# Bacterial Contamination of Parcel Vending Machines in Lublin, Poland
## 3 Results
### Qualitative Microbiological Analysis of the Surfaces of Parcel Vending Machines  
In this study, a total of 140 bacterial isolates were collected from the surfaces of PVMs in the urban area of the eastern Polish city of Lublin (Figure 4A). In the diagnostic workflow of the isolates, most of the bacterial species were analyzed and initially identified using routine diagnostic methods, including colony morphology and Gram staining, and all of them were analyzed using the MALDI-TOF MS system. Then, the results were verified to ensure that the macroscopic and microscopic characteristics of the isolates were in concordance with the results obtained with mass spectrometry. The results of the MALDI-TOF MS spectral profiles presented below indicated reliable or probable identification at the species level, while 6.4% (9/140) of the bacterial isolates had an unreliable identification. The most prevalent were rod-shaped _Bacillus_ spp. (74/140, 52.9%), comprising _B. licheniformis_ (12/74, 16.2%), _B. cereus_ (9/74, 12.2%) and _B. safensis_ (8/74, 10.8%; Figure 4B), followed by _Staphylococcus_ spp. (15/140, 10.7%), _S. warneri_, and _S. capitits_ (4/15, 26.7% each; Figure 4C) especially. Figure 3: **(A)** The correlation between the population density in analyzed city districts and the microbial contamination of parcel machines. **(B)** Microbial contamination of parcel vending machines, according to the company. **(C)** Visualization of average means and standard deviation of bacterial counts on touchscreens of parcel vending machines, according to the company—an asterisk denotes a statistically significant in the average bacterial count on PVMs between districts. **(D)** Percentage of parcel vending machines belonging to different companies. In all 16 analyzed city districts, only in 4 of them (Southern Czechow, Srodmiescie, Southern Czuby, Southern Weglin) were Gram-negative rods identified, namely _Pantoea agglomerans_ (5/140, 3.6%), _Pseudomonas_ spp. (4/140, 2.9%), _P. koreensis_ (2/140, 1.4%), and _Escherichia coli_ (1/140, 0.7%). _Fillifactor villosus_, a periodontal pathogen with a strong ability to adhere to various surfaces, was also found at a frequency of 3.6% (5/140). In the course of the study, numerous bacteria typical of the external environment were also identified, such as _Arthobacter gandavensis_, _Aromatoleum pretroleum_, _Bacillus horikoshii_, _Clostridium sporogenes_, _Exiguobacterium aurantiacum_, _Lysinibacillus fusiformis_, _Mycobacterium oleivorans_, _Paenibacillus amylolyticus_, _Paenibacillus lautus_, _Rhizobium radiobacter_, and _Solibacillus silvestris_, which were limited to 2.0% of all isolates collected. Most are commonly found in a variety of locations including soil, sediment in both marine and freshwater environments, water, rhizosphere, plant material, sediment, caves, humus, compost, rhizosphere, food, plants, insect larvae, and clinical specimens. Next, dendrograms were created to illustrate the phylogenetic relationships between bacterial strains isolated from PVMs. The analysis demonstrated a high diversity of _Staphylococcus_ species, with the most represented _Staphylococcus epidermidis_, _S. capitis_, _S. varneri_, and _S. hominis_ (Figure 5). These strains differed in their degree of relatedness, as expressed by the distance levels on the dendrogram. Strains such as _S. epidermidis_ 4A_1 and _S. epidermidis_ 7A_2 showed minimal divergence, indicating that they are closely related and may originate from similar environmental conditions or exhibit similar adaptive characteristics. In contrast, strains like _S. varneri_ and _S. capitis_ exhibited greater proteomic  
Figure 4: Distribution of all identified bacterial isolates (**A**) or bacilli (**B**) and staphylococci (**C**) species isolated from touchscreens of parcel vending machines located in Lublin, Poland. Percentages may not total 100 due to rounding. distances, reflecting a higher level of diversity between these species. The dendrogram also highlights the presence of less common species, such as _S. felis_ and _S.