This episode explores Mycoplasma, the smallest free-living bacteria and uniquely defined by the absence of a cell wall. Drawing from Murray’s Chapter 33, it examines how structural minimalism reshapes both pathogenesis and therapy.

Without peptidoglycan, Mycoplasma species are intrinsically resistant to beta-lactam antibiotics and exhibit pleomorphic morphology. Their sterol-rich cell membranes provide flexibility and resilience, allowing close adherence to respiratory and urogenital epithelium.

The primary clinical focus is Mycoplasma pneumoniae, a common cause of atypical pneumonia. Rather than producing lobar consolidation, it induces a more diffuse interstitial process, often accompanied by extrapulmonary manifestations driven by immune response rather than direct invasion.

The episode emphasises three conceptual themes:

* Absence of cell wall alters staining and antibiotic susceptibility

* Disease is often immune-mediated

* Laboratory diagnosis relies on molecular or serologic methods rather than traditional culture

Clinically, Mycoplasma teaches restraint: mild radiographic findings may accompany significant symptoms, and macrolides or tetracyclines are required for treatment.

Key Takeaways

* Mycoplasma lacks a cell wall

* Beta-lactam antibiotics are ineffective

* M. pneumoniae causes atypical pneumonia

* Immune-mediated symptoms may accompany infection

* Diagnosis often relies on molecular or serologic testing

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