Isolation and Identification of Staphylococcus xylosus in Nude Mice with Squamous Skin Scurfs

doi:10.12300/j.issn.1674-5817.2024.166

Abstract

Abstract:

Objective To isolate pathogenic bacteria from the skin of a nude mouse exhibiting squamous skin scurfs, and perform bacterial identification, traceability analysis, and pathogenicity studies to provide a new approach for the diagnosis of pathogens in nude mice with squamous skin scurfs. Methods Skin swab samples were collected from a nude mouse exhibiting squamous skin scurfs for nucleic acid testing, bacterial isolation and culture, biochemical identification, 16S rDNA gene amplification and sequencing, and whole genome sequencing to construct a phylogenetic tree. Fifteen BALB/c nude mice were randomized into a saline-treated control group, a high-concentration group treated with 1.8×10? CFU/mL of the isolated bacterial suspension, and a low-concentration group treated with 1.8×10? CFU/mL of the isolated bacterial suspension. Pathogenicity was assessed by animal infection experiments and observation of histopathological changes in skin tissue using HE staining. Results The nucleic acid test for Corynebacterium bovis was negative, excluding infection by this organism. The pathogen isolated on mannitol salt agar and blood agar, combined with Gram staining, suggested a Gram-positive Staphylococcus species. The isolated strain was identified by 16S rDNA sequencing and a fully automated microbial identification system as Staphylococcus xylosus. Phylogenetic tree analysis based on whole genome sequencing showed that the strain was most closely related to an isolate from leafy vegetables in South Korea (GenBank GCA_00207825.1). In the high-concentration group, squamous skin scurfs appeared on the head, neck, and back of nude mice on the 17th day post-infection, while in the low concentration group, similar symptoms appeared on the 20th day post-infection and gradually spread to other areas. The scaling symptoms were transient, lasting for 7 days in the high-concentration group and 3 days in the low-concentration group, after which the skin returned to normal. The infection rate was 33.33% in both the high- and low-concentration groups. No significant pathological changes were observed in the skin tissues of infected mice compared to the control group, indicating marked individual differences in the pathogenicity of the strain in nude mice. Conclusion A strain of Staphylococcus xylosus was isolated from the skin of a nude mouse exhibiting squamous skin scurfs. The strain is an opportunistic pathogen that causes transient squamous skin scurfs without significant histopathological changes, and there are individual differences in the sensitivity of nude mice to this strain. These findings can provide valuable data for pathogen identification in immunodeficient or gene knockout mice.

Key words: Nude mice, Squamous skin scurfs, Staphylococcus xylosus, Phylogenetic tree

CLC Number:

Q95-33

KONG Zhihao,WEI Xiaofeng,YU Lingzhi,et al. Isolation and Identification of Staphylococcus xylosus in Nude Mice with Squamous Skin Scurfs[J]. Laboratory Animal and Comparative Medicine, 2025, 45(3): 368-375. DOI: 10.12300/j.issn.1674-5817.2024.166.

Figures/Tables 6

Figure 1 Detection of Corynebacterium bovis was negative by real-time fluorescence PCRNote： Red curve shows the positive control. Black curve shows the negative control. Green curve shows the sample. Blue line shows the threshold line.

Figure 2 Colony morphology on mannitol salt agar plate （A） and blood agar plate （B） and Gram staining microscopic examination （C） of the isolated strain

Table 1 Biochemical identification results indicating that the isolated strain was Staphylococcus xylosus

生化项目 Biochemical items	鉴定结果 Results
D-苦杏仁甙 D-amygdalin	-
磷脂酰肌醇磷脂酶C Phosphatidylinositol phospholipase C	-
D-木糖 D-xylose	+
精氨酸双水解酶1 Arginine dihydrolase 1	+
β-半乳糖苷酶 β-galactosidase	+
α-葡糖苷酶 α-glucosidase	+
丙氨酸-苯丙氨酸-脯氨酸芳胺酶 Ala-Phe-Pro-arylamidase	-
环糊精 Cyclodextrin	-
L-天冬氨酸芳胺酶 L-aspartate arylamidase	-
β-半乳糖吡喃糖苷酶 β-galactopyranosidase	-
α-甘露糖苷酶 α-mannosidase	-
磷酸酶 Phosphatase	+
亮氨酸芳胺酶 Leucine arylamidase	-
L-脯氨酸芳胺酶 L-proline arylamidase	-
β-葡萄糖醛酸酶 β-glucuronidase	+
α-半乳糖苷酶 α-galactosidase	-
L-吡咯烷酮芳胺酶 L-pyrrolidonyl-arylamidase	+
β-葡萄糖醛酸酶 β-glucuronidase	+
丙氨酸芳胺酶 Alanine arylamidase	-
酪氨酸芳胺酶 Tyrosine arylamidase	-
D-山梨醇 D-sorbitol	-
尿素酶 Urease	+
多黏菌素B Polymyxin B	-
D-半乳糖 D-galactose	-
D-核糖 D-ribose	+
L-乳酸盐碱化 L-lactate alkalinization	+
乳糖 Lactose	+
N-乙酰-D-氨基葡萄糖 N-acetyl-D-glucosamine	+
D-麦芽糖 D-maltose	+
杆菌肽耐药 Bacitracin resistance	+
新生霉素耐药 Novobiocin resistance	+
6.5%NaCl中生长 Growth in 6.5% NaCl	+
D-甘露醇 D-mannitol	+
D-甘露糖 D-mannose	+
甲基-β-D-吡喃葡萄糖苷 Methyl-β-D-glucopyranoside	+
支链淀粉 Pullulan	-
D-棉子糖 D-raffinose	-
O/129耐药 O/129 resistance	+
水杨素 Salicin	-
蔗糖 Saccharose/Sucrose	+
D-海藻糖 D-trehalose	+
精氨酸双水解酶2 Arginine dihydrolase 2	-
奥普托欣耐药 Optochin resistance	+

Figure 3 Phylogenetic tree analysis based on single-copy orthologue of the isolated strainNote： “1” represents the isolated strain slarc01. “Bp” represents the bootstrap percentage.

Figure 4 Clinical manifestations of scaling in different groups of nude mice infected with isolated bacterial suspensionNote： A， Control group of applying physiological saline solution to the skin on the neck and back； B， Low concentration group of 1.8×107 CFU/mL isolated bacterial solution applied to the skin on the neck and back； C， Abdominal symptoms in the high concentration group of isolated bacterial solution with a concentration of 1.8×108 CFU/mL applied to the skin on the neck and back； D， Back symptoms in the high concentration group treated with 1.8×108 CFU/mL isolated bacterial solution applied to the skin on the neck and back.

Figure 5 Pathological changes in skin tissues of nude mice with squamous skin scurfs after infection with isolated bacteria （HE staining， ×100）Note： A， Control group； B， Low concentration group； C， High concentration group. Black arrow indicates dermal hair follicle； red arrow indicates sebaceous gland （Scale bar： 200 μm）.

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