Microbiology Flashcards

Question

Special stains for Corynebacterium Diphtheriae

Answer 1

**Albert's stain** and **Ponder's stain **are used to demonstrate metachromatic granules formed in polar regions of Corynebacterium Diphtheriae

Answer 2

1) Löffler's medium - enhance growth of corynebacterium only 2) Hoyle's medium (blood agar with **potassium tellurite**) - tellurite helps to differentially select Corynebacterium dophtheria from other URT flora, showing formation of **black colonies** 3)

Answer 3

1) Droplet transmission 2) Direct contact with respiratory secretions 3) Asymptomatic carrier state exists

Answer 4

a) Diphtheria is a exotoxin-mediated disease; *tox* gene carried by bacteriophage b) Exotoxin is absorbed into blood; causing inactivation of elongation factor 2 c) Systemic effects of toxin occur (may even cause heart and nerve problems, or skin infection) d) pseudomembrane may go down to affect lower airway; inflammation of glottic area may obstruct airway -\> life threatening in young patients

Answer 5

1) Diphtheria antitoxin 2) Penicillin, erythromycin 3) Supportive care

Answer 6

Vaccination with diphtheria toxoid

Answer 7

A rapidly progressive cellulitis of the epiglottis and adjacent structures

Answer 8

Infectious: Classically caused by **haemophilus influenzae type b** (Hib; esp. in children); more diverse etiology in adults, including Haemophilus influenzae, beta-haemolytic streptococci (streptococcus pneumoniae, streptococcus pyogenes), staphylococcus aureus, Klebsiella pneumoniae non-infectious: trauma, irradiation, caustic ingestion, inhalation injury, etc.

Answer 9

Children (2-4 years old) are most commonly affected; can occur in adults

Answer 10

Rapid onset of fever irritability dysphonia **(children won't yell as it will be too painful)** dysphagia **(drooling may be observed as swallowing will be too paindul)** sore throat respiratory distress May progress to complete airway obstruction at any time

Answer 11

May progress to life-threatening complete airway obstruction at any time

Answer 12

1) Laryngoscopy -\> cherry red epiglottis (red and swollen) 2) Lateral and frontal neck x-ray -\> Narrowed upper-end of trachea (due to oedema) 3) Auscultation -\> Stridor sound (can be heard without stethoscope)

Answer 13

Stridor is a high pitched wheezing sound resulting from turbulent air flow in the upper airway. It is primarily inspiratory. It can be indicative of serious airway obstruction from severe conditions such as epiglottitis, a foreign body lodged in the airway, or a laryngeal tumor. Stridor is indicative of a potential medical emergency and should always command attention. (Can be heard without using stethoscope)

Answer 14

Examine the epiglottis of the patient only when facilities for immediate intubation or tracheostomy are available, as laryngoscope and examination may provoke airway spasm leading to complete airway obstruction

Answer 15

Secretion of sinuses are normally drained into osteomeatal complex and then to pharynx; normal sinus are considered "sterile" with minimal microbes only

Answer 16

1 Obstruction of normal sinus drainage. 2 The commonest antecedent condition is an upper respiratory tract viral infection. 3 Other predisposing conditions: allergy; rarely, dental root infection (maxillary sinusitis). 4 Swelling of inflamed mucosal lining further impairs sinus drainage.

Answer 17

1 Streptococcus pneumoniae (∼40%), Haemophilus influenzae (∼20%), Moraxella catarrhalis (∼20%). 2 Respiratory viruses (rhinovirus, parainfluenza virus, adenovirus, influenza virus): ∼10%. 3 Sterile cultures in ~25%. 4 May be fungal infection in fungal sinusitis (e.g. bone marrow transplant recipient)

Answer 18

1 Persistent and severe symptoms after upper respiratory tract infection. 2 Purulent nasal and postnasal discharge (yellowish/greenish) 3 Facial pain, headache (frontal sinusitis), fever.

Answer 19

intra-orbital extension intracranial extension of infection: brain abscess, meningitis osteomyelitis of frontal bone (frontal or ethmoid sinus).

Answer 20

1 Clinical symptomatology 2 physical examination 3 Imaging: - sinus X ray: sinus opaque, no normal black air shadow - CT Scan: swollen mucosa in sinus 4 Culture: culture of nasal pus or sinus exudates not reliable. Sinus puncture and aspiration of sinus contents is preferred. Routine sinus puncture not necessary.

Answer 21

1) Acute community-acquired sinusitis 2) Nosocomial (hospital-acquired) sinusitis [e.g. nasogastric tube can cause irritation to nasal mucosa, causing it to be swollen -\> occlude osteomeatal complex -\> sinus secretion cannot be drained to nasopharynx] 3) chronic sinusitis 4) fungal sinusitis

Answer 22

1 Empirical antibiotic coverage (e.g. amoxicillin, amoxicillin-clavulanate, cefuroxime) against Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis, taking into account the local pattern of antibiotic resistance. 2 Surgical therapy for severe sinusitis, suspected intra-orbital or intracranial involvement, correction of sinus drainage in chronic sinusitis.

Answer 23

Defintion: Infection of the external auditory meatus Pathogens: Staphylocaccus aureus (acute localized otitis media), pseudomonas aeruginosa (Malignant otitis media, especially in elderly, diabetics, and immunocompromised hosts), normal flora similar to that on the skin Presentation: Red swollen ear; may have pus in the ear canal Treatment: Systemic antibiotics; surgical drainage of abscess and debridement may be necessary

Answer 24

Primarily affecting children; peak incidence between 6 to 24 months

Answer 25

1 Anatomical defects, e.g. cleft palate, cleft uvula. 2 Physiological abnormalities of Eustachian tube. 3 Congenital or acquired immunodeficiencies. 4 Colonization of the nasopharynx by potential bacterial pathogens at the time of viral upper respiratory tract infection.

Answer 26

1) Ear Pain, ear drainage, hearing loss 2) Fever, lethargy, irritability 3) Erythema of tympanic membrane (red, bulging outwards); fluid (pus) in middle ear

Answer 27

1 Anatomical or physiological dysfunction of the Eustachian tube. 2 Obstruction of Eustachian tube → accumulation of fluids and secretions in the middle ear → increased risk of infection. 3 Often preceded by a viral upper respiratory tract infection. Up to 37% of the episodes of upper respiratory tract infection may be complicated by the development of acute otitis media.

Answer 28

1 Bacteria: Streptococcus pneumoniae (35–40%), Haemophilus influenzae (30– 35%), Moraxella catarrhalis (15–18%). Uncommon: Streptococcus pyogenes (2– 4%), Staphylococcus aureus. 2 Viruses: less common. 3 Sterile culture in ~20%.

Answer 29

1) Clinical symptomology and examination 2) culture of the external auditory meatus not useful in predicting the pathogens. **Tympanocentesis** (aspiration of the middle ear content) is the method of choice but is not routinely needed unless patient is critically ill, not responsive to antibiotics, or has altered host defence.

Answer 30

1 Empirical antibiotic coverage (e.g. amoxicillin, amoxicillin-clavulanate, cefuroxime) against Streptococcus pneumoniae, Haemophilus influenzae, Moraxella catarrhalis, taking into account the local pattern of antibiotic resistance. 2 In neonates or immunosuppressed individuals, the possibility of infection due to more resistant or unusual organisms should be considered.

Answer 31

If it is not adequately treated, it may develop into chronic suppurative otitis media. Can go to other surrounding areas like * Mastoid cortex * Epidural abscess * Subdural abscess

Answer 32

Abnormal breathing sound (high-pitched, whistling sound) due to lower airway obstruction (e.g. asthma, croup)

Answer 33

Stridor is a high pitched wheezing sound resulting from turbulent air flow in the upper airway. It is primarily inspiratory. It can be indicative of serious airway obstruction from severe conditions such as epiglottitis, a foreign body lodged in the airway, or a laryngeal tumor. Stridor is indicative of a potential medical emergency and should always command attention. (Can be heard without using stethoscope)

Answer 34

Also known as croup; inflammation in the subglottic area resulting in dyspnoea and inspiratory stridor

Answer 35

relatively common in children (3 months to 3 years); peak incidence at 2 years of age

Answer 36

Mainly viruses such as parainfluenza virus, influenza virus, respiratory syncytial virus Mycoplasma pneumoniae

Answer 37

1) Fever 2) laryngitis 3) Insiratory stridor with or without respiratory distress 4) wheezing sound 5) tachypnoea or dyspnoea 6) rales 7) Hypoxaemia

Answer 38

Clinical diagnosis. Aetiological diagnosis by viral culture or antigen detection if necessary.

Answer 39

oxygen, nebulized bronchodilators.

Answer 40

whooping cough

Answer 41

Bordetella pertussis, a Gram negative coccobacillus

Answer 42

1) Epidemic in most populations; transmitted via respiratory droplets 2) Not just a disease of childhood. In developed countries, overall disease burden shifting to adolescents and adults. Pertussis is a **common but under-recognized cause of chronic cough** in adolescents and adults. 3) In many western countries, nosocomial outbreaks of pertussis have been described.

Answer 43

1) Filamentous haemagluttinin, helps in attachment to ciliated respiratory epithelium 2) Production of a number of toxins: - pertussis toxin (PT), adenylate cyclase toxin (ACT), tracheal cytotoxin, dermonecrotic toxin (DNT), pertactin (PTN) 3) Incubation period from less than 1 week to more than 3 weeks 4) 3 phases of disease a) Catarrhal phase: rhinorrhoea, conjunctival injection, malaise, low grade fever, dry cough b) Paraoxysmal phase: short expiratory bursts followed by an inspiraory gap (whoop) c) Convalescent phase

Answer 44

a) Catarrhal phase: rhinorrhoea, conjunctival injection, malaise, low grade fever, dry cough b) Paraoxysmal phase: short expiratory bursts followed by an inspiraory gap (whoop) Chronic cough in general; symptomatology in adolescents and adults differ from that in children

Answer 45

``` pneumonia; haemorrhage; pneumothorax; central nervous system abnormalities (convulsion, encephalopathy). ```

Answer 46

culture of nasopharyngeal aspirate or swab on special medium (Bordet-Gengou medium). Serology (not widely available and may not be useful in acute infection). PCR of nasopharyngeal specimens.

Answer 47

Specific antibiotic therapy: macrolides (e.g. erythromycin, clarithromycin, azithromycin).

Answer 48

1) Killed whole-cell vaccine - protection not life long - adults have partial or little immunity - lots of side effects (pain, swelling, high fever) 2) Acellular vaccine (aP) - A subunit vaccine presents an antigen to the immune system without introducing viral particles. It is the combination of different pathogenic mechanisms (e.g. filamentous haemagglutinin) instead of using whole cell - fewer side effects - From 2007, HK childhood immunization programme replaced killed whole-cell vaccine with aP vaccine delivered in combined formula DTaP-IPV. (D=diphtheria toxoid, T=tetanus toxoid, aP= acellular purtussis, IPV=inactivated poliomyelitis vaccine) - \*\*[IPV replaved oral poliomyelitis vaccine which is live attenuated)

Answer 49

Inflammation affecting the parenchyma of the lung (respiratory bronchioles and alveolar units).

Answer 50

a) Bacteria: Streptococcus pneumoniae, Haemophilus influenzae, Mycoplasma pneumoniae; in some clinical or epidemiological settings, Staphylococcus aureus, Enterobacteriaceae (especially Klebsiella pneumoniae), Legionella pneumophilia, and Burkholderia pseudomallei (melioidosis), and Mycobacterium tuberculosis (tuberculosis) are also important considerations. b) Viruses: respiratory syncytial virus (especially in infants, children), influenza virus, parainfluenza viruses, coronaviruses, etc.

Answer 51

1 Direct inhalation of infectious particles from ambient air. 2 Aspiration of secretions from the mouth and nasopharynx. 3 Rarely: haematogenous spread from another focus of infection in the body.

Answer 52

1 History. a) Clinical setting: **acute or chronic**; age, underlying illness, occupation, travel history, animal contacts, etc; **community- or hospital-acquired.** b) **Patient characteristics** - e.g. age, any defect in host resistance (opportunistic pathogens)? **Exposure history** - Possible exposure to specific pathogens (human, animals, environment)? 2 Physical examination. 3 Investigations. a) Blood counts, blood gas. b) Cultures: respiratory tract specimens, blood, pleural fluid. c) Radiological examinations: plain X ray; CT scan in selected cases. d) Sputum examination. i) Macroscopic examination: colour, amount, consistency, (odour); e.g. ‘rusty’ sputum (Streptococcus pneumoniae), ‘currant-jelly’ sputum (Klebsiella pneumoniae). Not sensitive or specific, though. ii) Gram stain: leukocytes (neutrophils, mononuclear cells), epithelial cells (quality of specimen), predominant flora. iii) Culture: blood agar, chocolate agar, selective media (e.g. Legionella) when indicated. e) Viral investigations on respiratory specimens: antigen detection (e.g. by direct immunofluorescent staining, immunochromatographic tests), viral culture, PCR/RT-PCR. f) Other respiratory tract specimens. i) More invasive procedure generally have a higher yield for the true pathogens. However, one needs to balance between risk of procedure and the anticipated pathogens and yields. ii) Transtracheal aspiration (seldom performed nowadays). iii) Endotracheal aspiration. iv) Fibre optic bronchoscopy + bronchoalveolar lavage (BAL). v) Transbronchial biopsy, open lung biopsy. vi) Pleural effusion, pleural biopsy. vii) Nasopharyngeal aspirate: mainly for respiratory viruses. g) Serology: mainly for ‘atypical’ pneumonia pathogens (e.g. Mycoplasma, Chlamydia, Chlamydophila, Legionella, viruses). Not always useful in the acute stage. h) Urine antigen detection assays: Streptococcus pneumoniae, Legionella pneumophila serogroup 1.

Answer 53

1) General supportive measures: oxygen, cardiovascular support, etc. 2) Treat as outpatients or inpatients? 3) Oral or parenteral antibiotics? 4) Empirical therapy or known-pathogen therapy? 5) Empirical therapy: usually a beta lactam antibiotic (e.g. penicillins or cephalosporins) ± a macrolide (e.g. erythromycin, clarithromycin, azithromycin) or a tetracycline. Different antibiotics have been used for the treatment of pneumonia in different clinical settings. However, antibiotics must be chosen carefully: a balance between clinical efficacy, antibiotic resistance, and cost is essential. Guidelines on the treatment of community-acquired pneumonia may be obtained from various authorities like British Thoracic Society

Answer 54

Fever, chills, pleuritic chest pain, cough, mucopurulent sputum. Mortality 6– 24%.

Answer 55

1) **Streptococcus pneumoniae**: commonest; average ~20% -\> pneumococcal pneumonia 2) Haemophilus influenzae: average ~7%. 3) Staphylococcus aureus (elderly; post-influenza pneumonia); average ~3%. Although S. aureus is often quoted as a typical pathogen seen in secondary bacterial pneumonia in patients with influenza, it is not necessarily the commonest one. In most epidemics or pandemics of influenza, Streptococcus pneumoniae is the commoner bacterial pathogen involved. 5) Other bacteria such as Klebsiella pneumoniae. 6) Viruses: especially in children (RSV, parainfluenza), primary influenza pneumonia.

Answer 56

Pathogen: Streptococcus pneumoniae (pneumococcus) Epidemiology: Accounts for 16–60% of acute community-acquired pneumonia.

Answer 57

Risk: Increasing problem of antibiotic resistance. Predisposing factors: old age, smoking, institutionalization, COAD, chronic liver and renal diseases, congestive heart failure, splenectomy.

Answer 58

Pneumococcal vaccines are available for the prevention of invasive pneumococcal diseases and pneumonia. There are 2 types of pneumococcal vaccine currently available, the **polysaccharide vaccine** (23-valent) and the **conjugate vaccines** (7- and 13-valent vaccines are registered in Hong Kong at the moment). Since 2009, the vaccine is made available to at-risk populations in Hong Kong.

Answer 59

a) Routine culture of sputum does not reveal significant pathogens. b) Not responding to beta lactam antibiotics commonly used for the treatment of pneumonia. c) Sometimes may have a more prolonged course of illness. d) May not appear very ill clinically ("walking pneumonia")

Answer 60

a) Bacteria: e.g. Mycoplasma pneumoniae, Chlamydia and Chlamydophila, **Legionella pneumophila**. b) Viruses: e.g. influenza virus, adenovirus, parainfluenza virus, respiratory syncytial virus, coronaviruses.

Answer 61

Can affect any age group but often more severe in the elderly.

Answer 62

Aerobic Gram negative non-spore-forming bacilli Occurs in natural and artificial fresh water environments.

Answer 63

a) Aerobic, Gram negative, non-spore-forming bacilli b) Colonizes artificial water sources, such as cooling towers and other water distribution systems, such as potable water. c) Aerosolization and aspiration are the commonest routes of transmission.

Answer 64

a) Pontiac fever: an acute, self-limiting, flu-like illness without pneumonia. b) Legionnaires’ disease: pneumonia; diarrhoea, nausea, vomiting, abdominal pain, extrapulmonary diseases.

Answer 65

Aerosolization and aspiration are the commonest routes of transmission. Ingestion of contaminated water source

Answer 66

bacterial culture, urine antigen detection, serology (antibody detection), direct immunofluorescent staining of clinical specimens.

Answer 67

macrolide or fluoroquinolone antibiotics. Beta lactam antibiotics are generally not effective for legionellosis.

Answer 68

Hospital-acquired pneumonia. Accounts for 10% to 20% of all nosocomial infections.

Answer 69

a Advanced age. b Underlying diseases. c Altered mental status. d Intubation and use of respiratory equipment. e Use of antacids and H2-antagonists with reduction of gastric acidity.

Answer 70

Often caused by aerobic Gram negative bacilli, e.g. Enterobacteriacae such as Escherichia coli, Klebsiella pneumoniae, or non-fermenters like Pseudomonas aeruginosa, Acinetobacter baumannii; or other multi-resistant bacteria such as meticillin-resistant Staphylococcus aureus.

Answer 71

Can occur in any condition in which consciousness is altered and the normal gag and swallowing reflexes are impaired; e.g. alcoholism, cerebrovascular disorders, convulsion. Three important pathogenic mechanisms: 1) chemical pneumonitis (acute, e.g. due to gastric acid) 2) bronchial obstruction with particulate matter (acute) 3) bacterial aspiration pneumonia (insidious, need incubation period, 2-4 days after aspiration episode)

Answer 72

1) acute 2) insidious: fever, weight loss, productive cough, putrid sputum

Answer 73

Predominantly the oral flora: anaerobes (Bacteroides, Porphyromonas, Prevotella, Fusobacterium, anaerobic cocci), Streptococcus (community- acquired); Gram negative bacilli, Staphylococcus aureus (community- acquired or nosocomial).

Answer 74

Often needs broad spectrum coverage against aerobic and anaerobic organisms.

Answer 75

Right lung, because the right bronchi is more vertical

Answer 76

a Aspiration due to impaired conscious level, e.g. alcoholism, stroke, general anaesthesia, drug overdose, seizures, etc. b Poor dental hygiene with periodontal disease, gingivitis. c Bronchiectasis, bronchial obstruction, cavitating pulmonary infection. d Septic embolization (e.g. infective endocarditis), bacteraemia. e Amoebic lung abscess (Entamoeba histolytica; very rare).

Answer 77

Usually due to mixed oral flora if the predisposing cause is aspiration - i.e. [anaerobes (Bacteroides, Porphyromonas, Prevotella, Fusobacterium, anaerobic cocci), Streptococcus (community- acquired); Gram negative bacilli, Staphylococcus aureus (community- acquired or nosocomial).]

Answer 78

Abscess in the pleural cavity.

Answer 79

a) Complication of pneumonia (50% to 60%). b) Complication of intrathoracic surgery or trauma: oesophagus, mediastinum, cardiac surgery (25%). c) Secondary to subdiaphragmatic sepsis.

Answer 80

a) Secondary to pneumonia: Staphylococcus aureus, Streptococcus pneumoniae, etc. b) Secondary to surgery or perforation of oesophagus: anaerobes; aerobic Gram negative bacilli, Staphylococcus aureus, Actinomyces, etc.

Answer 81

a) Adequate drainage of collections: percutaneous catheters, chest drains, surgery if necessary. b) Antibiotics: according to pathogen(s) involved; often requires a prolonged course of antibiotic. c) Decortication may be necessary in some patients.