Human microbial ecology: lactobacilli, probiotics, selective decontamination.

Area of Science:

• Microbiology
• Infectious Diseases
• Gastroenterology

Background:

• Medical interventions can disrupt the human microbiota, leading to opportunistic pathogen overgrowth and hospital-acquired infections.
• Selective decontamination of the digestive tract (SDD) aims to suppress pathogens but its impact on beneficial gut microbiota is unclear.
• Preserving gut microbiota balance is crucial for critically ill patients to prevent endogenous infections.

Purpose of the Study:

• To evaluate the safety of Infectious Diseases Society of America (IDSA) guidelines for intra-abdominal infections regarding Lactobacillus species.
• To determine the susceptibility of various Lactobacillus species to commonly used antimicrobials.
• To explore the potential for preserving beneficial gut bacteria during antimicrobial therapy in critically ill patients.

Main Methods:

• Review of antimicrobial treatment guidelines from the IDSA for intra-abdominal infections.
• Analysis of published data and in-house results on the antimicrobial susceptibility of approximately 100 Lactobacillus strains.
• Evaluation of microbial ecology data on Lactobacillus colonization in adult and elderly gastrointestinal tracts.

Main Results:

• All tested Lactobacillus strains demonstrated resistance to metronidazole.
• Different Lactobacillus species exhibited variable susceptibility to vancomycin, cefoxitin, ciprofloxacin, and newer tetracyclines.
• The gastrointestinal tract harbors multiple Lactobacillus species with intrinsic antimicrobial resistance.

Conclusions:

• Certain Lactobacillus species possess intrinsic resistance to antimicrobials, offering a potential to maintain gut colonization during treatment.
• Probiotic Lactobacillus strains could be used adjunctively during antibacterial therapy.
• Further clinical trials are needed to investigate the efficacy of using probiotics with antimicrobial treatment in critically ill patients.