Streptococcus pneumoniae, Streptococcus pyogenes (GAS), and Streptococcus agalactiae (GBS) are bacteria that can cause a range of infections, some of them life-threatening. This review examines the spread of antibiotic resistance and its mechanisms against antibiotics for streptococcal infections. Data on high-level penicillin-resistant invasive pneumococci have been found in Brazil (42.8%) and Japan (77%). The resistance is caused by mutations in genes that encode penicillin-binding proteins. Similarly, GAS and GBS strains reported from Asia, the USA, and Africa have undergone similar transformations in PBPs. Resistance to major alternatives of penicillins, macrolides, and lincosamides has become widespread among pneumococci and streptococci, especially in Asia (70–95%). The combination of several emm types with erm(B) is associated with the development of high-level macrolide resistance in GAS. Major mechanisms are ribosomal target modifications encoded by erm genes, ribosomal alterations, and active efflux pumps that regulate antibiotic entry due to mefA/E and msrD genes. Tetracycline resistance for streptococci in different countries varied from 22.4% in the USA to 83.7/100% in China, due to tet genes. Combined tetracycline/macrolide resistance is usually linked with the insertion of ermB into the transposon carrying tetM. New quinolone resistance is increasing by between 11.5 and 47.9% in Asia and Europe. The mechanism of quinolone resistance is based on mutations in gyrA/B, determinants for DNA gyrase, or parC/E encoding topoisomerase IV. The results for antibiotic resistance are alarming, and urgently call for increased monitoring of this problem and precautionary measures for control to prevent the spread of resistant mutant strains.

Streptococcus agalactiae ( group B Streptococcus , GBS) is an important human and animal pathogen. In recent years, the number of streptococcal isolates resistant to antimicrobial agents has increased in many parts of the world. Various mechanisms of antimicrobial resistance and capsular serotypes of GBS with different geographical distributions can be found. A prospective cross-sectional study was conducted from September 2021 to May 2024. The survey included 257 GBS isolates from Bulgarian inpatients and outpatients with streptococcal infections. Antibiotic resistance genes and capsular serotypes were detected and evaluated using polymerase chain reaction (PCR). We classified GBS isolates into groups according to their source as vaginal samples (191) and extra-vaginal samples (66), subdivided as invasive (36) and non-invasive specimens (30). The most common serotypes were Ia (26.5%), III (20.2%), and V (19.8%). Antimicrobial susceptibility testing revealed that all examined isolates were susceptible to penicillin and vancomycin. Resistance to macrolides, lincosamides, and tetracyclines was observed in 60.3%, 24.9%, and 89.1% of the isolates. The distribution of phenotypes was cMLSb 47.4%, iMLSb 30.8%, M-type 21.2%, and L-type 0.6%. PCR analysis revealed nine genes associated with macrolide and lincosamide resistance: ermB (54.2%), ermA / TR (30.3%), mefA (20.7%), ermC (18.1%), msrD (14.8%), mefE (8.4%), IsaC (8.4%), InuB (7.7%), and IsaE (6.5%). Two genes linked to tetracycline resistance tetM (89.1%) and tetO (14.4%) were detected. Compared to the previous period, we observed increased antibiotic resistance. There was no statistical significance between the distribution of serotypes and antimicrobial non-susceptibility depending on the sample source.

Moraxella catarrhalis has been recognized as an important cause of upper respiratory tract and middle ear infections in children, as well as chronic obstructive pulmonary disease and chronic bronchitis in adults. We aim to study the clonal structure, antimicrobial resistance, and serotypes of M. catarrhalis strains recovered from patients of different ages. Nasopharyngeal swabs, middle ear fluid, and sputum samples were collected. In vitro susceptibility testing was performed according to EUCAST criteria. The monoclonal Ab hybridoma technique was used for serotyping. All strains were subjected to MLST. The studied population demonstrated susceptibility to all tested antimicrobials M. catarrhalis strains, with the majority being serotype A (90.4%), followed by B (6.8%), and C (2.7%). We observed a predominant clonal complex CC224 (21.9%) along with other clusters including CC141 (8.2%), CC184 (8.2%), CC449 (6.8%), CC390 (5.5%), and CC67 (2.7%). Two primary founders, namely, ST224 and ST141, were identified. The analyzed genetic lineages displayed diversity but revealed the predominance of two main clusters, CC224 and CC141, encompassing multidrug-resistant sequence types distributed in other regions. These data underscore the need for ongoing epidemiological monitoring of successfully circulating clones and the implementation of adequate antibiotic policies to limit or delay the spread of multidrug-resistant strains in our region.

The study aimed to evaluate the presence of pili in non-invasive pediatric pneumococcal isolates and to elucidate possible links with genetic lineages, serotypes, and antimicrobial resistance. We examined 147 Streptococcus pneumoniae isolates from children with respiratory tract infections and acute otitis media. Serotyping was performed by latex agglutination and capsule swelling reaction. Serogroup 6 was subjected to PCR-serotyping. Minimum inhibitory concentrations were determined according to EUCAST breakpoints. PCRs for rlrA and pitB genes were performed to detect a presence of type 1 and type 2 pili. MLST was conducted to define the clonal structure of the piliated strains. Almost all children (96.5%) were vaccinated with the pneumococcal conjugate vaccine PCV10. We detected 76.8% non-PCV10 – serotypes (NVTs) and 14.3% PCV10 serotypes. The predominant serotypes were NVTs: 19A (14.3%), 6C (12.2%), 3 (9.5%), 15A (7.5%) and 6A (6.8%). PI-1 was detected among 10.9% non-PCV10 serotypes 6A, 6C, and 19A and 6.1% PCV10 serotypes 19F and 23F. Type 2 pili were not found in the studied population. High levels of antimicrobial nonsusceptibility to erythromycin (58.5%), oral penicillin (55.8%), clindamycin (46.9%), trimethoprim-sulfamethoxazole (45.6%), tetracycline (39.5%) and ceftriaxone (16.3%) were revealed. The multidrug-resistant strains (MDR) were 55.1%. MLST represented 18 STs and three CCs among the piliated pneumococci: CC386, CC320, and CC81. More than half of the piliated strains (56.0%) belonged to successfully circulating international clones. PI-1 was associated mainly with MDR 6A, 6C, 19A, 19F, and 23F isolates from the widespread CC386, CC320, and CC81.

The SARS-CoV-2 pandemic demonstrated the importance of proper understanding of the epidemiology of viral infections in the modern cosmopolitan world. In this retrospective study, we analyzed different factors associated with the spread of SARS-CoV-2 in the Sandanski municipality, a small and isolated region of Bulgaria, with a classical continental Mediterranean climate. We collected 418 serum samples from people without symptoms of SARS-CoV-2 infection or other respiratory diseases. The samples were tested for COVID-19 markers with qualitative and quantitative ELISA for anti-N and anti-S antibodies, and a rapid test for (IgM/G) antibodies. The methods were applied to complement each other with the different characteristics each of them has, thus allowing us to perform more accurate and more comprehensive detection of serum antibodies and to analyze the virus spread. We compared the results with the official government data for the SARS-CoV-2 distribution in Bulgaria. Based on the obtained results and available literature data, we discuss the importance of popular diagnostic methods, the role of the climate, the travel of people and pets, psychological stress and the individual reaction of subjects related to the spread of the virus.