Antibiotic Resistance in Dermatology — MCQs
A peculiar organism has resistance to azithromycin, but is sensitive to ticarcillin, clavulanic acid, cotrimoxazole. Identify the organism?
A child presents with complaints of fever, rash, body ache, and throat ache. He had a history of thorn prick injury a week back. What antibiotics would you give empirically to this child?
A diabetic patient developed cellulitis due to S. aureus, which was found to be methicillin resistant on the antibiotic sensitivity testing. All of the following antibiotics will be appropriate except ?
Drugs of choice for MRSA in skin and soft tissue infections are:
In a post operative intensive care unit, five patients developed post-operative wound infection on the same day. Which of the following is the best method to prevent cross infection among patients in the same ward?
A 45-year-old HIV-positive man presents with fever and cough. Sputum culture shows acid-fast bacilli. Which of the following drugs is essential in the treatment regimen?
A woman presents with a thick, curdy, white vaginal discharge. The best treatment for her is:
False regarding bacterial plasmids is:
What is the best way to control the MRSA infection in the ward?
Which of the following drug classes is commonly implicated in causing Stevens-Johnson syndrome?
Antibiotic Resistance in Dermatology Indian Medical PG Practice Questions and MCQs
Question 1: A peculiar organism has resistance to azithromycin, but is sensitive to ticarcillin, clavulanic acid, cotrimoxazole. Identify the organism?
- A. Pseudomonas
- B. Staphylococcus
- C. Stenotrophomonas (Correct Answer)
- D. Mycoplasma
Explanation: ***Stenotrophomonas*** - *Stenotrophomonas maltophilia* is intrinsically **resistant to azithromycin** and other macrolides due to its efflux pumps. - It is known to be sensitive to **ticarcillin-clavulanic acid** (a beta-lactam/beta-lactamase inhibitor combination) and **cotrimoxazole** (trimethoprim-sulfamethoxazole), which are common treatment options. *Pseudomonas* - *Pseudomonas aeruginosa* is generally **resistant to macrolides like azithromycin** but can exhibit varying sensitivity to antibiotics. - However, it often shows resistance to cotrimoxazole and ticarcillin-clavulanic acid is not a first-line agent, and it would typically be sensitive to other antipseudomonal beta-lactams (e.g., piperacillin-tazobactam, carbapenems). *Staphylococcus* - Many *Staphylococcus* species, particularly **MRSA**, are resistant to azithromycin. - However, *Staphylococcus* species are typically sensitive to other antibiotics like **vancomycin**, and are generally not sensitive to ticarcillin-clavulanic acid, and their susceptibility to cotrimoxazole varies depending on the species and resistance mechanisms. *Mycoplasma* - *Mycoplasma* species are **intrinsically resistant to beta-lactam antibiotics like ticarcillin** because they lack a cell wall, which is the target of these drugs. - They are typically sensitive to macrolides like azithromycin and also to cotrimoxazole.
Question 2: A child presents with complaints of fever, rash, body ache, and throat ache. He had a history of thorn prick injury a week back. What antibiotics would you give empirically to this child?
- A. Amoxicillin+ clavulanate (Correct Answer)
- B. Ceftriaxone
- C. Vancomycin
- D. Meropenem
Explanation: ***Amoxicillin + clavulanate*** - This combination provides **broad-spectrum coverage** against common skin flora including **Staphylococcus aureus**, **Streptococcus species**, and **anaerobes** that can be introduced by thorn prick injuries. - The **beta-lactamase inhibitor (clavulanate)** extends coverage to beta-lactamase producing organisms commonly found in skin infections. - Covers **Streptococcus pyogenes** which could explain the throat ache, making it ideal for this child with both skin infection and pharyngitis symptoms. - Most appropriate **first-line empiric therapy** for pediatric skin and soft tissue infections with systemic symptoms. *Ceftriaxone* - While this **third-generation cephalosporin** has good coverage against many gram-negative bacteria and some gram-positive organisms including **MSSA (methicillin-sensitive S. aureus)**, it is typically **reserved for parenteral therapy** in more severe infections. - For this clinical scenario, amoxicillin-clavulanate is preferred because it provides better **beta-lactamase coverage**, can be given orally, and covers both aerobic and anaerobic organisms relevant to thorn prick injuries. - Would be considered if the patient required **hospitalization** or failed first-line therapy. *Vancomycin* - This antibiotic is primarily used for serious infections caused by **multi-drug resistant gram-positive bacteria**, particularly **methicillin-resistant Staphylococcus aureus (MRSA)**. - Given the history of a thorn prick without specific risk factors for MRSA (no prior MRSA infection, hospital exposure, or failed beta-lactam therapy), there is **no indication for empiric vancomycin use**. - Using vancomycin empirically without specific indication contributes to **antibiotic resistance** and is not guideline-recommended. *Meropenem* - A **carbapenem** antibiotic reserved for **severe, life-threatening infections** caused by multi-drug resistant organisms or in cases of **septic shock** with unknown etiology. - The clinical presentation does not suggest severe sepsis, necrotizing fasciitis, or resistant pathogen requiring such broad coverage. - Empiric use in this scenario would represent **inappropriate antimicrobial stewardship** and promote development of carbapenem-resistant organisms.
Question 3: A diabetic patient developed cellulitis due to S. aureus, which was found to be methicillin resistant on the antibiotic sensitivity testing. All of the following antibiotics will be appropriate except ?
- A. Vancomycin
- B. Teicoplanin
- C. Linezolid
- D. Imipenem (Correct Answer)
Explanation: ***Imipenem*** - **Imipenem** is a carbapenem antibiotic that is effective against many Gram-positive and Gram-negative bacteria, but it is **not active against MRSA (methicillin-resistant *Staphylococcus aureus*)**. - MRSA strains are resistant to all beta-lactam antibiotics, including penicillins, cephalosporins, and carbapenems like imipenem, due to the presence of the **mecA gene** which encodes for an altered penicillin-binding protein (PBP2a). *Vancomycin* - **Vancomycin** is a glycopeptide antibiotic that is a primary choice for treating **MRSA infections**, including cellulitis. - It inhibits cell wall synthesis by binding to the D-Ala-D-Ala precursor, preventing cross-linking, and is specifically active against **Gram-positive bacteria**. *Teicoplanin* - **Teicoplanin** is another glycopeptide antibiotic, similar to vancomycin, and is also considered a suitable agent for treating **MRSA infections**. - It works by inhibiting bacterial cell wall synthesis and has a **longer half-life** than vancomycin, allowing for less frequent dosing. *Linezolid* - **Linezolid** is an oxazolidinone antibiotic known for its activity against **Gram-positive bacteria**, including **MRSA** and vancomycin-resistant enterococci (VRE). - It inhibits protein synthesis by binding to the 50S ribosomal subunit, preventing the formation of the initiation complex.
Question 4: Drugs of choice for MRSA in skin and soft tissue infections are:
- A. Clindamycin, Vancomycin
- B. Vancomycin, Linezolid (Correct Answer)
- C. Vancomycin, Teicoplanin
- D. Dicloxacillin, Vancomycin
Explanation: ***Vancomycin, Linezolid*** - **Vancomycin** is a cornerstone for treating **MRSA** infections, particularly severe ones, due to its efficacy against resistant staphylococci. - **Linezolid** is an alternative for **MRSA** infections, especially in cases of vancomycin resistance or intolerance, and offers good oral bioavailability. *Clindamycin, Vancomycin* - While **vancomycin** is correct, **clindamycin** has varying efficacy against **MRSA** and high rates of inducible resistance, making it less reliable as a primary drug of choice. - Clindamycin's use for MRSA often requires initial susceptibility testing, including a **D-test**, to rule out inducible clindamycin resistance. *Vancomycin, Teicoplanin* - **Vancomycin** is a primary **MRSA** drug, but **teicoplanin** is largely used in Europe and is structurally similar to vancomycin, often reserved for cases where vancomycin is not tolerated or preferred. - While effective, **teicoplanin** is not as universally recognized as a first-line option alongside vancomycin in all regions. *Dicloxacillin, Vancomycin* - **Vancomycin** is appropriate, but **dicloxacillin** is an **anti-staphylococcal penicillin** and is not effective against **MRSA** (Methicillin-Resistant Staphylococcus aureus) because MRSA, by definition, is resistant to all beta-lactam antibiotics. - Dicloxacillin is mainly used for **MSSA** (Methicillin-Sensitive Staphylococcus aureus) infections.
Question 5: In a post operative intensive care unit, five patients developed post-operative wound infection on the same day. Which of the following is the best method to prevent cross infection among patients in the same ward?
- A. Give antibiotics to all other patients in the ward
- B. Practice proper hand washing (Correct Answer)
- C. Disinfect the ward with sodium hypochlorite
- D. Fumigate the ward
Explanation: ***Practice proper hand washing*** - **Proper hand washing** is the **single most effective measure** to prevent hospital-acquired infections, including cross-transmission of pathogens between patients in a ward. - It physically removes transient microorganisms acquired from patient contact or the environment, thus breaking the chain of infection. *Give antibiotics to all other patients in the ward* - This approach promotes **antibiotic resistance** and can disrupt the patients' normal flora, potentially leading to other infections like *Clostridioides difficile*. - Administering antibiotics prophylactically to uninfected patients is generally discouraged due to these risks and the lack of specific indication. *Disinfect the ward with sodium hypochlorite* - While **surface disinfection** is important, it is less effective than hand hygiene in preventing direct patient-to-patient transmission of pathogens carried by healthcare workers. - Frequent chemical disinfection of an entire ward with strong agents like **sodium hypochlorite** can also be harmful to equipment and may not address all modes of transmission effectively. *Fumigate the ward* - **Fumigation** is a drastic measure typically reserved for specific outbreaks or terminal disinfection, not for routine infection prevention in an occupied ICU. - It is often impractical, costly, requires patient evacuation, and may not target the primary vectors of cross-infection, such as direct contact via healthcare worker hands.
Question 6: A 45-year-old HIV-positive man presents with fever and cough. Sputum culture shows acid-fast bacilli. Which of the following drugs is essential in the treatment regimen?
- A. Doxycycline
- B. Amoxicillin
- C. Isoniazid (Correct Answer)
- D. Ciprofloxacin
Explanation: ***Isoniazid*** - The presence of **acid-fast bacilli** (AFB) in sputum, especially in an **HIV-positive** individual with fever and cough, strongly indicates **tuberculosis (TB)** [1]. - **Isoniazid** is a cornerstone drug in **first-line anti-tuberculosis therapy** and is essential for effective treatment [1]. *Doxycycline* - **Doxycycline** is a tetracycline antibiotic primarily used for bacterial infections like **atypical pneumonia**, Lyme disease, and certain sexually transmitted infections. - It has **no significant activity against Mycobacterium tuberculosis** and is not part of TB treatment. *Amoxicillin* - **Amoxicillin** is a penicillin-class antibiotic effective against a range of common bacterial infections, but it is **ineffective against mycobacteria**. - It would not be used to treat **tuberculosis**. *Ciprofloxacin* - **Ciprofloxacin** is a fluoroquinolone antibiotic used for various bacterial infections, including some respiratory and urinary tract infections. - While some fluoroquinolones are used as **second-line agents** in specific multi-drug resistant TB regimens, **ciprofloxacin** is not a first-line drug and is generally reserved for particular circumstances, unlike isoniazid which is essential for initial therapy.
Question 7: A woman presents with a thick, curdy, white vaginal discharge. The best treatment for her is:
- A. Miconazole (Correct Answer)
- B. Metronidazole
- C. Nystatin
- D. Doxycycline
Explanation: ***Miconazole*** - **Miconazole** is an **azole antifungal medication** that is highly effective against *Candida* species, which commonly cause **vulvovaginal candidiasis** (yeast infections). - The classic presentation of **thick, curdy, white vaginal discharge** is highly suggestive of candidiasis. - **Topical azole antifungals** like miconazole are **first-line therapy** and offer the advantage of **shorter treatment courses** (1-7 days) with excellent efficacy. - This makes it the **best treatment option** among the choices given. *Nystatin* - **Nystatin** is also an **antifungal agent** that is effective against *Candida* species and can be used to treat vulvovaginal candidiasis. - However, azole antifungals like miconazole are generally **preferred** because they require **shorter treatment duration** (1-7 days vs. 14 days for nystatin) and have comparable or superior efficacy. - While nystatin is a reasonable alternative, **miconazole is the better choice** for most patients due to improved compliance with shorter regimens. *Metronidazole* - **Metronidazole** is an **antibiotic** and **antiprotozoal** medication primarily used to treat **bacterial vaginosis** and **trichomoniasis**. - These conditions typically present with a **thin, gray, watery discharge** and a **fishy odor**, which are not described here. - It is **not effective** against fungal infections like candidiasis. *Doxycycline* - **Doxycycline** is a **tetracycline antibiotic** used to treat bacterial infections, including **chlamydia** and **pelvic inflammatory disease**. - It is **not effective** against fungal infections like vulvovaginal candidiasis, and its use would be inappropriate given the described symptoms.
Question 8: False regarding bacterial plasmids is:
- A. Extrachromosomal
- B. Transmission to different species
- C. Eliminated by treating with radiation
- D. Can cause lysogenic conversion (Correct Answer)
Explanation: ***Can cause lysogenic conversion*** - **Lysogenic conversion** is a phenomenon caused by **bacteriophages**, which are viruses that infect bacteria, not by plasmids directly. - It involves the integration of a **phage genome** into the bacterial chromosome, altering the bacterium's phenotype (e.g., toxin production). *Extrachromosomal* - Bacterial plasmids are indeed **extrachromosomal DNA molecules**, meaning they exist independently of the bacterial chromosome. - This characteristic allows them to be easily transferred between bacteria. *Transmission of different species* - Plasmids can be transmitted horizontally between bacteria, even across **different species**, through mechanisms like **conjugation**, **transformation**, or **transduction**. - This interspecies transmission is a major factor in the spread of **antibiotic resistance**. *Eliminated by treating with radiation* - Plasmids, like all DNA, can be eliminated or degraded by treatments such as **radiation** (e.g., UV) or certain chemicals. - Such treatments disrupt the plasmid DNA structure, preventing its replication or function.
Question 9: What is the best way to control the MRSA infection in the ward?
- A. Fumigation of ward frequently
- B. Washing hand before and after attending patients (Correct Answer)
- C. Wearing masks during invasive procedures in ICU
- D. Vancomycin given empirically to all the patients
Explanation: **Washing hand before and after attending patients** - **Hand hygiene** is the single most effective measure in preventing the transmission of **healthcare-associated infections**, including **MRSA**. - **Healthcare workers' hands** are the primary vehicle for spreading pathogens from one patient to another. *Fumigation of ward frequently* - **Fumigation** is generally not recommended for routine infection control and has limited efficacy against resistant organisms like **MRSA** in this context. - It does not address the primary mode of transmission, which is direct contact via **contaminated hands** or surfaces. *Wearing masks during invasive procedures in ICU is important.* - While important for preventing infections during **invasive procedures** and protecting against **aerosolized pathogens**, masks are not the primary strategy for controlling the spread of **MRSA** in routine ward settings. - **MRSA transmission** is predominantly contact-based, not airborne. *Vancomycin given empirically to all the patients* - **Empirical broad-spectrum antibiotic use** for all patients is a significant driver of **antibiotic resistance**, including **MRSA**. - It should be reserved for patients with suspected or confirmed **MRSA infections** based on clinical criteria and culture results, not as a general preventive measure.
Question 10: Which of the following drug classes is commonly implicated in causing Stevens-Johnson syndrome?
- A. Antibiotics (Correct Answer)
- B. Corticosteroids
- C. Antifungals
- D. Proton pump inhibitors
Explanation: ***Antibiotics*** - **Antibiotics**, particularly **sulfonamides** (e.g., sulfamethoxazole-trimethoprim) and **beta-lactams** (e.g., penicillins, cephalosporins), are among the most common drug classes implicated in causing **Stevens-Johnson Syndrome (SJS)**. - SJS is a severe **idiosyncratic drug reaction**, and many antibiotics can trigger this immune-mediated response. - **Note:** Other major causative drug classes include **anticonvulsants** (carbamazepine, phenytoin, lamotrigine), **allopurinol**, and **NSAIDs**, but among the options listed, antibiotics are the most commonly implicated. *Corticosteroids* - **Corticosteroids** are typically used in the **treatment** of SJS to suppress the immune response and reduce inflammation, not to cause it. - While they have their own set of side effects, initiating SJS is not one of their known adverse reactions. *Antifungals* - Although some **antifungals** can cause adverse drug reactions, they are **not typically associated** with SJS compared to antibiotics, anticonvulsants, or allopurinol. - The risk of SJS with antifungal medications is generally very low. *Proton pump inhibitors* - **Proton pump inhibitors (PPIs)** are generally well-tolerated and are **rarely implicated** as a cause of SJS. - Their primary side effects are usually gastrointestinal and not severe dermatological reactions.
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