Biodeterioration of carbographic ribbon: Isolation, identification of causal agents and forensic implications

This study is part of a comprehensive investigation that was performed in regard to a case of alterations on a carbographic ribbon used in a typewriter that was found and seized by inner security operations of the Arma dei Carabinieri, Italy. Thirty‐six coded scripts possessing potentially and criminally liable content were present on the tape; however, only the 6th and 7th scripts exhibited alterations of an uncertain nature. The study included sampling that was performed under sterile conditions of a large surface area of carbographic ribbons. A protocol based on physico‐chemical, microbiological, and biomolecular tools was established. Preliminary results revealed the presence of fungal contamination that was primarily located on the inner surface of the 6th and 7th scripts on the black carbographic ribbon. One fungal strain was isolated and identified by universal ITS‐PCR primer and rDNA sequencing as Alternaria infectoria strain NIS4. Fungal growth was monitored for 3 weeks in the laboratory under different environmental conditions (temperature, open‐closed system, and substrate). The A. infectoria NIS4 strain exhibited the best growth at 28°C under a closed system with RH near saturation. We also noted that the fungal growth was abundant at 15°C. Moreover, this fungus (a potential human pathogen) possessed the ability to colonize the surface of the new carbographic ribbon even when using mineral medium; however, this only occurred in a closed system environment and not in open systems due to rapid desiccation. Under our experimental conditions, the A. infectoria NIS4 strain could degrade gelatin as an organic matter present in trace amounts that are often used as a binder in a carbographic ribbon emulsions. The results revealed that the isolated microorganism was the major biological candidate capable of altering the investigated carbographic ribbon; however, these alterations could only occur under favourable environmental conditions. Aims Identify the cause of microbial alterations on a carbographic ribbon in a typewriter used in a hypogean Italian criminal house named “covo.” Methods and Results The isolation and identification of biodeteriogens (Alternaria infectoria NIS4) were performed using both culture‐dependent and‐independent methods, including ITS regions‐primed PCR and rDNA techniques. Environmental scanning electron microscopy (ESEM) and optical observations were also performed. Growth tests and biodeterioration simulation tests on carbo