Analisis Molekuler dan Imunologis Sistem Pertahanan Streptococcus spp. yang Diisolasi dari Pernapasan Anjing dan Kucing di Semarang dan Daerah Istimewa Yogyakarta

Yasinta Rahma Setianingrum, Prof. Dr. drh. Siti Isrina Oktavia Salasia; Prof. Dr. drh. Agnesia Endang Tri Hastuti Wahyuni, M.Si

2026 | Tesis | S2 Sain Veteriner

Streptococcus merupakan bakteri penyebab infeksi saluran pernapasan pada anjing dan kucing serta berpotensi zoonosis. Streptococcus canis adalah spesies yang paling sering diisolasi dan memiliki faktor virulensi yang berperan dalam patogenesitas serta penghindaran fagositosis oleh makrofag. Kajian tentang infeksi Streptococcus pada hewan kesayangan masih terbatas. Penelitian ini bertujuan mengisolasi dan mengidentifikasi Streptococcus spp. dari sampel klinis anjing dan kucing, mendeteksi gen virulensi terkait antifagositosis, serta mengevaluasi interaksi bakteri dengan makrofag secara in vitro. Sebanyak 55 sampel swab nasal dan/atau orofaring dikoleksi dari anjing (n = 3) dan kucing (n = 52) bergejala pernapasan di Semarang dan Daerah Istimewa Yogyakarta. Isolasi bakteri dilakukan dengan inokulasi pada plat agar darah (PAD), pewarnaan Gram, dan uji katalase. Identifikasi molekuler dilakukan dengan polymerase chain reaction (PCR) menggunakan primer 16S rRNA Streptococcus spp., gen spesies spesifik, dan gen pengkode M- like protein (SCM). Aktivitas fagositosis diuji secara in vitro menggunakan sel makrofag RAW 264 dengan penghitungan indeks fagositosis dan diolah secara statistik dengan T-test. Hasil penelitian menunjukkan 32 isolat terkonfirmasi Streptococcus spp. berdasarkan isolasi fenotipik dan deteksi gen 16S rRNA. Streptococcus canis sebagai spesies dominan sebanyak 25 isolat (25/32, 78,13%), sementara spesies S. dysgalactiae dan S. equi subsp. zooepidemicus tidak terdeteksi pada sampel yang diuji. Gen scm terdeteksi pada  32% (8/25)  isolat S. canis. Isolat yang membawa gen scm menunjukkan indeks fagositosis yang lebih rendah (3,64 ± 0,93) dibandingkan isolat tanpa gen scm (5,88 ± 1,19). Hal ini berkaitan dengan peran protein M dalam menghambat proses opsonisasi. Berdasar analisis statistik menunjukkan adanya perbedaan yang signifikan antara kelompok isolat membawa gen scm dengan kelompok isolat tanpa gen scm (p < 0>Streptococcus spp. khususnya S. canis berperan penting pada kasus infeksi pernapasan anjing dan kucing. Keberadaan gen scm pada S. canis berkontribusi secara signifikan terhadap kemampuan bakteri menghindari eliminasi oleh sel makrofag.

Streptococcus spp. are bacterial pathogens associated with respiratory tract infections in dogs and cats and have zoonotic potential. Streptococcus canis is the most frequently isolated species and possesses virulence factors that contribute to pathogenicity and evasion of macrophage-mediated phagocytosis. Studies on Streptococcus infections in companion animals remain limited. This study aimed to isolate and identify Streptococcus spp. from clinical samples of dogs and cats, detect virulence genes associated with anti-phagocytic mechanisms, and evaluate bacterial–macrophage interactions in vitro. A total of 55 nasal and/or oropharyngeal swab samples were collected from dogs (n = 3) and cats (n = 52) showing respiratory clinical signs in Semarang and the Special Region of Yogyakarta, Indonesia. Bacterial isolation was performed using blood agar plates, followed by Gram staining and catalase testing. Molecular identification was conducted by polymerase chain reaction (PCR) using Streptococcus spp. 16S rRNA primers, species-specific gene primers, and primers for the M-like protein–encoding gene (SCM). Phagocytic activity was assessed in vitro using RAW 264 macrophage cells by calculating the phagocytic index, and statistical analysis was performed using a t-test. The results showed that 32 isolates were confirmed as Streptococcus spp. based on phenotypic characterization and 16S rRNA gene detection. Streptococcus canis was identified as the dominant species, accounting for 25 isolates (25/32, 78,1%), while S. dysgalactiae and S. equi subsp. zooepidemicus were not detected in the tested samples. The scm gene was detected in 32% (8/25) of S. canis isolates. Isolates carrying the scm gene exhibited a lower phagocytic index (3,64 ± 0,93) compared to isolates lacking the gene (5,88 ± 1,19), which is associated with the role of M protein in inhibiting opsonization. Isolates harboring the scm gene exhibited significantly lower phagocytic indices compared to isolates lacking the gene. Statistical analysis revealed a significant difference between the two groups (p < 0> Streptococcus spp., particularly S. canis, play an important role in respiratory infections in dogs and cats. The presence of the scm gene in S. canis significantly contributes to the bacterium’s ability to evade elimination by macrophages. 

Kata Kunci : Streptococcus spp., Faktor Virulensi, Makrofag, Infeksi Pernapasan, Hewan Kesayangan