Virulence factors and mechanisms of antimicrobial resistance in Shigella strains from periurban areas of Lima (Peru)

Abstract

The study was aimed to describe the serotype, mechanisms of antimicrobial resistance, and virulence determinants in Shigella spp. isolated from Peruvian children. Eighty three Shigella spp. were serogrouped and serotyped being established the antibiotic susceptibility. The presence of 12 virulence factors (VF) and integrase 1 and 2, along with commonly found antibiotic resistance genes was established by PCR. S. flexneri was the most relevant serogroup (55 isolates, 66%), with serotype 2a most frequently detected (27 of 55, 49%), followed by S. boydii and S. sonnei at 12 isolates each (14%) and S. dysenteriae (4 isolates, 5%). Fifty isolates (60%) were multi-drug resistant (MDR) including 100% of S. sonnei and 64% of S. flexneri. Resistance levels were high to trimethoprim-sulfamethoxazole (86%), tetracycline (74%), ampicillin (67%), and chloramphenicol (65%). Six isolates showed decreased azithromycin susceptibility. No isolate was resistant to nalidixic acid, ciprofloxacin, nitrofurantoin, or ceftriaxone. The most frequent resistance genes were sul2 (95%), tet(B) (92%), cat (80%), dfrA1 (47%), blaOXA-1 like (40%), with intl1 and intl2 detected in 51 and 52% of the isolates, respectively. Thirty-one different VF profiles were observed, being the ipaH (100%), sen (77%), virA and icsA (75%) genes the most frequently found. Differences in the prevalence of VF were observed between species with S. flexneri isolates, particularly serotype 2a, possessing high numbers of VF. In conclusion, this study highlights the high heterogeneity of Shigella VF and resistance genes, and prevalence of MDR organisms within this geographic region.

<p>High Rates of Antimicrobial Resistance and Virulence Gene Distribution Among<em> Shigella</em> spp. Isolated from Pediatric Patients in Tehran, Iran</p>

“…In our study, all isolates harbored ipaH, which was described previously in other studies. 6,32,33 ipaB, ipaC, and ipaD are essential virulence factors to develop shigellosis, because they are necessary for invasion and intracellular survival. Furthermore, they regulate secretion and translocation of some other effector proteins and play a principle role in the intracellular actin polymerization and depolymerization.…”

Macrolide resistance mechanisms inEnterobacteriaceae: Focus on azithromycin

“…This gene has also frequently been detected in both hospital recovered and commensal E. coli of different geographical origins (Nguyen et al, 2009). It is interesting to note that in microorganisms in which only the mph(A) gene has been identified and no other mechanism of macrolide-resistance has been detected, the levels of resistance varies greatly (Boumghar-Bourtchai et al, 2008;Gaudreau et al, 2014;Lluque et al, 2015;Sj€ olund Karlsson et al, 2013). This may be related to both the presence of specific alleles which might have different inactivation levels, by the concomitant presence of unidentified macrolide-resistance mechanisms or by mph(A) gene expression levels.…”

Antimicrobial sensitivity trends and virulence genes in Shigella spp. from the Oceania region

“…The ipaH gene was present in all isolates, while 60% of isolates contained all four ipaBCD, virF, invE and ial genes (Table 2). It is important to note that the latter virulence genes (ipaBCD, virF, invE and ial) all contribute to facilitating and maintaining the spread and survival of Shigella during infection (Broach et al, 2012;Lluque et al 2015;Schroeder et al, 2008). Our results suggest that there is a strong association between all of these genes, as they were invariably present/absent as a set (Table 2).…”