Pseudomonas aeruginosa adalah bakteri oportunistik Gram negatif yang menyebabkan infeksi pada mata, telinga, kulit, tulang, sistem saraf pusat, saluran pencernaan, sistem peredaran darah, jantung, sistem pernapasan, dan saluran kemih. Kloramfenikol saat ini tidak lagi digunakan sebagai obat pilihan karena banyaknya kasus resistensi terhadap antibiotik tersebut. Penelitian ini bertujuan untuk mendeteksi keberadaan gen resistensi kloramfenikol pada P. aeruginosa isolat klinik. Bakteri ini diisolasi dari nanah pasien otitis eksternal di Rumah Sakit Dr. Hasan Sadikin (RSHS) Bandung. Metode Polymerase Chain Reaction (PCR-koloni maupun PCR-DNA) digunakan untuk mendeteksi gen resistensi tersebut. Elektrogram dari produk PCR menunjukkan bahwa resistensi P. aeruginosa isolat klinik disebabkan oleh gen cat (317 pb). Berdasarkan hasil penelitian ini, gen cat dapat digunakan untuk mendeteksiresistensi antibiotik kloramfenikol pada pasien otitis eksternal.Kata kunci: cat, gen resistensi kloramfenikol, polymerase chain reaction, Pseudomonas aeruginosa Detection of Chloramphenicol Resistance Genes (cat) in Clinical Isolates of Pseudomonas aeruginosa with Polymerase Chain Reaction MethodPseudomonas aeruginosa is an opportunistic Gram negative bacteria, which may cause infection in eyes, ears, skin, bones, central nervous system, gastrointestinal tract, circulatory system, heart, respiratorysystem, and urinary tract. Recently, chloramphenicol is no longer used as the main option of the therapy due of its resistance case. The aim of this research was to detect the presence of gene which is responsible to chloramphenicol resistance in clinical isolates of P. aeruginosa. These bacteria isolated from pus of external otitis patients in Hasan Sadikin Hospital in Bandung City. Polymerase Chain Reaction (PCR) method (colony-PCR and DNA-PCR) were performed to detect this resistance gene. Electropherogram from PCR products showed that the chloramphenicol resistance in clinical isolates of P. aeruginosa was caused by cat gene (317 bp). Based on this research, cat gene may be used to detect the chloramphenico resistance in patients with external ostitis.Key words: cat, chloramphenicol resistance gene, polymerase chain reaction, Pseudomonas aeruginosa