Autism and gastrointestinal bacteria connection

Autism spectrum disorders (ASD) are neurodevelopmental disorders,  characterized by difficulties in social interactions, verbal and non-verbal communication, and stereotypic or repetitive behaviors.  Gastrointestinal (GI) distress is common in children with ASD and include,  abdominal pain, bloating, diarrhea and constipation. The high frequencies of these GI symptoms could be due to abnormal GI bacterial flora in individuals with ASD. The GI bacterial flora  are important for nutrition and metabolic processes and growing evidence suggest that they play a role in brain development, behavior, and gene expression via neural, endocrine, and immune pathways. Emerging research on the gut-microbiome-brain connection in both mice and humans has shed new light on the pathogenesis of various neurological diseases including ASD.

A total of 15 cross-sectional studies, with a combined sample of 562 individuals reported significant differences in the prevalence of GI bacteria between ASD children and controls, in some bacteria in the Firmicutes  (including Clostridium spp. ), Bacteroidetes  and Proteobacteria phyla. The level of the probiotic Bifidobacterium  spp. was lower in children with ASD than in controls. Some studies found an association between the severity of GI symptoms and the severity of autism.

Future research should explore whether administration of probiotic bacteria, and or antimicrobials could restore normal gut microbiota, reduce inflammation, restore epithelial barrier function, and potentially ameliorate behavioral symptoms associated with some children with ASD.

Is Fusobacterium associated with colon cancer?

Numerous cancers have been linked to microorganisms. Warren et al. from British Columbia Cancer Agency, Vancouver, Canada; investigated the relationship between gut mucosal microbiome and colorectal cancer using genetic methods. The investigation revealed an association between Fusobacterium species and colorectal carcinoma in eleven patients. These investigators have extended their studies with deeper sequencing of a much larger number (n = 130) of colorectal carcinoma and matched normal control tissues.

The new report has revealed differently abundant microbial genome sequence signatures of significance in tumor samples, including those belonging to the Fusobacterium, Campylobacter and Leptotrichia genera. These Gram-negative anaerobes are typically considered to be oral bacteria. However, tumor isolates for Fusobacterium and Campylobacter were genetically diverged from their oral counterparts and carry potential virulence genes. They also observed that sequence signatures from Fusobacterium co-occur with those from Leptotrichia and Campylobacter and that Fusobacterium and Campylobacter strains isolated from tumor tissue co-adhere in culture. A non-invasive assay to detect this polymicrobial signature of colorectal carcinoma may have utility in screening and risk assessment.

It remains unknown whether there is any etiological link between microorganisms and colorectal carcinoma. Any such link could provide a potential mode of intervention in the prevention of colonic cancer.

Fusobacterium necrophorum Gram stain

Propionibacterium acnes, an emerging pathogen: From acne to implant-infections

Propionibacterium acnes is a colonizer of the lipid-rich sebaceous glands of the skin. The pathogenicity of P. acnes has long been restricted to skin conditions. Its isolation from other anatomical sites or deep microbiological samples has often been considered as contamination. It is involved in the inflammation process of acne is well known, but until recently, it was neglected in other clinical presentations. P. acnes  has been considered to be of low virulence, but the new genomic, transcriptomic, and phylogenetic studies have allowed better understanding of this potential pathogen's importance in causing many chronic and recurrent infections, including orthopedic ( osteo-articular and spine )  and cardiac prosthetic, and breast or eye implant-infections, and neurosurgical infections of external ventricular shunts.

Hip Joint implant

These infections, are facilitated by the ability of P. acnes to produce a biofilm, requiring using anti-biofilm active antibiotics such as rifampicin. However, in the last 10 years, the rate of antibiotic-resistant bacteria has increased, especially for macrolides and tetracyclines. The antimicrobial susceptibility of P. acnes is not routinely performed in microbiology laboratories because of its susceptibility to a wide range of antibiotics.

Some antibiotics should be tested to adapt treatment because of the prevalence of antibiotic resistance in P. acnes: tetracycline, erythromycin, clindamycin, and cotrimoxazole. Furthermore, other antibiotics should be tested for severe infections, to optimize treatment and obtain a synergistic effect against P. acnes: penicillin, cephalosporins, vancomycin, quinolones, rifampicin, and the “new” antibiotics such as linezolid, daptomycin, and tigecycline, to which P. acnes is usually susceptible. Aminoglycosides and metronidazole are not active against P. acnes.

The treatment of severe infections caused by P. acnes includes a combination of antibiotics, administrated intravenously initially, and usually associated with optimal surgery (e.g., removal of the device and/or debridement of the surgical site). Penicillin G and ceftriaxone are still considered as first-line antibiotics for severe infections. Clindamycin, tetracycline, and levofloxacin are alternatives in those allergic to beta-lactams. Rifampicin and daptomycin are also active antimicrobial agents, effective also against P. acnes biofilm. Removal of the device associated with the infection is usually sufficient to reduce the inoculum causing chronic infection.

Gram stain of Propionibacterium acnes