This is probably the first reported outbreak of multidrug/carbapenem-resistant Klebsiella infection involving the OXA-48 gene from Saudi Arabia. Although the presence of ESBLs such as OXA, CTX-M, TEM, and SHV are predictable reasons for resistance, variations in the Omp-36 gene might also have precipitated this phenomenon. Disruption of the Omp-36 sequence by large insertional elements, the insertion of two amino acids in a very crucial part of this protein, and the presence of a premature stop codon in one isolate might have rendered this protein incomplete and non-functional. The study also demonstrated that more than one type of clone was responsible for this reported apparent outbreak and that ST29, a clone not reported from this region before, was the major clone responsible.

BackgroundThe nexus between resistance determinants, plasmid type, and clonality appears to play a crucial role in the dissemination and survival of carbapenem-resistant Klebsiella pneumoniae (CRKP). The incidence of infections involving CRKP in Saudi Arabia is increasing and there is a need for detailed molecular profiling of this pathogen for CRKP surveillance and control.MethodsThe resistance determinants of 71 non-redundant CRKP isolates were investigated by polymerase chain reaction (PCR) and sequencing. Plasmid typing was performed using PCR-based replicon typing and the clonality of isolates was determined by multilocus sequence typing. Capsular polysaccharide synthesis genes and other virulence factors were examined using multiplex PCR. Diversity was calculated using DIVEIN, clonal relationship was determined using eBURST, and phylogenetic analysis was performed using SplitsTree4.ResultsA polyclonal OXA-48 gene alone was the most common carbapenemase detected in 48/71 (67.6%) isolates followed by NDM-1 alone in 9/71 (12.7%) isolates. Coproduction of OXA-48 and NDM-1 was observed in 6/71 (8.5%) isolates. Both carbapenemase genes could be transferred into an Escherichia coli recipient. CTX-M-15 was the most abundant extended-spectrum β-lactamase gene detected in 47/71 (66.2%) isolates, whereas clone-specific CTX-M-14 (ST-199 and -709) was found in 15/71 (21%) isolates. Sixty-seven of 71 isolates were positive for one or more plasmid replicons. The replicons detected were: IncFII; IncFIIK; IncFIA; IncFIB; L/M; IncI1; and IncN. FIIK and L/M were predominant, with 69 and 67% positivity, respectively. All isolates were negative for the magA (K1), rmpA, and K2 genes and presented a non-hypermucoviscous phenotype.ConclusionA polyclonal CRKP reservoir of sequence types (STs)-37, − 199, and − 152 was observed and ST-152 appeared to be a “frequent carrier” of the NDM-1 gene. ST-199, a singleton not previously reported, showed a sequence diversity suggestive of positive selection. A significant association was evident between resistance determinants and the clonal types of K. pneumoniae: all ST-152 isolates were positive for NDM-1 but negative for OXA-48; ST-199 isolates were positive for OXA-48 but negative for NDM-1; and ST-709 and -199 isolates were positive for CTX-M-14. The incidence of certain clonal types in large numbers predicts an outbreak-like situation and warrants stringent surveillance and infection control.Electronic supplementary materialThe online version of this article (10.1186/s12879-018-3114-9) contains supplementary material, which is available to authorized users.

Non-typhoidal Salmonella (NTS) strains are Gram negative bacterial pathogens that are associated with foodborne illness worldwide. During the process of infection, Salmonella uses two molecular injectisomes known as Type 3 Secretion Systems (T3SS) to secrete virulence factors that are encoded by Salmonella Pathogenicity Island-1 (SPI-1) and SPI-2 into host cells. These secretion systems play a major role in virulence, as shown in various animal models, but little is known about their role in human infections. In Saudi Arabia, NTS strains frequently cause human infections but data regarding these pathogenic strains is fairly limited. The aim of this study was to characterize Salmonella human clinical isolates in Riyadh, Saudi Arabia, by determining their serotype, testing for the presence of SPI-1 and SPI-2 genes and to determine the antibiotic resistance profiles of these strains. Using the rapid Check and Trace Salmonella ™ (CTS) system our results demonstrate that S . Enteritidis and S . Typhimurium were the predominant serovars, followed by S . Livingstone, S . Kentucky and S . Poona among a list of 36 serovars reported for the first time in the country. In addition, SPI-1 genes were detected in 99% of the isolates, while the sifA gene (SPI-2) was not detected in 13.5% of the isolates. These results suggest that both the SPI-1 and SPI-2 virulence determinants are important for human infection. Moreover, we report the presence of a Multi-Drug (MDR) carbapenem resistant S . Kentucky isolate harboring the bla OXA−48 gene not reported previously in Saudi Arabia.