Inquilinus limosus Bacteremia in Lung Transplant Recipient after SARS-CoV-2 Infection

Inquilinus limosus is an environmental bacterium associated with respiratory tract colonization in cystic fibrosis patients. We report a case of I. limosus bacteremia in a patient in France who received a lung transplant and experienced chronic graft dysfunction and SARS-CoV-2 infection. This case suggests I. limosus displays virulence factors associated with invasion.

for meropenem plus amikacin and then ciprofloxacin on May 4. The patient improved but remained colonized with I. limosus, displaying a similar pattern of resistance, 3 months later. Of interest, she was colonized before the lung transplantation, but I. limosus has not been isolated since then.
I. limosus is a fastidious, gram-negative rod from environmental sources (1) that has rarely been associated with colonization of the respiratory tract of CF patients (2). The airways of CF are susceptible to colonization by respiratory pathogens (3), a condition that is improved in lung transplant recipients. Nevertheless, I. limosus infection has been reported twice in lung transplant recipients (4,5). In 1 case, a 22 yearold woman had pulmonary infiltrates develop within a month after lung transplantation (4). She completely recovered with antimicrobial drug treatment; I. limosus was not isolated during 1 year of follow-up. In the second case, a 31-year-old man experienced a bacteremic lung empyema 1 month posttransplant and a contralateral lung empyema 7 months later (5). He recovered from each episode with surgery and antimicrobial treatment with ciprofloxacin and meropenem. Both patients were lung transplant recipients for endstage cystic fibrosis (CF); they were colonized with I. limosus before lung transplantation. Indeed, the lung graft microbiome is affected by donor and recipient factors (6), but early posttransplant infections mainly involve the bacteria of the recipient rather than those of the donor (7).
In contrast to those patients, the case-patient we describe experienced a late infection several years after I. limosus clearance. Unfortunately, the pretransplant strain was not preserved, and we could not determine whether she was infected with the strain she was colonized with before the lung transplantation or another strain. It is possible that the chronic graft dysfunction, the recent intensification of immunosuppression, and the SARS-CoV-2 infection could have led to a modification of the graft microbiome and enabled colonization with I. limosus. In CF patients, colonization with I. limosus induces a specific Inquilinus limosus is an environmental bacterium associated with respiratory tract colonization in cystic fibrosis patients. We report a case of I. limosus bacteremia in a patient in France who received a lung transplant and experienced chronic graft dysfunction and SARS-CoV-2 infection. This case suggests I. limosus displays virulence factors associated with invasion.
serum antibody response (8). The intensification of immunosuppression and the clearance of I. limosus after lung transplantation could have reduced humoral immunity. Furthermore, the bacteremia suggested virulence factors involved in the invasion. Two other cases of I. limosus bacteremia have been reported previously (5,9).
Because I. limosus is a rarely encountered microorganism and because its colonies are of a mucoid morphotype, it could be misidentified using phenotypic characteristics as P. aeruginosa (8,10). The biochemical methods used previously provided inconsistent identification, and neither European Committee on Antimicrobial Susceptibility Testing nor  (9). It has been suggested that the multidrug resistance of I. limosus enhances its selection in CF patients (2). In our case, successive treatment with drugs that were ineffective against I. limosus could have enabled its selection.
In conclusion, we emphasize a pathogenic role of I. limosus in lung transplant recipients several years after respiratory clearance of the bacteria. Chronic graft dysfunction, intensifying immunosuppression, and SARS-CoV-2 infection in this patient could have favored colonization with I. limosus. Characteristics of the bacterium such as colony morphotypes and multidrug resistance could delay effective therapy.