Antimicrobial Resistance Profiles of Bacterial Conjunctivitis Isolates from a Secondary Hospital in Shanghai: A 5-Year Retrospective Study (2020–2024)

Weihong Xu,1 YiTing Yao,2 Yifei Jia,2 LiLun Jiang,1 Lei Li,1 Yunqi Pan,2 Yanan Lai2 1Department of Clinical Laboratory, Shibei Hospital, Shanghai, People’s Republic of China; 2Department of Clinical Laboratory, Tongren Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People’s Republic of ChinaCorrespondence: Weihong Xu, Department of Clinical Laboratory, Shibei Hospital, No. 4500 Gonghexin Road, Jing’an District, Shanghai, 200435, People’s Republic of China, Email [email protected]: To analyze the pathogen distribution, epidemiological characteristics, and antimicrobial resistance patterns of bacterial conjunctivitis in a Shanghai secondary hospital from 2020 to 2024, providing evidence for clinical treatment optimization.Patients and Methods: Conjunctival swab specimens from patients clinically diagnosed with bacterial conjunctivitis were collected between January 2020 and December 2024. Bacterial identification and antimicrobial susceptibility testing were performed using the VITEK 2 Compact system and Kirby-Bauer disk diffusion method, respectively. Statistical analyses were conducted using WHONET 5.6 and SPSS 26.0.Results: Among the 611 specimens, 58 bacterial isolates were identified (9.5% positivity rate). Gram-positive cocci predominated (70.7%, 41/58), primarily Staphylococcus epidermidis (21 strains) and Staphylococcus aureus (10 strains). Gram-negative bacilli accounted for 15.5% (9/58), including Pseudomonas aeruginosa and multidrug-resistant Acinetobacter baumannii. A significant seasonal variation was observed, with higher incidence in summer-autumn (72.4%) than in winter (12.1%, P=0.005). Cases in 2023– 2024 nearly doubled those in 2020– 2022 (65.5% vs 34.5%). The detection rate of S. aureus increased significantly annually (P=0.043). High resistance rates were observed among Gram-positive cocci to penicillin (89.5%), oxacillin (60.5%), and erythromycin (55.3%). All Gram-positive isolates remained susceptible to vancomycin, linezolid, and tigecycline. Gram-negative isolates exhibited 100% resistance to ampicillin, with A. baumannii demonstrating pandrug-resistance.Conclusion: Gram-positive cocci, particularly Staphylococcus spp. were the predominant pathogens in bacterial conjunctivitis, with an increasing trend of S. aureus and multidrug-resistant A. baumannii. The significant seasonal pattern and high resistance to first-line antibiotics emphasize the necessity for culture-guided therapy and enhanced antimicrobial stewardship in ocular infections.Plain Language Summary: Why we did this studyBacterial conjunctivitis (pink eye) is a common eye infection. We noticed that standard antibiotics sometimes fail to clear these infections in Shanghai. This study aimed to identify the bacteria causing conjunctivitis and track their changing responses to antibiotics over time.What we didWe examined 611 eye swabs from patients with bacterial conjunctivitis between 2020 and 2024. Laboratory tests helped us identify the bacteria and determine which antibiotics effectively treated them.What we foundStaphylococcal infections were common: Most cases (70.7%) involved staphylococcus bacteria, especially Staphylococcus epidermidis. Over half of these bacteria resisted common antibiotics like penicillin.Seasonal patterns emerged: Infections occurred more often in warm months (June–November) than in winter. Cases nearly doubled in 2023– 2024 compared to earlier years.Effective treatments exist: While resistance to first-line antibiotics was high, all tested bacteria remained susceptible to certain reserve antibiotics like vancomycin and linezolid.Why this mattersOur findings suggest that doctors can improve treatment by considering local resistance patterns when prescribing eye drops. Patients can support recovery by completing prescribed treatments and maintaining good hand hygiene, especially in summer. This research underscores the need for continuous monitoring of antibiotic resistance in eye infections to guide effective treatment strategies.Keywords: microbial sensitivity, drug resistance, eye infections, seasonal variation, bacterial pathogens