Optimization of pathogen detection in abscess specimens: a 6-year retrospective study

Abstract

Background: This study aimed to evaluate the impact of optimized diagnostic protocols on pathogen detection rates in abscess specimens.

Methods: Our retrospective study analyzed 1,297 abscess specimens collected between 2018 and 2024 using an enhanced diagnostic protocol combining four key methodologies: routine aerobic/anaerobic culture, gram-stain microscopy, acid-fast bacilli staining, and blood culture bottle enrichment techniques.

Results: The implementation of optimized diagnostic protocols significantly enhanced pathogen detection efficacy (P < 0.001, χ = 9.663), achieving an overall positivity rate of 81.9% (1,062/1,297)-a 20.1 percentage point improvement over conventional methods. Among culture-positive specimens, polymicrobial infections were identified in 27.6% of cases (293/1,062). A total of 1,651 microbial isolates were recovered, dominated by gram-negative bacteria (50.6%, 836/1,651) with Escherichia coli (55.0%), Klebsiella pneumoniae (23.0%), and Acinetobacter baumannii (4.0%) as predominant species. Gram-positive cocci accounted for 33.7% (557/1,651), primarily Streptococcus spp. (45.0%), Staphylococcus aureus (19.0%), and Enterococcus faecium (6.0%). Enhanced methodology detected 261 additional pathogens (20.1% of total yield), including anaerobes (33.7%), smear-positive organisms (32.2%), acid-fast bacilli (6.9%), and Brucella melitensis (1.5%). Anatomic distribution analysis revealed perianal abscesses (358 cases, 407 isolates) predominantly associated with E. coli (51.8%), K. pneumoniae (14.7%), and Streptococcus spp. (15.7%), followed by maxillofacial infections (244 cases, 297 isolates; 18.0%). Other significant sites included abdominal abscesses/peritonitis (17.0%), hepatic abscesses (5.2%), and Periappendicular abscess (5.5%).

Conclusions: Systematic optimization of diagnostic protocols significantly enhanced pathogen detection in abscess specimens, demonstrating substantial clinical utility for infectious disease management. These findings support the adoption of comprehensive, standardized approaches for abscess specimen processing.

Keywords: Abscess specimen; Anaerobic bacteria; Epidemiology; Optimized standardized operating procedures; Pathogen.

Fig. 1

Optimization of pus specimen detection process(n = 1297 cases) Adopting optimized standardized operating procedures, 1062 cases of patient’s abscess specimens were cultured positive accounting for 81.9% and the positivity rate increased by 20.1%. ① Clinical submission of pus specimens: it is recommended to submit sterile empty needle specimens with a volume greater than 1 mL. ② Anaerobic cultivation is recommended to use the anaerobic production bag method, which is compared with conventional cultivation. ③ Smear positive and report clinical findings, report clinical bacterial morphology and suspect bacterial type, and suggest fungal fluorescence staining for suspected fungi. ④ Brucella and Nocardia require aerobic cultivation at 35 ℃ for 3–7 days for growth. Fast-growing mycobacteria generally have negative acid-resistant staining in their original specimens and grow without aerobic cultivation for 3–7 days

Fig. 2

Culture and microscopic identification of rare bacterial species. A Hematological patient, back abscess puncture fluid fungal fluorescence staining × 400 microscope, Aspergillus spp. B Patient with pericardial effusion, positive acid-fast bacilli smear of pericardial effusion (purulent) under × 1000 microscope. C Tuberculous meningitis patient, cerebrospinal fluid (purulent) acid-fast rod positive × 1000 microscope. D Blood agar culture of lung abscess puncture fluid for 3 days, with Nocardia Wallace. E Spinal infection patient, lumbar abscess puncture fluid blood plate culture for 6 days, with B. melitensis. F Shrimp stab patient, hand pus specimen blood culture bottle with bacterial growth reported positive after 3 days, acid-fast staining × 1000 microscope, rapidly growing mycobacteria, RGM

Fig. 3

Infection site and pathogen of abscess specimens. A 836 strains of frequency of isolation of aerobic bacteria. were isolated and E.coli with 55%, followed by K. pneumoniae and Acinetobacter baumannii at 23% and 4%. B 557 frequency of isolation of aerobic bacteria. Streptococcus spp. was the first strain at 45%, followed by S. aureus and E. faecium at 19% and 6%. C 178 strains/cases were rare pathogen, 84 cases of bacterial smears, 28 cases of positive fungal cultures, and 7 cases of fungal spores smears, 18 cases of acid fast bacteria smears. D 67 strains of anaerobic bacteria including 20 strains Peptostreptococcus anaerobius 15 strains B. fragilis and 9 strains Lactococcus garviae

Fig. 4

First pathogen detected in abscess specimens was 407 strains (24.7%) of perianal abscess, followed by Maxillofacial infection, abdominal abscess and peritonitis, perpendicular abscess, liver abscess, and skin and soft tissue infections accounting for 17%,5.5%,5.2%, and 5%