Reference Raman spectrum and mapping of Cryptosporidium parvum oocysts

Abstract

Cryptosporidium parvum is a protozoan parasite and among the most infectious diarrhea-causing pathogens, leading to severe health problems for malnourished children and immunocompromised individuals. Outbreaks are common even in developed countries, originating from water or food contamination and resulting in suffering and large costs for society. Therefore, robust, fast, and highly specific detection strategies of Cryptosporidium are needed.Label-free detection techniques such as Raman spectroscopy have been suggested; however, high-resolution reported spectra in the literature are limited. In this work, we report reference Raman spectra at 3 cm À1 resolution for viable and inactivated Cryptosporidium oocysts of the species C. parvum, gathered at a single oocyst level using a laser tweezers Raman spectroscopy system.We furthermore provide tentative Raman peak assignments for the Cryptosporidium oocysts, along with Raman mapping of the oocysts' heterogeneous internal structure. Finally, we compare the C. parvum Raman spectrum with other common enterotoxigenic pathogens: Escherichia coli, Vibrio cholerae, Bacillus cereus, and Clostridium difficile. Our results show a significant difference between C. parvum Raman spectra and the other pathogens.

Characterisation of Clostridioides difficile spore response to sodium hypochlorite using EM-imaging and Raman Spectroscopy

“…A typical Raman spectrum of a C. difficile spore in the 600-1400 cm −1 spectral range is shown on Figure 3A, with major peaks at 660, 825, 1001, 1017 and 1395 cm −1 . This is in line with the Raman spectrum of C. difficile spores described in literature [29,30,10]. The spectrum is dominated by the Raman peaks of calcium dipicolinic acid (CaDPA), a key chemical in the spore's wet heat resistance that makes up to 25 % of the dry weight of the spore core.…”

“…Spectra in this group are also similar to vegetative cells, as shown by the marked vegetative control spectrum. These spectra are also similar to other vegetative cell spectra, with resonant peaks at 1101, 1245 and 1319 cm −1 [10].…”

“…The spectrum is dominated by the Raman peaks of calcium dipicolinic acid (CaDPA), a key chemical in the spore's wet heat resistance that makes up to 25 % of the dry weight of the spore core. The reported peaks of CaDPA are 660, 825, 1017, 1395 and 1575 cm −1 , while the 1001 cm −1 is due to phenylalanine [31,29,32,10]. During germination, or if the spore body is damaged, the intensity of the CaDPA Raman peaks are significantly reduced or disappears completely as the spore loses its CaDPA store [15].…”

“…As proof of concept, Raman spectroscopy has been used successfully to detect spores and also to track chemical changes in the spore body in time series. For example, Raman spectroscopy has been successfully used to identify and distinguish different pathogens [10], identify spore strains [11], track the germination process [12,13], and characterize the impact of disinfection chemicals on the spore body with time [14,15]. Sodium hypochlorite is a common disinfection chemical used in hospitals and in homes [16].…”

A Lab-on-A-Chip Utilizing Microwaves for Bacterial Spore Disruption and Detection

“…5A. Group 1 shows spectra similar to those described in previous literature on spores, with distinct peaks at 660, 825, 1001, 1017 and 1395 cm − 1 (Kong et al, 2012;Wang et al, 2015a;Malyshev et al, 2022a). The main component of this spectra is CaDPA from the spore core, accounting for all of the above mentioned peaks except for the 1001 cm − 1 peak caused by phenylalanine in the spores' protein structures (Zhang et al, 2010).…”