Acinetobacter baumannii is a Gram-negative bacterium frequently isolated in microbiology laboratories, particularly from intensive care patients, patients with burns, and those with skin infections and pneumonia. A. baumannii has been reported as one of the causes of necrotizing pneumonia,¹ alongside other common pathogens such as Streptococcus pneumoniae, Staphylococcus aureus, Klebsiella pneumoniae, Haemophilus influenzae, and Pseudomonas aeruginosa.² The inflammation and infection caused by these microorganisms weaken the lung tissue near the pleura, increasing its susceptibility to air leakage into the pleural cavity. The presence of air in the pleural cavity, known as pneumothorax, which occurs spontaneously (not due to trauma), can be classified as primary spontaneous pneumothorax (PSP), which occurs without any pre-existing lung disease, or secondary spontaneous pneumothorax (SSP), which is associated with underlying lung conditions such as infection, chronic obstructive pulmonary disease (COPD), or pulmonary fibrosis. Here, we report a case of A. baumannii isolated from a male patient who experienced secondary spontaneous pneumothorax twice. A deeper understanding of the relationship between A. baumannii infections and spontaneous pneumothorax is expected to enhance clinical awareness and optimize the management of high-risk patients.

Case presentation
A 69-year-old male patient presented to the emergency department of Dr. Soetomo General Hospital with complaints of cough and shortness of breath that had started 30 min earlier. At the time of admission, the patient was alert and febrile with a temperature of 37.9 °C. His blood pressure was 129/70 mmHg, heart rate was 120 beats/min, and respiratory rate 28 times/min. Oxygen saturation reached 98% while receiving oxygen through a non-rebreathing mask at a flow rate of 10 L/min; history revealed that the patient had experienced similar symptoms two weeks prior and was diagnosed with spontaneous pneumothorax. The patient was then suspected of having pulmonary tuberculosis, especially considering that tuberculosis is endemic to Indonesia. The patient immediately underwent needle thoracentesis, followed by a GeneXpert® MTB/RIF Ultra test on a sputum specimen, which yielded negative results. The patient also underwent chest tube placement with active suction during the previous hospitalization period. After several days with a chest tube in place, the patient underwent a bullectomy and wedge resection using Video-Assisted Thoracoscopic Surgery (VATS). Upon showing improvement, the patient was discharged in a stable condition, with no shortness of breath, occasional coughing, good oral intake, and oxygen saturation levels of 96-98% on room air. However, the patient returned to the emergency room one day after discharge with the same complaints, namely sudden onset of cough and shortness of breath. Asymmetrical chest wall movement was noted, with the right-side lagging, accompanied by diminished vesicular breath sounds on the right side. Chest radiography revealed signs of pneumonia and right-sided pneumothorax (Figure 1).

The patient was diagnosed with a second attack of secondary spontaneous pneumothorax and underwent the placement of an indwelling pleural catheter along with oxygen support via a non-rebreathing mask at 14 L/min. Two days later, a bronchoscopy revealed a narrowed lumen in the right middle lobe, likely due to external compression from the air inside the pleural cavity. Bronchoalveolar lavage (BAL) specimens were collected from the right and left sides for microbiological examination. The BAL specimen was then tested using the GeneXpert® MTB/RIF Ultra assay, and the result was negative. Gram staining of the right BAL specimen showed polymorphonuclear cells (3+), indicating an inflammatory process. No bacterial forms were observed in either specimen. The samples were then cultured on blood agar, MacConkey agar, and chocolate agar before incubation. After 24 h of incubation, small, round, convex gram-negative rod-shaped colonies were observed in both the right BAL (Figure 2) and left BAL (Figure 3) specimens. The grown colonies were then identified using the BD Phoenix™ Automated Microbiology System. The identification results confirmed A. baumannii in both right and left BAL specimens. After receiving treatment based on susceptibility testing with trimethoprim-sulfamethoxazole at a dose of 960 mg twice daily for 5 days and undergoing a second wedge resection, the patient’s condition improved.