The retrospective study analyzed specimens from inpatients admitted between January and December 2023. From 3,151 clinical specimens, the laboratory recovered 1,860 non-repetitive bacterial strains. After applying rigorous deduplication criteria—retaining only the first isolate per patient per infection site within seven days, unless the antibiogram changed significantly—the team assembled a patient-level dataset of 1,045 unique individuals. Six bacterial species dominated the sample: Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Staphylococcus aureus, Enterococcus faecium, and Enterococcus faecalis, together accounting for 70.1 percent of all non-repetitive isolates. Of the 1,045 patients, 253—24.21 percent—had infections caused by multidrug-resistant organisms, while 792 did not. Bacterial identification and antimicrobial susceptibility testing were performed using the VITEK2 compact automated system, with results interpreted according to the Clinical Laboratory Standards Institute M100-S31 breakpoints.

The baseline comparisons revealed telling differences between the two groups. Patients with multidrug-resistant infections were more often aged 60 or older (64.03 percent versus 56.82 percent), more frequently ESBL-positive (45.85 percent versus 20.96 percent), and more likely to be infected with S. aureus (29.25 percent versus 8.08 percent) or E. faecium (9.49 percent versus 1.01 percent). Interestingly, the multidrug-resistant group included fewer intensive care unit patients (17.00 percent versus 29.04 percent) and fewer respiratory tract infections, but more urinary tract infections (17.00 percent versus 8.84 percent), more patients from general surgical departments, and more from burn surgery. Sex distribution was similar between groups, and E. coli showed no significant difference. These patterns underscore that resistance risk is not confined to intensive care—it threads through surgical wards, burn units, and urology services alike.

Multivariable logistic regression distilled six independent predictors of multidrug-resistant infection: age of 60 years or older, urinary tract infection, ESBL production, P. aeruginosa, S. aureus, and E. faecium. The effect sizes varied dramatically. E. faecium carried the strongest association, with an odds ratio of 55.48 (95 percent confidence interval, 21.66 to 142.15), followed by S. aureus at 29.23 (16.41 to 52.07) and ESBL production at 15.18 (9.04 to 25.51). P. aeruginosa tripled the risk (odds ratio, 3.66), while urinary tract infection (odds ratio, 1.79) and older age (odds ratio, 1.47) contributed more modestly. Each predictor was assigned a score based on its regression coefficient, and the summed total projects onto a probability scale—turning a statistical model into a bedside-usable chart.

Performance metrics were encouraging. Internal validation with 1,000 bootstrap resamples yielded a corrected area under the receiver operating characteristic curve of 0.82 (95 percent confidence interval, 0.79 to 0.85), indicating good discrimination. The model achieved a sensitivity of 85 percent and a specificity of 70 percent, with a negative predictive value of 94 percent—a particularly valuable property, because a low score can help clinicians reasonably rule out multidrug resistance and avoid unnecessary broad-spectrum therapy. Calibration was excellent: the bootstrap-corrected calibration slope was 1.000 with an intercept of 0.000, the Hosmer-Lemeshow test returned a P value of 0.926, and the Brier score of 0.136 fell well below the 0.25 threshold for acceptable predictive accuracy. Decision curve analysis showed positive net benefit across threshold probabilities of roughly 20 to 45 percent, the range where antimicrobial decisions are most consequential.

The authors were notably careful about a subtle statistical pitfall: incorporation bias. Because ESBL positivity was included as a predictor while the outcome—resistance to at least three antibiotic families—is related to ESBL status, the team ran a sensitivity analysis excluding ESBL from the model. The area under the curve dropped from 0.82 to 0.70, confirming that ESBL contributes substantially to discrimination. Intriguingly, P. aeruginosa lost significance without ESBL adjustment (odds ratio falling to 0.74), suggesting its apparent effect was partially mediated by ESBL status, whereas S. aureus and E. faecium remained strongly significant, demonstrating that their predictive power is largely independent of the ESBL variable. The authors also emphasize that ESBL positivity does not equal multidrug resistance—many ESBL-producing isolates remain susceptible to aminoglycosides, fluoroquinolones, and carbapenems—which is precisely why a continuous probability estimate adds value beyond a binary ESBL result.

Robustness checks extended further. Firth penalized logistic regression, a technique that reduces small-sample bias for rare events, was applied because E. faecium isolates were sparse (only 47 isolates, of which 38 were multidrug-resistant). The penalized odds ratio for E. faecium, 51.40 (95 percent confidence interval, 21.24 to 135.52), closely matched the primary estimate. A patient-level sensitivity analysis confirmed that all six risk factors remained directionally and statistically consistent after deduplication. Notably, age failed to reach significance in the isolate-level data (P = 0.07) but became significant once repeated specimens were removed (P = 0.027), suggesting that multiple cultures from the same patient can dilute true risk signals—a methodological lesson with implications well beyond this single study.

The clinical logic of the tool is grounded in established biology. ESBLs are enzymes that inactivate most penicillins, cephalosporins, and related agents, and their encoding genes frequently travel with additional resistance mutations. Elderly patients face elevated risk through immunosenescence, frailty, and multimorbidity. Urinary tract infections are among the most common infections associated with resistant organisms, particularly when broad-spectrum antibiotics are prescribed empirically without urine culture. S. aureus in this cohort was predominantly recovered from burn wound secretions, while E. faecium—a gastrointestinal commensal turned opportunistic pathogen—appeared most often in urine and bile cultures from hepatobiliary surgery and urology patients. P. aeruginosa, a Gram-negative aerobe notorious for hospital-acquired pneumonia, was mostly isolated from sputum of intensive care patients, and its association with high mortality makes accurate early risk assessment especially consequential.

Important caveats temper the enthusiasm. This was a retrospective, single-center study at a county-level hospital, so the findings may reflect regional epidemiology that does not generalize elsewhere. Several potential confounders—prior antibiotic exposure, invasive devices, comorbidities, and immunosuppression—could not be fully captured, although an E-value analysis (E-value of 110 for E. faecium) suggests unmeasured confounding is unlikely to explain the strongest associations. More than 500 rare bacterial species were excluded for statistical stability, so extrapolation to uncommon pathogens should be cautious. The model’s prediction time point is also specific: it is designed for the window after species identification and ESBL phenotype are known but before full susceptibility results return, not for purely empirical decisions made before cultures are drawn.

For now, the authors position the nomogram as a supplementary reference within comprehensive clinical judgment, not a replacement for it. They call for prospective, multicenter external validation before widespread clinical implementation, and future versions may incorporate richer confounder data. Still, the study demonstrates that meaningful resistance prediction does not require academic medical centers or machine learning black boxes—it can emerge from careful, well-deduplicated patient-level data in a county hospital, using variables any microbiology laboratory already reports. As antimicrobial resistance continues to climb globally, tools that convert routine microbiology into early, individualized risk estimates could become a quiet but powerful ally in antibiotic stewardship, helping clinicians reserve last-line drugs for the patients who genuinely need them.

Subject of Research: Development and internal validation of a nomogram for predicting multidrug-resistant organism infections in a county-level hospital

Article Title: A practical nomogram for predicting multidrug-resistant organism infection in a tertiary county-level hospital to guide antimicrobial therapy

Article References: Han, L., Zhao, H., Cheng, J., & Gao, Y. (2026). A practical nomogram for predicting multidrug-resistant organism infection in a tertiary county-level hospital to guide antimicrobial therapy. New Microbes and New Infections, 74, Article 101853. https://doi.org/10.1016/j.nmni.2026.101853

Image Credits: AI Generated

DOI: 10.1016/j.nmni.2026.101853

Keywords: multidrug-resistant organisms, nomogram, antimicrobial resistance, ESBL, risk prediction model, antibiotic stewardship, county-level hospital, Enterococcus faecium, Staphylococcus aureus, urinary tract infection, logistic regression, infection control

Urinary tract infections are among the most frequently diagnosed infectious diseases in dogs, and uropathogenic E. coli, commonly abbreviated UPEC, causes the majority of these infections in both humans and animals. UPEC belongs to the broader family of extraintestinal pathogenic E. coli, or ExPEC, a group of strains that also includes avian pathogenic and sepsis-associated subpathotypes. What distinguishes UPEC is a toolkit of virulence factors that allows the bacterium to colonise and proliferate on the epithelial cells lining the bladder. Chief among these are fimbrial adhesins, particularly Type 1 fimbriae, extracellular protein appendages that anchor the bacteria to bladder cells and initiate infection.

The defining feature of the isolates in this study was their haemolytic activity, the ability to lyse red blood cells on sheep blood agar. That trait is driven by alpha-haemolysin, encoded by the hlyCABD operon. Alpha-haemolysin is a pore-forming toxin that inserts itself into target cell membranes, creating transmembrane pores whose dimensions and conductance properties have been fully characterised through decades of biochemical and structural work. The loss of membrane integrity causes the target cell to burst. In human medicine, roughly half of all UPEC strains carry the hlyA gene, but that proportion climbs with disease severity, reaching up to 78 percent in cases of pyelonephritis, a serious infection of the kidney. Previous work in companion animals has also linked hlyA genes to urinary infections in dogs and cats.

The Vienna team collected isolates from 32 dogs and 19 cats, most of which presented with cystitis, haematuria or dysuria. After recultivating the bacteria on 5 percent sheep blood agar, the researchers extracted DNA and deployed a custom-made DNA microarray platform to screen for a wide panel of virulence-associated genes. They also phylotyped the isolates using the quadruplex Clermont assignment method, determined clonal groups through two-locus CH-clonotyping based on the fumC and fimH sequences, and performed antimicrobial susceptibility testing by agar disc diffusion against fourteen antibiotic agents, following Clinical and Laboratory Standards Institute protocols.

The genetic picture that emerged was strikingly uniform. Fifty of the 51 isolates belonged to phylogenetic group B2, the lineage most commonly associated with extraintestinal pathogenic E. coli in both humans and animals; only a single isolate fell into group B1. Every single isolate carried both fimH, the adhesion gene regarded as a major UPEC virulence marker, and hlyA, the haemolysin gene. Nearly all isolates, 50 of 51, also carried cnf1, a toxin-encoding gene that codes for cytotoxic necrotising factor 1. Additional virulence factors appeared frequently but not universally: pic, which encodes a serine protease, was found in 15 isolates, while papC, part of the P-fimbriae apparatus, and iucD, an aerobactin synthesis gene found only in virulent strains, each appeared in 11 isolates, always occurring together.

The authors note that while the predominance of phylogroup B2 was expected, the complete conservation of the cnf1 and hlyA linkage within this geographic cohort offers novel insight into the regional clonal stability of UPEC in Austrian companion animals. Clonotyping differentiated 34 distinct CH clonotypes, with CH103-9 the most prevalent, accounting for seven isolates. Several other clonotypes appeared in pairs, suggesting limited clonal relatedness among the sampled animals. Notably, most of the detected clonotypes correspond to clonal complexes previously reported in UPEC studies elsewhere, including CC73, CC12, CC127, CC141 and CC372, the last of which has been primarily associated with dogs rather than humans.

Antimicrobial resistance proved to be rare. Forty-five of the 51 isolates, or about 88 percent, were susceptible to every antibiotic tested, a reassuring result for clinicians managing urinary infections in pets. Resistance, where it occurred, was well explained by the genotype. Detected resistance genes including blaTEM, blaOXA-2, sul1, sul2, dfrA1, dfrA5, tet(A), aac(3′)-IVa and catA matched the phenotypic findings, and four isolates displayed multidrug-resistant profiles.

One isolate, however, stood out as a cause for vigilance. This strain carried an extended-spectrum beta-lactamase phenotype and was resistant to beta-lactams, ciprofloxacin, tetracycline, gentamicin and fosfomycin. Sequencing of the quinolone resistance-determining regions revealed classic amino acid substitutions in gyrA and parC that explain the fluoroquinolone resistance. Genotypically, the isolate proved to belong to phylogroup B2, serogroup O25b, sequence type ST131 and clonotype CH40-30, and it carried both blaCTX-M-15 and blaOXA-2. The B2-O25b-ST131 clone is recognised as a major human-associated high-risk pandemic pathogen responsible for a wide range of infections worldwide. Its sporadic detection in Austrian animals, from wildlife, canine prostate tissue, porcine intestinal samples and most recently a faecal sample, had been documented before, but this is a noteworthy addition from a companion animal with a urinary infection.

The study has limitations the authors acknowledge candidly. By restricting the analysis to haemolytic isolates, the work introduces selection bias, and the virulence and resistance potential of non-haemolytic strains causing urinary infections remains to be investigated. The virulence gene panel, while extensive, was finite, and the researchers suggest that whole-genome sequencing of a larger strain collection would provide an even more comprehensive characterisation. The low number of resistant isolates also limits broader epidemiological conclusions about antimicrobial resistance in canine and feline urinary infections.

Nevertheless, the clinical message is broadly positive. The data indicate that a significant proportion of E. coli urinary tract infections in companion animals can still be successfully managed with existing antibiotic therapies. At the same time, the virulence potential of these strains poses a relevant concern for both public and animal health, and the risk of human infection or colonisation from pet-associated isolates has yet to be fully determined. The existence of multidrug-resistant strains in pets with zoonotic potential, exemplified by the ST131 finding, underscores, in the authors’ view, the critical need for a continuous One Health approach to monitor and control the virulence and antimicrobial resistance of E. coli at the interface between animals and people.

Subject of Research: Characterisation of haemolytic uropathogenic Escherichia coli isolated from dogs and cats with urinary tract infections

Article Title: Characterisation of Haemolytic Uropathogenic Escherichia coli Isolated From Dogs and Cats

Article References: Büttner, S., Spergser, J., Makarova, O., Szostak, M. P., Rosel, A. C., Ruppitsch, W., Schäfer‐Somi, S., Müller, E., Braun, S. D., Monecke, S., Ehricht, R., Künzel, F., & Loncaric, I. (2026). Characterisation of Haemolytic Uropathogenic Escherichia coli Isolated From Dogs and Cats. Veterinary Medicine and Science, 12(5), Article e71200. https://doi.org/10.1002/vms3.71200

Image Credits: AI Generated

DOI: 10.1002/vms3.71200

Keywords: uropathogenic E. coli, dogs, cats, urinary tract infections, alpha-haemolysin, virulence genes, phylogroup B2, ST131, antimicrobial resistance, ESBL, One Health, veterinary microbiology