How is Y. pestis typically transmitted?

How is Y. pestis typically transmitted?Answer: Rat-flea bite/contact with infected animal (bubonic plague) or via respiratory aerosols (pneumonic...

What diseases does Y. pestis cause?

What diseases does Y. pestis cause?Answer: Bubonic plague (most common), septicemic plague, and pneumonic pla...

Describe the morphology of Yersinia pestis:

Describe the morphology of Yersinia pestis:Answer: Nonmotile, bipolar staining pleomorphic gram-negative coccobacil...

Which zoonotic organisms are facultative intracellular organisms?

Which zoonotic organisms are facultative intracellular organisms?Answer: Francisella, Brucella, and Yersi...

Name the five medically important zoonotic gram-negative rods:

Name the five medically important zoonotic gram-negative rods:1. Yersinia2. Francisella3. Brucella4. Pasteurella5. Bartone...

A 70-year-old man with diabetes presents with severe left ear pain and discharge. On physical examination, there is granulation tissue seen in the ear canal.

A 70-year-old man with diabetes presents with severe left ear pain and discharge. On physical examination, there is granulation tissue seen in the ear...

A 10-year-old girl with cystic fibrosis presents with 2 days of high fever and a cough productive of purulent green sputum. On chest x-ray (CXR) there is a left upper lobe (LUL) infiltrate. What is the most likely pathogen contributing to her symptoms? Appropriate treatment?

A 10-year-old girl with cystic fibrosis presents with 2 days of high fever and a cough productive of purulent green sputum. On chest x-ray (CXR) there...

Which bacterium, which has reservoirs in water sources, causes hot tub folliculitis, characterized by pruritic or tender follicular lesions following bathing in a hot tub, whirlpool, or public swimming pool.

Which bacterium, which has reservoirs in water sources, causes hot tub folliculitis, characterized by pruritic or tender follicular lesions following...

A young child presents with a 2-week history of mild upper respiratory symptoms and a severe paroxysmal cough, followed by high-pitched inspiratory whoop. A complete blood count (CBC) reveals marked lymphocytosis. What is the likely diagnosis and causative organism?

A young child presents with a 2-week history of mild upper respiratory symptoms and a severe paroxysmal cough, followed by high-pitched inspiratory whoop....

An older man with a significant history of smoking and alcohol consumption presents with a fever, nonproductive cough, and shortness of breath. Several of his coworkers have had similar symptoms over the preceding months, and his workplace is investigating whether the air conditioner may be a source of infection. He also uses a humidifier in his home. What is the likely diagnosis and organism? How is the organism visualized?

An older man with a significant history of smoking and alcohol consumption presents with a fever, nonproductive cough, and shortness of breath. Several...

What population is especially susceptible to K. pneumoniae and what is the characteristic appearance of the sputum?

What population is especially susceptible to K. pneumoniae and what is the characteristic appearance of the sputum?Answer: Alcoholics, diabetics,...

Describe the appearance of K. pneumoniae colonies and whatgives them this appearance?

Describe the appearance of K. pneumoniae colonies and whatgives them this appearance?Answer: Appear as mucoid colonies due to large capsule s...

Klebsiella pneumoniae causes what diseases?

Klebsiella pneumoniae causes what diseases?Answer: Necrotizing lobar pneumonia, nosocomial UTIs, bacteremia, and wound infect...

Describe the biochemical characteristics of Klebsiella pneumoniae.

Describe the biochemical characteristics of Klebsiella pneumoniae.Answer: Lactose-fermenting, encapsulated, nonmotile (ie, lacks H antig...

What are the signs and symptoms of Pontiac fever and how does it differ from Legionnaires' disease?

What are the signs and symptoms of Pontiac fever and how does it differ from Legionnaires' disease?Answer: Pontiac fever includes generalized headache,...

What are the treatment options for Legionnaires' disease?

What are the treatment options for Legionnaires' disease?Answer: Mortality from Legionnaires' disease can approach 30% to 50% in untreated patients,...

What stain is required to visualize L. pneumophila?

What stain is required to visualize L. pneumophila?Answer: Silver staining or immunofluorescent staining. Legionella pneumophila stains poorly with...

What have been the major sources for Legionnaires' disease?

What have been the major sources for Legionnaires' disease?Answer: Water sources (air conditioners, water distribution systems, and the like) due...

How is Legionnaires' disease diagnosed?

How is Legionnaires' disease diagnosed?Answer: Most commonly with culture on selective media (buffered charcoal yeast extract agar; iron and cysteine...

Where is L. pneumophila found within infected patients? Why?

Where is L. pneumophila found within infected patients? Why?Answer: Intracellularly in alveolar monocytes/macrophages. It is a facultative intracellular...

What are the risk factors for Legionnaires' disease?

What are the risk factors for Legionnaires' disease?Answer: Cigarette smoking, alcoholics, chronic lung disease, and immunosuppressed sta...

How does Legionnaires' disease present?

How does Legionnaires' disease present?Answer: Severe atypical lobar pneumonia with neurologic (mental confusion) and gastrointestinal (nonbloody...

What diseases does Legionella pneumophila cause?

What diseases does Legionella pneumophila cause?Answer: Legionnaires' disease and Pontiac fe...

What is the treatment of P. aeruginosa?

What is the treatment of P. aeruginosa?Answer: For severe infections, typically a pseudomonas-specific penicillin (ticarcillin, piperacillin) or...

What characteristics of P. aeruginosa allow it aggressively invade tissues?

What characteristics of P. aeruginosa allow it aggressively invade tissues?Answer: Elastases allow P. aeruginosa to invade skin creating erythema...

What is the clinical significance of ecthyma gangrenosum?

What is the clinical significance of ecthyma gangrenosum?Answer: An ulcerated lesion with black eschar. It appears almost exclusively in Pseudomonas...

Why is P. aeruginosa one of the most feared bacteria?

Why is P. aeruginosa one of the most feared bacteria?Answer: It is ubiquitous, causes a large variety of diseases, can be very virulent in compromised...

What is a common source of P. aeruginosa?

What is a common source of P. aeruginosa?Answer: Pseudomonas aeruginosa is a water-loving organism and its common sources include hospital respiratory...

What three groups of patients are extremely susceptible to P. aeruginosa infections?

What three groups of patients are extremely susceptible to P. aeruginosa infections?1. Burn patients2. Cystic fibrosis patients3. Neutropenic patie...

A toxin produced by which other bacteria also inhibits EF-2?

A toxin produced by which other bacteria also inhibits EF-2?Answer: Corynebacterium diphther...

What is the mechanism of exotoxin A produced by P. aeruginosa?

What is the mechanism of exotoxin A produced by P. aeruginosa?Answer: Exotoxin A inhibits elongation factor 2 (EF-2), thereby inhibiting protein...

How is P. aeruginosa differentiated from Enterobacteriaceae?

How is P. aeruginosa differentiated from Enterobacteriaceae?Answer: All will grow on MacConkey agar, but P. aeruginosa is oxidase positive and lactose...

What is the characteristic smell of P. aeruginosa?

What is the characteristic smell of P. aeruginosa?Answer: Grapelike scent (another description is the smell of wet corn tortill...

Describe the important biochemical characteristics of P. aeruginosa:

Describe the important biochemical characteristics of P. aeruginosa:Answer: Obligate aerobe that grows on blood or MacConkey agar; does not ferment...

What diseases are commonly associated with Pseudomonas aeruginosa?

What diseases are commonly associated with Pseudomonas aeruginosa?Answer: Pneumonia (cystic fibrosis patients, mechanically ventilated patients),...

What vaccines are available for B. pertussis?

What vaccines are available for B. pertussis?Answer: A killed-whole cell vaccine and an acellular vaccine are available for children under 7 years....

The majority of whooping cough cases occur in whom today?

The majority of whooping cough cases occur in whom today?Answer: Classically unimmunized infants younger than 1 year. However, in the last 10 years...

What is the treatment of whooping cough and when should it be given?

What is the treatment of whooping cough and when should it be given?Answer: Macrolides (eg, azithromycin) should be given in the prodromal or catarrhal...

What is the clinical significance of increased cAMP?

What is the clinical significance of increased cAMP?Answer: Impaired cell function (especially neutrophils, macrophages, lymphocytes) and chemotaxis....

What is the mechanism of action of pertussis toxin?

What is the mechanism of action of pertussis toxin?Pertussis toxin inactivates Gi via adenosine diphosphate (ADP) ribosylation. Inactivated Gi cannot...

What is the mechanism of action of tracheal cytotoxin?

What is the mechanism of action of tracheal cytotoxin?Answer: Ciliostasis and epithelial cell death diminishing mucociliary cleara...

What is the mechanism of action of filamentous hemagglutinin (FHA)?

What is the mechanism of action of filamentous hemagglutinin (FHA)?Answer: FHA facilitates attachment to the cilia of respiratory epithelial cel...

What are the virulence factors of B. pertussis?

What are the virulence factors of B. pertussis?Answer: Attachment virulence factors (filamentous hemagglutinin [FHA]) and toxins (pertussis toxin,...

What are the three stages of whooping cough?

What are the three stages of whooping cough?1. Catarrhal (1-2 weeks with sympto: similar to a viral upper respiratory infection [URI]; most contagious...

What culture media does B. pertussis require for growth?

What culture media does B. pertussis require for growth?Answer: Bordet-Gengou (potato) agar.Note that B. pertussis is difficult to cultu...

How is B. pertussis diagnosed?

How is B. pertussis diagnosed?Answer: Bacterial culture (on Bordet-Gengou agar) or polymerase chain reaction (PCR) from nasopharyngeal swab or s...

BORDETELLA PERTUSSIS What disease does Bordetella pertussis cause?

BORDETELLA PERTUSSIS What disease does Bordetella pertussis cause?Answer: Pertussis or whooping co...

What drug is used for prophylaxis for close contacts?

What drug is used for prophylaxis for close contacts?Answer: Rifampin achieves a high concentration in secretions, thereby reducing spre...

What are the treatment options for H. influenzae!

What are the treatment options for H. influenzae!Answer: Local infections are treated with amoxicillin with clavulanate or second-or third-generation...

Why are patients with sickle cell disease especially susceptible to H. influenzae infection?

Why are patients with sickle cell disease especially susceptible to H. influenzae infection?Answer: The spleen is necessary to clear encapsulated...

What diseases are seen in the nonencapsulated strains versus encapsulated type B H. influenzae?

What diseases are seen in the nonencapsulated strains versus encapsulated type B H. influenzae?Answer: Nonencapsulated (nontypeable) strains cause...

Why has H. influenzae remained the second most common cause of otitis media in children vaccinated with Hib?

Why has H. influenzae remained the second most common cause of otitis media in children vaccinated with Hib?Answer: Ninety percent of otitis media...

Haemophilus influenzae is known for causing epiglottitis in children. How does this present?

Haemophilus influenzae is known for causing epiglottitis in children. How does this present?Answer: An initial sore throat with fever that progresses...

What is the pathognomonic radiographic sign seen with epiglottitis?

What is the pathognomonic radiographic sign seen with epiglottitis?Answer: "Thumbprint sign" seen on lateral cervical x-...

What is the H. influenzae vaccine composed of?

What is the H. influenzae vaccine composed of?Answer: The H. influenzae type B (Hib) vaccine is made of type B capsular polysaccharide conjugated...

How is H. influenzae diagnosed?

How is H. influenzae diagnosed?Answer: Culture in chocolate agar enriched with NAD (factor V) and hemin (factor X) and latex agglutination against...

What is unique about capsule serotype B of H. influenzae?

What is unique about capsule serotype B of H. influenzae?Answer: Associated with invasive infections in children. B capsule is composed of repeating...

What are the virulence factors of H. influenzae?

What are the virulence factors of H. influenzae?Answer: Capsule (six serotypes), lipopolysaccharide (LPS), attachment factors (pili, fibrils, protein...

What does Haemophilus mean? (It is a clue to its culture requirements.)

What does Haemophilus mean? (It is a clue to its culture requirements.)Answer: Blood lov...

What special culture requirements does H. influenzae have?

What special culture requirements does H. influenzae have?Answer: Chocolate agar with factors V (nicotinamide adenine dinucleotide [NAD]) and X (hematin)...

Describe the morphology of H. influenzae:

Describe the morphology of H. influenzae:Answer: Encapsulated gram-negative pleomorphic coccobacil...

What other organisms should be in the differential when considering H. influenzae infection of the head and neck?

What other organisms should be in the differential when considering H. influenzae infection of the head and neck?Answer: Moraxella catarrhalis and...

Name the diseases caused by Haemophilus influenzae:

Name the diseases caused by Haemophilus influenzae:Answer: Bronchitis, sinusitis, pneumonia, otitis media, conjunctivitis, epiglottitis, bacterial...

Name the five medically important respiratory Gram-negative rods:

Name the five medically important respiratory Gram-negative rods:1. Klebsiella2. Bordetella3. Legionella4. Haemophilus5. Pseudomo...

A 15-year-old girl presents with abdominal pain and diarrhea after eating a hamburger at a barbeque the day before. She is afebrile but on rectal examination there is gross blood. Stool analysis is positive for RBCs and negative for fecal leukocytes. What is the most likely diagnosis? How do you confirm the diagnosis? What is a possible sequela of this infection?

A 15-year-old girl presents with abdominal pain and diarrhea after eating a hamburger at a barbeque the day before. She is afebrile but on rectal examination...

A 30-year-old man presents with fever, abdominal cramps and watery diarrhea after consuming raw oysters on the prior day. On stool examination, there are RBCs and WBCs. What is the most likely diagnosis?

A 30-year-old man presents with fever, abdominal cramps and watery diarrhea after consuming raw oysters on the prior day. On stool examination, there...

CLINICAL VIGNETTES A 10-year-old girl with sickle cell disease presents with left knee pain, leukocytosis, and an increased erythrocyte sedimentation rate (ESR). What is the most likely diagnosis and what pathogen is most likely responsible?

CLINICAL VIGNETTES A 10-year-old girl with sickle cell disease presents with left knee pain, leukocytosis, and an increased erythrocyte sedimentation...

What is given as antimicrobial prophylaxis prior to abdominal surgery to prevent pathologic infection with B. fragilis among other GI pathogens?

What is given as antimicrobial prophylaxis prior to abdominal surgery to prevent pathologic infection with B. fragilis among other GI pathogens?Answer: Used...

Bacteroides fragilis is normal colonic flora, but under what conditions does it cause disease?

Bacteroides fragilis is normal colonic flora, but under what conditions does it cause disease?Answer: Bacteroides fragilis has very low virulence;...

What is the combination of medications used to treat H. pylori infection?

What is the combination of medications used to treat H. pylori infection?Answer: Triple therapy originally included bismuth salts, metronidazole,...

What are the long-term consequences of H. pylori infection?

What are the long-term consequences of H. pylori infection?Answer: Chronic gastritis, gastric adenocarcinoma, and mucosa-associated lymphoid tumor...

How is H. pylori diagnosed?

How is H. pylori diagnosed?Answer: Invasive (endoscopy with biopsy) or noninvasive (serology or urease breath test in which patients drink C14-labeled...

How can H. pylori be biochemically characterized?

How can H. pylori be biochemically characterized?Answer: Catalase positive, oxidase positive, and urease positive. Urease, an important pathogenic...

HELICOBACTER PYLORI What disorder does H. pylori most commonly cause?

HELICOBACTER PYLORI What disorder does H. pylori most commonly cause?Answer: Duodenal ulcers. Ninety percent of duodenal ulcers are associated with...

What neurological disorder is associated with C. jejuni infection?

What neurological disorder is associated with C. jejuni infection?Answer: Guillain-Barré syndrome, an autoimmune, demyelinating ascending motor ...

What is the most common cause of bloody diarrhea in the United States?

What is the most common cause of bloody diarrhea in the United States?Answer: Campylobac...

What are the common sources of C. jejuni and how is it transmitted?

What are the common sources of C. jejuni and how is it transmitted?Answer: Poultry (infrequently red meats) and in many domestic animals. Commonly...

What is the clinical progression of disease in an individual infected with Campylobacter jejuni?

What is the clinical progression of disease in an individual infected with Campylobacter jejuni?Answer: After incubation of approximately 3 days,...

Describe the morphology of Campylobacter?

Describe the morphology of Campylobacter?Answer: Corkscrew shaped with long bipolar flagellae. Similar to Helicobacter pylori, its specialized shape...

Which groups of patients are especially sensitive to V. vulnificus septicemia?

Which groups of patients are especially sensitive to V. vulnificus septicemia?Answer: Cirrhotic and immunocompromised patients are very susceptible...

How is Vibrio vulnificus transmitted and what are its symptoms?

How is Vibrio vulnificus transmitted and what are its symptoms?Answer: Direct inoculation of contaminated brackish water causes necrotizing wound...

How is Vibrio parahaemolyticus transmitted and what are its symptoms?

How is Vibrio parahaemolyticus transmitted and what are its symptoms?Answer: Vibrio parahaemolyticus is transmitted by ingestion of undercooked seafood...

How are V. cholerae infections treated?

How are V. cholerae infections treated?Answer: Rehydration with intravenous (IV) fluid and electrolytes. In milder cases, treat with oral rehydration...

What is the relationship between cholera and stomach acid?

What is the relationship between cholera and stomach acid?Answer: Vibrio cholerae is acid-sensitive, therefore, individuals taking medications to...

What are the physical findings in an individual infected with V. cholerae?

What are the physical findings in an individual infected with V. cholerae?Answer: Severe dehydration from continuous watery diarrhea with a rice...

What is the mechanism of action of cholera toxin?

What is the mechanism of action of cholera toxin?Answer: Constitutively activates Gs via ADP ribosylation leading to constant activation of adenylate...

What does V. cholerae require in order to cause the clinical disease cholera?

What does V. cholerae require in order to cause the clinical disease cholera?Answer: Infection of V. cholerae with the CTX phage that encodes the...

VIBRIO Describe the characteristic appearance of Vibrio cholerae:

VIBRIO Describe the characteristic appearance of Vibrio cholerae:Answer: Gram-negative rod with a single polar flagellum, giving it a comma sh...

What patients are at increased risk for Salmonella osteomyelitis and sepsis?

What patients are at increased risk for Salmonella osteomyelitis and sepsis?Answer: Sickle cells disease patients due to functional asple...

How do you treat Salmonella enterocolitis?

How do you treat Salmonella enterocolitis?Answer: Fluid/electrolyte replacement as the disease resolves within a w...

How does nontyphoidal Salmonella cause enterocolitis and describe the type of diarrhea?

How does nontyphoidal Salmonella cause enterocolitis and describe the type of diarrhea?Answer: Salmonella directly invades epithelial cells of the...

What are some sources of Salmonella?

What are some sources of Salmonella?Answer: Undercooked poultry, meat, eggs, gre...

What disease is typhoid fever often mistaken for? Why?

What disease is typhoid fever often mistaken for? Why?Answer: Appendicitis, patients present with right lower quadrant abdominal pain without ra...

What is the appropriate therapy for S. typhi infection?

What is the appropriate therapy for S. typhi infection?Answer: Ciprofloxacin, ceftriaxone, or azithromy...

Describe the location and appearance of the rash seen in week 2:

Describe the location and appearance of the rash seen in week 2:Answer: Rose spots, small, transient, pink rash located on the abdomen (seen in 30%...

Typhoid fever is a protracted disease of about 3 weeks. Describe the pathogenesis and symptoms seen in each week:

Typhoid fever is a protracted disease of about 3 weeks. Describe the pathogenesis and symptoms seen in each week:Week 1Bacteremia with fever/chillsWeek...

What cells in particular harbor S. typhi and facilitate its dissemination?

What cells in particular harbor S. typhi and facilitate its dissemination?Answer: Monocytes, those in Peyer patches in the ileocecal intestines are...

What organ harbors S. typhi in a chronic carrier state?

What organ harbors S. typhi in a chronic carrier state?Answer: Gallbladder (remember Typhoid Ma...

Where does infection with S. typhi begin and where does it spread to?

Where does infection with S. typhi begin and where does it spread to?Answer: Salmonella typhi begins in the ileocecal intestine and spreads hematogenously...

What makes S. typhi resistant to macrophage killing?

What makes S. typhi resistant to macrophage killing?Answer: Inhibits phagolysosome fusion and defensins resist O2-dependent and independent kill...

How do typhoidal strains differ from nontyphoidal strains of Salmonella in terms of reservoirs?

How do typhoidal strains differ from nontyphoidal strains of Salmonella in terms of reservoirs?Answer: Salmonella typhi and S. paratyphi have only...