Microbiology part 1

How many histone proteins make up a nucleosome in the making of eukaryotic chromosomes?

8

Porin is a structural molecule in bacteriology. Which one of the following is called porin?

A protein forming a channel for transport

How is the virulence of an organism defined?

Ability to cause disease

What is the name of the manifestation where a patient's immune response during infection with Streptococcus pyogenes produces antibodies that react with host sarcolemma, myosin, and synovium?

Acute rheumatic fever

Flagella can be in various arrangements in a typical bacterium. What type of bacterium has a single flagellum at opposite poles in the organism?

Amphitrichous

Transposable elements have the ability to embed genetic traits of a donor genome onto a natural vector and the ability to impose a stable association between the recipient genome and the transferred genes. This capacity for horizontal transmission of spontaneously acquired genes has led to what biomedical issue?

Antibiotic resistance

What term describes the transovarial spread within ticks that allows the cycle of R. rickettsii infection to perpetuate without a host?

Arthropod-sustained

Which of the following bacteria is the first microorganism linked to a specific disease?

Bacillus anthracis

There are different ways to classify microorganisms. What microorganism can be classified based on the peptidoglycans in its cell wall?

Bacteria

What is the site of action of beta-lactam antibiotics against Gram-positive organisms?

Bacterial cell wall

What is the standard recommended treatment in the United States for a patient undergoing secondary prevention for rheumatic fever once group A streptococcal pharyngitis is confirmed?

Benzathine penicillin once a month for several years

Bacteria have characteristics amenable to the study of spontaneous mutation, including haploidy, a highly studied and characterized genome, and what other feature?

Short generation time

What type of mutation changes the original codon into another codon that codes for the same amino acid?

Silent

Clostridium botulinum is an example of an organism that releases an exotoxin. How are exotoxins classified?

Soluble protein

In the bacteria name "Staphylococcus aureus," what does the word "aureus" represent?

Species

The bacterium Treponema pallidum appears in a helical corkscrew shape. How is it classified?

Spirochete

Mannitol salt agar is used to culture which of the following microorganisms?

Staphylococcus aureus

Rheumatic fever is a post-streptococcal disease caused by an immunologic response to the initial infection. It may lead to migratory polyarthritis and carditis. How long after an initial infection do the symptoms of rheumatic fever appear?

2-3 weeks

Following a camping trip, a patient exhibits symptoms of Lyme disease, contracted through a deer tick bite. What type of disease transmission is this?

Biological vector

What has a similar pathology to Pseudomonas aeruginosa and generally causes infections of burns, wounds, and lungs?

Burkholderia cepacia

Which molecule acts specifically by binding to the promotor site of the lac operon so that the genes can be effectively transcribed?

Catabolite activator protein

Transposition of mobile genetic elements includes insertion sequences (IS), transposons, and specific bacterial viruses. Each involves unique mechanisms for transposition. DNA rearrangements, such as inversion, deletion, fusion, and amplification, are potential outcomes of transposition. Transposases are enzymes encoded by the mobile elements that mediate what action?

Change in location of genetic material

What is the term for a strand of nucleic acids and associated proteins that carries the genetic information of an organism?

Chromosome

Which pair of organisms consists of 2 endospore-forming bacteria?

Clostridium and Bacillus

Which of the following microorganisms is considered an obligate anaerobe?

Clostridium tetani

What basic shape is the Gram-negative bacterium Vibrio cholerae?

Comma

Which infectious disease is most likely to be associated with the pathogens S. pneumoniae and H. influenzae?

Community-acquired pneumonia

Plasmids that encode for machinery employed in transfer by means of sex pilus use what to transfer genetic information?

Conjugation

What is the term for the transfer of genetic information from a donor cell to a recipient within close proximity that may use a plasmid?

Conjugation

Chlamydia trachomatis is generally associated with infection of what tissue?

Conjunctiva and genital

What is a likely route of transmission of anthrax to humans?

Contact with contaminated bone meal fertilizer

In response to nutrient limitations or a harsh environment, some bacteria are able to create a small dehydrated metabolically inactive structure within their cells. The production of this structure allows certain bacteria to survive desiccation, radiation, and exposure to chemicals. What are these called?

Endospores

What is a likely cause of death due to presence of bubonic plague?

Endotoxic shock

Bloody diarrhea and hemolytic uremic syndrome (HUS) are manifestations of what type of Escherichia coli infection?

Enterohemorrhagic

Which of the following is the most common causative agent of urinary tract infection (UTI) in women?

Escherichia coli

What structure only aids in surface adherence and has no other purpose?

Fimbriae

Which of the following structures is responsible for the motility of bacteria?

Flagella

What is the most likely route of transmission of bubonic plague?

Flea bite

What is the final step of initial Y. pestis infection for humans?

Flea bites, then it regurgitates Y. pestis into new host.

Site-specific DNA inversion is made possible by inherent flexibility of enzyme and double-stranded DNA molecules. DNA inversion at secondary crossover sites is a proposed mechanism for control of gene expression, but the stochastic nature of this mechanism has also led to proposals highlighting the adaptive nature of this event. What is a potential adaptive advantage of DNA inversion within bacterial populations?

Generation of variation

What is an operon in terms of the regulation of bacterial genes?

Genes that participate in the same metabolic activity

Which of the following microbes is the most common cause of subacute endocarditis in individuals?

Viridans group streptococcus

How does Streptococcus viridans appear on a Gram stain?

Gram-positive cocci in chains

What proteins are able to wrap DNA around them to condense the structure of DNA?

Histones

What reservoir is associated with the majority of cases of opportunistic Escherichia coli infection where infection may progress from cystitis to pyelonephritis?

Host intestinal microbiota

Wiskott-Aldrich syndrome is an X-linked hereditary condition. When can a doctor first diagnose the appearance of signs in a patient?

In the first year of life

One factor associated with the transmission of infectious disease is the time of survivability of a microorganism on a hard inanimate surface; e.g., E.coli bacteria can survive on hard inanimate surfaces for up to 16 months. This represents a risk for exposure to infectious disease by what type of contact?

Indirect vehicle contact

A patient presenting with cyanosis, hemorrhagic mediastinitis, and meningitis is proposed to have been exposed to Bacillus anthracis endospores (anthrax). What is the most likely route of transmission?

Inhalation of aerosolized endospores

Tuberculosis is a disease prevalent in the poor socioeconomic bracket of India and Pakistan, mostly due to dense population, poor healthcare, and malnutrition. The microorganism that causes TB is Mycobacterium tuberculosis (MTB). Why is this pathogen difficult to treat?

It has a thick, waxy lipid coating, which surrounds the entire bacterial cell and hides it from the human immune system.

What is the primary metabolic activity controlled by the lac operon in bacterial species?

Lactose catabolism

A high number of HIV-associated pneumonia patients in Colombia were found to be co-infected with Legionella bacteria, and these patients suffered a high mortality rate. Patients were often underdiagnosed because their cultures were negative, but quantitative polymerase chain reactions (PCR) showed that they were infected. What explains these findings?

Legionella is notoriously difficult to culture and is often diagnosed with PCR.

Between levofloxacin and doxycycline, which antibiotic would be most effective against Legionella and why?

Levofloxacin because it is a fluoroquinolone.

What does the slow progression of healing of cutaneous anthrax generally lead to?

Limited systemic symptoms

Gram-negative bacteria can release endotoxins during severe systemic infections. What component of the bacteria cell wall is released as part of an endotoxin?

Lipid A

Which type of microorganism is associated with the rancidity of spoiled foods?

Lipolytic organisms

In Gram-negative bacteria, the peptidoglycans in the cell wall are connected to an outer cell membrane. What connects these two layers?

Lipoproteins

What characteristic of microbes causes mutation to display a large influence within bacterial populations?

Low generation time

What parasitic infection is responsible for most deaths globally?

Malaria

What type of mutation is a single nucleotide substitution that causes a change in the codon, resulting in production of a different amino acid?

Missense

What structures lack a cell wall?

Mycoplasmas

What type of mutation is a change in codon specifying a premature termination codon?

Nonsense

What structure is observed for the identification of different Gram-negative bacterial species and strains?

O antigen

A siderophore is a compound produced by bacteria. What is the function of this chemical compound?

Obtain iron for growth

The pathology of Candida albicans depends on the area of colonization; for example, colonizing the genitals can cause a yeast infection. What is an additional manifestation of a C. albicans infection likely to occur within an immunocompetent host?

Oral thrush

What is the most critical factor in the spread of nosocomial infections involving Staphylococcus aureus?

Patients in a hospital setting have compromised biological defenses, either immuno-suppressed or with new portals of entry.

What manifestation of Neisseria gonorrhea can cause infertility and ectopic pregnancy?

Pelvic inflammatory disease

Which manifestation of Chlamydia trachomatis infection is commonly associated with potentially permanent fertility dysfunction?

Pelvic inflammatory disease

Peptidoglycan is the major component of the prokaryotic cell wall. Its arrangement is one determining factor in the results of a Gram stain. What peptidoglycan structural feature is only found in Gram-positive bacteria?

Pentaglycine cross-bridges

The Gram-negative prokaryotic bacterial cell wall is multilayered. What is the inner layer of the cell wall made of?

Peptidoglycans

A bacteria has flagella throughout its surface. What type of arrangement of flagella is this?

Peritrichous

Neisseria gonorrhoeae manifestations include genital gonorrhoeae and what other local infection?

Pharyngeal infection

Bordetella pertussis is a Gram-negative bacteria that causes whooping cough, also called 100-day cough. What is the most sensitive diagnostic test for the confirmation of whooping cough?

Polymerase chain reaction (PCR)

A 19-year-old man presents with a firm painless ulcer on the shaft of his penis. When asked about his sexual history, the patient reports having occasional unprotected sex with his new girlfriend.

Primary syphilis

What diverse group of unicellular eukaryotic microorganisms have motility and can be free-living or parasitic?

Protozoa

Diabetes is a known metabolic disease that causes a chronic decrease in the number of neutrophils. Which of the following bacteria causes a classic green-colored infection on the skin of an amputated part in people with diabetes?

Pseudomonas aeruginosa

Certain bacteria are capable of generating bioluminescent chemicals under specific conditions. Which of the following refers to the ability of bacteria to share cell density information and regulate patterns of gene expression?

Quorum sensing

What is involved in genes conferring resistance to antimicrobial agents?

R plasmid

A 60-year-old man presents with coughing, sweating, fever, fatigue, and weight loss. He reports previous diagnoses of diabetes and addiction to alcohol and nicotine. A chest X-ray indicates cavity formation within the lungs. What infection is likely to be responsible for these findings?

Reactivation tuberculosis

Restriction modification systems are traditionally considered a barrier to gene acquisition through their function of screening and cleaving fragments of foreign DNA. Why might this system contrarily promote gene acquisition?

Recombinogenic capability of fragmented DNA before degradation

Scalded skin syndrome is caused by Staphylococcus aureus. What is the mechanism of the disease progression?

Release of protease

Chlamydia trachomatis is categorized as an obligate intracellular bacteria due to which function of its reticulate body form?

Replication

Which of the following structures are found in ALL bacteria? Select all that apply.

Ribosomes, Cytoplasm, Cell membrane

What basic bacterial shape is the bacterium Bacillus anthracis?

Rod

A 22-year-old woman presents with a maculopapular rash on her palms and soles. Physical examination reveals several enlarged non-tender lymph nodes and slight fever. She has a history of multiple sexual partners and unprotected sex. What is the most likely diagnosis?

Secondary syphilis

A 5-year-old girl presents with sore throat, runny nose, and itchy eyes. Patient has no fever, but a rapid strep test is negative. A throat culture is sent into the lab. The patient is sent home and advised to return if there is fever or worsening symptoms. Gram stain shows a Gram-positive coccus in chains. In the following days, the culture shows alpha hemolysis, is green in color, and has small gray colonies. What is the most likely organism?

Streptococcus viridans

The process of nucleotide substitution (replication infidelity) occurs during DNA replication. Base pairing depends on electron distribution within nucleotides of parental and newly synthesized DNA. Short-lived physical forms (tautomers) arise and can result in mispairing of bases due to intrinsic pliability rather than a replicative misstep. What is a plausible mechanism for the process of nucleotide substitution?

Structural flexibility of enzyme and DNA molecules

A 38-year-old man presents with difficulties walking correctly and visual disturbances. Physical examination reveals a broad-based ataxic gait and a positive Romberg sign, which is indicative of neuropathy affecting proprioception. What is the most likely diagnosis?

Tertiary syphilis

What aspect of Gram-positive bacteria allows species like Clostridium and Bacillus to form endospores?

Thick peptidoglycan layer

Due to antimicrobial resistance, what does treatment of Neisseria gonorrhoeae often involve?

Third-generation cephalosporins

When adenine is the nitrogenous base on a segment of DNA, what is the other nitrogenous base it binds to on the opposite DNA strand through hydrogen bonding?

Thymine

What is the purpose of the cell wall in bacteria?

To prevent osmotic lysis of the cell

Which manifestation of Chlamydia trachomatis can be described by chronic inflammation of the eyelids and increased vascularization of the cornea with potential to cause severe corneal scarring and conjunctival deformities?

Trachoma

What is the process by which bacteriophage DNA is integrated into a host chromosome and potentially encodes toxins and other virulence factors?

Transduction

What is the term for the transmission of genetic material between organisms by means of bacteriophage gene vectors?

Transduction

Which of the following terms refers to bacteria's ability to take up DNA from the environment?

Transformation

Which of the following STD-causing bacteria cannot grow in culture media but are easily identified with the help of dark-field microscopy?

Treponema pallidum

A patient presents with large flattened plaques on the face and trunk with raised red edges and dry pale hairless centers. What condition is the most likely cause of infection?

Tuberculoid leprosy

The pathology of Escherichia coli depends on the area of colonization; for example, as the source of gastrointestinal illness, it can cause diarrhea. What is an additional manifestation of an E. coli infection?

Urinary tract infection

Which of the following antibiotics is used to treat methicillin-resistant Staphylococcus aureus (MRSA)?

Vancomycin

What species of staphylococcus commonly causes surgical wound infections of the skin?

aureus