1Q: What does URT stand for and what does it include?
A: Upper Respiratory Tract — all structures above the larynx
2Q: Which structures are part of the Upper Respiratory Tract (URT)?
A: Nose, throat, oropharynx, nasopharynx
3Q: Why can URT infections spread to other areas?
A: Because the mucosa is continuous with the mucosal lining of the sinuses, Eustachian tube, middle ear, and LRT
4Q: What does LRT stand for and what does it include?
A: Lower Respiratory Tract — all structures below the larynx
5Q: Which structures are part of the Lower Respiratory Tract (LRT)?
A: Trachea, bronchi, bronchioles, alveolar spaces
6Q: Where does gas exchange occur in the respiratory tract?
A: Alveolar spaces
7Q: What does the ability of an organism to establish an infection depend on?
A: Host factors
8Q: What nonspecific host mechanisms prevent access to the bronchi and lungs in a healthy host?
A:
Nasal hairs (trap large particles)
Mucus secretions (trap smaller particles)
Secretory IgA and enzymes (e.g., lysozyme)
Cilia and mucus lining of the trachea
Reflexes (cough, swallow, sneeze)
9Q: What role does normal flora of the nasopharynx and oropharynx play in pathogenesis?
A: Helps prevent colonization by pathogenic URT organisms by competing for space and nutrients
10Q: Why can colonizing organisms still cause disease?
A:
Small amounts of oropharyngeal material can be aspirated during sleep
Previous damage by viral infection
Loss of some host immunity
Physical damage to respiratory epithelium (e.g., smoking)
11Q: What is bronchitis?
A: Inflammation of the tracheobronchial tree due to or preceded by an upper respiratory tract infection, such as the flu
12Q: What is bronchiolitis and who does it usually affect?
A: Inflammation of the smaller bronchiolar surfaces, usually in neonates and pediatrics < 2 years old, mostly associated with viral infections
13Q: What is pneumonia?
A: Inflammation and accumulation of fluid in the lower respiratory tract (LRT)
14Q: Why is pneumonia clinically significant?
A: It is a major cause of illness and death
15Q: What are the main types of pneumonia based on acquisition?
A:
Community-acquired
Health care–associated (hospital-associated, ventilator-associated)
16Q: What are the four routes of infection in the pathogenesis of pneumonia?
A:
Upper airway colonization that extends to the lung
Aspiration of organisms (aspiration pneumonia)
Inhalation of airborne droplets
Seeding of the lung via blood
17Q: Which conditions increase the risk for aspiration pneumonia?
A:
Loss of consciousness due to seizure or anesthesia
Drug/alcohol abuse
Geriatric patients
18Q: What is essential for diagnosing pneumonia from a microbiology standpoint?
A: Recognition and separation of significant bacterial pathogens from resident microflora
19Q: What is expectorated sputum?
A: Sputum that is coughed up, which may be contaminated with saliva (oral flora contamination)
20Q: Why is a sputum screen performed?
A: To evaluate sputum quality
21Q: What makes a sputum specimen unacceptable?
A:
>10 epithelial cells/lpf and <25 WBC/lpf
>25 epithelial cells/lpf
22Q: What makes a sputum specimen acceptable?
A:
≤10 epithelial cells/lpf
11–25 epithelial cells/lpf with ≥25 WBC/lpf
23Q: What is induced sputum and how is it handled?
A:
Respiratory therapist–assisted collection for patients unable to produce sputum
Generally acceptable and does not need to be screened
24Q: When are endotracheal aspirates / tracheostomy suction specimens collected?
A: From patients with a tracheostomy who are unable to produce sputum
25Q: Why are patients with tracheostomies at risk for pneumonia?
A: They may become colonized with gram-negative rods (GNR) and other nosocomial pathogens, which can be aspirated into the lungs
26Q: How are LRT secretions from endotracheal aspirates handled?
A: Collected in a trap and treated as sputum
27Q: What is a bronchoscopy specimen?
A: A specimen obtained from the lungs using bronchoscopy techniques
28Q: What is bronchial washing/aspirate?
A: Saline is inserted into the bronchial tree and the fluid is collected
29Q: What is bronchoalveolar lavage (BAL)?
A: A large volume of saline is introduced into a lung segment to obtain material from the alveolar space
30Q: What is a bronchial brush specimen?
A: A specimen collected using a brush from the bronchial tree
31Q: What media are used for an LRT culture workup?
A: BAP, CHOC, MAC
32Q: When should complete identification and susceptibility testing be performed in an LRT culture?
A: When there is moderate, many, or predominant growth of 1 or 2 potential pathogens
33Q: When is descriptive identification used instead of full ID and susceptibility testing?
A: When >2 potential pathogens are found or when the quantity is rare or few
34Q: Why is quantitation of normal respiratory tract flora important in LRT cultures?
A: To help differentiate colonizers from true pathogens by comparing pathogenic species versus normal flora species
35Q: How is semi-quantitation of bacterial culture reported?
A: As Rare, Few, Moderate, or Many
36Q: What does Rare growth mean in semi-quantitation?
A: ≤5 colonies growing on the 1st quadrant
37Q: What does Few growth mean in semi-quantitation?
A: >5 colonies growing on the 1st quadrant only
38Q: What does Moderate growth mean in semi-quantitation?
A: Growth on the 1st quadrant and >5 colonies on the 2nd quadrant
39Q: What does Many growth mean in semi-quantitation?
A: Growth on the 1st and 2nd quadrants and >5 colonies on the 3rd quadrant
40Q: What organisms are considered normal respiratory tract flora? (8)
A:
Non-pathogenic Neisseria
Haemophilus species (not H. influenzae)
HACEK organisms
Rothia mucilaginosa (Stomatococcus; “sticky staph”)
Streptococcus anginosus (beta-hemolytic)
Viridans group streptococci
Coagulase-negative Staphylococcus
Corynebacterium species (not diphtheriae)
41Q: What are key identifying features of Streptococcus anginosus in normal respiratory flora?
A:
Beta-hemolytic
Tiny colonies
Can type as A, C, F, or G
Produces a distinct butterscotch/caramel odor
42Q: Which Haemophilus species are part of normal respiratory flora?
A: Haemophilus species other than H. influenzae
43Q: Which Corynebacterium species are part of normal respiratory flora?
A: Corynebacterium species excluding C. diphtheriae
44Q: Which organisms are commonly isolated as lower respiratory tract pathogens?
A:
Streptococcus pneumoniae
Moraxella catarrhalis
Staphylococcus aureus
Haemophilus influenzae
Enterobacterales (E. coli, Klebsiella spp., Enterobacter spp., etc.)
Non-glucose fermenters (Pseudomonas, Acinetobacter, etc.)
Beta-hemolytic Streptococcus spp. (A, C, G – large colonies)
Yeast, mold
45Q: What is cystic fibrosis (CF)?
A: A genetic disease that leads to persistent bacterial infection, causing airway damage and chronic obstruction of the lungs
46Q: Besides the lungs, what other systems can be affected by cystic fibrosis?
A: Digestive system, pancreas, liver, intestines, sinuses, and sex organs
47Q: How does cystic fibrosis affect mucus and bacterial clearance in the lungs?
A: CF causes thick mucus buildup, trapping bacteria that are normally cleared from the lungs
48Q: Why is monitoring colonization and detecting microorganisms important in cystic fibrosis patients?
A: It aids in maintenance and treatment of patients with cystic fibrosis
49Q: What specimens are accepted for cystic fibrosis (CF) cultures?
A:
Sputum (expectorated or induced; screening not performed)
Tracheal aspirates/suctions
Bronchial washing/lavage
Throat swab for children <10 years old if unable to produce sputum
50Q: What media are used for CF cultures?
A: BAP, CHOC, MAC, CNA, BCSA, Chromagar Staphylococcus aureus
51Q: What is BCSA and how is it used in CF cultures?
A:
Burkholderia cepacia selective agar
Incubated at 35°C in O₂ for 4 days, protected from light
Contains sucrose, lactose, crystal violet, gentamicin, vancomycin, and polymyxin B
52Q: What are the key characteristics of Chromagar Staphylococcus aureus?
A:
Produces mauve colonies
Incubated at 35°C in O₂ for 20–26 hours
If negative at 24 hours, incubate for a total of 3 days and protect from light
53Q: What medium was previously used to differentiate Staphylococcus aureus?
A: Mannitol salt agar — S. aureus ferments mannitol and produces yellow colonies
54Q: Which organisms are commonly isolated in cystic fibrosis (CF) cultures?
A:
Staphylococcus aureus (most prevalent in children <10 years)
Haemophilus influenzae
Pseudomonas aeruginosa (most prevalent in adults)
Burkholderia cepacia complex
55Q: Why is it important to distinguish mucoid vs non-mucoid Pseudomonas aeruginosa in CF cultures?
A:
Isolation of mucoid P. aeruginosa from sputum without a CF diagnosis may alert clinicians to possible underlying disease
56Q: What are key characteristics of mucoid Pseudomonas aeruginosa in CF patients?
A:
Produces alginate, a polysaccharide
Allows adherence to lung epithelial cells to form biofilms
Protects bacteria from antibiotics and the immune system
57Q: Why is Burkholderia cepacia complex clinically significant in CF patients?
A:
Colonization may be considered a contraindication for lung transplantation
First-time isolates are confirmed by sequencing and sent to a reference lab for confirmatory identification
58Q: What testing is performed on organisms isolated from CF cultures?
A: Identification and susceptibility testing are performed on all pathogens isolated
59Q: What specimens are used to identify patients infected with Bordetella spp. and carriers of Neisseria meningitidis?
A: Nasopharyngeal secretions or swab specimens
60Q: What is a nares specimen used to identify?
A: Carriers of MSSA and MRSA
61Q: What media are used to culture nares specimens for MSSA and MRSA?
A:
CHROMagar SA
CHROMagar MRSA
62Q: What is the Rapid Strep A antigen test and where can it be performed?
A: A CLIA-waived test that can be performed in clinics / as point-of-care testing (POCT)
63Q: What must be done if a Rapid Strep A antigen test is negative?
A: It must be reflexed to culture, which is the gold standard
64Q: What are the key features of Rapid Strep A PCR?
A: Rapid and more accurate, but costly
65Q: What does a multi-array respiratory panel detect?
A: Many targets, usually viruses, and a few bacteria such as Bordetella pertussis, Chlamydophila pneumoniae, and Mycoplasma pneumoniae
66Q: What are the limitations of a multi-array respiratory panel?
A: High cost and potential reimbursement issues for the laboratory
67Q: What is the primary purpose of throat cultures?
A: To diagnose pharyngitis caused by Streptococcus pyogenes
68Q: What are other causes of pharyngitis detected by throat cultures?
A:
Group C and G beta-hemolytic streptococci (large colony morphology)
Arcanobacterium haemolyticum (peritonsillar abscess)
Neisseria gonorrhoeae
69Q: How can throat swabs help in cases of epiglottitis?
A: They help determine etiology, usually Haemophilus influenzae serotype b, and occasionally Streptococcus pneumoniae and Streptococcus pyogenes
70Q: What media are used for routine throat cultures?
A: BAP, CHOC, MAC, SSA (screens for beta streptococci)
71Q: What media are used for throat gonorrhea cultures?
A: CHOC and MTM
72Q: Which organisms are considered upper respiratory pathogens (any quantity)?
A:
Streptococcus pyogenes
Neisseria gonorrhoeae
Corynebacterium diphtheriae (send-out)
Bordetella pertussis / parapertussis (PCR)
73Q: Which organisms are considered potential upper respiratory pathogens when many or predominant?
A:
Beta-hemolytic streptococci (not A)
Arcanobacterium haemolyticum
Streptococcus pneumoniae
Moraxella catarrhalis
Staphylococcus aureus
Haemophilus influenzae
Gram-negative rods (GNR)
Neisseria meningitidis
Yeast
74Q: What organism is Streptococcus pyogenes classified as?
A: Group A Streptococcus
75Q: What illness can some people develop from erythrogenic strains of S. pyogenes?
A: Scarlet fever
76Q: Who is most commonly affected by scarlet fever and what are the symptoms?
A:
Children 5–15 years old
Fever, bright red rash, sore throat
77Q: What serious complications can occur if strep throat or scarlet fever is not treated properly?
Acute glomerulonephritis → inflammation and damage to glomeruli → possible kidney failure
Rheumatic fever → affects heart, joints, brain → permanent heart valve damage and heart failure
78Q: What are the key lab identification characteristics of Streptococcus pyogenes?
A:
Gram-positive cocci in pairs/chains (GPCPrCh)
Catalase negative
PathoDX A positive
PYR positive
Bacitracin susceptible (±)
79Q: Which species most commonly affects humans in Group C Streptococci?
A: Streptococcus dysgalactiae subspecies equisimilis
80Q: What infections are associated with Group C Streptococci?
A: Puerperal sepsis, pharyngitis, pneumonia, osteomyelitis, endocarditis
81Q: Which species is associated with Group G Streptococci?
A: Streptococcus dysgalactiae subspecies equisimilis
82Q: What infections are associated with Group G Streptococci?
A: Puerperal and neonatal sepsis, otitis media, pneumonia, meningitis
83Q: When identifying beta-hemolytic streptococci, which isolates should be typed?
A: Only large colonies without a butterscotch odor
84Q: Which streptococcal group can type as A, C, F, or G?
A: Streptococcus anginosus group
85Q: What infections are associated with Arcanobacterium haemolyticum?
A: Upper respiratory, skin, and soft-tissue infections, including peritonsillar abscess
86Q: Who does Arcanobacterium haemolyticum commonly cause pharyngitis in?
A: Adolescents
87Q: What are the key laboratory characteristics of Arcanobacterium haemolyticum?
A:
Gram-positive pleomorphic rods
Catalase negative
88Q: What is the CAMP reaction of Arcanobacterium haemolyticum?
A: Reverse CAMP positive — inhibits Staphylococcus aureus ATCC 25923 hemolysis
89Q: What are HACEK (AACEK) organisms?
A: Fastidious gram-negative coccobacilli associated with subacute infective endocarditis and part of normal respiratory tract flora
90Q: Which organisms are included in the HACEK (AACEK) group?
A:
Aggregatibacter aphrophilus (previously Haemophilus aphrophilus)
Aggregatibacter actinomycetemcomitans (previously Actinobacillus actinomycetemcomitans)
Cardiobacterium hominis
Eikenella corrodens
Kingella kingae
91Q: What incubation conditions do HACEK organisms require?
A: Enriched incubation with 5–10% CO₂
92Q: What media do HACEK organisms NOT grow on?
A: Traditional enteric media, such as MAC
93Q: How are HACEK organisms fully identified?
A: Using the RAPID NH panel
94Q: Which Haemophilus species are isolated from humans?
A:
Haemophilus influenzae (most important species)
Haemophilus parainfluenzae
Haemophilus haemolyticus
Haemophilus parahaemolyticus
95Q: Where can Haemophilus species normally be found?
A: As part of the normal flora of the oropharynx and nasopharynx
96Q: What are the Gram stain characteristics of Haemophilus species?
A: Pleomorphic, gram-negative coccobacilli to filamentous gram-negative rods
97Q: What are the nutritional requirements of most Haemophilus species?
A: They require X factor, V factor, or both
98Q: What are X factor and V factor for Haemophilus?
A:
X factor = Hemin (intracellular in RBCs, extracellular in blood)
V factor = NAD (nicotinamide adenine dinucleotide) (intracellular in RBCs)
99Q: Why do most Haemophilus strains not grow on 5% sheep blood agar?
A: Sheep blood agar contains X factor (hemin) but lacks V factor (NAD)
Rarely, some strains may grow as pinpoint colonies
100Q: Why does Haemophilus grow on chocolate agar (CHOC)?
A: CHOC contains both X and V factors
101Q: How is chocolate agar prepared and why is it useful?
A: Blood agar is heated, releasing X and V factors, allowing Haemophilus and certain Neisseria to grow
102Q: What diseases can Haemophilus influenzae cause?
A: Meningitis, bacteremia, otitis media, epiglottitis (cellulitis of epiglottis), sinusitis, and pneumonia
103Q: What are the serotype characteristics of Haemophilus influenzae?
A: It may or may not be encapsulated and has 6 polysaccharide capsule types (a–f)
104Q: Which Haemophilus influenzae serotype is the most pathogenic?
A: Type b (Hib)
105Q: Is there a vaccine for Haemophilus influenzae?
A: Yes — a vaccine is available for Hib
106Q: What is the general significance of other Haemophilus species?
A: They are typically normal respiratory tract flora, but can be implicated in endocarditis
107Q: How are Haemophilus species identified in the lab?
A: By X and V growth requirements and hemolysis on rabbit blood agar
108Q: What are the key identification features of Haemophilus influenzae?
A:
Porphyrin test: negative
X factor: required
V factor: required
Hemolysis on rabbit BAP: gamma (none)
109Q: What are the key identification features of Haemophilus haemolyticus?
A:
Porphyrin test: negative
X factor: required
V factor: required
Hemolysis on rabbit BAP: beta
110Q: What are the key identification features of Haemophilus parainfluenzae?
A:
Porphyrin test: positive
X factor: not required
V factor: required
Hemolysis on rabbit BAP: gamma (none)
111Q: What are the key identification features of Haemophilus parahaemolyticus?
A:
Porphyrin test: positive
X factor: not required
V factor: required
Hemolysis on rabbit BAP: beta
112Q: What is the purpose of the X & V growth factor requirement test?
A: To determine X and/or V factor requirements of Haemophilus species and assess hemolysis on rabbit blood agar
113Q: How is the inoculum prepared for the X & V growth factor test?
A:
Inoculate BHI or MH broth with part of one isolated Haemophilus colony growing on CHOC
Do not cool the inoculating loop in agar (prevents carryover of X factor)
114Q: How is the MH agar plate prepared in the X & V growth factor test?
A:
Swab the surface of MH agar with the bacterial suspension
Place X, V, and XV disks on the plate forming an equilateral triangle
115Q: What additional plate is inoculated during the X & V growth factor test?
A: The same suspension is used to swab a rabbit blood agar plate
116Q: What are the incubation conditions for the X & V growth factor test?
Incubate both plates in CO₂ at 35–37 °C for 18–24 hours
117Q: What results are examined after incubation in the X & V growth factor test?
A:
Pattern of growth around X, V, and XV disks
Hemolysis on rabbit blood agar
118Q: What is the purpose of the Porphyrin test?
A: To detect heme synthesis and determine whether an isolate requires X factor or can make its own X factor
119Q: What does the Porphyrin test measure biochemically?
A: The ability to synthesize protoporphyrin intermediates from ALA (aminolevulinic acid)
120Q: Which Haemophilus species are Porphyrin test positive and what does this indicate?
A:
Haemophilus parainfluenzae
Haemophilus parahaemolyticus
→ Fluoresces orange-red, requires V factor only
121Q: Which Haemophilus species are Porphyrin test negative and what does this indicate?
A:
Haemophilus influenzae
Haemophilus haemolyticus
→ No fluorescence, requires X and V factors
122Q: Why do some Haemophilus species not require X factor?
A: They possess enzymes that convert ALA to hemin
123Q: What is the purpose of the Satellite test?
A: To determine whether an organism requires X factor, V factor, or both based on satelliting growth
124Q: How do organisms that require X and V factors behave in the Satellite test?
A: They satellite only on BAP
125Q: How do organisms that require V factor only behave in the Satellite test?
A: They satellite on both TSA and BAP
126Q: Why does satelliting occur near Staphylococcus aureus (SA)?
A: SA produces V factor (NAD)
127Q: What growth factors are provided by BAP and TSA/Nutrient agar?
A:
BAP: provides X factor
TSA/Nutrient agar: does not provide X factor
128Haemophilus influenzae (Satellite on BAP, Satellite on TSA, Hemolysis on RBA)
Satellite on BAP: Positive
Satellite on TSA: Negative
Hemolysis on RBA: Negative
Interpretation: Requires X and V factors
129Haemophilus aegypticus (Satellite on BAP, Satellite on TSA, Hemolysis on RBA)
Satellite on BAP: Positive
Satellite on TSA: Negative
Hemolysis on RBA: Negative
Interpretation: Requires X and V factors
130Haemophilus haemolyticus (Satellite on BAP, Satellite on TSA, Hemolysis on RBA)
Satellite on BAP: Positive
Satellite on TSA: Negative
Hemolysis on RBA: Positive (β-hemolysis)
Interpretation: Requires X and V factors
131Haemophilus parainfluenzae (Satellite on BAP, Satellite on TSA, Hemolysis on RBA)
Satellite on BAP: Positive
Satellite on TSA: Positive
Hemolysis on RBA: Negative
Interpretation: Requires V factor only
132Q: What is Haemophilus aegypticus also known as?
A: Haemophilus influenzae biotype aegypticus
133Q: What infection is Haemophilus aegypticus classically associated with?
A: Purulent conjunctivitis (pink eye)
134Q: What major outbreak is associated with Haemophilus aegypticus?
A: Brazilian purpuric fever epidemic (1984)
135Q: How does Brazilian purpuric fever present?
A: Begins as conjunctivitis and progresses to sepsis with purpura due to small blood vessel leakage under the skin
136Q: How does H. aegypticus compare morphologically to H. influenzae?
A: Looks like H. influenzae but grows slower
137Q: What are the growth factor and biochemical characteristics of H. aegypticus?
A:
Requires X and V factors
Always indole negative
Other H. influenzae strains are indole variable
138Q: What are the general characteristics of Aggregatibacter species?
A: Small gram-negative coccobacilli that are part of healthy periodontal flora
139Q: What infections can Aggregatibacter species cause?
A: Endocarditis, head and neck infections, and brain abscesses
140Q: Which species belong to the Aggregatibacter genus?
A:
Aggregatibacter actinomycetemcomitans (previously Actinobacillus)
Aggregatibacter aphrophilus (previously Haemophilus aphrophilus)
Aggregatibacter segnis
141Q: On which media do Aggregatibacter species grow?
A: BAP and CHOC
142Q: Which Cardiobacterium species is most common?
A: Cardiobacterium hominis
143Q: What are the Gram stain and morphology of Cardiobacterium hominis?
A: Pleomorphic gram-negative rods that may form rosettes and may retain crystal violet stain
144Q: What are the colony characteristics of Cardiobacterium hominis?
A: Smooth, moist, glistening opaque colonies that may pit agar
145Q: What are the growth characteristics of Cardiobacterium hominis?
A:
Microaerophilic
Grows on BAP and CHOC
Does not grow on MAC
146Q: What are the key biochemical and identification features of Cardiobacterium hominis?
A:
Oxidase positive
TSI A/A
Full identification using Rapid NH
147Q: Where is Eikenella corrodens normally found?
A: As normal oral flora of the mouth and upper respiratory tract
148Q: What common oral condition is associated with Eikenella corrodens?
A: Periodontal (gum) disease
149Q: What types of wounds are commonly infected by Eikenella corrodens?
A: Human bite wounds and clenched-fist wounds, often as mixed infections
150Q: What other infections can Eikenella corrodens cause?
A: Ocular infections, head and neck infections, endocarditis, and osteomyelitis
151Q: In what situation may Eikenella corrodens be recovered from blood?
A: Following tooth extractions
152Q: Which patient population is associated with soft tissue infections caused by Eikenella corrodens?
A: IV drug abusers
153Q: What is the Gram stain and morphology of Eikenella corrodens?
A: Slender, straight, small gram-negative bacilli
154Q: What are the colony characteristics of Eikenella corrodens after >24 hours?
A:
Moist, clear centers
Surrounded by flat, spreading growth
Slight yellow pigmentation in older cultures
155Q: What distinctive agar and odor features are seen with Eikenella corrodens?
A:
Pits or corrodes the agar
Produces a bleach-like odo
156Q: What are the growth factor and atmosphere requirements of Eikenella corrodens?
A:
CO₂ enhanced growth
Does not require X or V factors
157Q: What are the key biochemical reactions of Eikenella corrodens?
A:
Oxidase (+)
Catalase (-)
LDC (+)
ODC (+)
158Q: What carbohydrates does Eikenella corrodens ferment?
Does not ferment glucose, lactose, or sucrose
159Q: Which organisms are included in Kingella species?
A: Kingella kingae and Kingella denitrificans
160Q: What are the Gram stain and growth characteristics of Kingella species?
A:
Gram-negative coccobacilli (GNCB)
Grow on BAP and CHOC
Can grow on MTM
Kingella kingae is beta-hemolytic on BAP
May pit the agar
161Q: What infections are commonly associated with Kingella species in children?
A:
Pediatric bacteremia
Osteomyelitis and septic arthritis in children 6–36 months
162Q: How is Kingella typically carried and transmitted?
A:
Asymptomatically carried in the oropharynx
Disseminated by close contact
163Q: What are the Gram stain and morphology of Capnocytophaga species?
A: Long, thin, gram-negative rods with tapered ends
164Q: Where are Capnocytophaga species normally found?
A: As part of the normal flora of the human oral cavity
165Q: What are the colony characteristics of Capnocytophaga species?
A:
Flat, sweaty colonies that spread over the agar surface
Slight yellow pigment
Non-hemolytic
166Q: What are the biochemical characteristics of Capnocytophaga species?
A:
Catalase (-)
Oxidase (-)
167Q: What are the growth characteristics of Capnocytophaga species?
A:
Grow slowly on BAP and CHOC
Do not grow on MAC
Can grow on MTM agar
168Q: Are all Neisseria species part of normal flora?
A: Many species are part of normal flora, but Neisseria gonorrhoeae is NOT a normal flora organism
169Q: What is the Gram stain and morphology of Neisseria species?
A: Gram-negative diplococci, shaped like kidney beans or coffee beans
170Q: What are the growth and biochemical characteristics of Neisseria species?
A:
Capnophilic
Grow best in a moist environment
Oxidase (+)
Catalase (+)
171Q: What is Neisseria meningitidis also known as?
A: Meningococcus
172Q: Where is Neisseria meningitidis normally found and what diseases does it cause?
A:
Part of the normal flora of the upper respiratory tract
Causes meningococcemia and meningitis
173Q: How does Neisseria meningitidis cause systemic disease and how is it transmitted?
A:
Colonizes the URT → enters the bloodstream (meningococcemia) → spreads to the meninges (meningitis)
Transmitted person-to-person via airborne droplets
174Q: What serious complications can result from Neisseria meningitidis infection?
A: Disseminated intravascular coagulation (DIC) and Waterhouse–Friderichsen syndrome
175Q: What are the growth characteristics of Neisseria meningitidis?
A:
Grows well on BAP, CHOC, and MTM
May be encapsulated (mucoid strains)
176Q: What are the key biochemical reactions of Neisseria meningitidis?
A:
Oxidase (+) --- sufficient for jesada
Catalase (+)
Bactitracin Neiss: Glucose (+) -----sufficient for jesada
CTA: Glucose (+), Maltose (+)
177Q: When is BactiCard: Neisseria performed?
A: Only on oxidase-positive, gram-negative diplococci (GNC) growing from MTM
178Q: What substrates are included in the BactiCard: Neisseria test?
A:
IB: 5-bromo-4-chloro-3-indolyl butyrate
BGAL: 5-bromo-4-chloro-3-indolyl-β-D-galactoside
GLUT: gamma-glutamyl-β-naphthylamide
PRO: L-proline-β-naphthylamide
179Q: How is the IB test interpreted?
A:
Read at 2 minutes
Positive (bluereen) → Moraxella catarrhalis
180Q: How is the BGAL test interpreted?
A:
Read at 15 minutes
Positive (blue/ green) → Neisseria lactamica
181Q: How is the PRO/GLUT test performed and interpreted?
A:
After 15 minutes incubation, add color developer
Positive = pink/ red
PRO positive → Neisseria gonorrhoeae
GLUT positive → Neisseria meningitidis
182Q: What are the general features of non-pathogenic Neisseria?
A:
Part of normal flora
Some species may be beta-hemolytic
Oxidase test can help quickly rule them out from pathogens like Streptococcus pyogenes and Staphylococcus aureus
183Q: What are the key characteristics of Neisseria lactamica?
A:
Nonpigmented or yellowish, smooth, transparent
Grows on MTM or NYC and nutrient agar
CTA: Glucose +, Maltose +, Lactose +
184Q: What are the key characteristics of Neisseria sicca?
A:
Nonpigmented, wrinkled, coarse, dry colonies
Does not grow on MTM or NYC; grows on nutrient agar
Glucose +, Maltose +, Sucrose +, Fructose +
185Q: What are the key characteristics of Neisseria subflava?
A:
Greenish-yellow, smooth, adherent colonies
186Q: What are the key characteristics of Neisseria mucosa?
A:
Yellowish, sometimes mucoid
Glucose +, Maltose +, Sucrose +, Fructose +
187Q: What family does Moraxella catarrhalis belong to?
A: Neisseriaceae (formerly Neisseria catarrhalis)
188Q: What is unique about Moraxella catarrhalis within the Moraxella family?
A: It is the only true coccus; other Moraxella species are rod-shaped
189Q: Where is Moraxella catarrhalis normally found?
A: As normal flora of the upper respiratory tract
190Q: What infections are caused by Moraxella catarrhalis?
A: Otitis media, sinusitis, bronchitis, and pneumonia
191Q: What are the colony morphology characteristics of Moraxella catarrhalis?
A:
Non-pigmented
Colonies resemble cold butter (friable or cheesecake-like)
May appear dull and waxy
192Q: What confirmatory test is performed when Moraxella catarrhalis is suspected?
A: Butyrate test (catarrhalis disk)
193Q: What is the Gram stain of Moraxella catarrhalis?
A: Gram-negative diplococci (GNDC)
194Q: What are the growth and colony morphology features of Moraxella catarrhalis?
:
Grows on BAP and CHOC
Non-pigmented colonies
Colonies resemble cold butter (friable) or cheesecake
May appear dull and waxy
Colonies slide on agar like a hockey puck
195Q: What are the key biochemical characteristics of Moraxella catarrhalis?
A:
Oxidase (+)
Butyrate (+) (catarrhalis disk)
DNase (+)
Asaccharolytic
196Q: What are the key growth characteristics used for GNDC identification? (Growth on : MTM, BAP, CAP)
A:
Neisseria gonorrhoeae: MTM +, BAP –, CAP +
Neisseria meningitidis: MTM +, BAP +, CAP +
Moraxella catarrhalis: MTM variable, BAP +, CAP +
197Q: How do carbohydrate utilization patterns differentiate GNDC organisms?
A:
Neisseria gonorrhoeae: Glucose + only
Neisseria meningitidis: Glucose +, Maltose +
Moraxella catarrhalis: No glucose, maltose, lactose, or sucrose fermentation
198Q: Which GNDC organism is DNase/Butyrate positive?
A: Moraxella catarrhalis
199Q: What is Rothia mucilaginosa formerly known as?
A: Stomatococcus
200Q: What are the Gram stain and morphology of Rothia mucilaginosa?
A: Gram-positive cocci that are encapsulated and tend to form clumps and tetrads
201Q: What are the colony characteristics of Rothia mucilaginosa?
A: Gray-white colonies that strongly adhere to agar (“sticky staph”)
202Q: Where is Rothia mucilaginosa normally found and what infections can it cause?
A:
Part of normal respiratory flora
May cause opportunistic infections such as endocarditis and bacteremia
203Q: What are the key biochemical reactions of Rothia mucilaginosa?
A: Catalase negative and coagulase negative
204Q: What are the Gram stain characteristics of Bordetella species?
A: Small gram-negative coccobacilli with pale staining
Requires counterstain for 2 minutes with safranin or basic fuchsin
205Q: What specialized media are required for growing Bordetella species?
A: Bordet-Gengou and Regan-Lowe media
206Q: What are the key features of Bordet-Gengou agar?
A:
Contains glycerol (stabilizing agent), potato infusion (starch), and 20% sheep blood
Antibiotics (e.g., cephalexin, methicillin) may be added to make it selective
Short shelf-life (~1 week)
207Q: What are the key features of Regan-Lowe agar?
A:
Contains charcoal (absorbs/neutralizes inhibitory substances) and 10% horse blood
Available with or without cephalexin
Longer shelf-life (several weeks)
208Q: What disease is caused by Bordetella pertussis and Bordetella parapertussis?
A: Pertussis (whooping cough) — a highly contagious, acute upper respiratory tract infection, usually a disease of children
209Q: What are the three clinical stages of pertussis?
A:
Catarrhal – coughing with mucous
Paroxysmal – whooping cough
Convalescent
210Q: What specimens are used for culture and isolation of Bordetella?
A: Pernasal or nasopharyngeal swabs using calcium alginate swabs
211Q: How should Bordetella specimens be handled if bedside plating is not possible?
A: Use transport media, such as Regan-Lowe transport media
212Q: How can Bordetella species be detected in the laboratory?
A: PCR or DFA
213Q: What are the colony characteristics of Bordetella pertussis?
A:
On Regan-Lowe (RL): small, smooth, round, shiny, convex (“mercury droplet”); older colonies are whitish-gray
On Bordet-Gengou (BG): may show slight beta-hemolysis
214Q: How do Bordetella parapertussis colonies appear?
On Regan-Lowe (RL): duller, slightly larger than B. pertussis
Older colonies appear brown-ish green
215Q: What are the colony characteristics of Bordetella bronchiseptica?
Can grow on BAP
Appears as grayish-white, flat colonies
216Q: What infections are caused by Bordetella bronchiseptica?
A:
Respiratory tract infections in animals (e.g., kennel cough in dogs)
Human infections such as sepsis, bronchitis, and pneumonia, usually in immunocompromised individuals, sometimes linked to animal contact
217Q: What are the Gram stain and growth characteristics of Bordetella bronchiseptica?
A:
Medium gram-negative rods
Grows on BAP, CAP, and MacConkey
Growth in 1–2 days
218Q: Which organism can Bordetella bronchiseptica be biochemically confused with?
A: Alcaligenes species
219Q: What are the key biochemical reactions of Bordetella bronchiseptica?
A:
Motility: (+)
Oxidase: (+)
Catalase: (+)
Nitrate reduction: (+)
Urease: (+) (within 4 hours)
220Q: What are the key biochemical characteristics of Alcaligenes species?
A:
Motility: positive
Oxidase: positive
Catalase: positive
Nitrate reduction: positive
Urease: positive
Note: Biochemically similar to Bordetella bronchiseptica, which is why they can be confused
221Q: What are the key identifying features of Bordetella pertussis?
A:
Oxidase: +
Catalase: +
Motility: –
Nitrate reduction: –
Urease: –
Citrate: –
Pigment on heart infusion agar: –
Growth:
Bordet-Gengou: 2–6 days
Regan-Lowe: 3–6 days
No growth on Blood, Chocolate, or MacConkey agar
222Q: What are the key identifying features of Bordetella parapertussis?
Oxidase: –
Catalase: +
Motility: –
Nitrate reduction: –
Urease: + (24 hours)
Citrate: +
Pigment on heart infusion agar: + (brown pigment)
Growth:
Bordet-Gengou: 1–3 days
Regan-Lowe: 2–3 days
Blood agar: 1–3 days
Chocolate agar: 1–3 days
MacConkey: variable
223Q: What are the key identifying features of Bordetella bronchiseptica?
Oxidase: +
Catalase: +
Motility: +
Nitrate reduction: +
Urease: + (4 hours)
Citrate: +
Pigment on heart infusion agar: –
Growth:
Bordet-Gengou: 1–2 days
Regan-Lowe: 1–2 days
Blood agar: 1–2 days
Chocolate agar: growth
MacConkey: growth
224Q: Where is Corynebacterium diphtheriae found and what infection does it cause?
A: Found only in humans; infects the upper respiratory tract and causes diphtheria via a cytotoxic exotoxin
225Q: What is the difference between toxigenic and non-toxigenic strains of C. diphtheriae?
A:
Strains may be toxigenic or non-toxigenic
Only toxigenic strains cause diphtheria
Toxigenic strains may cause upper respiratory tract and systemic damage
226Q: What is the diphtheritic pseudomembrane and why is it dangerous?
Composed of necrotic epithelial cells, white blood cells, bacteria, and fibrin
Forms in the oropharynx and may obstruct the airway
227Q: How does diphtheria toxin cause systemic effects?
A:
Toxin produced in the respiratory tract is absorbed into the body
Can damage the heart and nervous system
228Q: Can people be colonized with Corynebacterium diphtheriae without disease?
A: Yes, some people are colonized with non-toxigenic strains
229Q: What other infections can be caused by C. diphtheriae?
A: Cutaneous diphtheria and endocarditis, caused by toxigenic or non-toxigenic strains
230Q: What is the treatment for diphtheria?
A: Antitoxin, airway clearance, and antibiotics
231Q: How is Corynebacterium diphtheriae most often diagnosed?
A: Diagnosis most often occurs through clinical presentation
232Q: What specimens are collected for suspected Corynebacterium diphtheriae?
A:
Throat swab of inflammatory lesion
Nasopharyngeal swab
233Q: What media are used to culture Corynebacterium diphtheriae?
A:
BAP
Loeffler’s serum medium
Cystine-tellurite medium or Tinsdale agar
234Q: What is Loeffler’s serum medium used for in C. diphtheriae identification?
A:
Contains horse serum and egg
Enhances deep blue metachromatic granules when stained with methylene blue
Not recommended for primary isolation
235Q: How does Corynebacterium diphtheriae appear on cystine-tellurite or Tinsdale agar?
A:
Normal flora inhibited by tellurite
Grayish-black colonies after 24–48 hours due to tellurite reductase
Brown halo due to cysteinase activity
236Q: What must be done if Corynebacterium diphtheriae is isolated?
A: Notify Public Health
237Q: What is the Gram stain and morphology of Corynebacterium diphtheriae?
A: Pleomorphic gram-positive rods
238Q: Which organisms must Corynebacterium diphtheriae be differentiated from?
A: Corynebacterium ulcerans and Corynebacterium pseudotuberculosis
239Q: What methods can be used to identify Corynebacterium diphtheriae?
A:
API Coryne
Molecular methods
EIA
240Q: What are the key biochemical reactions of Corynebacterium diphtheriae?
A:
Catalase: +
Esculin: –
Glucose: +
Urea: –
Nitrate: +
Reverse CAMP: –
241Q: How do C. ulcerans and C. pseudotuberculosis differ biochemically from C. diphtheriae?
A:
C. ulcerans:
Catalase +, Esculin –, Glucose +, Urea +, Nitrate –, revCAMP +
C. pseudotuberculosis:
Catalase +, Esculin –, Glucose +, Urea +, Nitrate variable, revCAMP +
242Q: What toxin tests are used for Corynebacterium diphtheriae?
A:
In vivo: guinea pig or rabbit
In vitro: ELEK test (precipitin test)
243Q: What does the ELEK test detect?
A: It detects diphtheria toxin production
244Q: How is the ELEK test set up?
A:
Filter paper strip saturated with diphtheria antitoxin is embedded in agar
Test isolate, positive control, and negative control are streaked onto the agar
Streaks are parallel to each other and perpendicular to the filter paper
245Q: How long is the ELEK test incubated?
A: 1–2 days
246Q: How is a positive ELEK test interpreted?
A:
A line of precipitate forms where diphtheria toxin reacts with antitoxin
Lines of identity between the test organism and positive control indicate the organism is toxigenic