Bacteriology Practice Questions

Q: A bacterial disease with oral manifestations is

Diphtheria. **Diphtheria** - **Diphtheria** is a bacterial infection caused by *Corynebacterium diphtheriae*, which produces a toxin leading to the formation of a **pseudomembrane** in the throat and tonsils, representing an oral manifestation [1]. - This **pseudomembrane** can cause difficulty breathing and swallowing, and if left untreated, the toxin can lead to systemic complications affecting the heart, kidneys, and nervous system [1]. *measles* - **Measles** (rubeola) is a viral infection characterized by a maculopapular rash and fever, and its classic oral manifestation is **Koplik's spots**, which are small white spots with a red halo found on the buccal mucosa. - Although Koplik's spots are an oral manifestation, measles is a **viral** disease, not bacterial. *Leishmaniasis* - **Leishmaniasis** is a parasitic disease caused by *Leishmania* parasites, transmitted by the bite of infected sandflies, and can present as cutaneous, mucocutaneous, or visceral forms. - While **mucocutaneous leishmaniasis** can affect the nose, mouth, and throat with ulcerative lesions, it is a **parasitic** disease, not bacterial. *Herpes* - **Herpes** is primarily caused by the **Herpes Simplex Virus (HSV)**, which is a **viral** infection, leading to cold sores (herpes labialis) or genital lesions. - Oral manifestations like **herpetic gingivostomatitis** are common, but the causative agent is viral, not bacterial [2].

Q: Which is NOT a sexually transmitted disease?

Yaws. ***Yaws*** - Yaws is a **chronic infectious disease** caused by the bacterium *Treponema pallidum pertenue*, a subspecies of *Treponema pallidum*, the same bacterium that causes syphilis. - It's primarily transmitted through **skin-to-skin contact** with infectious lesions, not sexual contact, and is common in warm, humid, tropical regions. *Granuloma Inguinale* - Also known as **Donovanosis**, this is a chronic, progressive **bacterial infection** caused by *Klebsiella granulomatis*. - It is **sexually transmitted** and primarily affects the skin and mucous membranes of the genital, inguinal, and perianal areas. *LGV* - **Lymphogranuloma Venereum (LGV)** is a sexually transmitted infection (STI) caused by specific serovars of *Chlamydia trachomatis*. - It is characterized by **lymphadenopathy** and can cause invasive infections of the lymph nodes and lymphatic tissue, particularly in the genital and anal regions. *Chancroid* - Chancroid is a **bacterial STI** caused by *Haemophilus ducreyi*. - It is characterized by the development of **painful genital ulcers** and often swelling of the lymph nodes in the groin.

Q: A child with fever with abdominal cramps & pus in stools, causative organism is ?

EAEC. ***EAEC (Enteroaggregative E. coli)*** - Among the E. coli strains listed, EAEC is the answer for this question, though **this is an atypical presentation**. - EAEC classically causes **persistent watery diarrhea** (>14 days) in children, often with **low-grade fever** and **abdominal pain**. - While EAEC primarily causes non-bloody diarrhea, it can occasionally produce **mucoid stools** with inflammatory cells due to mucosal inflammation from biofilm formation. - **Note:** The classic organism for fever + cramps + pus in stools would be **Shigella**, **Campylobacter**, or **EIEC (Enteroinvasive E. coli)** - not listed here. *EHEC (Enterohemorrhagic E. coli)* - EHEC (O157:H7) causes **hemorrhagic colitis** with bloody diarrhea due to **Shiga toxins**. - Can lead to **hemolytic uremic syndrome (HUS)** in children. - Characterized by **blood** rather than pus in stools, distinguishing it from typical dysentery. *ETEC (Enterotoxigenic E. coli)* - Most common cause of **traveler's diarrhea** and watery diarrhea in developing countries. - Produces **heat-labile (LT)** and **heat-stable (ST)** enterotoxins causing secretory diarrhea. - Results in profuse **watery stools without inflammation, blood, or pus**. *EPEC (Enteropathogenic E. coli)* - Leading cause of infantile diarrhea in developing countries. - Causes **attaching and effacing** lesions on intestinal mucosa. - Results in **watery diarrhea without significant inflammatory cells or pus** in stools.

Q: Which of the following are pleomorphic organisms?

Mycoplasma. ***Mycoplasma*** - **Mycoplasma** species are known for their **pleomorphic nature** because they lack a rigid **cell wall**, allowing them to assume various shapes. - This characteristic distinguishes them from most other bacteria, which have a defined shape due to their cell walls. *Pseudomonas* - **Pseudomonas** typically appears as **rod-shaped bacilli** and is not considered pleomorphic. - Its bacterial shape is consistent and relatively stable due to its **peptidoglycan cell wall**. *Corynebacterium* - **Corynebacterium** primarily exhibits a **rod-like** or **club-shaped morphology**, often described as diphtheroid. - While they can have slightly irregular shapes, they are not highly pleomorphic in the same sense as Mycoplasma. *Gonococcus* - **Gonococcus** (Neisseria gonorrhoeae) is characterized by its **gram-negative diplococcus** (kidney-bean shaped pairs) morphology. - Its shape is quite distinct and consistent, and it is not considered pleomorphic.

Q: Which is true about salmonella gastroenteritis?

Diarrhea is nonbloody. **Diarrhea is nonbloody** - In typical **Salmonella gastroenteritis** (non-typhoidal Salmonella), the diarrhea is usually **watery and non-bloody**, though in some cases, microscopic blood may be present [1]. - The illness is self-limiting and rarely progresses to invasive disease, unlike typhoidal salmonellosis. *Is due to exotoxin* - **Salmonella gastroenteritis** primarily results from the bacteria invading the intestinal mucosa and causing inflammation, rather than the action of a preformed exotoxin. - While Salmonella can produce some toxins, their primary pathogenesis involves **endotoxin (LPS)** and direct mucosal invasion, leading to an inflammatory response. *Always associated with blood and mucus in stools* - While some gastrointestinal infections, such as those caused by *Shigella* or enteroinvasive *E. coli*, are classically associated with **bloody and mucoid stools** (dysentery), this is not consistently true for **Salmonella gastroenteritis** [1]. - As mentioned, Salmonella typically causes watery, non-bloody diarrhea; gross blood and mucus are less common unless the infection is more severe or invasive [1]. *Mainly diagnosed by serological testing* - **Salmonella gastroenteritis** is primarily diagnosed by **stool culture**, which identifies the presence of the bacteria in the feces. - **Serological tests** (e.g., Widal test) are rarely used for acute gastroenteritis diagnosis as they detect antibody responses that may take time to develop and can be non-specific.

Q: Organism involved in cellulitis is:

S. pyogenes. ***Strept. pyogenes*** - *Streptococcus pyogenes* (Group A Streptococcus) is a common cause of **cellulitis**, an acute bacterial infection of the deep dermis and subcutaneous tissue. - It often spreads rapidly and can lead to systemic symptoms if untreated. *Strept. mutans* - *Streptococcus mutans* is primarily associated with **dental caries** (tooth decay) and is a significant component of oral biofilm. - It is not a common cause of cellulitis in typical settings. *Pneumococci* - **Pneumococci** (*Streptococcus pneumoniae*) are most commonly known for causing **pneumonia**, otitis media, and meningitis. - While they can cause invasive infections, they are not a primary cause of routine cellulitis. *Klebsiella* - *Klebsiella* species are common causes of **nosocomial infections**, particularly urinary tract infections, pneumonia, and bloodstream infections. - They can cause cellulitis, especially in immunocompromised individuals or those with specific risk factors, but *S. pyogenes* is more common in general cellulitis cases.

Q: A 34-year-old woman is at a family picnic where she has a ham sandwich and potato salad. Three hours after the meal, she feels nauseous and throws up.For the above patient with foodborne illness, select the most likely pathogen.

Staphylococcus aureus. ***Staphylococcus aureus*** - This pathogen produces **exotoxins** that cause rapid onset (1-6 hours) of severe nausea, vomiting, and abdominal cramps after ingesting contaminated food, consistent with the patient's symptoms. - Common sources include **creamy salads** (like potato salad) and **processed meats** (like ham), which are often left at room temperature, allowing toxin production. *C perfringens* - While *C. perfringens* can cause foodborne illness, its onset is typically longer (8-16 hours) and often presents with more pronounced **diarrhea** than vomiting. - It is often associated with **reheated meat dishes** and gravies. *Vibrio parahaemolyticus* - This bacterium is primarily associated with the consumption of **raw or undercooked seafood**, which is not mentioned in the patient's meal. - Symptoms usually include **watery diarrhea** with abdominal cramps, and the incubation period can range from 4 to 96 hours. *Shigella* - *Shigella* causes **dysentery**, characterized by fever, severe abdominal cramps, and bloody diarrhea, and typically has a longer incubation period (1-3 days). - Its transmission often involves the fecal-oral route, usually through contaminated water or food handled by infected individuals, and the clinical picture does not match the rapid onset and vomiting described.

Q: In cholangitis, the organism mostly responsible is ?

E.Coli. ***E.Coli*** - **_E. coli_** is the most common Gram-negative bacterium causing cholangitis due to its prevalence in the gut and ability to ascend the biliary tree. - Its presence is often linked to **biliary obstruction**, creating an environment conducive to bacterial proliferation. *Streptococcus* - While *Streptococcus spp.* can cause infections, they are **less common** as primary causes of cholangitis compared to **Gram-negative bacilli**. - **Enterococci**, a type of streptococcus, can be significant in **healthcare-associated cholangitis** or in recurrent cases. *Klebsiella* - **_Klebsiella_** species are **Gram-negative bacteria** that are the **second most common cause** of acute cholangitis after E. coli. - They are particularly associated with **healthcare-associated biliary infections** and **recurrent cholangitis**. - Like E. coli, they originate from the **gastrointestinal tract** and can ascend the biliary tree. *Clostridium* - **_Clostridium_** species are **anaerobic bacteria** and are generally **not primary pathogens in acute cholangitis** unless there is severe tissue damage or specific conditions. - While some species can cause **gas gangrene** or **colitis**, they are **rarely the sole cause** of acute cholangitis.

Q: Typhoid carriers harbor bacteria in

Gallbladder. ***Gallbladder*** - The **gallbladder** is the primary site where **Salmonella Typhi** bacteria can persist in chronic carriers, leading to asymptomatic shedding and potential transmission. - The bacteria form **biofilms** on gallstones or the gallbladder mucosa, making eradication difficult. *Spleen* - The spleen can be involved during the **acute phase** of typhoid fever, leading to **splenomegaly**, but it is not the primary site for chronic carriage. - While bacteria may transiently reside here, it does not typically harbor the persistent, high bacterial loads seen in chronic carriers. *Pancreas* - The pancreas is generally **not a site for chronic carriage** of Salmonella Typhi. - Pancreatic involvement in typhoid fever is rare and typically presents as **acute pancreatitis**, not persistent bacterial shedding. *Urinary bladder* - While **urinary carriage** of Salmonella Typhi can occur, it is **less common** than fecal carriage and usually associated with underlying urinary tract abnormalities. - The urine is not the primary body fluid through which chronic carriers typically transmit the infection.

Q: The causative agent of louse-borne relapsing fever is:

B recurrentis. ***B recurrentis*** - **_Borrelia recurrentis_** is the specific spirochete responsible for **louse-borne relapsing fever (LBRF)**, which is transmitted by the human body louse, _Pediculus humanus humanus_. - This infection is characterized by recurrent episodes of **fever**, **headache**, and **myalgia**, due to antigenic variation of the bacterium. *B parkeri* - **_Borrelia parkeri_** causes **tick-borne relapsing fever (TBRF)** and is primarily transmitted by soft-bodied ticks, not lice. - Its geographical distribution and clinical presentation, while similar to other relapsing fevers, are associated with tick exposure. *B burgdorferi* - **_Borrelia burgdorferi_** is the causative agent of **Lyme disease**, a distinct tick-borne illness, not relapsing fever. - Lyme disease is characterized by an **erythema migrans** rash, arthritis, and neurological symptoms, and typically does not present with recurrent fevers in the same manner as relapsing fever. *B duttoni* - **_Borrelia duttoni_** is another species that causes **tick-borne relapsing fever (TBRF)**, prevalent in parts of Africa, transmitted by soft ticks of the genus _Ornithodoros_ - It is not associated with louse transmission, differentiating it from louse-borne relapsing fever.

Question 1

A bacterial disease with oral manifestations is

Accepted Answer

Diphtheria

Answer

measles

Answer

Leishmaniasis

Answer

Herpes

Question 2

Which is NOT a sexually transmitted disease?

Accepted Answer

Yaws

Answer

Granuloma Inguinale

Answer

LGV

Answer

Chancroid

Question 3

A child with fever with abdominal cramps & pus in stools, causative organism is ?

Accepted Answer

EAEC

Answer

EHEC

Answer

ETEC

Answer

EPEC

Question 4

Which of the following are pleomorphic organisms?

Accepted Answer

Mycoplasma

Answer

Pseudomonas

Answer

Corynebacterium

Answer

Gonococcus

Question 5

Which is true about salmonella gastroenteritis?

Accepted Answer

Diarrhea is nonbloody

Answer

Is due to exotoxin

Answer

Always associated with blood and mucus in stools

Answer

Mainly diagnosed by serological testing

Question 6

Organism involved in cellulitis is:

Accepted Answer

S. pyogenes

Answer

S. mutans

Answer

Klebsiella

Answer

Pneumococci

Question 7

A 34-year-old woman is at a family picnic where she has a ham sandwich and potato salad. Three hours after the meal, she feels nauseous and throws up.For the above patient with foodborne illness, select the most likely pathogen.

Accepted Answer

Staphylococcus aureus

Answer

C perfringens

Answer

Vibrio parahaemolyticus

Answer

Shigella

Question 8

In cholangitis, the organism mostly responsible is ?

Accepted Answer

E.Coli

Answer

Streptococcus

Answer

Klebsiella

Answer

Clostridium

Question 9

Typhoid carriers harbor bacteria in

Accepted Answer

Gallbladder

Answer

Spleen

Answer

Pancreas

Answer

Urinary bladder

Question 10

The causative agent of louse-borne relapsing fever is:

Accepted Answer

B recurrentis

Answer

B parkeri

Answer

B burgdorferi

Answer

B duttoni

Bacteriology — MCQs

Bacteriology — MCQs

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