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HYPERAMMONEMIC SYNDROME AND UREAPLASMA IN LUNG TRANSPLANT RECIPIENTS and a prospective INHALED (NON-LIPSOSOMAL) AMIKACIN IN THE TREATMENT OF PULMONARY INFECTIONS DUE TO MYCOBACTERIUM ABSCESSUS

Buzo BF, Preiksaitis JK, Halloran K, Nagendran J, Townsend DR, Zelyas N, Sligl WI. Association between Mycoplasma and Ureaplasma airway positivity, ammonia levels, and outcomes post-lung transplantation: a prospective surveillance study. Am J Transplant. 2020 Nov 11. doi: 10.1111/ajt.16394. Epub ahead of print. PMID: 33179447. The hyparammonemic syndrome (HS), consisting of otherwise unexplained neurologic abnormalities in association with elevated serum ammonia levels without other explanation, can occur shortly after organ transplantation, particularly in lung recipients, although it has also been reported in nontransplant settings [1]. Its incidence in lung transplant recipients is reported to be as high as 6% and to be associated with a mortality as high as 75%. Recent evidence suggests that it may be related to colonization of donor lung with Ureaplasma, organisms producing urease that converts urea to CO2 and NH3. Buzo and colleagues prospectively tested 159 adults who underwent lung or heart-lung transplantation over a 2-year period for the presence of Mycoplasma and Ureaplasma by polymerase chain reaction (PCR) of post-procedure bronchoalveolar lavage (BAL). The test was positive in 42 (35.8%)., including (by sequencing) 26 with Mycoplasma salivarium, 7 with Ureaplasma paruvum and 5 with Ureaplasma urealyticum. Mean peak serum ammonia concentrations were 61 μmol/L and 52 μmol/L in those with Ureaplasma and Mycoplasma colonization, respectively, but were 45 μmol/L in those without such colonization (P = .04 compared to Ureaplasma colonization). In this study, HS was defined as “any new neurologic abnormality (agitation, decreased level of consciousness, seizures, or cerebral edema)” together with a serum ammonia concentration >50 μmol/L and normal liver enzymes in the absence of an alternative diagnosis. The presence of other metabolic disturbances, including urea cycle disorders, was ruled out. By this definition, 3 (1.9%) patients were deemed to have HS, all 3 of whom were colonized with Ureaplasma with 1 patient being co-colonized with Mycoplasma. Their median peak serum ammonia level was 79 μmol/L (interquartile range [IQR] 67.5–110.5), whereas that of the those without HS was 47.5 μmol/L (IQR 36–59.5), yielding a P=.19. The median time to diagnosis post-transplant was 5 days. One patient died while the other two were treated with a fluoroquinolone and/or a tetracycline, together with modification of diet, nitrogen scavenger agents, and renal replacement therapy. Roberts and colleagues recently reported that 8 of 60 (13.3%) recipients were transplanted with lungs from donors whose BAL specimen were found to contain Ureaplasma [2]. Three (37.5%) of the 8 (5.0% of the total cohort) developed HS, which, in this case, was defined as the new onset of altered mental status after transplant and serum ammonia concentration >200 μmol/L. The median time of onset was 7 days post-transplantation, and 2 of the 3 died. At one point in their clinical management protocol, all lung transplant recipients were given levofloxacin and azithromycin pending the results of Ureaplasma testing, and none who received this prophylaxis developed HS. Similarly, Kurihara and colleagues implemented universal prophylaxis in lung donors’ recipients, which was continued until microbiologic studies were negative [3]. These studies provide circumstantial evidence indicating that, in lung transplant recipients, colonization of the donor lung with Ureaplasma is associated with HS and suggest that prophylaxis may prevent this complication. Before these observations routinely alter prophylaxis, however, a number of issues should be considered, starting with a lack of a generally accepted definition of HS. Clearly, a multicenter prospective trial addressing HS is indicated and this should include rapid detection of Ureaplasma nucleic acid before prophylactic antibiotics directed at this organism are administered.