Page 217 - Review of Medical Microbiology and Immunology ( PDFDrive )

mebooksfree.com
mebooksfree.com
mebooksfree.com

mebooksfree.com
mebooksfree.com
mebooksfree.com
mebooksfree.com
mebooksfree.com mebooksfree.com mebooksfree.com participate in mixed anaerobic infections, infected human mebooksfree.com
mebooksfree.com
PART II Clinical Bacteriology
206
Doxycycline and ceftriaxone are effective treatment choices.
bites, stasis ulcers, etc.
There is no vaccine. Wearing clothing impregnated with
Permethrin can reduce the risk of tick bites.
LEPTOSPIRA

Leptospiras are tightly coiled spirochetes with hooked
1. Your patient is a 65-year-old man with gradually increasing confu-
ends. They stain poorly with dyes and so are not seen by
sion and unsteadiness while walking. A lumbar puncture revealed
light microscopy, but they are seen by dark field micros- SELF-ASSESSMENT QUESTIONS
clear spinal fluid, a normal glucose, and an elevated protein. There
copy. They grow in bacteriologic media containing serum.
mebooksfree.com mebooksfree.com mebooksfree.com (A) It is transmitted by tick bite. mebooksfree.com mebooksfree.com
mebooksfree.com
3
were 96 cells/mm , of which 86% were lymphocytes. Gram stain
Leptospira interrogans is the cause of leptospirosis. Lepto-
of the cerebrospinal fluid (CSF) was negative. Magnetic resonance
spirosis is common in tropical countries, especially in the
imaging (MRI) of the brain was normal. A sample of CSF reacted
rainy season, but is rare in the United States. Leptospira inter-
with beef heart cardiolipin at a titer of 1/1024. Regarding the caus-
rogans is divided into serogroups that occur in different
ative organism of his infection, which one of the following is most
accurate?
animals and geographic locations. Each serogroup is subdi-
vided into serovars by the response to agglutination tests.
(B) Resistance to penicillin G is common, so ceftriaxone should be
Leptospiras infect various animals, including rats and
used.
other rodents, domestic livestock, and household pets. In
(C) It has never been grown on bacteriologic media in the clinical
the United States, dogs are the most important reservoir.
laboratory.
Animals excrete leptospiras in urine, which contaminates
(D) It is unlikely to be eradicated because beef cattle are a major
water and soil.
reservoir for the organism.
Swimming in contaminated water or consuming con-
(E) A confirmatory test for this organism utilizes an agglutination
taminated food or drink can result in human infection.
mebooksfree.com
mebooksfree.com
mebooksfree.com mebooksfree.com mebooksfree.com 2. Your patient is a 20-year-old man with an erythematous, macular, mebooksfree.com
reaction with the capsular polysaccharide of the organism.
Outbreaks have occurred among participants in triathlons
and adventure tours involving swimming in contaminated
nonpainful rash on the right arm for the past 4 days. The rash is
waters. Miners, farmers, and people who work in sewers
approximately 10 cm in diameter. He also has a fever to 100°F and
are at high risk. In the United States, the urban poor have a
a mild headache. He reports hiking on several weekends recently
in New York State. You suspect the rash is erythema migrans and
high rate of infection as determined by the presence of
that he has Lyme disease. Which one of the following is the best
antibodies. Person-to-person transmission is rare.
approach to confirm your clinical diagnosis?
Human infection results when leptospiras are ingested
(A) Detect IgM antibodies in an ELISA assay
or pass through mucous membranes or skin. They circulate
(B) Determine the titer in a VDRL test
in the blood and multiply in various organs, producing
(C) Gram stain and culture on blood agar incubated aerobically
fever and dysfunction of the liver (jaundice), kidneys (ure-
(D) Gram stain and culture on blood agar incubated anaerobically
mia), lungs (hemorrhage), and central nervous system
(E) Grow on human cells in cell culture and identify with fluores-
(aseptic meningitis). The illness is typically biphasic, with
cent antibody
fever, chills, intense headache, and conjunctival suffusion 3. Assume the patient in Question 2 does have Lyme disease. Which
mebooksfree.com
mebooksfree.com mebooksfree.com mebooksfree.com 4. Regarding syphilis, which one of the following is most accurate? mebooksfree.com
mebooksfree.com
(diffuse reddening of the conjunctivae) appearing early in
one of the following antibiotics is the most appropriate to treat his
the disease, followed by a short period of resolution of these
infection?
symptoms as the organisms are cleared from the blood. The
(A) Azithromycin or trimethoprim-sulfamethoxazole
second, “immune,” phase is most often characterized by the
(B) Doxycycline or amoxicillin
findings of aseptic meningitis and, in severe cases, liver
(C) Gentamicin or amikacin
damage (jaundice) and impaired kidney function. Serovar-
(D) Metronidazole or clindamycin
(E) Penicillin G or levofloxacin
specific immunity develops with infection.
Diagnosis is based on history of possible exposure, sug-
(A) The characteristic lesion of primary syphilis is a painful vesicle
gestive clinical signs, and a marked rise in IgM antibody
on the genitals.
titers. Occasionally, leptospiras are isolated from blood and
urine cultures.
chance of transmitting the disease to others is low.
The treatment of choice is penicillin G. There is no signifi-
(C) In secondary syphilis, both the rapid plasma reagin (RPR) and
cant antibiotic resistance. Prevention primarily involves avoid- (B) In secondary syphilis, the number of organisms is low, so the
the fluorescent treponemal antibody-absorbed (FTA-ABS)
mebooksfree.com mebooksfree.com mebooksfree.com (E) In congenital syphilis, no antibody is formed against T. palli- mebooksfree.com
mebooksfree.com
mebooksfree.com
ing contact with the contaminated environment. Doxycycline
tests are usually positive.
is effective in preventing the disease in exposed persons.
(D) The antibody titer in the FTA-ABS test typically declines when
the patient has been treated adequately.
OTHER SPIROCHETES
dum because the fetus is tolerant to the organism.
Anaerobic saprophytic spirochetes are prominent in the
normal flora of the human mouth. Such spirochetes
mebooksfree.com mebooksfree.com mebooksfree.com mebooksfree.com mebooksfree.com mebooksfree.com