Introduction: The increasing of multidrug resistant Enterobacter pathogens to the last-line drugs including colistin, constitutes a major threat to public health worldwide especially in low-income countries, where last-line treatment is often unavailable.

Methodology: we conducted a phenotypic and molecular characterization of clinical Enterobacter spp. isolates from blood in Maputo Central Hospital, Hospital Provincial of Quelimane and Hospital Central of Quelimane. Isolates were identified by Maldi-ToF, antimicrobial Susceptibility Testing was performed by VITEK 2 system. Half of isolates were analyzed by Polymerase Chain Reaction for β-lactamases genes, and four isolates by Whole-Genome Sequencing (WGS).

Results: In total 8 isolates of Enterobacter cloacae complex were identified, of which 50% were multidrug resistant and ESBL producers carrying variable combinations of β-lactamases (CTX-M-15, SHV-12, ACT-7, CMH-3, TEM-1B and OXA-1) and other resistance genes including aac(3)-IId, aac(6')-IIC, aph(3')-Ia, aph(3'')-Ib, and aph(6)-Id, aadA1 and aadA2 (aminoglycosides resistance); aac(6')Ib-cr and qnrB1 plasmid-mediated quinolone resistance; dfrA1, dfrA14 and dfrA19 (trimethoprim resistance); catA1, catB3 and catB7 (chloramphenicol resistance); sul1 and sul2 (sulfonamide resistance), tet(A) and tet(D) (tetracycline resistance); mph(A) and ereA (macrolides resistance); fosA (fosfomycin resistance). IncF, IncY and IncHI2 plasmid replicons were identified. ST84, ST125 and two novel Sequence Types were assigned. Notably, one isolate even susceptible to colistin carried mcr-9 gene (reduced susceptibility to colistin).

Conclusion: The silence of mcr-9 gene from colistin-susceptible E. cloacae complex evading phenotypic detection, may be a serious problem in medical settings, acting as reservoir of colistin resistance. Therefore, further surveillance by both phenotypic and molecular approaches are needed to understand the prevalence of mcr-9 gene and prevent its furtherdissemination among Enterobacteriaceae in Mozambique.

Keywords: E. cloacae complex, ESBL, AmpC, mcr-9, Mozambique