Specific pathogens and their disease Flashcards
Toxoplasma gondii
- Protozoa infects the body via the GI tract, lung or broken skin. O
- ocysts release trophozoites ->migrate widely around the body including to the eye, brain and muscle. Animal reservoir is the cat but other animals also such as rats.
- Most infections are asymptomatic.
- Symptomatic patients usually have a self-limiting infection, often having clinical features resembling infectious mononucleosis (fever, malaise, lymphadenopathy).
- Other less common manifestations include meningioencephalitis and myocarditis.
- Investigation: antibody test + Sabin-Feldman dye test
- Treatment is usually reserved for those with severe infections or patients who are immunosuppressed -> pyrimethamine plus sulphadiazine for at least 6 weeks
Congenital toxoplasmosis
- Transplacental spread from the mother -> causes a variety of effects to the unborn child including microcephaly, hydrocephalus, cerebral calcification and choroidoretinitis
Glandular fever
- EBV aka HHV-4
- Classic triad of sore throat, pyrexia and lymphadenopathy is seen in around 98% of patients,
-
Other features include:
- malaise, anorexia, headache - palatal petechiae
- splenomegaly - occurs in around 50% of patients and may rarely predispose to splenic rupture
- hepatitis, transient rise in ALT
- lymphocytosis: presence of 50% lymphocytes with at least 10% atypical lymphocytes
- haemolytic anaemia secondary to cold agglutins (IgM)
- a maculopapular, pruritic rash develops in around 99% of patients who take ampicillin/amoxicillin whilst they have infectious mononucleosis
- Symptoms typically resolve after 2-4 weeks
- Diagnosis - heterophil antibody test (Monospot test)
Leprosy - Mycobacterium leprae.
- Features: patches of hypopigmented skin typically affecting the buttocks, face, and extensor surfaces of limbs with sensory loss
- The degree of cell mediated immunity determines the type of leprosy a patient will develop.
- Management with triple therapy: rifampicin, dapsone and clofazimine
Zika
- Mosquito borne, majority of infected have no symptoms.
- Those with symptoms, Zika virus tends to cause a mild, short-lived (2 to 7 days) febrile disease.
- Zika is linked with microcephaly and other congenital abnormalities therefore wait 6 months after possible exposure to concieve
Dog bite
- Pasteurella multocida is a gram-negative coccobacillus which is the most likely organism to be isolated after a dog bite.
- Co-amoxiclav is recommended OR if penicillin-allergic then doxycycline + metronidazole is recommended
TB meninigitis ?steroids
- use of steroids in patients with tuberculous meningitis is supported by a Cochrane review in 2008
Active TB treatment
Active tuberculosis:
- Initial phase - first 2 months (RIPE) Rifampicin Isoniazid, Pyrazinamide and Ethambutol
- Continuation phase - next 4 months: Rifampicin Isoniazid
Latent TB treatment
- 3 months of isoniazid (with pyridoxine) and rifampicin
- OR 6 months of isoniazid (with pyridoxine)
Meningeal tuberculosis
- Prolonged period (at least 12 months) with the addition of steroids
Leptospirosis
- Sewage workers, farmers, vets or people who work in an abattoir.
- Pathogen: spirochaete Leptospira interrogans (serogroup L icterohaemorrhagiae),
- Features: fever, flu-like symptoms renal failure (50% pts), jaundice, subconjunctival haemorrhage headache, may herald the onset of meningitis
- *the term Weil’s disease is sometimes reserved for the most severe 10% of cases that are associated with jaundice.
- Management: high-dose benzylpenicillin or doxycycline
Gram-negative cocci
- Neisseria meningitidis
- Neisseria gonorrhoeae,
- Moraxella catarrhalis
Gram-positive rods (bacilli)
ABCD L
- Actinomyces
- Bacillus anthracis (anthrax)
- Clostridium
- Diphtheria: Corynebacterium diphtheriae
- Listeria monocytogenes
Gram -negative rods
- Escherichia coli
- Haemophilus influenzae
- Pseudomonas aeruginosa
- Salmonella sp.
- Shigella sp.
- Campylobacter jejuni
Cat scratch disease
- *-Bartonella spp infection
- Most important species
- Disease and vector
- classic immunocompetent presentation
- Best initial test if suspected
- Treatment**
- Gram negative rod
- Bartonella henselae
- Features: fever, hx of a cat scratch tender regional lymphadenopathy, headache, malaise
- Immunocompromised develop bacillarly angiomatosis and get benign papular vascular lesions
Legionella
- Legionella pneumophilia.
- water tanks, air-conditioning systems or foreign holidays.
- Person-to-person transmission is not seen.
- Features flu-like symptoms including fever (present in > 95% of patients), dry cough, relative bradycardia confusion, lymphopaenia hyponatraemia, deranged LFTs, pleural effusion: seen in around 30% of patients
- Diagnosis: urinary antigen
- Tx: erythromycin/clarithromycin
Legionella vs Mycoplasma penumonia
- COMMON: atypical, fly like sx, dry cough, deranged LFTs, macrolide tx.
- MYCOPLASMA: haemolytic anaemia/ITP, erythema multiforme, encephalities/GBS, peri/myocarditis. Dx with serology
- LEGIONELLA: lymphopenia, hyponatremia, dx with urinary Ag
Lyme disease: features
- Early features: erythema migrans small papule often at site of the tick bite -> larger annular lesion with central clearing, ‘bulls-eye’ 70% of patients.
- Systemic symptoms: malaise, fever, arthralgia
- Later features: CVS: heart block, myocarditis neurological: cranial nerve palsies, meningitis polyarthritis
Bacillus anthracis
- Gram positive rod.
- Clinical fx: Painless black eschar, may cause marked oedema, can cause GI bleeding
- Tx: ciprofloxacin
Enteric fever (typhoid/paratyphoid)
- Spread via F-O route.
- Aerobic, Gram-negative rods which are not normally present as commensals in the gut,
- Presentation: initially systemic upset as above relative bradycardia, abdominal pain, distension constipation:
- although Salmonella is a recognised cause of diarrhoea, constipation is more common in typhoid
- rose spots: present on the trunk in 40% of patients, and are more common in paratyphoid
- Complications: OM (especially in sickle cell disease where Salmonella is one of the most common pathogens), GI bleed/perforation, meningitis, cholecystitis, chronic carriage
Schistosoma haematobium
- It commonly presents with terminal hematuria, due to bladder wall inflammation and ulcer, urinary calcifications, obstruction, and bladder cancer may eventually develop.
- “Swimmers itch” and Acute schistomiasis syndrome (Katayama fever)
Strongyloides stercoralis
- The larvae are present in soil and gain access to the body by penetrating the skin.
- Infection with Strongyloides stercoralis causes strongyloidiasis.
- Features diarrhoea abdominal pain/bloating papulovesicular lesions where the skin has been penetrated by infective larvae e.g. soles of feet and buttocks
- larva currens: pruritic, linear, urticarial rash if the larvae migrate to the lungs a pneumonitis similar to Loeffler’s syndrome may be triggered
- Treatment ivermectin and albendazole are used
clostridium botulinum,
- Sx produced by botulinum toxin: afebrile, descending, flaccid paralysis.
- Features typically include difficulty speaking or slurred speech, blurred or double vision, and/or dysphagia.
- Other features of bulbar palsy include ptosis and facial muscle weakness.
- Without treatment, paralysis may progress to the upper limbs, trunk, lower limbs and respiratory muscles. The treatment of botulism - supportive care and botulism antitoxin.
- Clostridium botulinum is sensitive to benzylpenicillin, and therefore this is also administered in patients with abscess formation at the injection site.
Acute schistomiasis syndrome
- Acute manifestations may include: swimmers’ itch acute
- schistosomiasis syndrome (Katayama fever) include: fever, urticaria/angioedema, arthralgia/myalgia, cough, diarrhoea,eosinophilia
Chagas’ disease (Trypanosoma cruzi)
- American trypanosomiasis, 95% are asymptomatic in the acute phase although a chagoma (an erythematous nodule at site of infection) and periorbital oedema are sometimes seen.
- Chronic Chagas’ disease mainly affects the heart and gastrointestinal tract.
- Myocarditis may lead to dilated cardiomyopathy (with apical atophy) and arrhythmias.
- Cardiomyopathy is the most frequent and most severe manifestation of chronic Chagas’ disease
- GI features includes megaoesophagus and megacolon causing dysphagia and constipation
- Management: treatment is most effective in the acute phase using azole or nitroderivatives such as benznidazole or nifurtimox chronic disease management involves treating the complications e.g., cardiomyopathy
African trypanosomiasis (sleeping sickness)
- Trypanosoma gambiense in West Africa and Trypanosoma rhodesiense in East Africa
- Clinical features include:
- Trypanosoma chancre - painless subcutaneous nodule at site of infection intermittent fever, enlargement of posterior cervical lymph nodes
- later: central nervous system involvement e.g. somnolence, headaches, mood changes, meningoencephalitis
- Management:
- early disease: IV pentamidine or suramin
- later disease or central nervous system involvement: IV melarsoprol
Listeria monocytogenes
- Gram-positive bacillus which has the unusual ability to multiply at low temperatures.
- Spread via contaminated food, typically unpasteurised dairy products.
- Infection is particularly dangerous to the unborn child where it can lead to miscarriage.
- Management -> Listeria is sensitive to amoxicillin/ampicillin (cephalosporins usually inadequate)
- Listeria meningitis should be treated with IV amoxicillin/ampicillin and gentamicin
Listeria monocytogenes in pregnant women
- Pregnant women are almost 20 times more likely to develop listeriosis compared with the rest of the population due to changes in the immune system
- fetal/neonatal infection can occur both transplacentally and vertically during child birth complications include miscarriage, premature labour, stillbirth and chorioamnionitis
- treatment is with amoxicillin
Parovirus B19
- Erythema infectiosum (also known as fifth disease or ‘slapped-cheek syndrome’)
- they are no longer infectious by the time the rash occurs.
- virus can affect an unborn baby in the first 20 weeks of pregnancy.
- Infection in a pregnant woman can lead to fetal hydrops and spontaneous miscarriage, particularly in the first trimester.
- This can be managed with the use of fetal blood transfusion.
- Other presentations include:
- asymptomatic pancytopaenia in immunosuppressed patients aplastic crises e.g. in sickle-cell disease (parvovirus B19 suppresses erythropoiesis for about a week so aplastic anaemia is rare unless there is a chronic haemolytic anaemia)
Hepatitis B
- dsDNA hepadnavirus spread through exposure to infected blood or body fluids - including vertical transmission.
- Incubation 6-20 weeks
-
Complications:
- chronic hepatitis (5-10%). ‘Ground-glass’ hepatocytes may be seen on light microscopy fulminant liver failure (1%) hepatocellular carcinoma, glomerulonephritis, polyarteritis nodosa, cryoglobulinaemia
Management of HepB
- pegylated interferon-alpha used to be the only treatment available.
- It reduces viral replication in up to 30% of chronic carriers.
- A better response is predicted by:
- being female, < 50 years old, low HBV DNA levels, non-Asian, HIV negative, high degree of inflammation on liver biopsy
- other antiviral medications are increasingly used with an aim to suppress viral replication (not in a dissimilar way to treating HIV patients) examples include tenofovir, entecavir and telbivudine (a synthetic thymidine nucleoside analogue)
Coagulase test
- Staph aureus is the most important of the coagulase positive Staphylococcus species and is highly pathogenic.
- Coagulase-negative Staph species are most likely to be skin commensal organisms of relatively low pathogenicity, such as Staph epidermidis or Staph saprophyticus, although some may still cause deeper infection or sepsis.
Neisseria gonorrhoea
- Gram negative diplococci
- Oxidase positive
Japanese encephalitis
- Japanese encephalitis is the most common cause of viral encephalitis in South East Asia,
- China the Western Pacific and India, with approx. 50,000 cases annually. It is a flavivirus transmitted by culex mosquitos which breeds in rice paddy fields. The reservoir hosts are aquatic birds, but pigs are an amplification host and therefore close domestic contact with pigs is a risk factor. The majority of infection is asymptomatic.
- Clinical features are headache, fever, seizures and confusion. Parkinsonian features indicate basal ganglia involvement. It can also present with acute flaccid paralysis.
- Diagnosis is by serology or PCR.
- Management is supportive.
- Prevention is a vaccine and there are a variety of different types.
Active HBV infection
HBsAg =
HBeAg =
Anti HBc =
Anti HBs =
HBV DNA =
Amoebiasis
- Cause
- Spread
- Risky occupation in the West
- Most common presentation
- Mx of the different forms
Antibiotic prophylaxis (for endocarditis): Dental Procedures
Most dental-procedure bacteraemias are caused by viridans group strep
When indicated, prophylaxis should be:
- Amoxy/ampicillin 2g PO 1 hour before procedure or IV 15 - 30min before procedure.
if hypersensitive can use:
- Cephalexin 2g PO 1 hour before procedure or Cephazolin 2g IV within 15-30min before procedure
if immediate hypersensitivity can use:
- Clindamycin 600mg PO 1 hour before procedure or IV over 20min within 60min of procedure
Best Serological Marker of an acute exacerbation of chronic hep B
Hepatitis B core IgM
Brucellosis
- Australian spp
- Main Aus RF
- Presentation
- Treatment
Buzzword: Gram negative bacilli with safety pin appearance
- Bug and condition
- Initial therapy
- Follow up therapy
- Burkholderia pseudomallei (Melioidosis)
- Other buzzwords: North Australia/Asia pacific, alcoholics
- Tx as per eTG ->
- Followed by Bactrim (+Folate) for 3 month
- if can’t have Bactrim use doxycycline or Augmentin
C. diff
- micro
- how it causes disease
- special strain - 4 features of it
- most important RF
Causes of Culture Negative Endocarditis
- Most common: ABx prior to culure with strep
- Other: Bartonella, Q fever, psittacosis, legionella, brucella, tropheryma whipplei (often diagnosed on serology)
Causes of eosinophilic meningitis
Role of prednisolone
Gene essential for methicillin resistance in MRSA
mec gene
Variant Creutzfeldt Jakob Disease
Haemolysis Test
IRIS - Immune Reconstitution Inflammatory Syndrome
Surveillance in HBV - who gets surveilled?
Also ATSI > 50
Risk of HBV reactivation according to therapy
Immunisation against HBV
HBsAg =
HBeAg =
AntiHBc =
AntiHBs =
HBV DNA =
Empirical treatment of nosocomial meningitis
Empirical therapy for bacterial meningitis
-which patients should be covered for listeria and how
Emperical cover = dexamethasonen 10mg IV before starting the first dose of antibiotic
Ceftriaxone 4g daily OR ceftriaxone 2g BD OR cefotaxime 2g IV 6 hrly
Listeria cover indicated in:
- -alcoholic
- -pregnant
- ->50years
- -immunocompromised
- -debilitated
Cover with benzylpenicllin 2.4g IV 4 hrly
Most common cause of viral encephalitis
Zika Virus - routes of transmission
- Mosquito-Human
- Vertical transmission
- Sexual transmission
- Likely blood borne - nil reported cases
Markers of Severe Malaria
Proteus UTI is associated with which type of renal calculus?
STRUVITE
Preferred agent for consolidation and maintenance therapy of cryptococcal meningitis
Fluconazole
- 8 weeks for consolidation
- 6 to 18months for maintenance if there is a response
- HIV patients also need for their CD4 count to recover > 100
Empirical therapy for febrile neutropenia
- when would you add Vancomycin
- when would you add anti-fungals
Consider gentamicin if concerns re resistance or critically unwell
Add vancomycin if fever persists > 48 hours
Add anti-fungal cover if fever persists > 96 hours
Treatment of typhoid
Secondary Prophylaxis in Rheumatic Fever
Benzathine penicillin G (PBG) - IM injections every 4 weeks
-for 10 years or until age 21 (whichever is longer)
-In moderate/severe RHD should continue up to 35-40 years
-PO penicillin is less effective
Penicillin allergy - use PO erythromycin
Indications for adding Vancomycin to empirical bacterial meningitis cover (4)
- Diplococci in gram stain
- Pneumococcal antigen positive on CSF
- Known/suspected otitis media or sinusitis
- Recent Rx with beta lactam
Covers strep. pneumoniae with reduced susceptibility/resistance to penicillin/cephalosporins
What is the diagnosis
- EBV VCA IgG positive
- EBV VCA IgM positive
- EBNA IgG negative
(EBNA = EB nuclear antigent)
Acute EBV Infection
Most common valvular lesion in rheumatic heart disease
Mitral regurgitation
Phases of opportunistic infections among allogenic HCT recipients
Hep B serology:
HBsAg Positive
Anti-HBc Positive
Anti-HBc IgM Negative
Anti-HBs Positive
Cause (1)
Next test
Related to immune complexes
Proceed to HBV DNA quantative PCR
Stages of Hep B infection
- What are the 4 stages
- Which require treatment
Ebola
- Region
- Incubation
- Management principles
Treatment of C-diff
Vaccines
Causes of eosinophilic meningitis
Role of prednisolone
angiostrongylus cantonensis (a helminth) and sometimes by Gnathostoma species
What is the diagnosis?
- EBV VCA IgG positive
- EBV VCA IgM negative
- EBNA IgG negative
EBV infection at some point
BUT as 5-10% of people won’t make EBNA antibodies can’t pinpoint time frame
Hep B serology:
HBsAg Positive
Total Anti-HBc Negative
Anti-HBc IgM Negative
Anti-HBs Negative
5 options
Early acute infection
Transient antigenaemia after vaccination
Immune tolerance
Defective mutants
Immunosuppressed patient
Next test would be:
HBeAg and Quantative HBV DNA
Dengue Warning Signs (7- Poor Prognostic Signs)
Hospital Acquired Pneumonia
Definition - pneumonia in patient hsopitalised for > 48 hours
Pathogenesis - microaspiration of bacteria colonising oropharynx or upper GIT
RF - intubation, previous Abx use (for resistant organisms)
Pathogens - note atypicals rare:
- Aerobic GNB
- MRSA
- Resistant enterobacteriaceae
- Pseudomonas
- Acinteobacter
Brucellosis
- Australian spp
- Main Aus RF
- Presentation
- Treatment
FERAL PIGS!
