Gram-negative pathogens dominated sterile body site infection cultures in Northwest Ethiopia
A five-year review from the University of Gondar Comprehensive Specialized and Referral Hospital points to a shifting microbiology profile in sterile body site infections. Among 1,368 patients whose laboratory records were reviewed from September 2021 through May 2026, culture-confirmed bacterial infection was documented in 5.48% of cases, yielding 75 bacterial isolates. The balance of organisms tilted sharply toward Gram-negative bacteria, which accounted for 88.0% of isolates, while Gram-positive organisms made up only 12.0%.
The dominant pathogens were familiar but clinically difficult: E. coli represented 33.3% of isolates, and K. pneumoniae accounted for 26.7%. In a hospital setting, that combination matters because both organisms are frequent drivers of severe invasive infection and both can rapidly accumulate resistance under selective antibiotic pressure. When they appear in normally sterile compartments, the margin for empirical error narrows quickly.
No mixed bacterial infections were identified in any patient. The absence of polymicrobial growth simplifies microbiologic interpretation, yet it does not ease the therapeutic challenge when the main organisms are already resistant to several commonly used agents.
Resistance pressure fell hardest on standard empiric antibiotics
Antimicrobial susceptibility testing showed resistance among Gram-negative isolates to drugs that remain widely used in routine practice, including ceftriaxone, trimethoprim-sulfamethoxazole, and ampicillin. In practical terms, this means empiric regimens built around these agents can be mismatched to local ecology before a culture result even returns. For invasive infection, delayed effective therapy can be costly.
The study also documented an overall multidrug resistance prevalence of 17.3% (13/75). The MDR burden was not evenly distributed across organisms. K. pneumoniae accounted for 35% of MDR isolates (6 cases), non-lactose fermenting Gram-negative rods made up 28.6% (2 cases), and E. coli represented 16% (4 cases). These are the organisms that tend to create the greatest bedside tension: they are common, they can be severe, and once resistance clusters across multiple antibiotic classes, treatment options become much less forgiving.
A one-sentence clinical reality sits at the center of these data: standard empirical therapy may be outpacing local susceptibility patterns.
MDR rates climbed over time, with a sharp peak in 2024/25
The five-year trend deserves attention because it suggests a worsening resistance environment rather than a static local problem. An especially high MDR prevalence was recorded in 2024/25, when the rate reached 46.2%. Among individual species, K. pneumoniae showed a striking MDR rate of 71.4% in 2024/25, with a statistically significant association reported for that period. The prevalence of MDR E. coli peaked at 50% during 2022/23 and again in 2024/25.
Those peaks matter because they suggest temporal clustering of resistance rather than a random fluctuation. In hospital microbiology, a rising MDR curve often reflects repeated exposure to broad-spectrum antibiotics, delayed microbiologic confirmation, and continued reliance on treatment pathways that were designed for an earlier susceptibility era. Once resistance becomes entrenched in the dominant gram-negative pathogens, local guidelines need to move much faster than annual habit.
The authors also found that being male was significantly associated with bacterial sterile body site infection, with p = 0.011. Study year was also associated with infection across multiple periods, including 2025/26, 2024/25, and 2023/24. Because this was a retrospective cross-sectional analysis, the findings identify statistical associations rather than causal pathways, but they still help map where the burden was concentrated during the study window.
Why invasive infection ecology matters for bedside care
Sterile body site infection is not a superficial microbiology problem. It is an indication that bacteria have crossed into compartments where host defenses and antibiotic penetration can be decisive. The organisms recovered in this cohort fit that pattern. E. coli and K. pneumoniae are enteric Gram-negative pathogens with a known ability to cause bloodstream-adjacent or deep-seated disease, and both are equipped to acquire beta-lactam resistance mechanisms that blunt older empiric choices.
The laboratory approach used in the hospital relied on sterile body fluid culture on blood agar, chocolate agar, MacConkey agar, and mannitol salt agar, followed by modified Kirby-Bauer disc diffusion testing. That workflow remains foundational in many settings because it delivers actionable data without requiring high-complexity infrastructure. Still, phenotype alone may not capture the full resistance picture, especially when organisms carry ESBLs, carbapenemases, or other mechanisms that can shape treatment failure even when the disc-diffusion pattern appears partially favorable.
This is where molecular detection becomes more than an academic upgrade. It becomes a surveillance tool that can reveal why resistance is rising, how resistance spreads, and which antibiotic classes are likely to lose ground next.
Hospital surveillance now needs to guide empiric therapy
The findings support a direct operational message for hospitals managing sterile body site infections in Northwest Ethiopia: local antibiograms should drive empiric decisions, not inherited assumptions about older susceptibility patterns. With Gram-negative bacteria dominating cultures and MDR concentrated in E. coli and K. pneumoniae, routine empiric regimens may need re-evaluation wherever similar resistance pressures are emerging.
The study’s retrospective design and reliance on existing laboratory records limit causal inference, and the dataset comes from a single referral hospital. Even so, the microbiology signal is strong enough to warrant practical changes in stewardship thinking. Continuous surveillance is not a luxury here; it is the only way to keep empiric therapy aligned with the organisms actually causing invasive disease.
No specific funding was received for the work, and ethical approval was secured for retrospective record review with anonymized data handling. The immediate unanswered question is not whether resistance exists, but which resistance genes are circulating behind the phenotype and how quickly they are spreading through the local hospital ecology.