Persistence and variability of Stenotrophomonas maltophilia in Cystic Fibrosis Patients, Madrid, 1991-1998

During 1991 to 1998 at least one Stenotrophomonas maltophilia pulmonary infection was observed in 25 (24%) of 104
cystic fibrosis (CF) patients at the same unit of our hospital in Spain. Ribotyping and pulse-field gel electrophoresis
(PFGE) characterization of 76 S. maltophilia isolates from these patients indicated an overall clonal incidence of 47.1%,
reflecting new strains in 44% of patients with repeated positive cultures for S. maltophilia. Six patients with repeated
episodes were persistently colonized (>6 months) with the same strain. S. maltophilia bacterial counts were higher
(geometric mean, 2.9 x108 cfu/mL) in patients with repeated episodes than in those with a single episode (8.4 x104
cfu/mL, p<0.01). Single episodes of S. maltophilia occurred in patients <10 years of age (43% [6/14]), whereas chronic
colonization occurred more frequently in older patients (>16 years of age).

S. maltophilia, an essentially environmental organism, is the fourth organism in prevalence in bronchial secretions of
CF patients, after P. aeruginosa, Staphylococcus aureus, and Haemophilus influenzae (5,18). Since it was first
reported in CF patients in 1979 (19), this organism has been investigated for its role in the progression of CF
pulmonary disease (5), and consensus documents have emphasized the importance of clinical microbiology
laboratories in detecting its presence in CF respiratory secretions (20). Despite some virulence factors shared with P.
aeruginosa, its potential for pathogenicity remains uncertain (21). We have reported a high incidence of S. maltophilia-
colonized CF patients (30.7%) over a 5-year period (3), but, as in other studies (2,6,22), we did not address (through
epidemiologic typing studies) whether this high rate was a consequence of patient-to-patient transmission or whether
bacterial colonization was sporadically or chronically established.
Emerging Infectious Diseases Journal Vol. 7, No. 1 Jan–Feb 2001

Extremely Late Pacemaker-Infective Endocarditis due to Stenotrophomonas maltophilia Abstract

This case report describes a patient with an intravascular infection of a pacemaker system with Stenotrophomonas
maltophilia, which occurred 17 years after the implantation. The patient was treated with appropriate antibiotics and
debridement of the infectious tissue in the pocket, and the entire pacemaker system was removed by open heart
surgery. She was discharged from our center after a 6-week course of antibiotics and implantation of a new pacemaker.

Cardiology 2008;110:226-229 (DOI: 10.1159/000112404)
Vol. 110, No. 4, 2008   

CDC  Emerging Infectious Diseases

Global Emergence of Trimethoprim/Sulfamethoxazole Resistance in Stenotrophomonas maltophilia
Mediated by Acquisition of sul Genes

Most studies of the location and dissemination of sul2 genes have concentrated on Enterobacteriaceae, such as E. coli
and Salmonella enterica. A recent study by Antunes et al. found sul1, sul2, or sul3 genes in most Portuguese isolates
(18); 24 of 200 isolates contained both sul1 and sul2. sul2 has also recently been identified in S. enterica from Brazil
(20). Similar results have been reported from E. coli urinary tract isolates in which ≈26% of strains possessed both sul1
and sul2 genes (21). A biased study examining TMP/SMX-resistant E. coli recently reported that 15 of 20 isolates
possessed sul2 and that 6 of those also carried sul1 on a class 1 integron (14). Additional studies of E. coli have
shown the intercontinental predominance of sul1 through class 1 integrons (22). A study by Pei et al. demonstrated the
correlation of anthropogenic activity with the presence of sul genes in environmental samples (23). However, none of
the studies demonstrated the genetic origin of the sul2.

In addition to sul genes associated with plasmids and class 1 integrons, we investigated whether the S. maltophilia
isolates possessed ISCR elements and whether these could be linked to dhfr or sul genes, as has been shown (18). Of
the 25 TMP/SMX-resistant isolates, 6 harbored sul2 linked to ISCR2. However, we could not detect any sul3 genes. In
the isolates with ISCR2, the element was directly linked to a deleted version of a phosphoglucosamine mutase gene,
ΔglmM, as has been reported on other occasions (Figure 2). This arrangement is identical to those of 5 other
sequences in the EMBL database, in E. coli isolated from cattle in France and Germany (24), in the plasmid pRVS1
isolated from a strain of Vibrio salmonicida from Norway, in a plasmid from a strain of S. enterica isolated in Japan, and
on the chromosome of Shigella flexneri isolated in the United States (18,24). In all cases, ΔglmM and sul2 are linked to
the end of ISCR2 that accommodates the IS91 oriIS equivalent (Figure 2). The dual arrangement of ΔglmM and sul2 is
also found in plasmids of marine psychotrophic bacteria isolated in Norway (GenBank accession no. AJ306553/4), but
in these cases the ISCR2 element appears not to be present.

Two of the isolates harbored a copy of the floR gene immediately upstream of a copy of ISCR2 (Figure 2), an
arrangement identical to that reported on
plasmids found in isolates of E. coli from cattle in France and Germany (24).
The S. maltophilia isolates investigated in this study came from Turkey and the United States. Two isolates from Spain
also carry the floR gene but not ISCR2. Instead, the isolates possess copies of ISCR3, which do not appear to be
linked to floR. The finding of florfenicol-resistant traits on plasmids in different bacterial species from different countries
highlights the wide geographic spread of this resistance mechanism. The location of floR next to ISCR2 is such that it is
possible, if not probable, that the resistance gene can be cotransposed with the ISCR element.

EID Journal Home > Volume 13, Number 4–April 2007

Posttraumatic Stenotrophomonas maltophilia Infectious Scleritis.

Case Report

Cornea. 27(2):232-235, February 2008.
Ramos-Esteban, Jerome C MD; Jeng, Bennie H MD

Purpose: To describe the history, clinical presentation, and successful surgical and antibiotic management of a case of
posttraumatic infectious scleritis secondary to Stenotrophomonas maltophilia.

Methods: A 51-year-old white man presented with worsening light sensitivity, localized conjunctival hyperemia, and a
painful scleral nodule in his right eye that developed over a period of 1 month after minor ocular trauma. The patient
was treated by his referring ophthalmologist for "episcleritis" with fluorometholone 0.1%, 1 drop 4 times a day, since
injury onset without clinical improvement. Evaluation consisted of slit-lamp examination, ultrasound biomicroscopy, and
surgical exploration with tissue cultures and histology.

Results: Ultrasound biomicroscopy of the right eye revealed the presence of a dome-shaped mass overlying an area of
partial-thickness scleral laceration in the inferotemporal quadrant. The scleral nodule was surgically excised, and the
scleral laceration was repaired with one 8-0 nylon suture. Culture results revealed infection by S. maltophilia, which was
resistant to gentamicin, tobramycin, and trimethoprim-sulfamethoxazole. The patient experienced immediate pain relief
after surgery, and treatment was continued with both topical ciprofloxacin 0.3% and prednisolone acetate 1% for 1
month with full recovery.

Conclusions: S. maltophilia should be considered in the differential diagnosis of posttraumatic infectious scleritis.
Submission of appropriate surgical specimens for microbiologic analysis and adequate antibiotic therapy may prevent
the development of endophthalmitis in cases of suspected posttraumatic infectious scleritis.

(C) 2008 Lippincott Williams & Wilkins, Inc.

Heavy Metal Tolerance in Stenotrophomonas maltophilia


Stenotrophomonas maltophilia is an aerobic, non-fermentative Gram-negative bacterium widespread in the
environment. S. maltophilia Sm777 exhibits innate resistance to multiple antimicrobial agents. Furthermore, this
bacterium tolerates high levels (0.1 to 50 mM) of various toxic metals, such as Cd, Pb, Co, Zn, Hg, Ag, selenite, tellurite
and uranyl. S. maltophilia Sm777 was able to grow in the presence of 50 mM selenite and 25 mM tellurite and to reduce
them to elemental selenium (Se0) and tellurium (Te0) respectively. Transmission electron microscopy and energy
dispersive X-ray analysis showed cytoplasmic nanometer-sized electron-dense Se0 granules and Te0 crystals.
Moreover, this bacterium can withstand up to 2 mM CdCl2 and accumulate this metal up to 4% of its biomass. The
analysis of soluble thiols in response to ten different metals showed eightfold increase of the intracellular pool of
cysteine only in response to cadmium. Measurements by Cd K-edge EXAFS spectroscopy indicated the formation of
Cd-S clusters in strain Sm777. Cysteine is likely to be involved in Cd tolerance and in CdS-clusters formation. Our data
suggest that besides high tolerance to antibiotics by efflux mechanisms, S. maltophilia Sm777 has developed at least
two different mechanisms to overcome metal toxicity, reduction of oxyanions to non-toxic elemental ions and
detoxification of Cd into CdS.  
Citation: Pages D, Rose J, Conrod S, Cuine S, Carrier P, et al.
(2008) Heavy Metal Tolerance in Stenotrophomonas
maltophilia. PLoS ONE 3(2): e1539. doi:10.1371/journal.pone.0001539