Bacteriology Practice Questions

Q: The arrow points to the presence of which bacteria?

Clostridium tetani. ***Clostridium tetani*** - The image displays **long, filamentous bacteria** with **terminal spores**, giving them a classic "tennis racket" or "drumstick" appearance, which is characteristic of *Clostridium tetani*. - *Clostridium tetani* is a **Gram-positive, anaerobic bacillus** known for producing spores, especially in unfavorable conditions. *Streptococcus bovis* - *Streptococcus bovis* (now reclassified as *Streptococcus gallolyticus*) typically appears as **Gram-positive cocci** in chains, rather than long rods with terminal spores. - It is associated with **bacteremia**, endocarditis, and colon cancer, and its morphology does not match the image. *Hemophilus influenzae* - *Hemophilus influenzae* is a **Gram-negative coccobacillus** that can appear as short rods or cocci, often pleomorphic, and does not form spores or long filaments. - This bacterium is a common cause of respiratory infections, otitis media, and meningitis. *Bacillus cereus* - *Bacillus cereus* is a **Gram-positive rod** that forms spores, but these spores are typically **central or subterminal** and do not give the distinctive "tennis racket" morphology seen with *Clostridium tetani*. - It is known for causing **food poisoning** due to enterotoxin production.

Q: Which of the following organisms is incriminated in a patient of left sided endocarditis involving the mitral valve? (Recent NEET Pattern 2016-17)

Streptococcus viridans. ***Streptococcus viridans*** - This group of bacteria is the **most common cause** of **subacute infective endocarditis** on native, previously damaged valves, particularly the mitral valve. - They typically colonize the oral cavity and can enter the bloodstream after dental procedures or poor oral hygiene, leading to seeding of cardiac valves. *Candida albicans* - *Candida albicans* is a common cause of **fungal endocarditis**, which typically presents as a more subacute or chronic illness and can occur in immunocompromised individuals or those with indwelling catheters. - While it can affect the mitral valve, it is less common than bacterial causes, especially in the context of left-sided endocarditis unless specific risk factors (e.g., intravenous drug use, prosthetic valves, prolonged antibiotic use) are present. *Enterococci* - **Enterococcal endocarditis** often occurs in older patients, those with underlying genitourinary or gastrointestinal tract pathology, or healthcare-associated infections. - While they can affect native or prosthetic valves, they are not the most common cause of native valve endocarditis involving the mitral valve in the general population. *Pseudomonas* - **Pseudomonas endocarditis** is typically associated with **intravenous drug use** and commonly affects the **tricuspid valve** (right-sided endocarditis). - While it can involve left-sided valves, it is less frequent in the absence of intravenous drug use compared to *Streptococcus viridans*.

Q: What is incorrect about the bacteria causing the following colonies? (Recent NEET Pattern 2016-17)

Carbon dioxide promotes sporulation. ***Carbon dioxide promotes sporulation*** - This statement is incorrect because **carbon dioxide inhibits sporulation** and promotes the vegetative state of *Bacillus anthracis*. - **Bicarbonate** (often added as sodium bicarbonate) is required for the expression of the capsule in vivo, but not for sporulation. *Medusa head colony* - This is a characteristic appearance of **Bacillus anthracis colonies** on blood agar, often described as having curled margins and irregular projections. - The image provided clearly shows this **distinct morphology**. *Bamboo Rod appearance* - This describes the typical morphology of **Bacillus anthracis** under microscopy, specifically showing **Gram-positive, non-motile rods** arranged in long chains. - This appearance is a key diagnostic feature of the bacteria. *Biological warfare* - *Bacillus anthracis* is a well-known agent for **biological warfare** because its spores are highly stable, easily disseminated, and can cause severe, often fatal, disease (anthrax) upon inhalation. - Its use in bioweapons programs has been documented historically.

Q: Identify the bacteria based on the colony morphology shown in the image.

Bacillus anthracis. ***Bacillus anthracis*** - The image displays characteristic **“Medusa head” colonies** with irregular, wavy margins and a dull, ground-glass appearance, which are classic for *Bacillus anthracis*. - These colonies are often non-hemolytic on blood agar and are notably **non-motile**, a key differentiator from *Bacillus cereus* or *Bacillus subtilis*. *Bacillus subtilis* - While also a *Bacillus* species, *Bacillus subtilis* typically forms **spreading colonies** with a more uniform, often granular or wrinkled texture, distinct from the Medusa head morphology. - It is generally **motile** and can produce various pigments, unlike the non-motile, grayish-white colonies of *B. anthracis*. *Mycoplasma hominis* - *Mycoplasma hominis* forms very tiny colonies, often described as having a **"fried egg" appearance** due to central growth sinking into the agar and a peripheral translucent ring. - These colonies are typically **much smaller** than those seen in the image and require specialized media for growth, making them easily distinguishable. *Mycoplasma pneumoniae* - *Mycoplasma pneumoniae* also produces miniature colonies, typically taking on a **"fried egg" morphology**, but even more fastidious in their growth requirements and size than *M. hominis*. - It would not produce the large, irregular, and distinctly textured colonies observed in the provided image.

Q: Which organism is incriminated in causing the following lesions? (Recent NEET Pattern 2016-17)

Streptococcus pyogenes. ***Streptococcus pyogenes*** - The image depicts **impetigo**, characterized by crusted lesions, often found on the face. - **Streptococcus pyogenes** (Group A Streptococcus) is a common cause of impetigo, either alone or in combination with *Staphylococcus aureus*. *Streptococcus pneumoniae* - *Streptococcus pneumoniae* is primarily associated with **respiratory tract infections**, such as pneumonia and otitis media, not skin lesions like impetigo. - While it can cause invasive diseases, its primary presentation is typically not superficial skin infections. *Enterococcus* - *Enterococcus* species are common inhabitants of the normal **gastrointestinal flora** and are frequently implicated in **urinary tract infections**, endocarditis, and hospital-acquired infections. - They are generally not a primary cause of impetigo or similar superficial skin infections. *Staphylococcus aureus* - While *Staphylococcus aureus* is a very common cause of **impetigo**, the question asks for "the organism" as if there is only one most specific answer without providing other context, suggesting **Streptococcus pyogenes** as a highly relevant primary pathogen, especially if non-bullous impetigo is implied by the crusted appearance. - *S. aureus* often presents with **purulent lesions** (e.g., boils, carbuncles) and bullous impetigo with fluid-filled blisters which eventually rupture and crust.

Q: A 35-year-old male farmer presents with multiple discharging cervical sinuses. Which of these stains will be useful for the diagnosis and where does this organism normally colonize in the body? (AIIMS Nov 2015)

Modified kinyoun acid fast stain, mouth. ***Modified Kinyoun acid-fast stain, mouth*** - This clinical presentation of **multiple discharging cervical sinuses** in a farmer is highly suggestive of **actinomycosis**, caused by *Actinomyces israelii*. - *Actinomyces israelii* is a **Gram-positive, non-spore-forming, anaerobic to microaerophilic rod** that is **partially acid-fast (modified Kinyoun acid-fast stain)** and a normal inhabitant of the **oral cavity, gastrointestinal tract, and female genital tract**. *Gram stain, hypopharynx* - While *Actinomyces israelii* would stain Gram-positive, the **Gram stain** alone is not specific enough to confirm actinomycosis, especially given the characteristic partially acid-fast nature. - The **hypopharynx** is not the primary or most common normal colonization site for *Actinomyces israelii*; the mouth is more accurate. *PAS, intestine* - The **Periodic Acid-Schiff (PAS) stain** is typically used to identify fungi, carbohydrates, and glycogen, not primarily *Actinomyces*. - While *Actinomyces* can be found in the intestine, it's not the most common colonization site associated with cervicofacial actinomycosis. *Grocott methenamine silver stain, vagina* - **Grocott Methenamine Silver (GMS) stain** is primarily used for the detection of fungi and some encapsulated bacteria, but not specifically *Actinomyces*. - Though *Actinomyces* can colonize the vagina, it's more commonly associated with pelvic actinomycosis, not the cervical presentation described.

Q: The gram stain given below shows which organism most likely? (AIIMS May 2016)

Neisseria meningitidis. ***Neisseria meningitidis*** - The image shows **Gram-negative diplococci** (pink/red, paired cocci) both extracellularly and **intracellularly within neutrophils** (large pink cells). This morphology is classic for *Neisseria meningitidis* in cerebrospinal fluid. - *N. meningitidis* is a common cause of **bacterial meningitis**, and its presence as intracellular Gram-negative diplococci in CSF is diagnostic. *Staphylococcus aureus* - *Staphylococcus aureus* are **Gram-positive cocci** (purple/blue), typically appearing in **clusters** like grapes. The organisms in the image are Gram-negative and often in pairs. - While *S. aureus* can cause meningitis, its characteristic Gram stain appearance is distinctly different from what is shown. *Streptococcus pneumoniae* - *Streptococcus pneumoniae* are **Gram-positive cocci** (purple/blue) typically arranged in **pairs (diplococci)** or short chains. The organisms in the image are Gram-negative. - Although *S. pneumoniae* is a common cause of bacterial meningitis, its Gram stain morphology is different (Gram-positive). *Streptococcus pyogenes* - *Streptococcus pyogenes* are **Gram-positive cocci** (purple/blue) arranged in **chains**. The organisms in the image are Gram-negative and appear as diplococci. - *S. pyogenes* is more commonly associated with pharyngitis and skin infections, and rarely causes meningitis, but its Gram stain morphology is not consistent with the image.

Q: A 24-year-old female presented with an ulcer in the genital area. A giemsa stained cervical smear was prepared. Identify the causative agent: (AIIMS Nov 2015)

Haemophilus ducreyi. ***Hemophilus ducreyi*** - The image shows numerous small, pleomorphic, gram-negative coccobacilli arranged in **'school of fish'** or parallel chains, characteristic of **_Haemophilus ducreyi_** on a Giemsa-stained smear. - This morphology, especially from a genital ulcer, is highly indicative of **chancroid**, caused by _H. ducreyi_. *Gardnerella vaginalis* - _Gardnerella vaginalis_ is associated with **bacterial vaginosis** and is characterized by the presence of **"clue cells"** (vaginal epithelial cells covered with coccobacilli) on microscopy. - It does not form the "school of fish" arrangement seen in the image, nor does it typically cause ulcerative lesions. *Chlamydia* - **_Chlamydia trachomatis_** causes various infections, including genital ulcers in cases of **lymphogranuloma venereum (LGV)**, but it is an obligate intracellular bacterium. - It would appear as **intracellular inclusions** on a Giemsa stain and would not show extracellular coccobacillary forms arranged in clusters as depicted. *Calymmatobacterium granulomatosis* - Previously known as _Calymmatobacterium granulomatosis_, now designated as **_Klebsiella granulomatis_**, this bacterium causes **granuloma inguinale (donovanosis)**, characterized by large, beefy-red ulcers. - Diagnostic features on Giemsa stain include **Donovan bodies** (intracellular bacilli within macrophages), which are not a prominent feature in the provided image.

Q: A 23-year-old female presents with fever and altered sensorium for two days with rashes on legs as shown. Her BP is 70/50 mm Hg and neck stiffness is present. Lumbar puncture reveals cloudy CSF with 4200 cells/ $\mu \mathrm{L}$, protein level 198 and glucose $21 \mathrm{mg} /$ dL. Which of the following correctly describes the organism causing this condition?

Gram negative diplococci (kidney shaped), oxidase positive. ***Gram negative diplococci (kidney shaped), oxidase positive*** - The clinical presentation of **fever**, **altered sensorium**, **neck stiffness**, **petechial rash** (shown on legs), **hypotension**, and characteristic CSF findings (cloudy, high protein, low glucose, high cell count) is highly suggestive of **meningococcal meningitis**. - **Neisseria meningitidis**, the causative agent, is a **Gram-negative diplococcus** with a characteristic **kidney-bean shape** and is **oxidase-positive**. *Gram positive cocci catalase negative, bacitracin sensitive* - This description refers to **Streptococcus pyogenes** (Group A Streptococcus), which causes pharyngitis, skin infections, and rarely meningitis. - S. pyogenes meningitis is **uncommon** and does not typically present with the widespread **petechial rash** characteristic of meningococcemia. *Gram positive diplococci (lanceolate), catalase negative, optochin sensitive* - This describes **Streptococcus pneumoniae**, which is a common cause of **bacterial meningitis**, especially in adults and children. - While S. pneumoniae can cause similar CSF findings, it does not typically present with the prominent **petechial rash** and **meningococcemia** seen in this case. *Gram negative diplococci, ferments glucose only (not maltose)* - This describes **Neisseria gonorrhoeae**, which ferments **glucose** but **not maltose**, unlike N. meningitidis which ferments both. - N. gonorrhoeae typically causes **sexually transmitted infections** (urethritis, cervicitis) and rarely causes meningitis, making it unsuitable for this clinical scenario.

Q: All are correct about the condition shown in the image except:

Aspirated material shows LCL bodies. ***Correct: Aspirated material shows LCL bodies*** - **"LCL bodies" is NOT a recognized diagnostic term** for lymphogranuloma venereum (LGV) - The aspirated material from buboes in LGV shows **Chlamydia trachomatis elementary bodies and reticulate bodies**, along with inflammatory cells - This is the EXCEPTION as it is an incorrect statement about LGV *Incorrect: Groove sign of LGV* - The **groove sign is a classic clinical feature** of LGV - Formed by enlarged inguinal lymph nodes above and below the inguinal (Poupart's) ligament, creating a characteristic depression - This is a TRUE statement about LGV *Incorrect: Most common cause of this infection is L2 biovar* - LGV is caused by **Chlamydia trachomatis serovars L1, L2, and L3** - **L2 serovar is the most prevalent cause** of LGV infections worldwide - This is a TRUE statement about LGV *Incorrect: Females develop esthiomene* - **Esthiomene is a late complication** of chronic untreated LGV in females - Characterized by progressive genital elephantiasis, ulceration, and destruction of vulvo-perineal tissues - Results from persistent lymphatic obstruction and chronic inflammation - This is a TRUE statement about LGV

Question 1

The arrow points to the presence of which bacteria?

Accepted Answer

Clostridium tetani

Answer

Streptococcus bovis

Answer

Hemophilus influenzae

Answer

Bacillus cereus

Question 2

Which of the following organisms is incriminated in a patient of left sided endocarditis involving the mitral valve? (Recent NEET Pattern 2016-17)

Accepted Answer

Streptococcus viridans

Answer

Candida albicans

Answer

Enterococci

Answer

Pseudomonas

Question 3

What is incorrect about the bacteria causing the following colonies? (Recent NEET Pattern 2016-17)

Accepted Answer

Carbon dioxide promotes sporulation

Answer

Medusa head colony

Answer

Bamboo Rod appearance

Answer

Biological warfare

Question 4

Identify the bacteria based on the colony morphology shown in the image.

Accepted Answer

Bacillus anthracis

Answer

Bacillus subtilis

Answer

Mycoplasma hominis

Answer

Mycoplasma pneumoniae

Question 5

Which organism is incriminated in causing the following lesions? (Recent NEET Pattern 2016-17)

Accepted Answer

Streptococcus pyogenes

Answer

Streptococcus pneumoniae

Answer

Enterococcus

Answer

Staphylococcus aureus

Question 6

A 35-year-old male farmer presents with multiple discharging cervical sinuses. Which of these stains will be useful for the diagnosis and where does this organism normally colonize in the body? (AIIMS Nov 2015)

Accepted Answer

Modified kinyoun acid fast stain, mouth

Answer

Gram stain, hypopharynx

Answer

PAS, intestine

Answer

Grocott methenamine silver stain, vagina

Question 7

The gram stain given below shows which organism most likely? (AIIMS May 2016)

Accepted Answer

Neisseria meningitidis

Answer

Staphylococcus aureus

Answer

Streptococcus pneumoniae

Answer

Streptococcus pyogenes

Question 8

A 24-year-old female presented with an ulcer in the genital area. A giemsa stained cervical smear was prepared. Identify the causative agent: (AIIMS Nov 2015)

Accepted Answer

Haemophilus ducreyi

Answer

Gardnerella vaginalis

Answer

Chlamydia

Answer

Calymmatobacterium granulomatosis

Question 9

A 23-year-old female presents with fever and altered sensorium for two days with rashes on legs as shown. Her BP is 70/50 mm Hg and neck stiffness is present. Lumbar puncture reveals cloudy CSF with 4200 cells/ $\mu \mathrm{L}$, protein level 198 and glucose $21 \mathrm{mg} /$ dL. Which of the following correctly describes the organism causing this condition?

Accepted Answer

Gram negative diplococci (kidney shaped), oxidase positive

Answer

Gram positive cocci catalase negative, bacitracin sensitive

Answer

Gram positive diplococci (lanceolate), catalase negative, optochin sensitive

Answer

Gram negative diplococci, ferments glucose only (not maltose)

Question 10

All are correct about the condition shown in the image except:

Accepted Answer

Aspirated material shows LCL bodies

Answer

Groove sign of LGV

Answer

Most common cause of this infection is L2 biovar

Answer

Females develop esthiomene

Bacteriology — MCQs

Bacteriology — MCQs

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