Infectious Disease Compendium



Mycoplasma amphoriforme, M. genetalium, M. hominus, M. incognitus, M. pneumoniae. They all lack cell walls and are not gram stainable. There are many strains, 14 of which cause human disease: M. amphoriforme, M. buccale, M. faucium, M. fermentans, M. genitalium, M. hominis, M. lipophilum, M. orale, M. penetrans, M. pirum, M. pneumoniae, M. primatum, M. salivarium, M. spermatophilum.

And there is Mycoplasma laboratorium a synthesized genome of mycoplasma based entirely on synthetic DNA which can self-replicate (PubMed).

Epidemiologic Risks

Person to person spread, M. pneumoniae is spread by coughing; rates go up when it is humid (PubMed).

Up to 25% of vectors, I mean young children, can be asymptomatic carriers. Since asymptomatic carriage is common, it makes false positive tests likely (PubMed).


M. pneumoniae: the classic atypical pneumonia: diffuse infiltrates and negative gram stain and culture. Most have a URI, some go on to pneumonia with the CXR looks worse than the patient.

Cold agglutinins, hemolytic anemia, bullous myringitis (almost certainly a myth (PubMed)), encephalitis, myocarditis and pericarditis, erythema nodosum, urticaria, erythema multiforme, Stevens-Johnson (PubMed), and polyarthralgias are part of this endlessly curious disease. Maybe methemoglobinemia (PubMed).

Diagnose with PCR or serology.

The neurologic manifestations may be due to cross reacting antibodies rather than direct CNS invasion (PubMed).

A new Mycoplasma (Hemoplasma) can cause a severe hemolytic anemia with fever (PubMed).

Mycoplasma amphoriforme causes pneumonia, including chronic/relapsing pneumonia in patients with primary antibody deficiency (PubMed).

M. genetalium: nongonococcal urethritis (PubMed). Mycoplasma genitalium can cause a milder form of PID and cervicitis with less elevation in inflammatory markers like ESR (PubMed)(Review).

M. hominis: pyelonephritis, part of bacterial vaginitis, post abortion fever. Rare CNS infections (Pubmed).

I had a young female with SBP, culture negative, that had M. hominis on PCR (Medscape).

M. hominus also has caused wound infections from tissue grafts from amniotic tissue (PubMed). Blech.

And there are outbreaks due to organ transplantation (PubMed).


Macrolides (although resistance is increasing especially in Asia) OR doxycycline. The quinolones are also active. As of 2012, 8.2% are resistant to macrolides (PubMed), although depending on the population, up to 66% of Mycoplasma pneumoniae can be macrolide resistant.

In severe cases, steroids get the patient better faster (PubMed) although a different study suggests no efficacy, only complications (PubMed).

One meta-analysis suggests 5 days of azithromycin is better than a single 1 gm dose (PubMed).

Despite resistance, no difference in outcomes no matter which antibiotic is given to hospitalized patients with pneumonia; likely as it is a self limited disease (PubMed).

Mycoplasma genitalium may be better treated with 1 gram of azithromycin rather than doxycycline (PubMed, PubMed) but moxifloxacin is the only drug always effective (PubMed). 10% are resistant and resistance is increasing to quinolones and macrolides (PubMed). Other studies have found macrolide resistance in 38% of the M. genitalium patients, with 43% resistance in patients tested at sexually transmitted disease clinics (PubMed). Resistance common in MSM (PubMed)

Resistance to macrolides can be as high at 69% in some series and is associated with a prolonged fever.

Pristinamycin is effective in treatment failures (PubMed) (PubMed). Not available in US. Sorry. Maybe quinupristin-dalfopristin in the US (PubMed)?


They are the smallest bacteria known.

Curious Cases

Relevant links to my Medscape blog

How Low Can You Go?


Last Update: 04/02/18.