2025 – PAGE 299 – INFECTIOUS DISEASES

LISTERIA MONOCYTOGENES

Listeria monocytogenes is a gram-positive DIPHTHEROID (rod). Look for a history of NODULES ON THE PLACENTA, or a mild maternal fever with virus-like symptoms. The treatment is the same as for suspected GBS, ampicillin.

PEARL: If the bug has not been clearly identified, treat with both ampicillin and gentamicin for neonatal sepsis. The ampicillin will cover GBS, Enterococcus, and Listeria. The gentamicin will cover some gram negatives.

CLOSTRIDIUM TETANI (AKA TETANUS)

Clostridium tetani (AKA tetanus) is an anaerobic organism. Look for a history of a puncture wound. Causes uncontrollable muscle spasms and contractions. Look for an arched back or “lock jaw.” Treat with debridement of infected tissue + tetanus immunoglobulin + metronidazole OR penicillin.

(DOUBLE TAKE) CLOSTRIDIUM BOTULINUM

Clostridium botulinum is a gram-positive organism. The most common sources of botulism are food (think “bulging cans”) and wound infections. Look for a child less than 6 months of age with progressive descending weakness. It can progress from progressive ptosis and a poor suck to urinary retention within hours. The botulism toxin inhibits release of acetylcholine into the neurosynaptic junction. Treatment involves either supportive care (intubate if needed) or the antitoxin if it’s available.

PEARLS: For the exam, progressive ptosis in a baby probably means botulism! Children are usually less than 6 months of age since they are too young at that age to prevent colonization in the gut. This is why honey should not be given to infants < 1 year old.

(DOUBLE TAKE) CORYNEBACTERIUM DIPHTHERIAE

Corynebacterium diphtheriae is a gram-positive rod that can cause diphtheria. It starts off with a low fever and URI symptoms, including a sore throat. Eventually a pseudomembrane forms on the tonsils and pharynx. The swelling can be so bad that intubation is needed. It can also cause motor and sensory problems along with a loss of reflexes. The D in DTaP is for Diphtheria, so it’s no longer seen in the U.S. but could be seen in a child of immigrant status. Treat with erythromycin or penicillin G.

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STREPTOCOCCAL INFECTIONS

NOTE: ALWAYS CHECK WHICH STREP YOU ARE DEALING WITH. The ones most commonly seen on the exam are Group A Streptococcus (pyogenes), Group B Streptococcus (GBS/agalactiae), and Streptococcus pneumoniae. The others are less commonly seen (viridans, mutans, and bovis).

STREPTOCOCCUS (AKA STREP)

In cases of streptococcus, look for gram-positive cocci in PAIRS and CHAINS! Gram staining will show BLUE organisms.