We aimed to assess the prevalence of nasopharyngeal pneumococcal carriage and to determine serotype distribution, antibiotic susceptibility patterns, and evolutionary dynamics of Streptococcus pneumoniae isolates in healthy under-five children. Nasopharyngeal swabs were collected from healthy children over three survey periods between 2020 and 2022. All pneumococcal isolates were serotyped and tested for antimicrobial susceptibility. A total of 309 S. pneumoniae isolates were collected, with an overall prevalence of nasopharyngeal pneumococcal carriage of 24.4% (CI95%: [22–26.8%]). These isolates were classified into 25 different serotypes. The most common serotypes were 14 (14.9%), 19F (12%), 6B (10.4%), and 23F (7.4%), which are covered by the PCV10 vaccine, as well as 19A (8.4%) and 6A (7.8%), which are covered by the PCV13 vaccine. A significant decrease in the proportion of serotype 19F (p = 0.001) and an increase in serotypes 19A (p = 0.034) and 6A (p = 0.029) were observed between the three survey periods. Multidrug resistance (MDR) was noted for 56.6% of the isolates. A significant association with antimicrobial resistance was observed for the most frequent serotypes, mainly serotype 19A. In conclusion, one-quarter of healthy under-five children in Tunisia carried S. pneumoniae in their nasopharynx. A dominance of vaccine serotypes significantly associated with antimicrobial resistance was recorded.

Purpose. Invasive pneumococcal disease (IPD) remains a major global public health concern due to its high morbidity and mortality rates, particularly among children and the elderly. This study aimed to apply whole-genome sequencing (WGS) to characterize Streptococcus pneumoniae strains responsible for IPD in south Tunisia, including serotype distribution, clonal relationship and antimicrobial resistance (AMR) profiles. Methods. A total of 148 IPD S. pneumoniae isolates were collected from the microbiology laboratory at Habib Bourguiba University Hospital in Sfax, Tunisia, between 2012 and 2022. These isolates underwent WGS using Illumina technology. Bioinformatic analyses were performed to determine serotype distribution, sequence types (STs), Global Pneumococcal Sequence Clusters (GPSCs), phylogenetic relationships and AMR determinants. Results. Twenty-six different serotypes were identified, with the most prevalent being 14 (18%), 3 (13%), 19A (12%) and 19F (11%). The isolates showed high genomic diversity, as they belonged to 32 GPSCs and 59 STs. The most common GPSCs were GPSC-6, GPSC-10 and GPSC-44, associated with serotypes 14, 19A and 19F, respectively. The most frequent STs were ST2918, ST179 and ST3772. The most common resistance genes were ermB (53%) and tetM (55%), which were linked to resistance against erythromycin and tetracycline, respectively. There was a considerable concordance between WGS-based and phenotypic resistance profiles for most tested antibiotics, with few major and very major errors for most antibiotics. Temporal analysis showed a decline in serotypes 19F and 9V throughout the study period, which was associated with slight decreases in GPSC-6 and GPSC-44, while serotype 19A and GPSC-10 sharply increased. Conclusion. This study highlights the substantial genomic diversity, serotype distribution and high prevalence of AMR among IPD S. pneumoniae isolates in south Tunisia, underscoring the need for continued surveillance and effective vaccination strategies to combat this persistent public health threat.

Background/Objectives: As antimicrobial resistance patterns of Gram-negative bacteria change over time, this study aimed to analyze the antimicrobial susceptibility trends of Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii isolates in Tunisia. Methods: From 1999 to 2019, non-duplicate isolates of Gram-negative bacteria were collected from 11 Tunisian hospitals as part of an antimicrobial resistance surveillance program. Antimicrobial susceptibility testing was performed using the disk diffusion method according to the European Committee on Antimicrobial Susceptibility Testing guidelines. Results: Out of 213,434 isolates collected during the study period, 58.8% were E. coli, 22% were K. pneumoniae, 14.4% were A. baumannii, and 4.8% were P. aeruginosa, with 67% of the isolates sourced from urine samples. E. coli showed a significant increase in resistance to third-generation cephalosporins (3GC), from 5.4% in 2004 to 16.5% in 2019, but K. pneumoniae displayed a rising trend of resistance to imipenem, from 1% in 2005 to 18.6% in 2019; meanwhile, amikacin remained effective against K. pneumoniae isolates. P. aeruginosa did not exhibit a significant change in resistance to imipenem. A. baumannii had a high resistance rate to imipenem that increased from 34.5% in 2008 to 84.2% in 2019 and had low susceptibility rates to all other antibiotics tested. Conclusions: This study reveals high carbapenem resistance among K. pneumoniae and A. baumannii in Tunisia. A. baumannii shows alarming multidrug resistance that requires urgent control measures.

CTX-M beta-lactamases have become the predominant extended-spectrum beta-lactamases (ESBLs) globally, contributing to increased patient morbidity, mortality, and healthcare costs. This study investigated the prevalence of biofilm formation and CTX-M genes in Klebsiella pneumoniae strains isolated from Baghdad hospitals, aiming to better understand antimicrobial resistance mechanisms and support the development of targeted interventions. A total of 300 samples were collected from various clinical and hospital sources, and antibiotic susceptibility testing was performed using the Kirby–Bauer disc diffusion method. ESBL production was also confirmed using specifically designed primers. Platanus orientalis Linn extract was evaluated for its antimicrobial and antibiofilm activity against K. pneumoniae isolates. The results showed significant resistance to the majority of antibiotics, including cefotaxime, gentamicin, levofloxacin, ceftazidime, and ceftriaxone. A high prevalence of the CTX-M gene (100%) was detected in the isolates, with the most frequent alleles being blaCTX-M-15 (65.2%) and blaCTX-M-1 (30%). Furthermore, 95.6% of the isolates were capable of forming biofilms. However, when treated with P. orientalis Linn extract, most isolates exhibited reduced biofilm production, becoming weak biofilm producers. Phytochemical analysis of P. orientalis Linn revealed significant amounts of phenolic compounds, tannins, and glycosides, as well as the presence of alkaloids and carbohydrates. Overall, this study demonstrates a correlation between CTX-M production and biofilm-forming ability in K. pneumoniae and highlights the potential role of P. orientalis Linn extract in combating antibiotic-resistant infections.

The antimicrobial resistance (AMR) surveillance network has been monitoring bloodstream bacterial pathogens and their resistance since 1999 in Tunisia. We report the long-term trends in the distribution of bloodstream bacterial pathogens and their resistance patterns from this surveillance database. We analyzed antibiotic resistance rates in 11 tertiary teaching hospital laboratories under the AMR surveillance network during 2011–2023, focusing on six priority bacterial pathogens, using the Cochrane–Armitage test for trend analysis. Of 22,795 isolates, K. pneumoniae (38.5%) was the most common, followed by S. aureus (20.4%), E. coli (13.6%), and A. baumannii (10.3%). Carbapenem resistance was highest in A. baumannii (77%), followed by Pseudomonas aeruginosa (29.3%), K. pneumoniae (19.4%), and Enterobacter cloacae (6.8%). Carbapenem-resistant Enterobacterales and third-generation cephalosporin-resistant Enterobacterales (3GCREB) increased from 10.6% to 26.3% (p-value < 0.001), and from 39% to 50.2%, respectively, during 2011–2023 (p-value < 0.001). Vancomycin resistance (38.3%) and the emergence of linezolid resistance in 2019 (2.4%) were reported in E. faecium isolates. Resistance to carbapenems and 3GC is a major challenge to controlling BSI in Tunisia. The national AMR surveillance network helps monitor annual patterns and guides empirical therapy. An integrated database combining clinical profiles and resistance data via real-time data-sharing platforms could improve clinical decision-making.