Gram-positive

Gram-positive US Medical PG Question 1: A 51-year-old man comes to the physician because of a 4-day history of fever and cough productive of foul-smelling, dark red, gelatinous sputum. He has smoked 1 pack of cigarettes daily for 30 years and drinks two 12-oz bottles of beer daily. An x-ray of the chest shows a cavity with air-fluid levels in the right lower lobe. Sputum culture grows gram-negative rods. Which of the following virulence factors is most likely involved in the pathogenesis of this patient's condition?

• A. IgA protease
• B. Exotoxin A
• C. Capsular polysaccharide (Correct Answer)
• D. P-fimbriae
• E. Heat-stable toxin

Gram-positive Explanation: ***Capsular polysaccharide*** - The patient's symptoms (fever, foul-smelling sputum, cavitation with air-fluid levels) and risk factors (smoking) suggest a **lung abscess** likely caused by **_Klebsiella pneumoniae_**. - **Capsular polysaccharide** is a major virulence factor for _Klebsiella pneumoniae_, providing resistance to phagocytosis and contributing to its invasive potential. *IgA protease* - **IgA protease** is a virulence factor produced by bacteria such as _Neisseria gonorrhoeae_, _Neisseria meningitidis_, and _Haemophilus influenzae_ to cleave IgA antibodies. - While important for mucosal infections, it is not characteristic of the severe lung pathology described, nor a primary virulence factor for a gram-negative rod causing lung abscesses like _Klebsiella_. *Exotoxin A* - **Exotoxin A** is a potent exotoxin produced by _Pseudomonas aeruginosa_, which inhibits protein synthesis by ADP-ribosylation of elongation factor 2. - While _Pseudomonas_ can cause lung infections in compromised patients, the classic description of dark red, gelatinous sputum and the strong association with gram-negative rods causing lung abscesses points more directly to _Klebsiella_. *P-fimbriae* - **P-fimbriae** (pyelonephritis-associated fimbriae) are adhesion factors found on uropathogenic _E. coli_, enabling them to bind to uroepithelial cells and cause urinary tract infections. - These fimbriae are not relevant to the pathogenesis of a lung abscess caused by gram-negative rods in this clinical context. *Heat-stable toxin* - **Heat-stable toxin** is typically associated with enterotoxigenic _E. coli_ (ETEC), causing watery diarrhea by activating guanylate cyclase. - This toxin is involved in gastrointestinal infections and has no role in the pathogenesis of a lung abscess.

Gram-positive US Medical PG Question 2: A 53-year-old diabetic man with cellulitis of the right lower limb presents to the emergency department because of symptoms of fever and chills. His pulse is 122/min, the blood pressure is 76/50 mm Hg, the respirations are 26/min, and the temperature is 40.0°C (104.0°F). His urine output is < 0.5mL/kg/h. He has warm peripheral extremities. The hemodynamic status of the patient is not improving in spite of the initiation of adequate fluid resuscitation. He is admitted to the hospital. Which of the following is the most likely laboratory profile?

• A. WBC count: 11,670/mm3; low CVP; blood culture: gram-negative bacteremia; blood lactate level: 0.9 mmol/L
• B. WBC count: 1234/mm3; high CVP; blood culture: gram-negative bacteremia; blood lactate level: 1.6 mmol/L
• C. WBC count: 16,670/mm3; low CVP; blood culture: gram-negative bacteremia; blood lactate level: 2.2 mmol/L (Correct Answer)
• D. WBC count: 6670/mm3; low CVP; blood culture: gram-positive bacteremia; blood lactate level: 1.1 mmol/L
• E. WBC count: 8880/mm3; high CVP; blood culture: gram-positive bacteremia; blood lactate level: 2.1 mmol/L

Gram-positive Explanation: ***WBC count: 16,670/mm3; low CVP; blood culture: gram-negative bacteremia; blood lactate level: 2.2 mmol/L*** - This profile aligns with **septic shock** driven by gram-negative bacteria, presenting with **tachycardia**, **hypotension**, **fever**, and **poor urine output** despite fluid resuscitation. - A **high WBC count** (leukocytosis), **low CVP** (due to vasodilation and relative hypovolemia), **gram-negative bacteremia** (common in severe sepsis), and **elevated lactate** (indicating tissue hypoperfusion) are characteristic findings. *WBC count: 11,670/mm3; low CVP; blood culture: gram-negative bacteremia; blood lactate level: 0.9 mmol/L* - While most components suggest sepsis (WBC count and low CVP), a **lactate level of 0.9 mmol/L** is within the normal range, contradicting the severe hypoperfusion and shock observed in the patient. - The patient's presentation with **hypotension** unresponsive to fluids and **oliguria** strongly indicates significant tissue hypoperfusion, which would typically result in a higher lactate. *WBC count: 1234/mm3; high CVP; blood culture: gram-negative bacteremia; blood lactate level: 1.6 mmol/L* - A **WBC count of 1234/mm3 (leukopenia)** is an atypical response for severe infection and sepsis; often, sepsis presents with leukocytosis. - A **high CVP** indicates fluid overload or cardiac dysfunction, which is not consistent with the initial low blood pressure and the need for fluid resuscitation seen in distributive shock. *WBC count: 6670/mm3; low central venous pressure (CVP); blood culture: gram-positive bacteremia; blood lactate level: 1.1 mmol/L* - A **WBC count of 6670/mm3** is within the normal range and does not reflect an adequate inflammatory response to severe infection and shock. - A **normal lactate level (1.1 mmol/L)** does not support the clinical picture of shock and tissue hypoperfusion despite the presence of gram-positive bacteremia. *WBC count: 8880/mm3; high CVP; blood culture: gram-positive bacteremia; blood lactate level: 2.1 mmol/L* - A **WBC count of 8880/mm3** is normal, which is unlikely in a severe sepsis presentation. - A **high CVP** is not consistent with the distributive shock state where there is often relative hypovolemia and vasodilation leading to low CVP.

Gram-positive US Medical PG Question 3: A 33-year-old man presents to the emergency department complaining of weakness and fatigue. He states that his symptoms have worsened over the past day. He has a past medical history of IV drug abuse and alcoholism and he currently smells of alcohol. His temperature is 102°F (38.9°C), blood pressure is 111/68 mmHg, pulse is 110/min, respirations are 17/min, and oxygen saturation is 98% on room air. Physical exam is notable for focal tenderness over the lumbar spine. Initial lab values and blood cultures are drawn and are notable for leukocytosis and an elevated C-reactive protein (CRP). Which of the following is the best treatment for this patient?

• A. Nafcillin
• B. Ceftriaxone
• C. Piperacillin-tazobactam
• D. Vancomycin (Correct Answer)
• E. Ibuprofen and warm compresses

Gram-positive Explanation: ***Vancomycin*** - The patient's history of **IV drug abuse**, fever, leukocytosis, elevated CRP, and focal lumbar tenderness is highly suggestive of **vertebral osteomyelitis** or **discitis**, often caused by methicillin-resistant *Staphylococcus aureus* (MRSA). - **Vancomycin** is the appropriate empiric treatment for suspected severe *S. aureus* infections in patients with risk factors for MRSA until culture and sensitivity results are available. *Nafcillin* - **Nafcillin** is effective against **methicillin-sensitive *Staphylococcus aureus* (MSSA)**. - Given the patient's history of IV drug abuse, there's a high likelihood of MRSA, making nafcillin an inadequate empiric choice. *Ceftriaxone* - **Ceftriaxone** is a broad-spectrum cephalosporin effective against many gram-negative and some gram-positive bacteria, but it has **poor coverage against *Staphylococcus aureus***, particularly MRSA. - It would be ineffective as a monotherapy for the suspected staphylococcal infection. *Piperacillin-tazobactam* - This combination provides broad-spectrum coverage, including **Pseudomonas** and many gram-negative and anaerobic bacteria, but its coverage for **MRSA is limited**. - It would not be the first-line empiric choice for a suspected MRSA infection in this setting. *Ibuprofen and warm compresses* - This treatment addresses pain and inflammation but does not treat the underlying **infectious process**. - Overlooking the infection would lead to significant morbidity and potential mortality, making this an inappropriate primary treatment.

Gram-positive US Medical PG Question 4: A 57-year-old HIV-positive male with a history of intravenous drug abuse presents to the emergency room complaining of arm swelling. He reports that he developed progressively worsening swelling and tenderness over the right antecubital fossa three days prior. He recently returned from a trip to Nicaragua. His past medical history is notable for an anaphylactoid reaction to vancomycin. His temperature is 101.4°F (38.6°C), blood pressure is 140/70 mmHg, pulse is 110/min, and respirations are 20/min. Physical examination reveals an erythematous, fluctuant, and tender mass overlying the right antecubital fossa. Multiple injection marks are noted across both upper extremities. He undergoes incision and drainage and is started on an antibiotic that targets the 50S ribosome. He is discharged with plans to follow up in one week. However, five days later he presents to the same emergency room complaining of abdominal cramps and watery diarrhea. Which of the following classes of pathogens is most likely responsible for this patient’s current symptoms?

• A. Gram-negative curved bacillus
• B. Gram-negative bacillus
• C. Anaerobic flagellated protozoan
• D. Gram-positive bacillus (Correct Answer)
• E. Gram-positive coccus

Gram-positive Explanation: ***Gram-positive bacillus*** - The patient was administered an antibiotic targeting the **50S ribosomal subunit** following incision and drainage for a suspected skin infection (likely **MRSA** given IV drug abuse). This strongly suggests **clindamycin** was used. - **Clindamycin** is a known risk factor for developing **Clostridioides (formerly Clostridium) difficile infection (CDI)**, which is caused by a **Gram-positive, spore-forming bacillus** and manifests with **abdominal cramps and watery diarrhea**. *Gram-negative curved bacillus* - This class of pathogens includes organisms like **Vibrio cholerae** or **Campylobacter jejuni**, which can cause diarrhea. - However, the patient's presentation with **colitis** after antibiotic use is more consistent with **Clostridioides difficile**, not typically a curved Gram-negative bacillus. *Gram-negative bacillus* - While some Gram-negative bacilli (e.g., E. coli, Salmonella) can cause diarrhea, their association with **antibiotic-induced colitis** following treatment for a skin abscess is less direct than that of *Clostridioides difficile*. - The initial skin infection in IV drug users is most commonly staphylococcal (Gram-positive coccus), for which a 50S targeting antibiotic would be prescribed. *Anaerobic flagellated protozoan* - This description often refers to pathogens like **Giardia lamblia** or **Trichomonas vaginalis**, which are not bacteria. - While *Giardia* can cause diarrhea, it typically causes **malabsorption** and **greasy stools**, and wouldn't be triggered by recent antibiotic use for a skin infection. *Gram-positive coccus* - **Gram-positive cocci** (e.g., Staphylococcus aureus) are the likely cause of the initial skin infection/abscess. - However, they do not typically cause **antibiotic-associated colitis** with watery diarrhea; rather, the *antibiotic treatment itself* for these organisms can predispose to *Clostridioides difficile*.

Gram-positive US Medical PG Question 5: A 27-year-old man presents to the emergency department with weakness and a fever for the past week. The patient is homeless and has a past medical history of alcohol and IV drug abuse. His temperature is 102°F (38.9°C), blood pressure is 107/68 mmHg, pulse is 120/min, respirations are 17/min, and oxygen saturation is 98% on room air. Physical exam is notable for a tremulous patient with antecubital scars and a murmur over the left lower sternal border. Blood cultures are drawn and the patient is started on vancomycin and ceftriaxone and is admitted to the ICU. The patient's fever and symptoms do not improve despite antibiotic therapy for which the initial identified organism is susceptible. Cultures currently reveal MRSA as one of the infective organisms. Which of the following is the best next step in management?

• A. Transesophageal echocardiography (Correct Answer)
• B. Obtain new blood cultures
• C. CT scan of the chest
• D. Nafcillin and piperacillin-tazobactam
• E. Vancomycin and gentamicin

Gram-positive Explanation: ***Transesophageal echocardiography*** - The patient's history of **IV drug abuse**, **fever**, **new murmur**, and identification of **MRSA** strongly suggest **infective endocarditis**. - A Transesophageal echocardiography (TEE) is the **most sensitive and specific imaging modality** to detect vegetations, abscesses, or valvular damage, which is crucial for guiding further management. *Obtain new blood cultures* - While repeating blood cultures can be useful to confirm eradication or identify new pathogens, the initial blood cultures already revealed MRSA, which is a common cause of **endocarditis in IV drug users**. - The immediate priority given the lack of improvement and high suspicion of endocarditis is to visualize the heart valves for vegetations. *CT scan of the chest* - A CT scan of the chest would be useful to look for complications such as **septic emboli in the lungs** or other pulmonary pathologies. - However, it would not provide the detailed visualization of heart valves necessary to diagnose or rule out valvular vegetations characteristic of endocarditis. *Nafcillin and piperacillin-tazobactam* - **Nafcillin** is active against **methicillin-susceptible Staphylococcus aureus (MSSA)**, but the patient's cultures already identified **MRSA**. - **Piperacillin-tazobactam** is a broad-spectrum antibiotic but not a first-line treatment for MRSA infections and would not be appropriate given the identified pathogen. *Vancomycin and gentamicin* - The patient is already on **Vancomycin**, which is appropriate for MRSA, but adding **gentamicin** without clear indication would not be the best next step. - While gentamicin is sometimes used as an adjunct in specific endocarditis regimens (e.g., enterococcal), the primary concern here is the lack of clinical improvement despite appropriate MRSA coverage, pointing towards a structural cardiac issue.

Gram-positive US Medical PG Question 6: A 24-year-old man presents with low-grade fever and shortness of breath for the last 3 weeks. Past medical history is significant for severe mitral regurgitation status post mitral valve replacement five years ago. His temperature is 38.3°C (101.0°F) and respiratory rate is 18/min. Physical examination reveals vertical hemorrhages under his nails, multiple painless erythematous lesions on his palms, and two tender, raised nodules on his fingers. Cardiac auscultation reveals a new-onset 2/6 holosystolic murmur loudest at the apex with the patient in the left lateral decubitus position. A transesophageal echocardiogram reveals vegetations on the prosthetic valve. Blood cultures reveal catalase-positive, gram-positive cocci. Which of the following characteristics is associated with the organism most likely responsible for this patient’s condition?

• A. Coagulase positive
• B. DNAse positive
• C. Hemolysis
• D. Novobiocin sensitive (Correct Answer)
• E. Optochin sensitive

Gram-positive Explanation: ***Novobiocin sensitive*** - The patient has **prosthetic valve endocarditis** caused by a **catalase-positive, gram-positive coccus**, which is most likely **_Staphylococcus epidermidis_** due to its association with foreign bodies and prosthetic devices. - _Staphylococcus epidermidis_ is a **coagulase-negative staphylococcus** that is **novobiocin sensitive**, helping to differentiate it from other coagulase-negative staphylococci like **_Staphylococcus saprophyticus_** (novobiocin resistant). - Although this is late prosthetic valve endocarditis (5 years post-surgery), _S. epidermidis_ remains a common pathogen due to biofilm formation on prosthetic materials. *Coagulase positive* - **Coagulase-positive** gram-positive cocci, such as **_Staphylococcus aureus_**, are a common cause of endocarditis, especially in intravenous drug users and can also cause prosthetic valve endocarditis. - However, the correct answer requires identifying the characteristic that differentiates the most likely organism, and **coagulase-negative** staphylococci like _S. epidermidis_ are more characteristically associated with prosthetic device infections due to their biofilm-forming capabilities. - A positive coagulase test differentiates _S. aureus_ from coagulase-negative staphylococci. *DNAse positive* - **DNAse positivity** is characteristic of **_Staphylococcus aureus_** and group A beta-hemolytic streptococci (_Streptococcus pyogenes_). - While _S. aureus_ can cause prosthetic valve endocarditis, the question asks for the characteristic most associated with the likely organism, which in the context of prosthetic devices is typically **_S. epidermidis_** (DNAse negative). *Hemolysis* - **Hemolysis patterns** are primarily used to differentiate **streptococcal species**, not staphylococci. For example, **beta-hemolytic streptococci** cause complete hemolysis. - While some staphylococci can show hemolytic activity, it is not a primary characteristic used to differentiate between the most likely staphylococcal causes of prosthetic valve endocarditis. *Optochin sensitive* - **Optochin sensitivity** is a key characteristic used to identify **_Streptococcus pneumoniae_**. - _S. pneumoniae_ is **catalase-negative**, while the described organism is **catalase-positive**, ruling out _S. pneumoniae_ as the causative agent.

Gram-positive US Medical PG Question 7: A 54-year-old woman comes to the physician because of lower back pain, night sweats, and a 5-kg (11-lb) weight loss during the past 4 weeks. She has rheumatoid arthritis treated with adalimumab. Her temperature is 38°C (100.4°F). Physical examination shows tenderness over the T10 and L1 spinous processes. Passive extension of the right hip causes pain in the right lower quadrant. The patient's symptoms are most likely caused by an organism with which of the following virulence factors?

• A. Proteins that bind to the Fc region of immunoglobulin G
• B. Protease that cleaves immunoglobulin A
• C. Polysaccharide capsule that prevents phagocytosis
• D. Surface glycolipids that prevent phagolysosome fusion (Correct Answer)
• E. Polypeptides that inactivate elongation factor 2

Gram-positive Explanation: ***Surface glycolipids that prevent phagolysosome fusion*** - The patient's symptoms (low back pain, night sweats, weight loss, fever, spinal tenderness, and hip pain) in a patient on **adalimumab** (a TNF-alpha inhibitor) suggest **disseminated tuberculosis** (Pott disease). - *Mycobacterium tuberculosis* uses **mycolic acids** and other surface glycolipids to prevent phagolysosome fusion, allowing it to survive and replicate within macrophages. *Proteins that bind to the Fc region of immunoglobulin G* - This virulence factor is characteristic of bacteria like *Staphylococcus aureus* (Protein A) and *Streptococcus pyogenes* (Protein G), which is not consistent with the clinical picture. - These proteins interfere with opsonization and antibody-mediated immunity, but are not the primary mechanism of *Mycobacterium tuberculosis* survival within macrophages. *Protease that cleaves immunoglobulin A* - **IgA protease** is a virulence factor for bacteria such as *Neisseria gonorrhoeae*, *Neisseria meningitidis*, and *Streptococcus pneumoniae*, which colonize mucosal surfaces. - This mechanism helps these bacteria evade mucosal immunity, but it is not relevant to the pathogenesis of tuberculosis. *Polysaccharide capsule that prevents phagocytosis* - A polysaccharide capsule is a major virulence factor for many encapsulated bacteria (e.g., *Streptococcus pneumoniae*, *Haemophilus influenzae*, *Neisseria meningitidis*) that helps them evade phagocytosis. - However, *Mycobacterium tuberculosis* is not primarily characterized by a polysaccharide capsule for immune evasion; its internal survival within macrophages is more critical. *Polypeptides that inactivate elongation factor 2* - Toxins that inactivate **elongation factor 2** are associated with *Corynebacterium diphtheriae* (**diphtheria toxin**) and *Pseudomonas aeruginosa* (**exotoxin A**), leading to inhibition of protein synthesis. - This mechanism is not involved in the pathogenesis of *Mycobacterium tuberculosis* infection or its ability to cause disseminated disease.

Gram-positive US Medical PG Question 8: Blood cultures are sent to the laboratory and empiric treatment with intravenous vancomycin is started. Blood cultures grow gram-negative bacilli identified as Cardiobacterium hominis. Which of the following is the most appropriate next step in management?

• A. Switch to intravenous gentamicin
• B. Switch to intravenous ampicillin
• C. Switch to intravenous ceftriaxone (Correct Answer)
• D. Switch to intravenous cefazolin
• E. Add intravenous rifampin

Gram-positive Explanation: ***Switch to intravenous ceftriaxone*** - **Cardiobacterium hominis** is part of the **HACEK group** of bacteria, which are known for causing **endocarditis**. - These organisms are typically susceptible to **beta-lactam antibiotics**, with **third-generation cephalosporins** like ceftriaxone being the drug of choice due to their excellent activity and good penetration. *Switch to intravenous gentamicin* - While **aminoglycosides** like gentamicin can be used in combination regimens for serious infections, they are generally **not monotherapy** for HACEK endocarditis and are associated with **nephrotoxicity** and **ototoxicity**. - The primary treatment for HACEK endocarditis is a **beta-lactam antibiotic**, not an aminoglycoside alone. *Switch to intravenous ampicillin* - **Ampicillin** is a beta-lactam, but it may not consistently provide optimal coverage for all HACEK organisms, and some strains may have reduced susceptibility. - **Third-generation cephalosporins** are preferred due to their broader and more consistent activity against this group. *Switch to intravenous cefazolin* - **Cefazolin** is a first-generation cephalosporin and typically has **limited activity** against gram-negative bacilli, especially those like Cardiobacterium hominis which require broader-spectrum beta-lactams. - Its spectrum of activity is primarily against **gram-positive bacteria** and some **gram-negative cocci**. *Add intravenous rifampin* - **Rifampin** is primarily used for **mycobacterial infections** and in combination regimens for specific bacterial infections (e.g., bone and joint infections, prosthetic device infections) often due to resistant staphylococci. - It is **not a first-line agent** for Cardiobacterium hominis infections and there's no indication for its use here with an organism susceptible to ceftriaxone.

Gram-positive US Medical PG Question 9: A young woman from the Ohio River Valley in the United States currently on corticosteroid therapy for ulcerative colitis presented to a clinic complaining of fever, sweat, headache, nonproductive cough, malaise, and general weakness. A chest radiograph revealed patchy pneumonia in the lower lung fields, together with enlarged mediastinal and hilar lymph nodes. Skin changes suggestive of erythema nodosum (i.e. an acute erythematous eruption) were noted. Because the patient was from a region endemic for fungal infections associated with her symptoms and the patient was in close contact with a person presenting similar symptoms, the attending physician suspected that systemic fungal infection might be responsible for this woman’s illness. Which of the following laboratory tests can the physician use to ensure early detection of the disease, and also effectively monitor the treatment response?

• A. Skin tests
• B. Fungal staining
• C. Antigen detection (Correct Answer)
• D. Culture method
• E. Antibody testing

Gram-positive Explanation: ***Antigen detection*** - **Antigen detection assays** (e.g., *Histoplasma galactomannan antigen*) are highly sensitive for **disseminated histoplasmosis**, especially in immunosuppressed patients like this one on corticosteroids. - They provide **early diagnosis** and are effective for **monitoring treatment response**, as antigen levels typically decrease with successful therapy. *Skin tests* - **Skin tests** (e.g., *histoplasmin skin test*) indicate **prior exposure** to the fungus and are not useful for diagnosing active, acute infection. - A positive skin test does not differentiate between past exposure and current disease, making it unsuitable for early detection or monitoring. *Fungal staining* - **Fungal staining** of patient samples (e.g., sputum, biopsy) can reveal fungal elements but has **limited sensitivity** and may not identify the specific pathogen. - It often requires **invasive procedures** to obtain suitable specimens and is not ideal for routine monitoring of treatment response due to variability. *Culture method* - **Fungal cultures** are a **definitive diagnostic method** but can take **several weeks** to yield results, which is too slow for early detection in an acutely ill patient. - While useful for species identification and susceptibility testing, the **delayed turnaround time** makes it impractical for monitoring rapid treatment changes. *Antibody testing* - **Antibody tests** for fungal infections can be useful but may show **false negatives in immunocompromised patients** (like this patient on corticosteroids) due to a blunted immune response. - Seroconversion or a significant rise in antibody titers can indicate infection, but antibodies may **persist long after resolution**, making them less reliable for monitoring acute treatment efficacy.

Gram-positive US Medical PG Question 10: A 24-hour-old newborn presents to the emergency department after a home birth because of fever, irritability alternating with lethargy, and poor feeding. The patient’s mother says symptoms acutely onset 12 hours ago and have not improved. No significant past medical history. His mother did not receive any prenatal care, and she had rupture of membranes 20 hours prior to delivery. His vital signs include: heart rate 150/min, respiratory rate 65/min, temperature 39.0°C (102.2°F), and blood pressure 60/40 mm Hg. On physical examination, the patient has delayed capillary refill. Laboratory studies show a pleocytosis and a low glucose level in the patient’s cerebrospinal fluid. Which of the following is the most likely causative organism for this patient’s condition?

• A. Group A Streptococcus
• B. Enterovirus
• C. Group B Streptococcus (Correct Answer)
• D. Streptococcus pneumoniae
• E. Cryptococcus neoformans

Gram-positive Explanation: ***Group B Streptococcus*** - This newborn presents with **fever, irritability/lethargy, poor feeding**, and signs of **sepsis (tachycardia, tachypnea, hypotension, delayed capillary refill)**, along with **abnormal CSF (pleocytosis, low glucose)**, indicating **neonatal meningitis**. - **Group B Streptococcus (GBS)** is the **most common cause of early-onset neonatal sepsis and meningitis**, especially with risk factors such as **lack of prenatal care** and **prolonged rupture of membranes (>18 hours)**, as seen in this case. *Group A Streptococcus* - While Group A Streptococcus can cause severe infections, it is an **uncommon cause of neonatal sepsis and meningitis** compared to GBS. - More typically associated with **pharyngitis, impetigo, and necrotizing fasciitis** in older children and adults. *Enterovirus* - Enteroviruses are a common cause of **viral meningitis in neonates and infants**, but typically present with a **lymphocytic pleocytosis** and **normal CSF glucose**, in contrast to the features (pleocytosis, low glucose) seen here. - While fever and irritability can be present, the CSF findings point more towards a bacterial infection. *Streptococcus pneumoniae* - *Streptococcus pneumoniae* can cause bacterial meningitis but is **less common in the immediate neonatal period** (first 7 days of life) compared to GBS. - Risk factors often include **preterm birth** or **underlying immune deficiencies**, which are not specified here. *Cryptococcus neoformans* - *Cryptococcus neoformans* is an **opportunistic fungal pathogen** that typically causes meningitis in **immunocompromised individuals**, such as those with HIV/AIDS. - It is **extremely rare** in immunocompetent newborns and would not be the most likely cause in this clinical scenario.

Gram-positive Flashcard 1 of 10

Question: Gram _____ bacteria have a much thicker cell wall

Answer: positive

Gram-positive Flashcard 2 of 10

Question: _____ is a filamentous-branching gram-positive organism that can cause brain abscess.

Answer: Nocardia

Gram-positive Flashcard 3 of 10

Question: Staphylococcus aureus is gram _____

Answer: positive

Gram-positive Flashcard 4 of 10

Question: Strep pneumonia contains _____, allowing bacteria to adhere and colonize the mucous membranes.

Answer: IgA protease

Gram-positive Flashcard 5 of 10

Question: Enterococcus spp. can become resistant to ampicillin due to _____ production

Answer: beta-lactamase

Gram-positive Flashcard 6 of 10

Question: Gas gangrene

Answer: Clostridium perfringens

Extra Information: alpha toxin causes myonecrosis and hemolysis

Gram-positive Flashcard 7 of 10

Question: Clostridium perfringens

Answer: +

Extra Information: bacillianerobegangrenealpha toxin

Gram-positive Flashcard 8 of 10

Question: Clostridium botulinum

Answer: +

Extra Information: bacillianerobebotulism, floppy baby syndromebotulinum toxin

Gram-positive Flashcard 9 of 10

Question: Clostridium tetani

Answer: +

Extra Information: bacillianerobetetanustetanospasmin

Gram-positive Flashcard 10 of 10

Question: _____, _____, and _____ are important spore-forming Gram-positive bacteria found in soil.

Answer: Bacillus anthracis