bacterial infection (D-M) Flashcards
which bacteria causes diphtheria?
- toxigenic strains of Corynebacterium diphtheriae biotype mitis, gravis, intermedius, or belfanti.
- toxigenic strains of C. ulcerans also cause rare cases of a diphtheria-like illness.
how does diphtheria get tramismitted?
person-to-person - respiratory dropelts or direct contact with secretions
where is diphtheria endemic to?
Haiti, Dominican Republic, Asia and South Pacific, Eastern Europe, the Middle East
Since 2016, respiratory diph outbreak occurred in Bangladesh, Burma (Myanmar), Haiti, Indonesia, S Africa, Ukraine, Venezuela, Vietnam, Yemen
Cutnaneous diph common in tropical countries
symptoms of diphtheria?
- incubation period 2-5 days
- respiratory diph: gradual onset, mild fever (38.3), sore throat, difficulty swallowing, malaise, loss of appetite, hoarseness; pseudomembrane (firm, fleshy, grey, adherent) - 5-10% fatal
how to diagnose diphtheria?
culture taken from area and test for toxin production by the Elek test.
how to treat diphtheria
- hospitalization required!
- DAT (equine diphtheria antitoxin)
- AB: erythromycin or penicillin
- supportive care
- close contacts of patients should receive AB prophylaxis with erythromycin or penicillin
which E. coli pathoptypes are associated with diarrhea?
ETEC, STEC, EPEC, EAEC, EIEC, (DAEC)
ETEC: enterotoxigenic
STEC: shiga toxin-producing, also called verotoxigenic (VTEC); eterohemorrhagic E.coli (EHEC) is commonly used to specify STEC strains capable of causing human illness, especially bloody diarrhea and hemolytic uremic syndrome (HUS)
EPEC: enteropathogenic
EAEC: enteroaggregative
EIEC: enteroinvasive
DAEC: diffusely adherent
how does diarrheagenic E. coli pathotypes can be trasmitted?
feces of humans and other animals; fecal-oral
humans - non-STEC pathotypes
animals (cattle and other ruminants) - STEC
what is the global burden of diarrheagenic E.coli?
111 million illnesses, 63,000 deaths / year
ETEC are associated with travel to low- and middle-income countries
which countries has high risk for traveller’s diarrhea?
Afhanistan, Burma (Myanmar), the Indian subcontinent, Indonesia, Iran, Malaysia, Mexico, Papua New Guinea, most countries in Africa, countries in Central America and northern South America, including Bolivia and Paraguay
what is incubation period of non-STEC diarrheagenic E.coli and STEC?
8 hours to 3 days for non-STEC
3-4 days for STEC
what is the symptoms of STEC, and how to diagnose STEC infection? why is it important to diagnose STEC?
watery diarrhea that progresses to bloody diarrhea in 1-3 days (often for STEC O157) ; abdominal cramps and tenderness; fever low-grade, if present
stool samples - test for Shiga toxins or the genes that encode them
Hemolytic uremic syndrome complicates ~6% of diagnosed STEC O157 infections (15% kids <5 years) and 1% of non-O157 STEC infections)
how to treat diarrheagenic E.coli?
hydration and electroylte balance
loperamide - if mild and non-bloody diarrhea
AB - moderate to severe diarrhea
why is azithromycin preferred over fluoroquinolones for traveler’s diarrhea?
less resistant - fluoroquinolone resistance increase in Asia
fluoroquinolone side effect: tendinopathies, QT interval prolognation, C. diff enterocolitis
what do you need to do if AB treatment does not improve diarrhea within 24 hours?
- continue AB for no longer than 3 days
- 3-day rifaximin is effective for some non-bloody diarrheal illnesses.
- if STEC suspected, certain AB can increase risk of developing HUS (hemolytic uremia syndrome); IV fluids withing the first 4 days of diarrhea onset) might decrease the risk of oligoanuric renal failure
is there a vaccine for E.coli infection?
no vaccine is available.
what is helicobacter pylori?
gram -, rod-shaped, small, curved, microaerophilic
how does H. pylori trasmitted?
fecal-oral route, oral-roal possible
what illness does H. pylori infection cause?
peptic ulcer disease, gastritis, risk factor for non-cardia gastric adenocarcinoma (2-6 times increased risk of developing gastric cancer and mucosal assoicated-lymphoid-type (MALT) lymphoma)
how to diagnose H.pylori?
fecal antigen assay, urea breath test, rapid urease test, histology of a biopsy specimen
A positive serology indicates present or past infection
how to treat h. pylori?
standard - bismuth quadruple therapy
- PPI or H2 blocker, bismuth, metronidazole, tetracycline
Clarithromycin triple therapy: in regions where clarithromycin resistance is <15% and in patients with no previous history of macrolide exposure
- PPI, clarithromycin, amoxicillin or metronidazole
Refractory cases: combination tx with rifabutin
what is Legionnaires’ disease and Pontiac fever caused by ?
genus Legionella - gram negative - most cases of Legionnaires’ disease are caused by Legionella pneumophila
how dose Legionnaires’ disease trasmitted?
inhalation of aerosolized water containing the bacteria
freshwater; warm water, water stagnation, presence of scale, sediment, and biofilm in the pipes and fixtures, absence of disinfectant
potable water (via showerheads and faucets), cooling towers, hot tubs, decorative fountains
which country is Legionnaires’ disease affected?
worldwid
who is at risk of getting Legionnaire’s disease?
> 50 years, current or former smokers, chronic lung conditions, immunocompromised
what are the symptoms of Legionnaires’ disease?
severe pneumonia - fatal 10%
symptoms onset occurs 2-10 days after exposure
<5% of people exposed to the source of the outbreak develop Legionnaires’ disease
what is the difference between Legionnaires’ disease and Pontiac Fever?
Pontiac Fever is milder than Legionnaires’ disease and presents with fever, headache, or muscle aches, but no signs of pneumonia.
- symptoms occur within 72 hours of exposure
- fully recover without AB drug therapy or hospitalization
- upto 95% of ppl exposed during outbreaks of Pontiac fever can develop symptoms of disease.
how to diagnose Legionnaires’ disease?
Legionella urinary antigen test and culture of lower respiratory secretions (sputum, bronchoalveolar lavage)
- urinary antigen test only detects L. pneumophila serogroup 1; 80-90% of cases
- Legionella spp. cannot be isolated in people who have Pontiac fever.
how to treat Legionnaires’ disease?
AB stat - fluoroquinolones and macrolides
how to prevent Legionnaire’s disease?
water management programs and devices
what is the causative agent of leptospirosis?
Leptospira spp - obligate aerobic, gram negative spirochete bacteria
how are Leptospira trasmitted?
abrasions or cuts in the skin or through the conjuctiva and mucous membranes; macerated skin resulting from prolonged water exposure
direct contact with urine or reproductive fluids from animals (rodents!! dogs, horses, cattle, swine, many wildlife species), urine-contaminated freshwater sources or wet soil
eating contaminated food or water
rarely through animal bites or human-to-human contact
what is the distrubtion of Leptospirosis?
worldwide - but greater in tropical climates
highest morbidity and mortality - sub-Saharan Africa, parts of Latin America, and in the Caribbean, South and Southeast Asia, Oceania
who is at increased risk of Leptospirosis?
participate in recreational freshwater activities (boating, swimming) after heavy rainfall or flooding
participate in activities involving mud (adventure races)
working directly with animals in endemic areas