Discrimination of biofilm-producing Stenotrophomonas maltophilia clinical strains by matrix-assisted laser desorption ionization-time of flight

Drug Resistance in Biofilm and Planktonic Cells of Achromobacter spp., Burkholderia spp., and Stenotrophomonas maltophilia Clinical Isolates

Background: Biofilm production in nonfermenting Gram-negative bacteria influences drug resistance. The aim of this work was to evaluate the effect of different antibiotics on biofilm eradication of clinical isolates of Achromobacter, Burkholderia, and Stenotrophomonas maltophilia. Methods: Clinical isolates were identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry in a third-level hospital in Monterrey, Mexico. Crystal violet staining was used to determine biofilm production. Drug susceptibility testing was determined by broth microdilution in planktonic cells and biofilm cells. Results: Resistance in planktonic cells was moderate to trimethoprim-sulfamethoxazole, and low to chloramphenicol, minocycline, levofloxacin (S. maltophilia and Burkholderia), ceftazidime, and meropenem (Burkholderia and Achromobacter). Biofilm eradication required higher drug concentrations of ceftazidime, chloramphenicol, levofloxacin, and trimethoprim-sulfamethoxazole than planktonic cells (p < 0.05). Levofloxacin showed biofilm eradication activity in S. maltophilia, minocycline and meropenem in Burkholderia, and meropenem in Achromobacter. Conclusions: Drug resistance increased due to biofilm production for some antibiotics, particularly ceftazidime and trimethoprim-sulfamethoxazole for all three pathogens, chloramphenicol for S. maltophilia and Burkholderia, and levofloxacin for Burkholderia. Some antibiotics could be used for the treatment of biofilm-associated infections in our population, such as levofloxacin for S. maltophilia, minocycline and meropenem for Burkholderia, and meropenem for Achromobacter.

Stenotrophomonas maltophilia outbreak originating from a pull-out faucet in a pediatric intensive care unit in Turkey: Insights from clinical records and molecular typing

BACKGROUND

Nosocomial Stenotrophomonas maltophilia-related cases are rising and pose a threat to immunocompromised patients. Twelve patients from our pediatric intensive care unit (PICU) presented with S maltophilia-associated bloodstream infection.

METHODS

This outbreak investigation includes 12 patients from PICU between the ages of 2 months and 4 years (mean 16 months, 7 male). To identify the origin, samples from all possible sources throughout the hospital were collected and ran through DNA isolation and Pulse Field Gel Electrophoresis.

RESULTS

120 samples were collected during the outbreak. 31 samples (26%) were positive for S maltophilia. 30 S maltophilia isolates were analyzed, 10 different genotypes were identified. Clustering isolates were grouped into 3 different clusters (tolerance and optimization 1.0, cutoff 90%). The largest cluster was genotype 1, which included 19 isolates, those belong to patients' samples and a sample from a pull-out faucet inside the PICU. The Pull-out faucet was the origin of the bloodstream infection.

DISCUSSION

Pull-out faucets allow biofilm production, due its structure. Pulse Field Gel Electrophoresis identifies the transmission dynamics of the outbreak, with its high discriminatory power.

CONCLUSIONS

Water sources should be monitored on a regular basis. Pull-out faucets enable bacterial overgrowth; therefore, we recommend water surveillance during outbreak investigations.

Quorum Quenching with a Diffusible Signal Factor Analog in Stenotrophomonas maltophilia

Stenotrophomonas maltophilia is a multidrug-resistant Gram-negative bacillus associated with nosocomial infections in intensive care units, and nowadays, its acquired resistance to trimethoprim-sulfamethoxazole (SXT) by sul genes within class 1 integrons is a worldwide health problem. Biofilm and motility are two of the major virulence factors in this bacterium and are auto-induced by the diffusible signal factor (DSF). In recent studies, retinoids have been used to inhibit (Quorum Quenching) these virulence factors and for their antimicrobial effect. The aim was to reduce biofilm formation and motility with retinoic acid (RA) in S. maltophilia SXT-resistant strains. Eleven SXT-resistant strains and two SXT-susceptible strains were tested for biofilm formation/reduction and planktonic/sessile cell viability with RA and SXT-MIC50/RA; motility (twitching, swimming, swarming) was measured with/without RA; and MLST typing was determined. The biofilm formation of the strains was classified as follows: 15.38% (2/13) as low, 61.54% (8/13) as moderate, and 23.08% (3/13) as high. It was significantly reduced with RA and SXT-MIC50/RA (p < 0.05); cell viability was not significantly reduced with RA (p > 0.05), but it was with SXT-MIC50/RA (p < 0.05); and swimming (p < 0.05) and swarming (p < 0.05) decreased significantly. MLST typing showed the first and novel strains of Mexican S. maltophilia registered in PubMLST (ST479-485, ST497, ST23, ST122, ST175, ST212, and ST300). In conclusion, RA reduced biofilm formation and motility without affecting cell viability; furthermore, antimicrobial synergism with SXT-MIC50/RA in different and novel STs of S. maltophilia was observed.

The Relationship between the Biofilm Genes and Antibiotic Resistance in Stenotrophomonas maltophilia

Objectives

Today, Stenotrophomonas maltophilia (S. maltophilia) is a major opportunistic pathogen among hospitalized or immunocompromised patients. Antibiotic-resistant clinical isolates are increasing in several parts of the world. Various antibiotic-resistance and biofilm-forming genes are identified in this bacterium. Its capacity to form biofilms is an important virulence factor that may impact antibiotic-resistance patterns. In the current study, we evaluated the biofilm-formation capacity, antibiotic-resistance profile, and prevalence of biofilm-forming genes as well as antibiotic resistance genes among S. maltophilia isolates.

Materials and Methods

In this cross-sectional study, 94 clinical S. maltophilia isolates were recovered from four tertiary-care hospitals in Iran between 2021 and 2022. The presence of the selected antibiotic-resistance genes and biofilm-forming genes was examined by polymerase chain reaction (PCR). The ability of biofilm formation was examined by microtiter plate assay. The Kirby-Bauer disc diffusion method was used to evaluate the trimethoprim-sulfamethoxazole (TMP-SMX), levofloxacin, and minocycline resistance.

Results

S. maltophilia is mainly isolated from bloodstream infections. Notably, 98.93% of isolates were biofilm producers, of which 19.35%, 60.22%, and 20.43% produced strong, moderate, and weak biofilm, respectively. The frequency of biofilm genes was 100%, 97.88%, 96.80%, and 75.53% for spgM, rmlA, smf-1, and rpfF, respectively. Isolates with the genotype of smf-1+/rmlA+/spgM+/rpfF+ were mostly strong biofilm producers. Among the antibiotic-resistance genes, the Smqnr, L1, and sul1 had the highest prevalence (76.59%, 72.34%, and 64.89), respectively. Antimicrobial susceptibility evaluation showed 1.06%, 3.19%, and 6.3% resistance to minocycline, TMP-SMX, and levofloxacin.

Conclusion

The results of the current study demonstrated that S. maltophilia isolates differ in biofilm-forming ability. Moreover, smf-1, rmlA, and spgM genes were presented in all strong biofilm producers. Although the overall resistance rate to the evaluated antibiotics was high, there was no statistically significant relation between antibiotic resistance and the type of biofilm.

Environmental, Microbiological, and Immunological Features of Bacterial Biofilms Associated with Implanted Medical Devices

The spread of biofilms on medical implants represents one of the principal triggers of persistent and chronic infections in clinical settings, and it has been the subject of many studies in the past few years, with most of them focused on prosthetic joint infections. We review here recent works on biofilm formation and microbial colonization on a large variety of indwelling devices, ranging from heart valves and pacemakers to urological and breast implants and from biliary stents and endoscopic tubes to contact lenses and neurosurgical implants. We focus on bacterial abundance and distribution across different devices and body sites and on the role of environmental features, such as the presence of fluid flow and properties of the implant surface, as well as on the interplay between bacterial colonization and the response of the human immune system.