2025 – PAGE 307 – INFECTIOUS DISEASES

MYCOPLASMA PNEUMONIAE

Mycoplasma pneumoniae can cause an atypical pneumonia or bullous myringitis. Some patients have also been known to get neurological symptoms following an infection. Diagnose with PCR or serum IgM titers, NOT cold agglutinins because they are only suggestive of the diagnosis when positive. Treat with a macrolide.

MNEMONIC: MMMMM for Mycoplasma! Get IgM titers for the diagnosis, use a Macrolide for treatment, look in the ears for a bullous Myringitis, and watch out for delayed “Meurologic” symptoms.

HAEMOPHILUS INFLUENZAE (AKA H. FLU)

Although Haemophilus influenzae, AKA H. flu, CAN cause bacteremia, pneumonia, meningitis, otitis, epiglottitis, sinusitis, and conjunctivitis, it usually doesn’t because of immunizations. For unimmunized patients, immigrants, and asplenic patients, it can still cause severe disease. If the Gram stain is described, the phrase “pleomorphic organism” may be used. Treat with ceftriaxone.

BORDETELLA PERTUSSIS (AKA WHOOPING COUGH)

Bordetella pertussis (AKA whooping cough) patients are described as having bursts, or “paroxysms,” of coughing. They cough so much they can’t breathe, then they inspire deeply, causing a WHOOP! Patients may have a HIGH WBC (lymphocytosis) of > 20,000. Diagnose is made by PCR with a nasopharyngeal swab. Erythro­mycin, clarithromycin, and azithromycin are all acceptable agents. Use azithromycin for children under six weeks of age due to concerns about erythromycin-induced pyloric stenosis. Any macrolide should be okay to use after six weeks of age. Bactrim is an alternative for children older than one month. All contacts (even if immunized) need to be given prophylaxis since immunity of the vaccination wanes.

PEARLS: Consider this diagnosis in any patient with a chronic cough. Antibiotic treatment shortens the early stage of pertussis in which the patient is infectious and has URI-type symptoms (known as the catarrhal stage). It does NOT decrease the “whooping,” or paroxysmal stage. Also, because of FDA regulations and much uncertainty as to exactly which macrolide “should” be used in infants, you will NOT be expected to choose one macrolide over another for infants > 1 month of age.

PSEUDOMONAS

Pseudomonas can cause skin infections, pneumonia, otitis externa, UTIs, osteomyelitis, sepsis, etc. Look for a history of a puncture wound leading to osteomyelitis, or a history of cystic fibrosis (or any ventilator patient) having pneumonia. Anti-pseudomonal drugs include ceftazidime, cefepime, ticarcillin, carbenicillin, piperacillin, gentamicin, tobramycin, ciprofloxacin, and levofloxacin. If the patient has an otitis externa, give ear drops.

MNEMONIC: Imagine the TAZ-MONIAN devil (cefTAZadime, pseudoMONas) dressed like a cool GENTle­man (GENTamicin) and riding around in James Bond’s CAR (CARbenicillin). The CAR is filled with cool gadgets like a PIPE bomb (PIPEeracillin) and a TICking time bomb (TICarcillin). Of course, as he drives through a city, a woman THROWS A BRA (TOBRAmycin) at him. Distracted, he crashed into a BEAM (cefePIME). He then pulls a LEVer (LEVofloxacin) which automatically fixes the damage on his car. Then he goes home and CIPs on (CIProfloxacin) his favorite shaken drink.

(DOUBLE TAKE) ERYTHEMA CHRONICUM MIGRANS

Erythema chronicum migrans (AKA erythema migrans) is caused by BORRELIA BURGDORFERI, the spirochete that causes LYME DISEASE. Look for a large, flat lesion (> 5 cm) that is annular and has a red border. It is located at the tick bite site in about 75% of patients. The classic description is a “bulls eye” lesion. The rash shows up 1–2 weeks after the bite. Titers may still be negative during this period. Borrelia is transmitted via the Ixodes deer tick. Oral doxycycline is usually the first-line treatment for Lyme disease, including for arthritis, disseminated erythema migrans, a palsy (BELL’S PALSY), or neuropathy. For children under 8 years old, doxycycline is safe to use for up to 21 days. Use amoxicillin for children < 8 years old who need treatment for longer than 21 days. IV ceftriaxone is preferred for unstable or hospitalized patients, such as patients with encephalitis or symptomatic CARDITIS, or for RECURRENT arthritis if the patient has failed doxycycline therapy. Arthritis is usually located at the large joints (especially the knees). Diagnosing using labs is often difficult. Obtain Lyme antibody titers. If these are positive, confirm with a Western blot. Lyme Disease is often a clinical diagnosis (for example, if you see erythema migrans, TREAT).

• IMAGE: (BULLSEYE LESION) www.pbrlinks.com/ERYTHEMA-C1
• IMAGE: (BELL’S PALSY) www.pbrlinks.com/ERYTHEMA-C2
• SIDE NOTES
  • BELL’S PALSY: Unilateral facial nerve paralysis (CN VII). It is often idiopathic.
  • The Jarisch-Herxheimer reaction results in fever, chills, hypotension, headache, myalgia, and exacerbation of skin lesions during antibiotic treatment of a bacterial disease (typically spirochetes). This is due to large quantities of toxins released into the body. It is classically associated with syphilis but can also occur with Lyme disease. It may only last a few hours.
• MNEMONICS:
  • From now on, think/say borreLIYME. “Don’t ever throw a borreLIYME to MY GRANny!” Or, “Don’t ever borre-LIE to MY GRANny.” borreLIYME = Borrelia. MY GRANny = Migrans.
  • Imagine that BULL’S EYES are made of two bright neon-green LIMES! This should remind of you of the classic description.
  • Imagine squeezing LYME into a CAN = Carditis, Arthritis, and Neuritis.