Infectious Disease Compendium

Mycoplasma

Microbiology

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. Mycoplasma phocacerebrale.

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

Candidatus Mycoplasma haemohominis.

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).

"Amoung 1139 women, 233 were M. genitalium positive, for a prevalence of 20.5% 42 of 204 had persistent M. genitalium (20.6%). Among 801 M. genitalium–negative women at baseline, the M. genitalium incidence was 36.6 per 100 person-years. Black race, age ≤21 years, and prior pregnancy were associated with prevalent M. genitalium (PubMed).

The most common cause of hospitalized CAP in children (PubMed).

MSM can have extra-genital disease.

Syndromes

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 severe hemolytic anemia with fever (PubMed).

There may be other mycoplasmas that cause fever, like Candidatus Mycoplasma haemohominis (Pubmed).

Mycoplasma amphoriforme causes pneumonia, including chronic/relapsing pneumonia in patients with primary antibody deficiency (PubMed) and in COPD patients (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). Can split urea to make ammonia. In immunoincompetent patients, infection can lead to hyperammonemia with normal liver function (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).

Mycoplasma phocacerebrale: seal finger, cellulitis from contact with seals (PubMed).

Treatment

M. pneumonaie

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 China, 88.3% of isolates were macrolide-resistant (PubMed).

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

M. genitalium

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

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

"90% of MG infections were resistant to macrolides and fluoroquinolones. Men who took macrolides in the 30 days prior to enrollment had higher rates (97%) of macrolide-resistant MG (Pubmed)".

One approach is to use PCR resistance testing combined with sequential antibiotics for a high cure rate (PubMed).

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

Notes

They are the smallest bacteria known.

Curious Cases

Relevant links to my Medscape blog

How Low Can You Go?

SMP

Joint Infection

Last update: 02/29/20