Mycobacterium iranicum has recently been recognised as an opportunistic human pathogen. Although infectious conditions represent frequent triggers for hemophagocytic lymphohistiocytosis, non-tuberculous mycobacterial infections are rarely associated with this entity. To this date, M. iranicum infection has never been reported in France, has never been associated with hemophagocytic lymphohistiocytosis and has never been found to be multi-resistant on standardized antimicrobial susceptibility testing. We report a case of a French Caucasian man with secondary hemophagocytic lymphohistiocytosis in the context of M. iranicum bacteraemia and Hodgkin’s disease. We review available data concerning M. iranicum antimycobacterial susceptibility testing and treatment outcomes. We also review the association between hemophagocytic lymphohistiocytosis and non-tuberculous mycobacterial infections. Interpretation of M. iranicum positive cultures remains a clinical challenge and non-tuberculous mycobacterial infections need to be considered in secondary hemophagocytic lymphohistiocytosis differential diagnosis.
To the Editor: Inquilinus limosus, a new multidrug-resistant species, was reported in 1999 as an unidentified gram-negative bacterium in a lung transplant patient with cystic fibrosis (CF) (1). This species was later characterized by the description of 7 new isolates of I. limosus and 1 isolate of Inquilinus sp (2). Infections and colonizations by I. limosus have been documented mainly in adolescent or adult patients with CF. To date, 8 clinical cases have been described in Germany (3,4), 1 case in the United States (1), 5 cases in France (5), and 1 case in the United Kingdom (6) (Table). Only 1 isolate of Inquilinus sp. has been recovered from blood samples of a patient without CF who had prosthetic valve endocarditis (7).
Table
Clinical and epidemiologic features of cystic fibrosis (CF) patients with Inquilinus limosus*
Because this bacterium is not recorded in all commercial identification system databases currently available, a longitudinal study for I. limosus detection with a new real-time PCR assay with a Taqman probe (Applied Biosystems, Foster City, CA, USA), that targets the 16S rRNA gene, has been developed and compared with the culture isolation. Primers il1d (5′-TAATACGAAGGGGGCAAGCGT-3′) and il1r (5′-CACCCTCTCTTGGATTCAAGC-3′) and probe ilProbe (6FAM-GGTTCGTTGCGTCAGATGTGAAAG-TAMRA), which were used in this study, were designed on the basis of multisequence alignment of all I. limosus 16S rDNA sequences available in the GenBank database.
To confirm specificity, the primers and probe were checked by using the BLAST program (www.ncbi.nlm.nih.gov/blast/Blast.cgi) and also by using suspension of several bacteria recovered habitually in patients with CF. For sensitivity of the Taqman PCR assay (Applied Biosystems), the minimal CFU detectable was 2 CFU/PCR. From January 2006 through June 2007, 365 sputum samples recovered from 84 children and 61 adults with CF and 71 sputum samples recovered from 54 patients without CF were screened blindly for I. limosus. By using our real-time PCR, we detected 9 I. limosus-positive samples from 4 patients with CF (Table); 8 of these samples were also culture positive. However, all sputum samples from patients without CF were negative. In 1 patient (Table, case 17), I. limosus was detected by using real-time PCR 3 months before the culture was positive. Retrospectively, the patient’s medical file was rechecked and his clinical respiratory condition worsened briefly at that stage, which indicates an infection by this bacterium. Thus, in our study, the incidence of I. limosus was 2.8% (4.9% for adults with CF and 1.2% for children with CF). The incidence of Burkholderia cepacia complex during the same period and in the same patients was 2.1% (3 adults with CF were positive, data not shown).
The genus Inquilinus belongs to the α-Proteobacteria; the genus Azospirillum is the most closely related bacteria (2). This cluster of bacteria contains several strains that are able to grow under saline conditions and in biofilms (8,9). The mucoid phenotype of I. limosus may contribute to its colonization and resistance to many antimicrobial drugs. Recently, the exopolysaccharides (EPS) produced by I. limosus were studied. The authors indicated that I. limosus produces mainly 2 EPSs that exhibit the same charge per sugar residue present in alginate, the EPS produced by Pseudomonas aeruginosa in patients with CF. This similarity may be related to common features of the EPS produced by these 2 opportunistic pathogens that are related to lung infections (10). Transmission of I. limosus between patients with CF is not known, but in the report from Chiron et al., 1 of the 5 patients with I. limosus had a brother who had never been colonized with this bacterium despite living in the same home (5). Schmoldt et al. reported that 3 patients were treated in the same outpatient CF clinic during overlapping time periods and each patient was infected/colonized by an individual I. limosus clone, which suggests that there was no transmission among these patients (4). This bacterium has been recovered mainly from sputum of adolescents (mean age 17 ± 6.47 years, range 8–35), except in our study with a 2-year-old boy, which suggests that this emerging bacterium may be hospital acquired, as recently suggested (7). Because this bacterium is multiresistant to several antimicrobial drugs, particularly colistin, which is widely used for treatment for P. aeruginosa colonization (as was the case for our 4 patients), we hypothesize that this bacterium is selected during the evolution of the disease.
We have developed a real-time PCR molecular method that is faster and easier than amplification-sequencing for prompt detection and accurate identification of I. limosus with good specificity and sensitivity. By using this screening assay, we identified 4 additional cases of patients with CF who were also infected with this bacterium, including a 2-year-old child. In addition, by using this technique, we were able to detect I. limosus in a patient with deteriorated respiratory function 3 months before the culture-based isolation, indicating that a low bacterial load, insufficient for being isolated in culture, can be detected by PCR in the lower respiratory tract of patients with CF.
To the Editor: A 66-year-old man had a bone graft for treatment of an oroantral fistula in March 2007 in Marseille, France. The surgery consisted of a bilateral maxillary sinus filling with a parietal osseous graft to close the fistula (position 24–25). Painful edema of the hemiface and mild fever developed in the patient in July 2007. Computed tomography showed areas of hypodensity in the osseous graft in the left maxillary sinus consistent with osteolysis. Microscopic examination of a bone biopsy specimen after gram staining did not reveal any organisms but this specimen did grow Enterobacter cloacae and colonies of a gram-positive bacillus after a 2-day inoculation on 5% blood agar incubated at 37°C in an atmosphere of 5% CO2. Tentative identification of this catalase-positive, oxidase-negative gram-positive rod (isolate 74023791) by an API Coryne strip (API bioMerieux, La Balme-les Grottes, France) remained inconclusive. Isolate 74023791 exhibited acid fastness and was further identified by comparing its 16S rDNA (1) and heat shock protein 65 (hsp65) (2) sequences with those in the GenBank database and its RNA polymerase subunit B (rpoB) sequences (3) with those of Mycobacterium spp. in our local rpoB database.
Antimicrobial susceptibility testing using E-test (AB Biodisk, Bruz, France) indicated that isolate 74023791 was susceptible to ciprofloxacin with an MIC of 0.047 μg/mL and resistant to amoxicillin (MIC >256 μg/mL), ceftriaxone (MIC >256 μg/mL), erythromycin (MIC >256 μg/mL), clarithromycin (MIC >256 μg/mL), and rifampin (MIC >32 μg/mL). Disk testing and reference broth dilution method (4) showed that isolate 74023791 was susceptible to imipenem after a 3-day incubation. However, E-test showed heterogeneous resistance with colonies exhibiting an MIC >256 μg/mL. The same observations were made for Mycobacterium setense type strain CIP109395T (Collection de l’Institut Pasteur, Paris, France) (5). Daily treatment with 2 g imipenem and 1.5 g ciprofloxacin was prescribed for 1 month before the imipenem E-test and broth dilution results were available, and was followed by 1.5 g/day ciprofloxacin for 3 months, resulting in a favorable clinical and radiologic evaluation at 5-month follow-up.
Phylogenetic analyses indicated that isolate 74023791 belonged to the M. fortuitum group, along with M. porcinum and M. conceptionense, and was most closely related to M. setense, a recently described species of this group (5) (Figure). Isolate 74023791 shared 100% 16S rDNA (GenBank accession no. {type:entrez-nucleotide,attrs:{text:EU371507,term_id:189187657}}EU371507), 99.5% hsp65 (accession no. {type:entrez-nucleotide,attrs:{text:EU371508,term_id:189187658}}EU371508), and 99.0% rpoB (accession no. {type:entrez-nucleotide,attrs:{text:EU371509,term_id:189187660}}EU371509) sequence similarity with M. setense (accession nos. {type:entrez-nucleotide,attrs:{text:EF138818,term_id:133872965}}EF138818 and {type:entrez-nucleotide,attrs:{text:EU371504,term_id:189187652}}EU371504, {type:entrez-nucleotide,attrs:{text:EF138819,term_id:133872966}}EF138819 and {type:entrez-nucleotide,attrs:{text:EU371505,term_id:189187653,term_text:EU371505}}EU371505, and {type:entrez-nucleotide,attrs:{text:EF414447,term_id:145284379}}EF414447 and {type:entrez-nucleotide,attrs:{text:EU371506,term_id:189187655}}EU371506, respectively). Because the 99% rpoB sequence similarity of the patient’s isolate was above the 97% rpoB sequence similarity cut-off value used to identify rapidly growing mycobacteria (3), isolate 74023791 was therefore identified as M. setense.
Figure
Phylogenetic position of isolate 74023791 and 16 rapidly growing Mycobacterium species based on A) 16S rDNA, B) partial RNA polymerase subunit B, and C) partial heat shock protein 65 sequences analyzed by using the neighbor-joining method and Kimura's ...
M. setense, in association with an E. cloacae strain susceptible to antimicrobial drug therapy, was an agent of infection in our patient. It is noteworthy that M. setense and the closely-related species M. conceptionense were isolated from patients with posttraumatic osteitis (5,6); M. porcinum was isolated from 7/46 cases of osteomyelitis and additional cases of postsurgical infection, respectively (7); M. fortuitum osteomyelitis has also been reported (8). These data emphasize the role of M. fortuitum group organisms in posttraumatic and postsurgical osteitis.
In a later interview, the patient disclosed that he rinsed his mouth with well water during the weeks after receiving the bone graft. We initially suspected that the water was the source of M. setense, as previously suspected for M. conceptionense (6) and reported for M. porcinum (7). However, neither M. setense nor M. setense DNA were detected in the well water in October 2007.
Initially, M. setense was reported to be susceptible to imipenem by the disk diffusion method, which is not the reference method (5). In this report, the disk and reference broth dilution methods showed that both clinical and reference M. setense strains were initially susceptible to imipenem but the E-test disclosed that both strains exhibited heterogeneous resistance to imipenem; colonies exhibited an MIC >256 μg/mL. This result was unexpected because the E-test showed that related species M. fortuitum CIP104534T, M. conceptionense, CIP 108544T and M. porcinum CIP105392T were susceptible to imipenem (6). Likewise, the modified broth dilution method showed that the MIC for imipenem was <4 μg/ml for M. fortuitum (9). However, when a broth dilution method was used, the MIC for imipenem ranged from 0.5 μg/mL to 8 μg/mL in 42 M. porcinum strains (7). Together, these data challenge the susceptibility to imipenem in organisms of the M. fortuitum group.
M. setense is an emerging organism of the M. fortuitum group that must be added to the growing list of rapidly growing mycobacteria isolated from humans. The initial gram-positive rod appearance of M. setense may delay its accurate identification. Determination of antimicrobial drug susceptibility needs to be conducted by the reference broth dilution method. Further reports are warranted to characterize the role of M. setense in infection.
Streptomyces are environmental gram-positive bacilli that can cause ubiquitous mycetoma and, more rarely, invasive infections. We describe the clinical relevance of Streptomyces spp. identified in human samples and characteristics of patients with invasive Streptomyces infections.We conducted a retrospective (2006-2017) study of Streptomyces isolates identified in clinical samples in French microbiology laboratories. Streptomyces genus was confirmed by a specific 16S rRNA polymerase chain reaction, and antibiotic susceptibility testing was performed by disk diffusion and trimethoprim-sulfamethoxazole minimum inhibitory concentration (E-test) if resistance was suspected. Patient characteristics, treatments, and outcomes were collected. Invasive infection was defined as a positive culture from a sterile site with signs of infection but without cutaneous inoculation.Of 137 Streptomyces isolates, all were susceptible to amikacin (113/113) and linezolid (112/112), and 92.9% to imipenem (105/113). Using disk diffusion, 50.9% (57/112) of isolates were susceptible to trimethoprim-sulfamethoxazole, but most of the apparently resistant isolates (25/36, 69.4%) tested by E-test were ultimately classified as susceptible. Clinical data were obtained for 63/137 (45.9%) isolates: 30 (47.6%) invasive infections, 8 (12.7%) primary cutaneous infections, 22 (34.9%) contaminations, 3 (4.7%) respiratory colonization. Patients with invasive infection were more frequently receiving corticosteroids than patients without invasive infection (11/30, 36.7%, vs 2/25, 8.0%; P = .03), and at 6-month follow-up, 14 of them were cured, 3 had relapsed, 4 were dead, and 9 were lost to follow-up.Half of the clinical samples that grew Streptomyces were from patients with invasive infection. In that case, antimicrobial therapy should include 1 or 2 antibiotics among linezolid, amikacin, or imipenem.
Current microfluidic techniques are powerful to study bacteria and determine their response to antibiotic treatment, but they are currently limited by their complex manipulation. Chitosan films are fully biocompatible and could thus be a viable replacement for existing commercial devices that currently use polylysine. Thus, the low cost of chitosan slides and their simple implementation make them highly versatile for research as well as clinical use.
Abstract Single cell microfluidics is powerful to study bacteria and determine their susceptibility to antibiotics treatment. Glass treatment by adhesive molecules is a potential solution to immobilize bacterial cells and perform microscopy but traditional cationic polymers such as poly-lysine deeply affect bacterial physiology. In this work, we chemically characterized a class of chitosan polymers for their biocompatibility when adsorbed to glass. Chitosan chains of known length and composition allowed growth of Escherichia coli cells without any deleterious effects on cell physiology. Combined with a machine-learning approach, this method could measure the antibiotics susceptibility of a diversity of clinical strains in less than 1 hour and with higher accuracy than current methods. Last, chitosan polymers also supported growth of Klebsiella pneumoniae , another bacterial pathogen of clinical significance. The low cost of chitosan slides and their simple implementation makes them highly versatile for research as well as clinical use.
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