Infectious conditions Flashcards
What is an abscess?
Collection of pus built up within tissue over time, associated with Bacteria
What causes an abscess?
Most common sites: Axillae, Anus, Vagina (Bartholin’s abscess), pilonidal and tooth (dental) and groin
Incisional abscesses occur secondary to surgical incision
Caused by obstruction of sebaceous glands or sweat glands, or inflammation of hair follicles, or through minor skin breaks
Caused by bacteria - usually MRSA
What are the Risk Factors for Abscesses?
Immunocompromised i.e. steroid use, AIDS, IV drug use
What are the signs and symptoms for abscesses?
Tender, soft swelling filled with pus
Warm to touch
Surrounded by erythema
May have fever and rigors
What investigations are done for Abscess?
Usually clinical
Can use Ultrasound scan
How do you manage abscesses?
Drain pus from the abscess
- Skin: Cut top of skin and allows pus to drain w/ local anaesthetics, if deep put a small piece of gauze
- In the body: Prescribe Abx
What are the complications of abscesses?
Skin abscesses would normally burst on to skin and let out pus after enlarging and becoming more painful
If in body, very serious
What is Behcet’s disease?
Systemic vasculitis, most commonly seen in Turkey and israel.
Causes skin and mucosal lesions, uveitis, major arterial and venous vessel disease, and GI and Neurological manifestations
What causes Behcet’s disease?
Unknown cause
Associated with HLA-B51
Small vessel ANCA negative vasculitis
What are the Risk factors for Behcet’s disease?
Age 20-40 years
Family history
Genetic predisposition
What are the signs and symptoms of Behcet’s disease?
Tiredness Malaise Muscle pains Transient fevers Headaches Oral ulceration Genital ulceration Eye disease Uveitis Arthritis Vasculitis Myo/pericarditis CNS symptoms Colitis Skin lesions (e.g. Erythema nodosum)
What is the classic triad of Behcet’s disease?
Oral ulceration
Genital ulceration
Eye disease
What are the investigations for Behcet’s disease?
Pathergy testing - SC skin prick performed using a 21-gauge needle & observed formation of a papule / pustule 48 hrs later (positive in 60%)
Rheumatoid factor - Negative
ANA - Negative
Anti-neutralising cytoplasmic ABs - negative
What is Encephalitis?
Inflammation of brain parenchyma associated with neurological dysfunction such as: altered state of consciousness, seizures, personality changes, cranial nerve palsies, speech problems and motor and sensory deficits.
What are the viral causes of encephalitis?
Herpes simplex virus, EBV, VZV Enteroviruses (Enterovirus-71, coxsackievirus, poliovirus) Parechovirus Flavivirus Bunyavirus Togavirus Paramyxovirus Others: Mumps, HIV, Rabies, Measles, Adenovirus, Hep C, Rotavirus, Parvovirus B19
What are the non-viral causes of encephalitis?
Bacterial meningitis TB Malaria Listeria Lyme disease Legionella Leptospirosis Aspergillosis Cryptococcus Schistosomiasis Typhus
What are the signs and symptoms for encephalitis?
Bizarre encephalopathic behaviour Decreased GCS or Coma Fever Headache Focal neurological signs Seizures History of travel / animal bite
What are the investigations for Encephalitis?
Culture
Serum for viral PCR
Toxoplasma IgM tire
Malaria film
Contrast-enhanced CT (B/L temporal lobe involvement suggests HSV encephalitis.)
Lumbar puncture (Raised CSF protein and lymphocytes, and decreased glucose)
EEG (diffuse abnormalities confirm diagnosis)
What is HIV?
Infection with the human immunodeficiency virus
What causes HIV?
Infects and replicates primarily in human CD4+ T cells and macrophages
Reverse transcriptase incorporates HIV genetic material into host genome
Leads to dissemination of HIB, cell death adn eventually T cell depletion
How is HIV transmitted?
Sexual intercourse Bodily fluids (Blood transfusion/organ transplantation) Vertical transmission Breast milk Needles
What are the Risk factors for HIV?
IV drug users Unprotected intercourse Percutaneous needle stick injury High maternal viral load HSV-2 infection
What are the 3 phases of HIV?
Seroconversion (Self-limiting)
Early/asymptomatic
AIDS
What are the signs and symptoms of seroconversion?
Fever Night sweats Generalised lymphadenopathy Sore throat Oral ulcers Rash Myalgia Headache Encephalitis Diarrhoea
What are the signs and symptoms of Early/asymptomatic disease?
Apparently well with progression of symptoms from serconversion
What are the signs and symptoms of AIDS?
Syndrome of secondary diseases due to immunodeficiency?
What are the AIDS defining conditions?
PCP Kaposi's sarcoma Oesophageal candidiasis Salmonella septicaemia Burkitt's lymphoma Immunoblastic lymphoma Primary brain lymphoma
What investigations are done for HIV?
Serum ELISA (positive) Serum HIV rapid test (Positive) HIV non-invasive tests (Positive) Serum western blot Serum HIV DNA PCR Serum p24 antigen Serum viral load Drug resistance Investigations for AIDS defining conditions
What is infectious mononucleosis?
Known as glandular fever
Clinical syndrome most commonly caused by EBV
Other causes a lot less common. Called mononucleosis syndrome when non-EBV pathology
What causes infectious mononucleosis?
EBV aka Human Herpes virus 4 - 80-90% of IM cases
Mononucleosis syndrome may be caused by: Herpes virus 6, CMV, HSV-1 and rarely strep
Pyogenes, toxoplasma gondii, HIV-1, adenovirus
May be caused by a connective tissue disorders, malignancy and drug reactions
What are the symptoms of infectious mononucleosis?
Malaise Fever Rash Yellowing of skin Muscle pains
What are the signs of infectious mononucleosis?
Splenomegaly
Hepatomegaly
Cervical or generalised lymphadenopathy
Pharyngitis
What are the investigations for Infectious mononucleosis?
FBC (lymphocytosis, atypical lymphocytes)
Heterophile antibodies (Positive) but is non-specific
EBV-specified antibodies (positive for: VCA-IgM, VCA-IgG, EA, EBV, EBNA)
Real-time PCR
Throat swabs
CT of abdomen
Ultrasonography of abdomen (splenomegaly)
What is the management for infectious mononucleosis?
-All patients:
Supportive care (paracetamol or ibuprofen)
- With upper airway obstruction or haemolytic anamia:
Corticosteroid (prednisolone)
- With thrombocytopenia:
Corticosteroids or IV immunoglobulin (prednisolone or methylprednisolone or dexamethasone or normal immunoglobulin human)
What are the complications of Infectious mononucleosis?
Antibiotic induced rash Splenic rupture Neurological complication Chronic active EBV infection AI diseases, non-haematological Malignancy Fatigue Acute acalculous cholecystitis Renal complications
What is malaria?
Infection with plasmodium protozoan
5 types of plasmodium
Transmitted by an infected female anopheles mosquito but may be transmitted by blood transfusion of organ transplantation
What are the 5 types of plasmodium?
Mosquitos Know Our Vital Fear Plasmodium Malariae Plasmodium Knowlesi Plasmodium Ovale Plasmodium Vivax Plasmodium Falciparum (most serious)
What causes malaria?
Protozoa grow in red cells
Gametocytes taken up when another mosquito feeds, an develops into sporozites in the gut of the mosquito
Then move to salivary gland to be transmitted next bite
What is the life cycle of malarian protozoa?
Injection of sporozites into blood stream by mosquito
Invasion and replication in hepatocytes to form merozites
Released into blood and enters RBCs
Replicate in RBCs and develop ring forms, and then trophozites
RBC’s rupture and release merozites, which reinfects other RBC’s
Trophozites form merozites and gametocytes
Which populations have immunity to malaria?
Sickle cell trait/disease
G6PD deficiency
Pyruvate kinase deficiency
Thalassemia
What are the Risk factors for malaria?
Low socioeconomic status Travel/live in endemic area Immunocompromised Pregnancy <5 or old age
What are the symptoms of malaria?
Can be up to 1 year Cyclical symptoms: High fever Flu-like symptoms Severe sweating Shivering cold/rigors Cerebral symptoms: Headache Disorientation Coma
What are the signs of malaria?
Pyrexia
Anaemia (Haemolytic)
Jaundice
Hepatosplenomegaly
What are the investigations for malaria?
Giemsa thick and thin blood smears - Thick (Parasitaemia) - Thin (Type of parasite) FBC (thrombocytopenia, anaemia) U&Es (Impaired renal funciton) LFTs (Slightly raised) ABG (Acidosis in severe disease) Urinalysis (Slightly raised proteins)
What is Meningitis?
Inflammation of leptomeninges and underlying subarachnoid cerebrospinal fluid.
Inflammation may be caused by infection with viruses, bacteria, other micro-organisms or non-infective causes.
Viral meningitis more common and more benign than bacterial.
What causes viral meningitis?
Human enterovirus most common cause 5 subgenres (Coxsackieviruses, echoviruses, polioviruses, herpes, mumps)
What causes bacterial meningitis?
Haemophilus influenzae B (was most common)
Streptococcus pneumoniae (18%)
Neisseria meningitides (14%)
HiB only children, rest in both!
Listeria monocytogenes in immunocompromised patients
In neonates, E.coli and Streptococcus agalactiae common causes
What are the less common causes of meningitis?
Fungal: Cryptococcus (AIDS defining disease)
Other:
Aseptic meningitis
Mollaret’s meningitis (recurrent benign lymphocytic meningitis)
What are the risk factors for viral meningitis?
Infant and younger children Young adults Older people Summer and autumn Exposure to mosquito or tick vector Unvaccinated for mumps Use of swimming pools and ponds Immunosuppression Exposure to rodents
What are the risk factors for bacterial meningitis?
=5 or 65= Crowding Exposure to pathogens Non-immunised infants Immunodeficiency Cancer Asplenia/hyposplenic state Cranial anatomical defects Cochlear implants Contiguous infectoin
What are the early symptoms of meningitis?
Severe headache
Leg pain
Cold hands and feet
Abnormal skin
What are the later symptoms of meningitis?
Neck stiffness Photophobia Kernig's sign Fever Irritability/altered mental state Reduced consciousness Vomiting Children: High pitched crying/fits, Hypothermia, irritability, poor feeding Petechial rash - non-blanching
What are the signs of meningism?
Photophobia Neck stiffness Kernig's sign Brudzinski's sign Pyrexia Tachycardia Hypotension Skin Rash Altered mental state
What is Kernig’s sign?
Hip and knee at 90 degree angle, further extension of knee has resistance
What is Brudzinski’s sign?
Flexion of hips and knees when neck is flexed hurts
When thinking of meningism, a detailed history is needed.
What do you need to take note of exposure for? And what organism causes meningism?
Rodents (Lymphocytic choriomeningitis virus)
Ticks (Lyme borrelia, rocky mountain spotted fever)
Mosquitos (West nile virus)
Sexual activity (HSV-2, HIV, syphilis)
Travel
What investigations are done for Viral meningitis?
LP: CSF microscopy (Raised WBC) CSF Gram stain (Negative) CSF Bacterial culture (Negative) CSF protein (Normal or raised) CSF glucose (May be low) CT/MRI head (unremarkable)
What investigations are done for bacterial meningitis?
CSF cell count and differential (polymorphonuclear pleocytosis)
CSF protein (Raised)
CSF glucose (Low)
CSF gram stain (positive)
CSF culture (Specific bacteria)
FBC and differentials (Leukocytosis, anaemia, thrombocytopenia)
CRP (High)
What is the management of viral meningitis?
Initially antibiotics + Dexamethasone IV
Confirmed viral agent:
- Other than HSV, Varicella zoster or CMV: Supportive care
- HSV or Varicella zoster: Acyclovir > Foscarnet
- CMV: Ganciclovir > Foscarnet
Recurrent:
Recurrent benign lymphocytic meningitis (mollaret meningitis) most commonly caused by HSV-2
What is the initial management for bacterial meningitis?
Immunocompetent:
= 1month old: Empirical ABx (ampicillin & Cefotaxime) + supportive therapy
>1month or <50:
Vancomycin and ceftriaxone + supportive + dexamethasone
>/=50:
Ampicillin & Vancomycin and ceftriaxone) with supportive therapy
What is the management for Bacterial meningitis?
Antibiotics per causative organism + supportive therapy + Dexamethasone (if >1 month of age)
What are the complications of meningitis?
Septicaemia Shock DIC Renal failure Seizues Peripheral gangrene Cerebral oedema Cranial nerve lesions Cerebral venous thrombosis Hydrocephalus Waterhouse-friderichsen syndrome
What is Necrotising fasciitis?
Life-threatening subcutaneous soft-tissue infection that may extend to the deep fascia, but not underlying muscle tissue.
Aerobic, anaerobic or mixed floral causative organisms
What are the 2 types of necrotising fasciitis?
Type 1: Polymicrobial infection with an anaerobe e.g. bacteroides or peptostreptococcus and a facultative anaerobe e.g. enterobacteriaceae or non-group A streptococcus
Type 2: Monomicrobial infection with streptococcus pyogenes or more rarely: Aeromonas hydrophilia (fresh water expoure), vibrio vulnificus (salt water exposure)
What are the risk factors for necrotising fasciitis?
Inpatient contact with index case Varicella zoster infection Cutaneous injury, surgery, trauma Non-traumatic skin lesions IV drug use Chronic illness Immunosuppresson NSAID use Varicella zoster infection in children Alcohol abuse, chronic liver or renal disease, diabetes
What are the signs and symptoms of Necrotising fasciitis?
Typically over a few days but can progress more rapidly in some cases e.g. Vibrio spp. and A. Hydrophila can be fatal in 48
Changes day to day! Overall: Anaesthesia / severe pain Fever Palpitations Nausea and vomiting Delirium Crepitus Vesciles or bullae Grey discolouration of skin Oedema or induration Location of lesion
How do the signs and symptoms present in the first 2 days?
Local pain, swelling and erythema - mimics cellulitis or erysipelas - necrotising depp and not visible
Severe constant pain, out of proportion
Margins poorly defined, tender beyond visible area. No Abx respons
Lymphangitis rarely seen
Systemic illness - malaise, tachycardia +/- fever and dehydration - WORST theyve felt
What are the signs and symptoms day 2-4?
Tense oedema extending beyond erythema
Bullae, indicating skin ischaemia
Discoloured, progress to grey necrosed skin which breaks down
SC tissues have wooden-hard feel. Fascial planes and muscles not palpable
Crepitus due to gas
Goes from intense tenderness to painless as nerves are destroyed
Broad erythematous tract along route of infection as it advances
If open wound, can separate layers of fascia
What are the signs and symptoms day 4-5?
Hypotension and septic shock develop
Patient becomes confused and apathetic
Fournier’s gangrene: Rapidly progressive form of infective NF of the perineal, genital or perianal regions, leading to thrombosis of the small SC vessels and necrosis of the overlying skin
What are the investigations for Necrotising fasciitis?
FBC (Abnormally high or low WCC) U&Es (Possible decreased sodium, raised urea and creatinine) CRP (Raised) CK (Raised) Lactate (Raised) ABG (Hypoxaemia, acidosis)
What is Neutropenic sepsis?
Development of sepsis in a patient with Neutropenia
What conditions define neutropenic sepsis?
Temperature >38 sustained over an hour
Neutrophil count <0.5
Temperature may be masked by anti-pyretic medications/steroids
What causes Neutropenic sepsis?
Drugs Infections Autoimmune Bone marrow failure B12/folate deficiency Congenital (rare)
What drugs cause neutropenic sepsis?
- Cytotoxic chemotherapy
- Haematopoietic stem cell transplant
- Immunosupportive drugs (Azathioprine/methotrexate/sulfasalazine/infliximab)
What infections cause neutropenic sepsis?
HIV/Influenza/CMV/EBV
TB/Shigella
What AI conditions cause neutropenic sepsi?
Crohn’s
Rheumatoid arthritis
SLE
What Risk factors are there for Neutropenic spesis?
Age >65 Albumin <35 Preexisting organ dysfunctino Pre-treatment haemoglobin Full-dose intensity chemotherapy Low first-cycle neutrophil count (<0.5) Haematological malignancies Concurrent radiotherapy Prior episodes of neutropenia following chemo Female sex ECOG PS > 1 Advanced stage disease Prior chemo Corticosteroids
What are the signs and symptoms of Neutropenic sepsis?
Pyrexia Infective endocarditis symptoms (Tachycardia, hypotension, N&V) Mucositis, oral ulcers Lymphadenopathy Skin rashed
What are the investigations for neutropenic sepsis?
FBC (neutrophils <0.5)
Temperature >/= 38.0
Blood cultures (Identify causative agents)
Whats important to know about Neutropenic fever?
Often those with neutropenic fever have pneumonia without cough or SOB
