Common Bacterial Pathogens 2 Flashcards
Streptococci are _________.
Gram-positive cocci, usually in chains or pairs, that are catalase negative
Gram-positive cocci are usually either ______ (catalase +) or __________ (catalase-).
staphylococcus; streptococcus
Staphylococci are usually either _______ (coagulase+) or ________ (coagulase-).
aureus; SSNA
Group A streptococci are ______.
streptococcus pyogenes
Group A typically cause __________.
throat infections, wound infections, and post-strep sequlae
What factors allow streptococcus pyogenes to cause pharyngitis?
Adherence proteins (especially M-protein); invasion proteins (such as streptolysin S); anti-phagocytic proteins (M-protein again, because it reduces C3b’s ability to bind by binding to Factor H, a natural anti-opsonin)
People recover from strep by ________.
developing antibodies against M proteins
Streptolysin O might play a role in rheumatic fever by ________.
damaging the heart valves and exposing sequestered antigens
The three most common causes of bacterial endocarditis are _________.
staphylococcus aureus, streptococcus viridans, and coagulase negative staphylococci
Gamma hemolysis is __________.
actually non-hemolytic
Beta-hemolysis is ____________.
complete clearance of RBCs
There are both invasive (___________) and non-invasive (____________) forms of streptococcal infections.
meningitis and septicemia; pneumonia, sinusitis, and bronchitis
Streptococcus pneumoniae can become pathogenic by __________.
developing anti-phagocytic capsules
In pneumococcal pneumonia, the alveolae will have _________.
exudates due to the inflammatory response
Predisposing factors to pneumococcal pneumonia include ___________.
alcoholism, viral infection, and being very young or very old
Enterococcus faecium and faecalis are _____________.
normal flora that cause UTIs and GI infections (upon breaching the GI epithelium)
Nosocomial infections are _____________.
infections acquired in hospitals
Of the Gram-positive rods, the ones that are most associated with human disease are _________.
clostridium
Clostridia are _________.
strict anaerobes that form endospores
The genus clostridium includes _________.
the agents that cause C. difficile, tetanus, botulism, and gangrene
Clostridium difficile causes ___________.
nosocomial diarrhea and (more rarely) pseudomembranous colitis
Suspect C. difficile when patients develop diarrhea _________.
after being admitted to the hospital and receiving antibiotics
Clostridium tetani often infect sites of local infection because _________.
they need anaerobic sites to grow, and the inflammatory response to an injury can produce such a walled-off site
C. tetani toxin blocks __________.
inhibitory neurons of the central nervous system
Clostridium botulinum is a __________.
Gram-positive rod that is found in soil and on animals; it can survive the canning process–uncooked food can be lethal, because the toxin blocks the acetylcholine receptor and results in flaccid paralysis
The cause of gas gangrene is ____________.
clostridium perfringens
C. perfringens kills cells by __________.
secreting alpha toxin, which cleaves phospholipases that then induces apoptosis
Enterotoxins are not __________.
endotoxins–they are substances secreted by the cell that damage the host
_________ and _________ are Gram-negative rods.
Eschericia coli; pseudomonas aeruginosa
ETECs are ____________.
enterotoxogenic bacteria
Toxic E. coli do not kill cells, rather, they _________.
disrupt the electrolyte balance of the gut
Pseudomonas aeruginosa are everywhere; they typically only become a problem in ____________.
wounds (like traumas, burns, or surgeries) and those with cystic fibrosis
Those with cystic fibrosis are usually infected with ______ early in life and _______ later in life.
staphylococcus aureus; pseudomonas aeruginosa, possibly because of P. aeruginosa’s resistance to anti-staph antibiotics
Neisseria are _________.
Gram-negative diplococci
Neisseria gonorrhoeae can fight leukocytes by ________.
using their pili to interfere with neutrophil killing
Because neisseria gonorrhoeae infect mucosal surfaces, they __________.
induce an inflammatory response that creates exudate
In males, N. gonorrhoeae usually leads to just ________, while in females, _________ often occur.
urethritis (if any symptoms arise); inflammation of the vagina, cervix, and fallopian tubes, with resultant fibrosis producing infertility
Anaerobic niches include __________.
the colon, mouth, skin (“down in the pores”), and female genital tract
Anaerobic bacteria usually cause ______ infections.
mixed (with aerotolerant bacteria)
__________ is rather aerotolerant anaerobe that is found in many abscesses below the diaphragm.
Bacteroides fragilis
Chlamydia trachomatis is an ____________.
obligate intracellular bacteria; it causes trachoma (a chronic infection of the conjunctivae that leads to scarring), sexually transmitted urethritis, neonatal conjunctivitis, and neonatal pneumonia
Mycoplasmic bacteria lack __________.
cell walls, thus they are resistant to drugs that attack bacterial cell walls
Mycoplasma pneumoniae causes __________.
community-acquired pneumonia (“walking pneumonia,” that is, a milder pneumonia); it adheres to respiratory epithelia and destroys host cells by producing hydrogen peroxide and superoxide
Walking pneumonias do not have _________.
product/phlegm
