Hydrogen sulfide (H₂S) detection is a screening method for distinguishing and identifying Salmonella strains from other bacteria in the intestine. Incidences of H₂S-negative Salmonella have recently been reported in different countries. Although a high resistance rate against antimicrobial agents has been reported for H₂S-positive Salmonella in many regions of the world, there is increasing evidence that high resistance to antibiotics has also increased in many H₂S-negative Salmonella isolates. In this study, molecular characterisation of three H₂S-negative Salmonella Havana, isolated from cloacal swab samples of broiler chickens, was performed. The phsA, phsB and phsC genes of the phs operon, which is responsible for hydrogen sulfide production, were amplified. Sequence analysis was then performed to identify mutations in the gene cluster. The antimicrobial resistance profiles of the isolates were determined by disc diffusion. Molecular characterisation was performed by multilocus sequence typing (MLST) and pulsed field gel electrophoresis (PFGE). The sequence analysis showed identified five point mutations in the phsA gene and one point mutation in the phsC gene in all isolates. The antibiotic resistance profile showed that the strains were resistant to cefoxitin and ceftazidime. MLST analysis showed that all strains belonged to sequence type (ST) 1621. This study is the first to report the H₂S-negative S. Havana serotype.

硫化氢（H ₂ S）检测是一种从肠中其他细菌中区分和鉴定沙门氏菌菌株的筛选方法。最近在不同国家报道了H ₂ S阴性沙门氏菌的发病率。尽管在世界许多地区已报告了H ₂ S阳性沙门氏菌对抗菌剂的高耐药率，但越来越多的证据表明，在许多H ₂ S阴性沙门氏菌分离物中对抗生素的高耐药性也有所增加。在这项研究中，三种H ₂ S阴性沙门氏菌的分子表征从肉鸡的泄殖腔拭子样本中分离出哈瓦那。负责硫化氢产生的phs操纵子的phsA，phsB和phsC基因被扩增。然后进行序列分析以鉴定基因簇中的突变。分离物的抗药性通过圆盘扩散来确定。通过多基因座序列分型（MLST）和脉冲场凝胶电泳（PFGE）进行分子表征。序列分析表明在phsA基因中鉴定出5个点突变，在phsC中鉴定出1个点突变所有分离物中的基因。抗生素抗性谱显示该菌株对头孢西丁和头孢他啶具有抗性。MLST分析表明，所有的菌株属于序列类型（ST）1621这项研究是首次报道为H ₂ S-负S.哈瓦那血清型。