Chapter 17 Flashcards
Where are vibrios found?
Vibrios are among the most common bacteria in marine and estuarine waters, worldwide.
Describe vibrios
gram (-); comma-shaped, curved, facultatively anaerobic, fermentative rods; catalase and oxidase positive; most species are motile by means of monotrichous/multitrichous polar flagella; grow within a broad temperature range (14–40°C); halophilic.
Pathogenic vibrios:
Vibrio cholera, Vibrio parahaemolyticus, Vibrio vulnificus.
Typical organisms of V cholera:
gram (-); comma-shaped, curved rod 2-4μm long; motile with polar flagellum; prolonged cultivation may resemble other gram(-) enteric bacteria
Culture of V cholera:
convex, smooth, round; opaque and granular in transmitted light; grows well on 37°C; grows on selective TCBS agar; yellow colonies (sucrose fermenting);
What color colonies do V. parahaemolyticus and V. vulnificus produce on TCBS agar?
green colonies
Optimal pH for V. cholera:
very high pH (8.5-9.5); they are rapidly killed by acid
How are V. cholera specimen collected?
for optimal recovery, specimens should be collected early in the course of the diarrheal illness and inoculated onto agar; if this process is delayed, specimen should be mixed with Cary-Blari medium and refrigerated.
Growth characteristics of V. cholera:
oxidase (+); ferments sucrose and mannose, doesn’t ferment arabinose; halophilic, need presence of NaCl for growth;
How many serogroupd of V. cholera are there?
over 200; determined by O lipopolysaccharide
Which serogroups of V. cholera are epidemic?
V. cholera serogroup O1 and O139
Serotypes of V. cholera O1:
Ogawa, Inaba, Hikojima
Biotypes of V. cholera O1:
classic and E1 Tor
V. cholera E1 Tor is:
hemolysisn (+); positive results on Voges-Proskauer test, resistant to polymyxin B
Vibrio cholera enterotoxin:
heat-liable; subunits A and B; GM1 receptor for subunit B, prompts entry of subunit A; increases intacellular cAMP levels, resulting in hypersecretion of water and electrolytes
The infectious dose of V. cholera in healthy persons:
10^10 or more V. cholera
Which persons are more suceptible to V. cholera infections?
In a persons with achlorhydria or hypochlorhydria; taking medication (PPIs) or conditions that reduce the acidity of the stomach
True or false: V. cholera infects the bloodstream.
False, V. cholera is a noninvasive mucosal pathogen; it doesn’t reach the bloodstream and remains in the GI tract.
Incubation period of V. cholera is:
12 hours to 3 days after ingestion.
Symptoms of V. cholera infection:
sudden onset nausea, vomiting, followed by profuse diarrhea w/ abdominal cramps; stool resembles “rice water”
What is present in the stool of a person with V. cholera infection?
resembles “rice water” and contains mucus, epithelial cells, and large number of vibrios.
The rate of the fluid loss in V. cholera infection:
1L/hour
What does rapid loss of fluid lead to in patients with V. cholera infection?
profound dehydration, painful muscle spasms, metabolic acidosis, hypokalemia, and hypovolemic shock with circulatory collapse, and anuria with associated renal failure.
Which type of microscope is used to observe Vibrio cholera?
Dark-field microscopy and phase-contrast microscopy
What is the motility type in V. cholera O1?
“Shooting star” motility; used to detect these organism; by addition of O1 antiserum the movement stops
What provides the immunity to V. cholera infection?
gastric acid is the main source of immunity to V. cholera; presence of antitoxin antibodies has not been associated with protection; in experimental animals presence of IgA antibodies have been described.
Which drugs are used against V. cholera?
Tetracycline; Erythromycin and azithromycin (children, pregnant women); trimethoprim-sulfamethoxazole, fluoroquinolones, and doxycycline.
