MOLECULAR TECHNIQUES TO PROCESS BODY FLUID SAMPLES

Question 1

PCR techniques for the detection of bacteria or fungi are

Answer 1

available for the improved management of
immunosuppressed or high-risk patients

Question 2

Most available PCR techniques rely on

Answer 2

the amplification
and sequencing of the 16SrRNA gene in bacteria and the internal transcribed region 2 in fungi

Question 3

Amniotic fluid is often sent for molecular analysis for

Answer 3

the presence of specific genetic markers linked to diseases, such as Down syndrome and cystic fibrosis, or infection, such as cytomegalovirus

Question 4

PCR methods focus on

Answer 4

the amplification of gene sequences unique to the disease
being tested for.

Question 5

COMMON PATHOGENS OF NORMALLY STERILE BODY FLUIDS

Answer 5

Neisseria species
S. aureus
Beta-hemolytic streptococci
Enterococcus
Enterobacteriaceae
P. aeruginosa
C. perfringens
B. fragilis

Question 6

Neissera species in body fluids

Answer 6

Outer membrane pili: enhance adhesion and inhibit phagocytosis
o Lipopolysaccharide endotoxin and IgA proteases
o Encapsulated strains: resistant to phagocytosis and complement-mediated lysis

Question 7

S. aureus in body fluids

Answer 7

Exotoxins: hemolysins, leukocidins, spreading factor by coagulase and hyaluronidase,
nuclease, protease, and lipase
o Most strains; penicillin resistance due to beta-lactamase
o MRSA: methicillin-resistant strain

Question 8

Beta-hemolytic streptococcus in body fluids

Answer 8

O2-stable streptolysin S, O2-labile streptolysin O
o Streptococcal pyrogenic exotoxin B: inhibits action of immunoglobulins, cytokines, and
complement
o Hyaluronidase acts as a bacterial spreading factor

Question 9

Enterococcus species in body fluid

Answer 9

Adhesion factors facilitating binding to host cells, inducing cell and tissue destruction
o Intrinsic antibiotic resistance of various species:
❖ Beta-lactam antibiotics: penicillin, cephalosporin, carbapenem
❖ Aminoglycosides: vancomycin-resistant Enterococcus (VRE)

Question 10

Enterobacteriaceae in body fluids

Answer 10

All species release lipopolysaccharide endotoxin; some also produce exotoxins
o H, K, and O antigens
o Some strains express resistance to carbapenem antibiotics

Question 11

P. aeruginosa in body fluids

Answer 11

Lipopolysaccharide endotoxin, hemolysins, protease
o Exotoxin A: toxic to macrophages, prevents phagocytosis
o Encapsulated: inhibits phagocytosis and actions of complement

Question 12

C. perfringens in body fluids

Answer 12

enterotoxin, alpha and beta toxins: damage tissues, blood vessels, and
blood cells
o Hemolysins, proteases, lipases, collagenase, and hyaluronidase: aid in invasive
processes

Question 13

B. fragilis in body fluids

Answer 13

Polysaccharide encapsulation: protects from phagocytosis, stimulates abscess formation
o Penicillin resistance due to beta-lactamase