Centre for Microbiology Research, Kenya Medical Research Institute, Nairobi, Kenya.
Department of Medical Microbiology and Immunology, University of Nairobi, Nairobi, Kenya.
BMC Infect Dis. 2024 Oct 25;24(1):1205. doi: 10.1186/s12879-024-10104-w.
The emergence and persistence of multidrug-resistant (MDR) Salmonella Typhi (S. Typhi) infections is a significant global health problem. The carrier state of typhoid makes it prudent to conduct routine surveillance for both acute cases and carriers especially those caused by MDR S. Typhi. We report on the prevalence of MDR S. Typhi, resistance phenotypes and antimicrobial resistance genes detected in symptomatic and asymptomatic children living in informal settlements in Nairobi, Kenya.
215 archived presumed S. Typhi isolates from stool samples provided by children ≤ 16 years collected from 2013 to 2018 were revived in May, 2022 and confirmed using culture and antisera serotyping. The Kirby Bauer disc diffusion technique was used to test the S. Typhi against 14 antibiotics. The MDR S. Typhi (resistant to ampicillin, chloramphenicol and sulfamethoxazole trimethoprim) which in addition were also resistant to either a cephalosporin or a fluoroquinolone were analyzed for Beta lactams and quinolone resistance genes using polymerase chain reaction.
A total of 215 isolates were confirmed to be positively S. Typhi; of these, 105 (49%) and 110 (51%) were from symptomatic and asymptomatic children respectively. On average, S. Typhi resistance from asymptomatic and symptomatic children against 1st line drugs was observed at; 77% &70%, ampicillin; 60% & 64%, sulfamethoxazole-trimethoprim, and 45% & 54%, chloramphenicol respectively. Multi drug resistance was observed in 90 (42%) of the isolates, of these, 44 (49%) were isolated from symptomatic and 46 (51%) from asymptomatic children. Fifteen resistance phenotypes (p) were observed with, ampicillin/chloramphenicol/sulfamethoxazole-trimethoprim/nalidixic acid (amp/chl/sxt/na) as the most common among the symptomatic 43/90 (48%) and asymptomatic 55/90 (61%) children. The bla, AMR genes were detected in 37/44 (84%) S. Typhi isolates, out of this 18 (49%) were from symptomatic while 19 (51%) were from asymptomatic children respectively.
The carriage of MDR S. Typhi among the asymptomatic children is concerning as they can act as potential transmitters of the typhoid disease to unsuspecting children. These study findings highlight the need for continued surveillance of antimicrobial resistance and mass immunization of children living in these urban informal areas.
多重耐药（MDR）伤寒沙门氏菌（S. Typhi）感染的出现和持续是一个重大的全球健康问题。伤寒带菌者使对急性病例和带菌者（尤其是由 MDR S. Typhi 引起的）进行常规监测变得谨慎。我们报告了在肯尼亚内罗毕非正规住区生活的有症状和无症状儿童中检测到的 MDR S. Typhi、耐药表型和抗微生物药物耐药基因的流行情况。
2013 年至 2018 年间，从≤16 岁儿童提供的粪便样本中收集了 215 份推定的 S. Typhi 存档样本，这些样本于 2022 年 5 月复苏，并通过培养和抗血清血清分型进行确认。使用 Kirby Bauer 圆盘扩散技术对 S. Typhi 进行了 14 种抗生素的检测。除了对头孢菌素或氟喹诺酮类药物耐药外，还对 MDR S. Typhi（对氨苄西林、氯霉素和磺胺甲恶唑-甲氧苄啶耐药）进行了β-内酰胺类和喹诺酮类耐药基因的分析，方法是聚合酶链反应。
共确认 215 株为阳性 S. Typhi；其中，105 株（49%）和 110 株（51%）分别来自有症状和无症状儿童。平均而言，无症状和有症状儿童的 S. Typhi 对一线药物的耐药率分别为：氨苄西林 77%和 70%，磺胺甲恶唑-甲氧苄啶 60%和 64%，氯霉素 45%和 54%。90 株（42%）存在多药耐药，其中 44 株（49%）分离自有症状儿童，46 株（51%）分离自无症状儿童。观察到 15 种耐药表型（p），其中氨苄西林/氯霉素/磺胺甲恶唑-甲氧苄啶/萘啶酸（amp/chl/sxt/na）在有症状儿童中最为常见，43/90（48%），在无症状儿童中为 55/90（61%）。在 44 株 S. Typhi 分离株中检测到 bla、AMR 基因，其中 18 株（49%）来自有症状儿童，19 株（51%）来自无症状儿童。
无症状儿童携带 MDR S. Typhi 令人担忧，因为他们可能成为伤寒病向毫无戒心的儿童传播的潜在传播者。这些研究结果强调需要继续监测抗微生物药物耐药性，并对居住在这些城市非正规地区的儿童进行大规模免疫接种。
