The coast of the Bulgarian Black Sea is a popular summer holiday destination. The Dam of Iskar is the largest artificial dam in Bulgaria, with a capacity of 675 million m³. It is the main source of tap water for the capital Sofia and for irrigating the surrounding valley. There is a close relationship between the quality of aquatic ecosystems and human health as many infections are waterborne. Rapid molecular methods for the analysis of highly pathogenic bacteria have been developed for monitoring quality. Mycobacterial species can be isolated from waste, surface, recreational, ground and tap waters and human pathogenicity of nontuberculose mycobacteria (NTM) is well recognized. The objective of our study was to perform molecular analysis for key-pathogens, with a focus on mycobacteria, in water samples collected from the Black Sea and the Dam of Iskar. In a two year period, 38 water samples were collected—24 from the Dam of Iskar and 14 from the Black Sea coastal zone. Fifty liter water samples were concentrated by ultrafiltration. Molecular analysis for 15 pathogens, including all species of genus Mycobacterium was performed. Our results showed presence of Vibrio spp. in the Black Sea. Rotavirus A was also identified in four samples from the Dam of Iskar. Toxigenic Escherichia coli was present in both locations, based on markers for stx1 and stx2 genes. No detectable amounts of Cryptosporidium were detected in either location using immunomagnetic separation and fluorescence microscopy. Furthermore, mass spectrometry analyses did not detect key cyanobacterial toxins. On the basis of the results obtained we can conclude that for the period 2012–2014 no Mycobacterium species were present in the water samples. During the study period no cases of waterborne infections were reported.

Introduction: An effective vaccination strategy requires monitoring serotype changes by geography and age. This study analyzed Streptococcus pneumoniae serotypes in healthy children under 6 years of age vaccinated with PCV10 in Bulgaria from October 2021 to May 2025. Methods: A total of 569 children were screened for the lytA and cpsA genes viareal-time polymerase chain reaction (real-time PCR). Positive samples were typed using relevant kits, and 76 serotypes/serogroups of S. pneumoniae were identified. Results: Nasopharyngeal swabs from 232 children (40.8%) were found to carry S. pneumoniae, and a total of 255 serotypes were detected, with 19B/19C (17.2%), 6C (10.7%), and 15B/15C (9.8%) being the most prevalent. Of these, 91 serotypes (15.9%) were included in at least one vaccine, while the remaining 164 serotypes (25.4%) were not. The carriage rate reduced to 22% in 2023 but increased to 47% in 2024. Overall, younger children had lower carriage rates (p < 0.05), with serotype 6C being more common in children under 12 months of age (25%). Approximately 9.1% of pneumococcal carriage cases involved co-detected serotypes, with significantly higher co-detection rates for 19B/19C, 15B/15C, 10B, 10F/C, 23B, 7C/40, 23A, and 24A compared with mono-detection rates (p < 0.05). Conclusions: 19B/19C, 6C, 15B/15C, and 19A were identified as the main serotypes. Children over 3 years of age were also more likely to carry multiple pneumococci. These findings emphasize the need to reassess childhood vaccination strategies to curb the spread of antibiotic-resistant serotypes.

Whooping cough is a vaccine-preventable, acute respiratory disease caused by the gram-negative bacterium Bordetella pertussis. In recent years there has been a worldwide reccurrence of pertussis infection. The most vulnerable group in society are infants under one year of age, they are at the greatest risk of severe complications or even death. Whooping cough is usually associated with infection caused by B. pertussis, but Bordetella parapertussis can also cause pertussis-like symptoms. The disease is known as parapertussisл Clinical data alone are not sufficient to differentiate between the two infections. Modern, fast and reliable diagnostic is .needed. Bordetella holmesii, viral infections caused by RSV, adenovirus, etc. can present with pertussis-like symptoms and should be diagnosed and treated accordingly. The aim of this study is to present a clinical case of a child with pertussis infection followed by parapertussis infection. To diagnose and differentiate the two infections, a real-time PCR molecular genetic method was used to detect the genes specific for the causative agents. Pertussis vaccination does not protect against B. parapertussis infections, and cross-immunity between the two bacteria has not been observed. Therefore, in the presence of pertussis-like symptoms (paroxysms of persistent cough, vomiting after coughing), it is advisable to differentiate between B. pertussis and B.parapertussis infection, especially in populations with high pertussis vaccination coverage.

Background: An effective vaccination strategy requires monitoring serotype changes by geography and age. This study analyzed Streptococcus pneumoniae serotypes in healthy children under 6 years of age vaccinated with PCV10 in Bulgaria from October 2021 to May 2025. Methods: A total of 569 children were screened for the lytA and cpsA genes viаreal-time polymerase chain reaction (real-time PCR). Positive samples were typed using relevant kits, and 76 serotypes/serogroups of S. pneumoniae were identified. Nasopharyngeal swabs from 232 children (40.8%) were found to carry S. pneumoniae, and a total of 255 serotypes were detected, with 19B/19C (17.2%), 6C (12%), and 15B/15C (8.15%) being the most prevalent. Of these, 91 serotypes (15.9%) were included in at least one vaccine, while the remaining 164 serotypes (25.4%) were not. The carriage rate reduced to 22% in 2023 but increased to 47% in 2024. Overall, younger children had lower carriage rates (p < 0.05), with serotype 6C being more common in children under 12 months of age (25%). Approximately 9.1% of pneumococcal carriage cases involved co-detected serotypes, with significantly higher co-detection rates for 19B/19C, 15B/15C, 10B, 10F/C, 23B, 7C/40, 23A, and 24A compared with mono-detection rates (p < 0.05). Conclusions: 19B/19C, 6C, 15B/15C, and 19A were identified as the main serotypes. Children over 3 years of age were also more likely to carry multiple pneumococci. These findings emphasize the need to reassess childhood vaccination strategies to curb the spread of antibiotic-resistant serotypes.