Effect of a serum lactate monitoring recommendation policy on patients treated with linezolid

Severe lactic acidosis associated with oral linezolid

We present the case of a patient with cystic fibrosis on long-term oral linezolid treatment for Mycobacteria abscessus lung infection who developed severe linezolid-induced lactic acidosis (LILA) resulting in deranged clotting and pancytopenia. The lactic acidosis was resistant to treatment with intravenous fluid but resolved within 20 hours of initiating continuous veno-venous haemofiltration. An unintended consequence of haemofiltration was that vascular access interfered with effective chest physiotherapy, resulting in worsened lung consolidation requiring prolonged intravenous antibiotic therapy for coexisting Pseudomonas aeruginosa infection. Given the potential mortality and morbidity of LILA, monitoring lactate levels may be clinically important but the optimum timing of monitoring is currently unclear.

Excess fermentation and lactic acidosis as detrimental functions of the gut microbes in treatment-naive TB patients

Introduction

The link between gut microbiota and host immunity motivated numerous studies of the gut microbiome in tuberculosis (TB) patients. However, these studies did not explore the metabolic capacity of the gut community, which is a key axis of impact on the host's immunity.

Methods

We used deep sequencing of fecal samples from 23 treatment-naive TB patients and 48 healthy donors to reconstruct the gut microbiome's metabolic capacity and strain/species-level content.

Results

We show that the systematic depletion of the commensal flora of the large intestine, Bacteroidetes, and an increase in Actinobacteria, Firmicutes, and Proteobacteria such as Streptococcaceae, Erysipelotrichaceae, Lachnospiraceae, and Enterobacteriaceae explains the strong taxonomic divergence of the gut community in TB patients. The cumulative expansion of diverse disease-associated pathobionts in patients reached 1/4 of the total gut microbiota, suggesting a heavy toll on host immunity along with MTB infection. Reconstruction of metabolic pathways showed that the microbial community in patients shifted toward rapid growth using glycolysis and excess fermentation to produce acetate and lactate. Higher glucose availability in the intestine likely drives fermentation to lactate and growth, causing acidosis and endotoxemia.

Discussion

Excessive fermentation and lactic acidosis likely characterize TB patients' disturbed gut microbiomes. Since lactic acidosis strongly suppresses the normal gut flora, directly interferes with macrophage function, and is linked to mortality in TB patients, our findings highlight gut lactate acidosis as a novel research focus. If confirmed, gut acidosis may be a novel potential host-directed treatment target to augment traditional TB treatment.