Anaerobic and Intracellular Bacteria Practice Questions Flashcards
Which of the following organisms cannot produce its own ATP? Rickettsia Orientia Anaplasma Ehrlichia Chlamydia
Chlamydia
General Feedback:
Don’t forget to look at the other intracellular bacteria we have seen so far–check back to the Major Bacterial Genera lecture. Most intracellular organisms are capable of making ATP, although they will often steal it from the host if they can. Chlamydia and Chlamydophila, however, have lost this ability and therefore must be energy thieves!
A 5-year-old boy from North Carolina presents with his mother to an outpatient clinic with nausea, vomiting and loss of appetite. After examination, the child is returned home with a diagnosis of viral infection. The next day, the boy presents to the emergency department with abdominal pain, a petechial rash, and conjunctival injection. The child is treated with doxycycline and fully recovers. The laboratory later reports that the causative agent responsible for this child’s illness was Rickettsia rickettsii. Where is this organism most likely to reside in the host cell?
Vacuole
Cytosol
Cytosol
A 17-year-old adolescent developed a headache, fever, chills, nausea, and muscle pain 1 week after returning from a fishing trip with his father in Minnesota. During the interview, the patient remembers removing ticks from his skin. Laboratory investigations reveal elevated liver enzymes, thrombocytopenia, and leukopenia. The patient is treated with a 7-day course of doxycycline (100 mg every 12 hours) and recovers fully. Serological tests later confirm an infection with the intracellular, Gram-negative bacterium, Anaplasma phagocytophilum. Where is this organism most likely to reside in the host cell?
Vacuole
Cytosol
Vacuole
A 48-year-old alcoholic, homeless man presents to his local emergency department complaining of a severe headache, chills, fever, myalgias, and arthralgias. The physician finds that the patient is infested with body lice and has a maculopapular rash covering his trunk. Serologic studies confirm the patient is infected with Rickettsia prowazekii. Which of the following bacterial genera is most similar in terms of where it replicates in the host? Chlamydia Listeria Legionella Ehrlichia Coxiella
Listeria
General Feedback:
Rickettsiae replicate within the cytosol (and some species the nucleus) of an infected host cell. Chlamydia, Legionella, Ehrlichia, and Coxiella remain in a variety of membrane-bound vacuoles, and do not replicate within the cytosol. Listeria escapes the phagosome and replicates in the cytosol, so in that way is similar to rickettsiae.
A research lab has identified a novel organism inside infected host cells from a biopsy specimen. Initial attempts to culture the organism on a wide variety of media and under many conditions are unsuccessful. The research fellow leading the study used to work with an obligate intracellular bacterium, and suggests following the cell culture protocol for it. Which of the following organisms did the fellow most likely work with in the past? Listeria Orientia Yersinia Streptococcus Mycoplasma
Orientia
General Feedback:
Of these organisms, the only obligate intracellular bacterium is Orientia. Listeria and Yersinia are facultatively intracellular organisms, and Streptococcus and Mycoplasma are considered extracellular organisms.
Following an outbreak of atypical pneumonia in a nursing home, investigators testing the building’s cooling system isolate a Gram-negative, oxidase-positive, catalase-positive, non-fermentative rod on buffered charcoal yeast-extract agar. What bacterial product helps this organism evade killing in alveolar macrophages? Pore-forming toxin Nitric oxide Type IV secretion system Pilin protein Endoplasmic reticulum
Type IV secretion system
General Feedback:
This question is describing Legionella pneumophila. Once inside the macrophage, this organism produces a type IV secretion system which injects bacterial effectors into the host cell leading to the recruitment of vesicles derived from the host endoplasmic reticulum. The vacuole containing the bacteria, resembling host ER, does not acidify or fuse with lysosomes, allowing the organism to survive and replicate within. Pore-forming toxin could refer to listeriolysin O, produced by Listeria; nitric oxide is produced by host cells to kill bacteria; pili are useful to Legionella in entering the host cell, but not in intracellular survival, and ER, while important in the process, is not a bacterial product.
A 45-year-old sheep farmer in New Zealand develops a pneumonitis caused by a Gram-negative, obligately intracellular bacterium. This organism survives in the environment in a dormant form. What condition within the host cell permits activation of this bacterium to a replicative form? Reduced oxygen tension Low pH Exposure to cationic peptides Exposure to nitric oxide Entry into the nucleus
Low pH
General Feedback:
The signal to Coxiella burnettii to re-start its metabolism is provided by the drop in pH encountered upon acidification of the endocytic vacuole in which the dormant organism is phagocytosed. While the organism is a microaerophile once replicating, this is not a relevant environmental signal. The organism might encounter cationic peptides, but this does not provide the necessary signal. The organism also does not activate iNOS, leading to less exposure to NO; again, this is not the signal. Finally, the organism does not enter the nucleus.
Which of the following signs or symptoms is commonly associated with infections caused by anaerobes? Blue-green pus Generalized myalgias Lymphocytic pleocytosis Foul odor
Foul odor
General Feedback:
The fermentation products and reduced molecules frequently produced during anaerobic metabolism often lead to a particularly foul odor associated with purulence or tissue damage. While these infections are often associated with inflammation and purulence (neutrophils, not lymphocytes), pain is usually localized and the pus is yellowish or perhaps greenish in colour. A blue-green pus is more characteristically associated with Pseudomonas infection.
A 28-year-old man presents with severe periodontal inflammation caused by a member of the normal oral flora. Of the following, which genus is most likely causing his oral disease? Candida Porphyromonas Nocardia Borrelia Staphylococcus
Porphyromonas
General Feedback:
The periodontal pocket is an anaerobic environment, and organisms causing periodontal inflammation (periodontitis). Porphyromonas is one organism linked to periodontitis, but there are other anaerobes that could be involved. Spirochetes are present in the normal microbiota, but are less likely to be associated with disease. Staphylococcus is a facultative anaerobes, but are not linked to this type of disease. Candida is found in the oral cavity, and can cause disease when it overgrows, but is not linked to periodontitis. Nocardia is an aerobe and would not be expected in this anatomic location.
A 28-year-old man presents with gingivitis. One of the causative agents is unable to grow in the presence of oxygen. Why? Absence of an electron transport chain Production of superoxide dismutase Absence of catalase Absence of lysozyme Uses fermentation to produce energy
Absence of catalase
General Feedback:
Anaerobes are sensitive to oxygen because they lack enzymes that detoxify reactive molecules derived from oxygen. Catalase is one of these enzymes, key to detoxifying hydrogen peroxide. Many anaerobes use fermentation rather than respiration to produce energy (choices a and e). This does not explain their sensitivity to oxygen, but does explain their lack of a need for it. Superoxide dismutase is another reactive oxygen detoxifying enzyme, so production of it would facilitate growth in the presence of oxygen. Lysozyme cleaves peptidoglycan, and is a component of the innate immune system of mammals. It is not produced by bacteria and has nothing to do with ability to grow in oxygen.
A 54-year-old woman presents with fever, tachycardia, abdominal rigidity, and nausea. She has a history of diverticulitis, and recent imaging showed that she had developed abscesses on the wall of her colon. Rupture of one of these abscesses is suspected. What is a characteristic of the most likely causative agent? Oxidase positive Fastidious nutritional requirements Gram-positive Filamentous morphology Bile resistant
Bile resistant
General Feedback:
Diverticulitis is an inflammation of the intestinal wall. Complications can include abscess formation, and these abscesses can rupture to cause peritonitis (being described here). The most likely causative agent here, as with any other intra-abdominal abscess, is Bacteroides fragilis. This organism is Gram-negative, coccobacillary to rod-shaped, grows well on blood agar, and grows well on bile-esculin agar.
