Microbiology Exam Review Quiz Dec 2012

The optimal specimen to collect for the diagnosis of gonorrhea by culture in males is a urethral swab. This is because gonorrhea primarily affects the urethra in males, so collecting a swab from this area provides the best chance of detecting the bacteria responsible for the infection. Swabbing other areas such as the pharynx, rectum, or cervix may not yield accurate results as these sites are less likely to be affected by gonorrhea in males.

The statement suggests that the viridians strep, a type of bacteria, thrive in conditions with low levels of oxygen. This means that they prefer environments where there is less oxygen present than what is typically found in the atmosphere. This preference for microaerophilic conditions allows the viridians strep to grow and reproduce more effectively. Therefore, the given answer is true.

Neisseria species are a type of bacteria that have a spherical shape, which is characteristic of cocci. Unlike other bacteria, when exposed to penicillin, Neisseria species do not elongate or change their shape. Therefore, the statement that Neisseria species are true cocci that do not elongate when exposed to penicillin is true.

The beta-lactamase test should be performed on all isolates of M. catarrhalis because this test helps to determine whether the bacteria produce beta-lactamase enzyme, which can inactivate beta-lactam antibiotics such as penicillins and cephalosporins. This information is crucial for selecting the appropriate antibiotic treatment for infections caused by M. catarrhalis, as beta-lactamase production can confer resistance to these antibiotics. Therefore, performing the beta-lactamase test on all isolates of M. catarrhalis is necessary to guide effective treatment decisions.

Penicillin G is the drug of choice for all treponemal infections. Treponemal infections are caused by bacteria of the genus Treponema, including syphilis and yaws. Penicillin G is highly effective against these bacteria and is the recommended treatment due to its ability to effectively kill the bacteria and prevent further complications. Doxycycline and tetracycline are antibiotics commonly used for other types of infections, but they are not the preferred treatment for treponemal infections. Ceftriaxone is a broad-spectrum antibiotic that is effective against many types of bacteria, but it is not the first-line treatment for treponemal infections.

All of the above options can cause false positive results in the RPR test. Rheumatoid disease, old age, and tuberculosis can all lead to the presence of antibodies in the blood that can be detected by the RPR test, even if the person does not have syphilis. Therefore, if any of these conditions are present, it can result in a false positive result in the RPR test.

The most common form of gonococcal infection in neonates is conjunctivitis. This is because during childbirth, if the mother has a gonococcal infection, the bacteria can be transmitted to the baby's eyes as it passes through the birth canal. This can lead to inflammation and infection of the conjunctiva, which is the thin membrane that covers the white part of the eye and the inner surface of the eyelids. Conjunctivitis in neonates is a serious condition that requires prompt medical attention to prevent complications and long-term damage to the eyes.

Based on the given information, the most likely organism is Bacillus cereus. This is because Bacillus cereus is a gram-positive, spore-forming bacillus that is commonly associated with food poisoning and gastroenteritis outbreaks. It produces B-hemolysis, is catalase positive, and is motile. Bacillus anthracis is not typically associated with gastroenteritis outbreaks, while Nocardia asteroides and Tsukamurella spp are not known to produce B-hemolysis.

C. diphtheriae is only found in humans because it is a bacterium that causes the infectious disease diphtheria. It is primarily transmitted through respiratory droplets from infected individuals. The bacterium colonizes in the respiratory tract of humans, particularly in the throat and nose, where it produces toxins that can cause severe damage to the respiratory system and other organs. It does not naturally occur in other animals or the environment. Therefore, the statement that C. diphtheriae is only found in humans is true.

The statement is true because the diagnosis of leptospirosis is typically done by detecting IgM antibodies in both acute and convalescent sera. IgM antibodies are produced by the immune system in response to an infection, so their presence indicates a recent or ongoing infection with the bacteria that causes leptospirosis. By testing for these antibodies in blood samples taken during the acute phase of the illness and again during the recovery phase, healthcare professionals can confirm a diagnosis of leptospirosis.

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N.meningitidis isolates should be serogrouped because this bacterium can cause meningococcal meningitis, a potentially life-threatening infection. Serogrouping is necessary to determine the specific serogroup of the bacteria, as different serogroups can cause different disease patterns and may require different preventive measures. Serogrouping also helps in tracking the spread of the disease and in developing vaccines targeted against specific serogroups. Therefore, serogrouping is important for effective management and control of meningococcal meningitis.

Mannitol salt agar is a selective medium that can be used to isolate staphylococci. This medium contains a high concentration of salt, which inhibits the growth of many other bacteria, allowing staphylococci to grow. In addition, mannitol, a type of sugar, is included in the agar. Staphylococci that can ferment mannitol will produce acid, causing the medium to turn yellow. This helps differentiate staphylococci from other bacteria that do not ferment mannitol. Therefore, Mannitol salt agar is an effective selective medium for isolating staphylococci.

B. anthracis can be quickly differentiated from the other Bacillus species by its lack of motility. While most Bacillus species are motile, B. anthracis is non-motile, meaning it does not have the ability to move on its own. This characteristic can be used as a distinguishing factor when trying to identify B. anthracis among other Bacillus species.

Bacterial vaginosis is a condition characterized by an imbalance in the vaginal bacteria, with a decrease in beneficial lactobacilli and an increase in harmful bacteria such as Gardnerella vaginalis. Therefore, the correct answer is that bacterial vaginosis is associated with a predominance of G. vaginalis. Serology testing is not used for diagnosing bacterial vaginosis, and the growth of Gardnerella on MacConkey agar is not a specific diagnostic criterion.

Relapsing fever is caused by B.recurrentis. This bacterium is transmitted to humans through the bite of infected lice or ticks. It is responsible for causing recurrent episodes of fever, along with other symptoms such as headache, muscle aches, and joint pain. B.recurrentis is primarily found in Africa, Asia, and South America, and it infects the bloodstream of its host, leading to the characteristic relapses of fever.

Some species of treponeme are considered to be part of the normal flora in the oral and genital regions. This means that they naturally exist in these areas without causing any harm or disease. Therefore, the statement is true.

An oil overlay is used when testing carbohydrate utilization because it creates an anaerobic environment. This is important because some bacteria or microorganisms that are being tested for their ability to utilize carbohydrates may require an oxygen-free environment to carry out their metabolic processes effectively. The oil overlay forms a barrier that prevents the entry of oxygen into the test system, creating the necessary anaerobic conditions for these organisms to thrive and metabolize the carbohydrates being tested.

It should be read every half hour for 4 hours.

Streptococci are a group of bacteria that are known to be negative for the catalase test. This means that they do not produce the enzyme catalase, which is responsible for breaking down hydrogen peroxide into water and oxygen. Other bacteria, such as staphylococci, are positive for the catalase test because they produce catalase. Therefore, if a bacterium is negative for the catalase test, it is likely to be a streptococcus.

Acute gastroenteritis is a condition characterized by inflammation of the stomach and intestines, leading to symptoms like vomiting and diarrhea. B. cereus is a bacterium that can cause food poisoning and is a known cause of acute gastroenteritis. It produces toxins that can contaminate food and cause illness when ingested. Therefore, B. cereus is a likely cause of acute gastroenteritis.

S. agalactiae spp, also known as Group B Streptococcus (GBS), is the correct answer. GBS is known to colonize approximately 30% of American women and is a common cause of meningitis in neonates. It is important to identify and treat GBS colonization in pregnant women to prevent transmission to their newborns, as GBS infection in neonates can be severe and life-threatening.

The Methyl red test is used to detect the production of mixed acids as a result of subsequent metabolism of pyruvate. This test determines if an organism produces stable acids from glucose fermentation. If the pH of the medium drops below 4.4, it indicates the production of mixed acids, which is detected by a positive methyl red test. The other tests listed (VP test, Citrate test, Indole test) do not specifically detect the production of mixed acids from pyruvate metabolism.

Staphylococcus species are considered facultative anaerobes because they can survive and grow in both the presence and absence of oxygen. They have the ability to switch their metabolic pathways depending on the availability of oxygen. In the presence of oxygen, they can perform aerobic respiration, utilizing oxygen as a terminal electron acceptor. In the absence of oxygen, they can switch to fermentation or anaerobic respiration, using alternative electron acceptors. This flexibility allows Staphylococcus species to adapt to various environments, making them facultative anaerobes.

Only requires V factor - "para"

Erysipeloid is a bacterial infection caused by E.rhusiopathiae. It is commonly found in fish handlers. The diagnosis of erysipeloid is not made by skin culture, but rather by clinical presentation and history of exposure. The drug of choice for treating erysipeloid is penicillin, not metronidazole. Therefore, the statement "Drug of choice is metronidazole" is false.

The given information states that the coccus is resistant to bacitracin and sulfamethoxazole. Group B streptococci is known to be resistant to bacitracin and sulfamethoxazole, making it the presumptive identification in this case.

Martin Lewis media is a selective and differential medium used to isolate Neisseria gonorrhoeae. It contains antimicrobial agents that inhibit the growth of other bacteria, allowing for the isolation of N. gonorrhoeae. Additionally, the medium contains specific nutrients and indicators that help differentiate N. gonorrhoeae based on its ability to ferment certain carbohydrates. Therefore, Martin Lewis media is specifically designed to support the growth and identification of N. gonorrhoeae.

Moraxella is the correct answer because it is known to produce dry white colonies on chocolate agar. Additionally, Moraxella can be nudged along the agar in a sinus culture, indicating its motility. Haemophilus, E.coli, and Staphylococci do not typically exhibit these characteristics, making Moraxella the most likely option.

The VDRL test is the correct test for syphilis that should be performed on CSF (Cerebrospinal Fluid). VDRL stands for Venereal Disease Research Laboratory, and it is a screening test used to detect the presence of antibodies against the bacteria that causes syphilis. CSF is the fluid that surrounds the brain and spinal cord, and testing it for syphilis can help diagnose neurosyphilis, which is the infection of the central nervous system. Therefore, performing the VDRL test on CSF is essential for accurate diagnosis and appropriate treatment of syphilis.

Corynebacterium do not form spores. Spore formation is a characteristic feature of certain bacteria, such as Bacillus and Clostridium, but not Corynebacterium.

A nonhemolytic, catalase-negative, gram-positive coccus that is PYR-positive indicates that the isolate is likely a Streptococcus species. Streptococcus species are known to be bile esculin positive, meaning they can hydrolyze esculin in the presence of bile. Additionally, Streptococcus species are salt tolerant, meaning they can grow in the presence of high salt concentrations. Therefore, it is expected that the isolate would be both bile esculin positive and salt tolerant.

B.Burgdorferi is transmitted through vectors, which are organisms that can transmit the infection from one host to another. In the case of B.Burgdorferi, the primary vector is the black-legged tick (Ixodes scapularis or Ixodes pacificus), which acquires the bacteria by feeding on infected animals and then transmits it to humans or other animals during subsequent feedings. This transmission occurs through the tick's saliva, which contains the bacteria. Therefore, vectors play a crucial role in the transmission of B.Burgdorferi.

Darkfield microscopy is the most commonly used type of microscopy in the direct microscopic examination of T.pallidum. Darkfield microscopy is a technique that uses a special condenser to illuminate the specimen with oblique light, making the specimen appear bright against a dark background. This technique is particularly useful for visualizing transparent or unstained specimens, such as T.pallidum, which can be difficult to see using other types of microscopy. By using darkfield microscopy, the T.pallidum bacteria can be easily observed and identified.

S. pyogenes will as well

After incubation, the addition of Kovacs reagent to the tryptophan broth results in the development of a red color at the surface. This indicates the presence of indole, which is a product of tryptophan metabolism. Indole is produced by certain bacteria through the breakdown of tryptophan, and the red color is a result of the reaction between indole and Kovacs reagent. Therefore, the correct answer is indole.

S.mutans is a bacteria that requires the addition of vitamin B6 in order to grow on sheep blood agar. Without the presence of vitamin B6, S.mutans will not be able to thrive on this medium. This indicates that S.mutans is dependent on the presence of vitamin B6 for its growth and survival.

A patient testing positive for anti-DNase B and negative for antistreptolysin O suggests a strep throat infection. DNase B is an enzyme produced by Streptococcus pyogenes, the bacteria responsible for strep throat. The presence of anti-DNase B antibodies indicates an immune response to the bacteria. Antistreptolysin O is an antibody produced in response to streptolysin O, a toxin produced by Streptococcus pyogenes. The negative result for antistreptolysin O suggests that the patient has not been exposed to streptolysin O, which is consistent with an early or recent strep throat infection.

A.haemolyticum is a bacterium that can be missed in throat cultures if it is not specifically sought. One characteristic of A.haemolyticum is that it pits the agar under colonies growing on sheep blood agar. This means that when the bacteria grow on this type of agar, they produce substances that cause the agar to appear indented or pitted beneath the colonies. This characteristic can help in identifying A.haemolyticum in the laboratory.

Older they get - stain gram variable

S.saprophyticus is the correct answer because it is the only option that meets all the given criteria. It is a gram-positive coccus, catalase positive, coagulase negative, and resistant to novobiocin. S.aureus is catalase positive and coagulase positive, S.epidermidis is catalase positive and coagulase negative, and S.lugdunensis is catalase positive and coagulase negative but not resistant to novobiocin. Therefore, S.saprophyticus is the only choice that fits all the given characteristics.

Anthrax cannot be acquired through direct contact with an infected person because it is primarily a disease that affects animals, particularly livestock. The bacteria that causes anthrax, Bacillus anthracis, forms spores that can survive in the environment for long periods of time. These spores are typically found in soil and can be ingested by animals grazing on contaminated land. Humans can become infected with anthrax by coming into contact with contaminated animal products, such as meat or hides, but direct person-to-person transmission is extremely rare.

B.subtilis is the correct answer because it is a known cause of serious eye infections. This bacterium can enter the eye through various means such as contaminated contact lenses or eye makeup. Once inside the eye, it can cause infections such as keratitis, which can lead to serious complications and even vision loss if left untreated. Therefore, it is important to maintain good hygiene practices and properly clean and handle any items that come into contact with the eyes to prevent B.subtilis infections.

The statement "Neisseria meningitidis is the most common cause of meningitis in the general population" is false. While Neisseria meningitidis is indeed a common cause of meningitis, it is not the most common cause. Other bacteria and viruses, such as Streptococcus pneumoniae and Haemophilus influenzae, can also cause meningitis. Therefore, the correct answer is false.

Motility is the correct answer because L.monocytogenes is a motile bacterium. Motility refers to the ability of a bacterium to move or exhibit self-propulsion. L.monocytogenes displays a characteristic tumbling or darting motility under a microscope. Gram reaction, catalase reaction, and esculin reaction are not specific tests for identifying L.monocytogenes.

Infection with H.influenzae type b prior to immunization programs commonly presented as meningitis. This is a serious infection that affects the membranes surrounding the brain and spinal cord. It can cause symptoms such as fever, headache, stiff neck, and sensitivity to light. Meningitis caused by H.influenzae type b was a major concern before immunization programs were implemented, but the incidence of this infection has significantly decreased with the introduction of the Hib vaccine.

Erysipelothrix rhusiopathiae is the correct answer because it is the only catalase-negative, non-spore forming bacillus that produces H2S. Gardnerella vaginalis and Lactobacillus spp are not bacilli, and Arcanobacterium haemolyticum does not produce H2S.

The recommended treatment for close family contacts of a patient with meningococcal meningitis is Rifampin. Rifampin is a bactericidal antibiotic that is effective against the bacteria Neisseria meningitidis, which causes meningococcal meningitis. It is commonly used as prophylaxis to prevent the spread of the infection to close contacts of an infected individual. Rifampin is preferred over other antibiotics like penicillin, ampicillin, and erythromycin due to its effectiveness against the specific bacteria causing meningococcal meningitis.

Specimens for anaerobic culture should never be refrigerated.

Some strains produce B-lactamase

It is SPS - Sodium polyethanol sulfonate

Leptospires are bacteria that cause leptospirosis, a disease that can affect humans and animals. The most common mode of transmission of leptospires is through contaminated urine. Infected animals, such as rats or livestock, excrete the bacteria in their urine, which can contaminate water sources or soil. Humans can then become infected by coming into contact with the contaminated urine, either directly or indirectly. This can occur through activities like swimming in contaminated water, handling infected animals, or consuming food or water that has been contaminated with urine.

H.influenzae is a bacterium that can be classified into different serotypes based on the presence or absence of a polysaccharide capsule. The correct answer, "F, non-encapsulated," indicates that H.influenzae does not have a capsule and therefore belongs to serotype F. It is important to note that most infections caused by H.influenzae are indeed caused by non-encapsulated strains, as the capsule helps the bacteria evade the immune system and cause more severe disease.

Borrelia recurrentis and Borrelia hermsi are the two species of Borrelia commonly implicated in cases of relapsing fever. The transmission of these species of Borrelia is through vectors, specifically lice for Borrelia recurrentis and ticks for Borrelia hermsi.

The optochin test is most valuable in the identification of a-streptococci. This test is used to differentiate between different species of streptococci, specifically Streptococcus pneumoniae. Optochin is a chemical compound that inhibits the growth of S. pneumoniae, but has no effect on other streptococci. Therefore, if a sample of bacteria is sensitive to optochin, it is likely to be S. pneumoniae, which falls under the category of a-streptococci.

They are obligate aerobes

M.catarrhalis is a relatively common cause of otitis media in children. Otitis media is an infection of the middle ear, and M.catarrhalis is one of the bacteria that can cause this infection. It is particularly common in children due to their immature immune systems and smaller Eustachian tubes, which makes it easier for the bacteria to enter the middle ear. Therefore, M.catarrhalis is the correct answer as it is a known organism that frequently causes otitis media in children.

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C.urealyticum is a well-documented cause of alkaline-encrusted cystitis. This organism is known to infect the urinary tract and can lead to the formation of encrusted bladder stones. It is often found in patients with underlying urinary tract abnormalities or those with compromised immune systems. The presence of C.urealyticum in the urine can be confirmed through laboratory testing, and treatment typically involves antibiotics to eliminate the infection and prevent recurrence.

They are normal flora

Specimens for Neisseria species should be transported and held at a temperature of 37°C in the laboratory until plated. This is because Neisseria species, such as Neisseria gonorrhoeae and Neisseria meningitidis, are fastidious bacteria that require specific growth conditions, including a temperature of 37°C, to grow and survive. Keeping the specimens at this temperature ensures optimal growth and accurate laboratory results.

Clue cells are not covered with streptococci. In fact, clue cells are vaginal epithelial cells that are covered with bacteria called Gardnerella vaginalis. These cells are used as a diagnostic feature for bacterial vaginosis, a common vaginal infection. Therefore, the correct answer is False.

It takes more than one hour, you can prevent Lyme disease by removing the ticks in the first hour.

The PYR test is used to differentiate between Staphylococcus aureus and Staphylococcus lugdunensis. This test detects the presence of the enzyme pyrrolidonyl arylamidase, which is produced by S. aureus but not by S. lugdunensis. By observing the reaction of the test medium to the enzyme, it is possible to determine whether the bacteria being tested is S. aureus or S. lugdunensis.

To prevent misidentification of the staph species, additional tests should be performed to confirm the identification. The PYR (pyrrolidonyl arylamidase) test is used to differentiate between Staphylococcus aureus and other staphylococci species. Staphylococcus aureus is PYR positive, while other staphylococci species are PYR negative. The VP (Voges-Proskauer) test is used to differentiate between Staphylococcus epidermidis and Staphylococcus saprophyticus. Staphylococcus epidermidis is VP positive, while Staphylococcus saprophyticus is VP negative. These additional tests will help in accurately identifying the staph species causing the wound infection.

They represent a quantitative culture because a known amount of material is put onto the plate.

Spore formation is a characteristic feature that can help differentiate Listeria from Bacillus. Listeria does not form spores, whereas some species of Bacillus do. Spore formation is a survival mechanism used by certain bacteria to withstand harsh conditions, such as heat, desiccation, and disinfectants. Therefore, the absence of spore formation in Listeria can be used as a distinguishing factor between the two bacteria.

This statement is false because C.jeikeium is not associated with stone formation in the bladder. The other statements are true. Corynebacteria are gram-positive, lipophilic species of corynebacteria grow well on blood agar with Tween 80, and C.diphtheriae colonies appear black on Tinsdale agar.

Culture is the most common method used to identify the causative agent of leptospirosis. Culture involves growing the bacteria in a laboratory setting, which allows for further testing and identification. This method is reliable and can provide a pure culture of the bacteria for further analysis. PCR, biochemical testing, serology, and antigen detection can also be used to diagnose leptospirosis, but culture is considered the gold standard for identification.

The best laboratory practice would be to use the swab to inoculate a SBA plate because a negative rapid strep test does not completely rule out the possibility of a strep infection. By inoculating a SBA plate, the bacteria can be cultured and further tested to confirm the presence or absence of strep bacteria. This allows for a more accurate diagnosis and appropriate treatment if necessary. Using a second swab may not be necessary as the first swab can still provide valid results. Placing a bacitracin disk is not necessary in this case as it is used for differentiating between different types of strep bacteria.

Antibodies are produced due to the disease process, not just the organism.

Susceptibility testing of Borrelia spp. to doxycycline should not always be done because the incidence of treatment failure is low. Doxycycline is an effective antibiotic for treating Borrelia spp. infections, and resistance to this antibiotic is rare. Therefore, routine susceptibility testing is not necessary in most cases.

A HBT plate should not be included in the battery of media for routine genital cultures. This is because HBT (Hektoen Enteric Agar) is a selective and differential medium primarily used for the isolation and differentiation of enteric pathogens from clinical specimens, such as stool samples, to identify Salmonella and Shigella species. Routine genital cultures typically focus on the isolation and identification of organisms causing sexually transmitted infections, which are not typically enteric pathogens. Therefore, HBT plates are not necessary for routine genital cultures.

During severe cases of Leptospirosis, the bacteria can spread throughout the body via the bloodstream, leading to multiple organ involvement. The kidneys are commonly affected as the bacteria can cause acute kidney injury. The liver can also be affected, resulting in liver dysfunction. Additionally, the bacteria can invade the central nervous system, leading to meningitis, encephalitis, or other neurological complications. Therefore, the most commonly affected organs during severe cases of Leptospirosis are the kidneys, liver, and central nervous system.

During the progression of Lyme Disease, multiple organs can be affected. The bacteria that causes Lyme Disease can spread through the bloodstream and affect various parts of the body. The skin is commonly affected, leading to rashes and skin lesions. The bacteria can also invade the blood vessels, causing inflammation and damage. The brain can be affected, leading to neurological symptoms such as memory problems and difficulty concentrating. The heart can also be affected, leading to heart rhythm abnormalities. Additionally, the joints can be affected, causing pain and swelling.

The given answer is correct. It lists all the Haemophilus species of clinical importance, including H.influenzae, H.ducreyi, H.aegyptius, and H.aphrophilus. These species are known to cause various clinical conditions in humans, such as respiratory tract infections, sexually transmitted infections, and other systemic diseases.

The screening test for secondary and tertiary syphilis aims to detect antibodies to cardiolipin, a type of phospholipid found in the cell membranes of T-pallidum bacteria. This test helps identify individuals who may have been exposed to the bacteria. On the other hand, the specific test for syphilis attempts to detect antibodies specifically targeting T-pallidum antigens. This test confirms the presence of syphilis infection and is more specific than the screening test.