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Background: The emergence and spread of carbapenem-resistant Acinetobacter baumannii are critical in hospitals, particularly in intensive care units (ICUs), which represents a public health concern worldwide. In this study, we investigated the molecular epidemiology of multi-drug resistant A. baumannii (MDR-AB) in Dakar, Senegal. Methods. The A. baumannii was isolated from Eosin Methylene Blue Agar culture and identified using API 20NE strip test and MALDI-TOF. The antimicrobial susceptibility testing was performed using the disk diffusion method. Simplex and multiplex-polymerase chain reactions with appropriate primers were used to detect and sequence the following β-lactamase genes: Two class D carbapenem hydrolyzing oxacillinases (blaOXA-51 and blaOXA-23), three class B metallo-β-lactamase genes (blaIMP, blaVIM and blaNDM), and five class A β-lactamase genes (blaPER, blaSHV, blaVEB, blaTEM, and blaGES). Results: A total of 29 strains of MDR-AB were isolated from patients hospitalized at Aristide Le Dantec University teaching hospital in Dakar, Senegal. Among the 29 MDR-AB strains isolated, 11 (37.9%) were isolated from ICUs, 5 (17.2%) from pediatric surgery, and 13 (44.8%) from other departments. The MDR strains were isolated from urine and pus samples with 12 (41.4%) and 9 (31.0%), respectively. All isolates were positive for the A. baumannii specific gene blaOXA-51. The blaOXA-51 and blaOXA-23 genes coexisted in 26 (89.65%) of the strains. The blaIMP and blaVIM genes were not detected among the selected strains. Moreover1 (3.4%) strain elicited the gene coding for metallo-β-lactamase NDM-1. 2 (6.9%) isolates turned out to produce the penicillinase TEM-2. Conclusions: Carbapenem resistance in Senegalese strains of A. baumannii is predominantly due to the worldwide disseminated gene blaOXA-23, with a subset of strains due to NDM-1 and TEM-2. Systemic molecular surveillance network should be established for further efficient monitoring of MDR strains in Senegal.

Extra-intestinal pathogenic Escherichia coli (ExPEC), a predominant Gram-negative bacterial pathogen, express a wide range of virulence factors and is responsible of several diseases including urinary tract infections (UTI), nosocomial pneumonia, bacteremia, and neonatal meningitis. ExPEC isolates are often multidrug resistant (MDR) and clones producing extended-spectrum beta-lactamases (ESBL) are increasingly reported all over the world.Seventy-eight clinical ExPEC strains were selected for this study. The majority was from UTIs (n=51), while the rest (n=27) was from pus, sputum, bronchial fluid and vaginal samples (non-uropathogenic ExPEC). Interestingly, 49 out of the 78 ExPEC isolates where considered as community-acquired (CA) and 29 hospital-acquired (HA) bacteria. Antibiotic susceptibility testing was performed using the Kirby-Bauer disc diffusion method. Standard polymerase chain reaction (PCR) was used to screen major ESBL genes (blaCTX-M, blaOXA-1, blaTEM, blaSHV) and blaCTX-M variants (blaCTX-M-1, blaCTX-M-9, blaCTX-M-15, blaCTX-M-25).All the ExPEC strains were resistant to ampicillin, ticarcillin, amoxicillin/clavulanic acid combination, cefalotin, cefotaxime, ceftazidime, cefepime and aztreonam, but showed a high susceptibity to fosfomycin (98.7%, n = 77), ertapenem (96.2%, n = 75), and imipenem (100%). Moreover, isolates harbored at least one ESBL gene, including blaCTX-M (98.7%), blaOXA-1 (78.2%), blaTEM (44.9%) and blaSHV (3.8%). The CTX-M variants were also found with the predominance of blaCTX-M-1 (90.9%) and blaCTX-M-15 (90.9%) followed by blaCTX-M-9 (11.7%), while blaCTX-M-25 was not detected.Despite the resistance to most of the tested antibiotics, ExPEC isolates showed fortunately a good susceptibility to fosfomycin and carbapenems. blaCTX-M (blaCTX-M1, blaCTX-M15) and blaOXA-1 seem to be E. coli major ESBL genes circulating in Senegal. No significant difference was noted when comparing prevalence of ESBL genes detected from CA and HA strains, and from UPEC and non-uropathogenic ExPEC. The high level of resistance to antimicrobials observed stresses the need of establishing an epidemiological surveillance of antimicrobial resistance in both community and hospital settings.