage capillaries which both cause red rash).
• It usually only occurs in children (90% <10yoa).
• Much less common and less serious than it once was. Full recovery is usual.
Scarlet Fever: Cause
•Bacterial: Streptococcus pyogenes (haemolytic streptococcus).
Scarlet Fever: Transmission and Incubation Period
Droplet transmission
3-4 days
Scarlet Fever: Signs and Symptoms
- Sore throat, fever, scarlet rash (blanches under pressure, unlike meningitis spots).
- Haemorrhagic spots on palate.
- First two days: white tongue with red papillae. After this, more raw / red.
Scarlet Fever: Treatment
Antibiotics (penicillin)
Cold Sores
Cold sores are caused by the herpes simplex virus (Type I).
•The virus remains dormant in the trigeminal nerve.
Cold Sores: Transmission
• Direct contact or indirect — saliva (viruses can be present in saliva for weeks after symptoms).
Cold Sores: Signs and Symptoms
- Commonly asymptomatic.
- Begins as tingling on lip as virus travels down nerve.
- Painful fluid lesions around mouth that scab then heal.
- Re-occurrence can be triggered by infection, stress, sun, etc.
Cold Sores: Complications
Spreading to the eyes
Cold Sores: Treatment
Acyclovir
Chicken Pox
Highly infectious viral disease, mostly in children (90%).
Chicken Pox: Cause
•Varicella zoster virus (part of herpes viral family).
Chicken Pox: Transmission and incubation time
- Droplets into upper respiratory tract mucosa and direct contact.
- Two–three weeks.
Chicken Pox: Signs and Symptoms
- Duration approx. two weeks: Prodromal fever and malaise.
- Vesicular eruptions on the skin appear over three–five days mostly on head / neck / trunk. Itchy.
- Infective two days before rash until all lesions at ‘crusting’.
Chicken Pox: Complications
- Infection because of scratching.
- Encephalitis.
- Viral pneumonia.
Chicken Pox: Treatment
None or acyclovir
Shingles
Infection by the Varicella zoster virus following chicken pox infection.
Shingles: Cause
- Varicella zoster virus — travels down infected nerve causing neuritis (nerve inflammation) in an immune-compromised individual.
- Commonly affects thoracic nerves or trigeminal nerve (head / face).
Shingles: Signs and Symptoms
- For one–two days before rash, burning / itching / tingling.
- Then ‘eruptive phase’, producing skin lesions similar to chicken pox, causing severe dermatomal pain, altered sensation and vesicular rash only in the affected dermatome.
Shingles: Treatment
Acyclovir
Whooping Cough
A bacterial infection with characteristic coughing attacks where there is a desperate attempt to breathe in, creating ‘whooping’.
Whooping Cough: Cause
Bordetella pertussis (bacterial).