Respiratory Pathogens: Bacteria and Mycobacteria Flashcards
A 30-year-old female presents with high fever, sore throat, lymphadenopathy, splenomegaly and fatigue. Infectious mononucleosis is suspected. Which of the is the most common lab testing method for diagnosing this condition?
A test for heterophile antibody, which cross reacts with antigens found on a variety of animal red blood cells
An unvaccinated 60-year-old man develops a sore throat and difficulties in swallowing while on 2 weeks long trip to rural India. Two days after his arrival in Mannitoba, he visited a local hospital. A tough, adherent gray fibrinous exudate in oropharynx along with bilateral cervical lymphadenopathy was noted on physical examination. Which organism is most likely responsible for patient’s symptoms?
Diptheria
Gram positive rods with granules
What is an important characterisitic of the streptococcus bacteria?
Gram Positive
Catalase NEGATIVE- Used to differentiate from (see panopto 9/10 42min)
What are syndromes that affect the upper respiratory tract?
- Common Cold
- Pharyngitis
- Influenza
- Diphtheria
- Sinusitis & Otitis media
- Rhinocerebral mucormycosis
- Epiglottitis
- Croup /Laryngitis
What are the syndromes that afect the lower respiratory tract?
- Whooping Cough
- Bronchitis/ Bronchiolitis
- Influenza
- Pneumonias –
- Typical and Atypical
- Community, Nosocomial, Occupational, Regional, Opportunistic
- Pulmonary Tuberculosis
- Mycobacterium tuberculosis
What are the physical defenses of the respiratory tract?
- Nose: hair, cilia, turbinates and mucus- filter dust and particles; Sneezing
- Change in direction of the airway
- Lymphoid tissue: Waldeyer’s tonsillar ring
- Normal flora
- Mucus and ciliated cells – coughing
- Respiratory secretions: lysozyme, sIgA, lactoferrin, mucus
- Alveolar macrophages
How do pathogens avoid immune defense?
- Bacterial adherence - surface structures
- (Avoid being caught up in the mucus and expelled out)
- Extracellular toxins – cytotoxins,
- Growth in host tissue – intracellular
- Evasion of host defense mechanism
- Capsules (avoid phagocytosis), existence in multiple types, production of IgA proteases
What are the gram postive bacterial respiratory pathogens?
Streptococcus pyogenes
Streptococcus pneumoniae
Staphylococcus aureus *
Bacillus anthracis
Corynebacterium diphtheriae
What are the gram negative bacterial respiratory pathogens?
Legionella pneumophila
Bordetella pertussis
Moraxella catarrhalis
Burkholderia cepacia
Pseudomonas aeruginosa
Acinetobacter baumannii
Klebsiella pneumoniae
Haemophilus influenzae
Francisella tularensis *
What are the bacterial repiratory pathogens (acid fast and non staining)?
Mycobacterium tuberculosis (acid fast)
Chlamydophila pneumoniae
Chlamydophila psittaci
Mycoplasma pneumoniae
Coxiella burnetti*
What are the fungal respiratory pathogens?
- Aspergillus spp.
- Blastomyces dermatitidis
- Coccidioides immitis
- Histoplasma capsulatum
- Rhizopus spp.
- Mucor spp.
- Pneumocystis jiroveci
what are the parasitic respiratory pathogens?
Ascaris lumbricoides
Strongyloides stercoralis
Hookworms
Paragonimus westermani
Patient presents with sinusitis and otitis media. What pathogens can be at fault?
•Streptococcus pneumoniae
- Haemophilus influenzae
- Moraxella catarrhalis
- Pseudomonas aeruginosa
Patient presents with sore throat, dysphagia, fever and swollen lymph glands in the neck in the middle of december. What pathogens could be the cause of these symptoms?
Pharyngitis
Adenovirus
Coxsackie virus
Epstein-Barr virus
Herpes Simplex virus
Corynebacterium diphtheriae
Streptococcus pyogenes
A pateint with rhinocerebral mucorycosis could be infected with
Rhizopus spp.
Mucor spp.
Patient presents with the symptoms shown. Diagnosis of Diptheria is made. What is the culprit of this disease?
Corynebacterium diphtheriae
A baby comes to the clinic with a cough and a high pitched air intake before each cough. What bacterial infection is causing this baby’s symptoms?
The baby has whooping cough. Bordetalla pertussis
What is the cause of tuberculosis?
mycobacterium tuberculosis
Causes of typical pneumonia
- Streptococcus pneumoniae
- Staphylococcus aureus
- Pseudomonas aeruginosa
- Burkholderia cepacia
- Klebsiella pneumoniae
- Acinetobacter baumannii
Causes of atypical pneumonia
- Mycoplasma pneumoniae
- Chlamydophila pneumoniae
- Legionella pneumophila
Causes of regional/ occupational/ opportunistic pneumonias
- Regional/Geographic Pneumonias
- Blastomyces dermatitidis
- Histoplasma capsulatum
- Coccidioides immitis
- Occupational Pneumonias
- Bacillus anthracis
- Chlamydophila psittaci
- Opportunistic Pneumonias
- Aspergillus spp.
- Pneumocystis jiroveci
What are the characterisitics of the streptococcus genus?
Gram positive cocci
Catalase negative
In chains or pairs
Hemolytic patterns: α, β and γ
Catalase Test
Catalase producing organism + H2O2= O2 (bubble)+water
Classification of Streptococcus based on hemolytic properties
- Antigenic grouping – cell wall carbohydrate
- Lancefield groups: A-H, K-V (Group A is S. pyogens)
- Serotyping , Group A (GAS)- M protein – M1, M2 etc
Group A Streptococcus (S. pyogens)
general properties
- Gram positive cocci in chains,
- Catalase negative,
- beta hemolytic on blood agar plate,
- bacitracin sensitive,
- Lancefield group A, PYR +.
- Group specific carbohydrate (A antigen)
What are the virulance facotrs of S. pyogenes?
- Capsule: Hyaluronic acid - antiphagocytosis
-
M protein: used for serotyping (>150 types)
- Antiphagocytic: binds to Fc region of IgG and IgA
- Adhesion factor: binds to collagen, fibrinogen, plasminogen etc.
- Avoids host immune response –due to antigenic variation
- F protein: binds to fibronectin
What are the enzymatic virulence factors of S. pyogenes?
-
Hemolysins: Streptolysin S and Streptolysin O
- O is immunogenic (oxygen labile) , S is nonimmunogenic (oxygen stable)
- Pyrogenic exotoxins: superantigens
- C5a peptidase: inactivates C5a
- Streptokinase: lyses blood clots; dissemination
- Streptodornase (DNase) - dissemination
- Hyaluronidase: degrades hyaluronic acid
Most Impotant GAS virulance factor
M protein
Patient tests positive for strptococcus pyogenes (GAS). What list of diseases could it inflict on the patient?
- Pyogenic infections –include pharyngitis, otitis media, pneumonia, skin and soft tissue infections
- Toxin mediated – scarlet fever, toxic shock syndrome, fasciitis
- Rheumatic fever
- Glomerulonephritis
10 year old presents to you office in Febuary. He hassudden onset of tender enlarged anterior cervial nodes. fever, sore throat for a couple days. Claims to have no cough. What is the diagnoisis?
GAS Pharyngitis.
S. Pyogenes
Patient comes with pharyngitis and a rash on the chest and extremities with the presentation below. What is the cause of this presentation?
Streptococcal pyrogenic exotoxin A- (Spe A)/ Erythrogenic toxin, which is a super antigen) – produced by lysogenized strains
Scarlet fever- 2nd disease (Streptococcus pyogenes) the bacteria must be infected by a phage
6 yr old boy has a history of pharyngitis 3 weeks ago. Currently presents with fever, migratory polyarthritis, skin rash, subcutaneous nodules. What other symptom do you expect?
Patient has Rheumatic Fever. Caused by a type 2 hypersensitivity- immune mediated inflammation. Caused by cross reactivity with M protein.
- You would expect the patient to have carditis and chorea.
Treat within 3 days of onset for reduced incidence
2 weeks after a skin infection patient presents with edema, hematuria, proteinuria and smoky urine. What is the cause of this patients symptoms?
Patient has Acte Post Streptococcal Glomerulonephritis.
Antigen antibody complex deposition on the GBM.
You suspect a patient has a strep pharyngitis. How do you diagnose?
- Throat swab, beta-hemolytic on blood agar, bacitracin sensitive, catalase negative, Gram positive cocci in chains
- Group A antigen
- ELISA
- streptococcal group A cell wall carbohydrate antigen.
What criteria is used to make a rheumatic faver diagnosis?
Jones Criteria
Diagnosis based on serological findings (step O (ASO))
How do you diagnose glomerulonephritis?
Clinical, history of skin or throat infections, Serology- anti streptolysin O (ASO) and anti-DNase.
how is pharyngitis treated?
Penicillin G/or amoxicillin ,
For allergic – Macrolides such as azithro/erythromycin
Treatment of acute glomerulonephritis and rheumatic fever?
After onset, antibiotics DONT help
Recovered from rheumatic fever are given monthly dose of benzathine penicillin to prevent further infection
What are the general properties of Streptococcus pneumoniae?
- Gram +ve, encapsulated
- lancet-shaped (elongated)
- paired cocci or short chains
- alpha hemolytic
- optochin sensitive
- bile soluble
- autolyses
- No Group specific cell wall carbohydrate,
- >90 capsular serotypes – vaccine antigen
What populations are at risk for a s. pneumoniae inffection?
- Children and elderly
- Antecedent viral RT infection, such as post- influenza infection
- Alcoholics, smoking, asthma, chronic pulmonary disease, congestive heart failure (aspiration)
- Asplenic/splenectomy patients = sepsis/bacteremia
- Trauma/leakage of CSF to the nose= meningitis
How does strp. pneumoniae colonize cells?
- IgA proteases - disrupt secretory IgA activity
- Surface protein adhesins
- Cytotoxin-binds cholesterol in cell-creates pores
How does step. pneumoniae cause tissue infection?
- Teichoic acid and peptidoglycan – activate alternative complem.
- Pneumolysin: activate classical complem. pathway-inflammation
- Phosphorylcholine: cell wall binds to receptors (for plasma activiating factor) – bacteria “hide” inside the non-professional phagocytes
What is the main deffence mechanism of s. pneumoniae?
Polysaccharide capsule (90 serotypes) –Antiphagocytic
Patient presents with abrupt onset, fever, chills, rigors, cough, chest pain with rusty (blood tinged) sputum. Diagnosis? Pathogen?
Lobular Pnaumonia
Pneumoccocal (most common cause of community aquired typical pneumonia)
What are the dieases caused by s/ pneumoniae?
- Meningitis
- Bacteremia
- Pneumonia
- Otitis Media (Sinusitis)- most common