Prospective insights into acute cholangitis: microbial patterns, resistance, risk factors, and outcomes

Abstract

Aim:

This study investigated the microbiological profile, risk factors, antimicrobial resistance, and clinical outcomes in patients with acute cholangitis.

Background:

Acute cholangitis is a critical infection resulting from biliary obstruction, with risks of sepsis and high mortality.

Methods:

This prospective study included 105 patients undergoing biliary drainage for acute cholangitis via endoscopic retrograde cholangiopancreatography or percutaneous transhepatic drainage. Bile and blood cultures were collected. Antimicrobial susceptibility testing was performed. In-hospital outcomes were analysed.

Results:

Bacteriologically confirmed cholangitis was identified in nearly half of the patients, with Gram-negative bacteria predominating in both bile and blood cultures. Klebsiella pneumoniae and Escherichia coli were the most common Gram-negative isolates, Staphylococcus aureus was the leading Gram-positive organism, and a small number of Candida species (n=5) were also recovered. Malignant biliary obstruction and higher SOFA scores were associated with positive cultures. Multidrug-resistant organisms (51.8% of isolates), including ESBL-producers and carbapenem-resistant strains, were common. Enterobacteriaceae remained sensitive to carbapenems and tigecycline, whereas Staphylococci were sensitive to linezolid and vancomycin. Culture-positive patients experienced longer hospital stays (P< 0.001) and higher mortality (10%, P= 0.016) compared with negative-culture patients.

Conclusion:

-negative bacteria are the primary pathogens in acute cholangitis, and the high burden of multidrug resistance is linked to worse clinical outcomes, particularly in patients with malignant obstruction. Ongoing antibiotic stewardship and local resistance are crucial to optimize empiric therapy and improve patient outcomes.

Introduction

Acute cholangitis (AC) is a potentially life-threatening infection of the biliary tract, usually caused by bacterial infection from biliary obstruction (1). Its clinical presentation ranges from mild to severe, with complications including sepsis, shock, and multiorgan failure. If left untreated, mortality exceeds 50% (1-3). Early risk identification and prompt management are crucial for improving outcomes (2, 4).

The microbiological profile of AC has evolved significantly, with shifts in predominant pathogens and increasing antibiotic resistance posing challenges for clinicians (5). Gram-negative bacteria, particularly those of the Enterobacteriaceae family, have been the primary organisms. They typically enter the biliary tract from the intestine or portal vein, proliferate due to obstruction-induced stasis, and trigger inflammation with bacterial reflux into the bloodstream, resulting in bacteremia and potentially fatal systemic inflammation (6).

Management of AC includes antibiotic therapy and biliary drainage. According to the Tokyo Guideline 2018 (TG18) (2), endoscopic retrograde cholangiopancreatography (ERCP) is the first-line drainage procedure, especially in moderate and severe cases. In contrast, drainage in mild instances depends on the patient's response to antibiotics. Effective empirical antibiotic therapy is crucial for the initial management, but the rise of multidrug-resistant organisms (MDROs) complicates regimen selection (5, 7). Understanding local microbiology and resistance patterns is vital for guiding treatment decisions.

Despite its clinical importance, recent data on the microbiological aspects, sequelae, and antibiotic susceptibility of AC from developing countries remain limited. The links between culture results, clinical characteristics, and outcomes also require further exploration to enhance risk stratification and management. Therefore, this study aimed to investigate the microbiological profile in bile and blood, risk factors, antibiotic resistance patterns, and clinical outcomes in AC patients.

Methods

Study design

This prospective cohort study was conducted at Assiut University Hospital, a tertiary care facility in Upper Egypt, from January 2022 to January 2025. It was approved by the Local Ethics Committee of the Faculty of Medicine, Assiut University (IRB no. 17101013), adhered to the Declaration of Helsinki, and was registered with ClinicalTrials.gov (NCT04216745). Written informed consent was obtained from all participants.

Patients

Adult patients undergoing biliary drainage for acute cholangitis via ERCP or percutaneous transhepatic drainage (PTD) at the Al-Rajhi Liver Hospital, Assiut University, Egypt were included. According to TG18 (2), AC diagnostic criteria were based on systemic inflammation (e.g., fever, elevated leukocytes or C-reactive protein (CRP)), cholestasis (e.g., jaundice, abnormal liver tests), and imaging evidence of biliary obstruction; Charcot’s triad was not required. The Sequential Organ Failure Assessment (SOFA) score was recorded at study entry to evaluate infection severity (8). Patients with concomitant infections or who declined participation were excluded.

Sample size calculation: Given the relatively uncommon rate of AC (0.3–1.6%) (9), all eligible adult patients undergoing biliary drainage for AC during the study period were included.

Methods

At study entry, a comprehensive medical history and physical examination were conducted to collect data, including age, sex, smoking status, comorbidities, fever, abdominal pain, jaundice, itching, and precipitating factors (e.g., previous antibiotic use, prior hospitalization, infection signs, hemodynamic status, and consciousness level). Imaging, including B-mode ultrasonography, contrast-enhanced computed tomography, or magnetic resonance cholangiopancreatography, was used to determine the cause of obstruction. Laboratory investigations included complete blood count, liver function tests, serum creatinine, lipase, CRP, and arterial blood gases. Blood and bile samples were collected. In-hospital mortality was assessed.

Microbiologic studies

Samples were collected from patients, transported, and processed at the Microbiology Laboratory Unit, Clinical Pathology Department, Assiut University Hospital, Egypt. Organisms were identified using both conventional and automated methods, in accordance with standard laboratory protocols and universal safety precautions (10).

Blood samples and culture

Five to ten milliliters of blood were aseptically collected from each patient within two days before biliary intervention. Two culture bottles (aerobic and anaerobic) were incubated using the BacT/Alert 3D system (BioMérieux, Marcy l’Étoile, France) according to the manufacturer's instructions and were considered harmful after five days. Positive cultures underwent Gram staining and were subcultured on blood, MacConkey, chocolate, or bile esculin azide agar, incubated at 37°C for 24–48 hours. Two Sabouraud agar plates were also incubated aerobically at 37°C and 25°C for up to 14 days. Blood agar plates were incubated at 37 °C in an anaerobic jar for 3 days. Grown cultures were processed for identification and antimicrobial/antifungal susceptibility testing using the VITEK 2 COMPACT-15 system (bioMérieux, Marcy l’Etoile, France) in accordance with the manufacturer’s guidelines. We used ID-GNB and AST-N73 cards for gram-negative bacilli, ID-GP and AST-P67 cards for gram-positive cocci, IDYST and AST-Yeast07 cards for yeasts, and the ID-ANC card for anaerobes. During the study, anaerobic cultures were attempted but yielded unreliable results due to technical limitations and were therefore excluded from the analysis.

MDROs were defined as resistant to more than two antibiotic classes (11). Results were interpreted according to the Clinical and Laboratory Standards Institute (CLSI) (12).

Bile sample and culture

During ERCP, bile was aseptically aspirated using a single-use 5F sphincterotome catheter before the therapeutic procedure. The first 5 mL of aspirate was discarded, and the subsequent 5 mL was collected with a new syringe. For PTD, bile was aspirated using a single-use 8F catheter after sonographic-guided puncture and before contrast injection. Samples were placed in sterile screw-cap tubes, inoculated onto appropriate media, and the organisms were identified using the VITEK 2 COMPACT-15 (BioMérieux) as previously described.

Follow-up

Following admission and confirmed diagnosis of acute cholangitis, all patients received empirical cefoprazone (1 g intravenously every 12 hours) according to the TG18 (13). Antibiotic regimens were subsequently adjusted based on susceptibility results. After biliary intervention, patients were monitored throughout hospitalization for symptoms (fever, chills, or upper abdominal pain), laboratory assessments (complete blood count, liver function tests, INR, and CRP), and SOFA scores to evaluate complications. In-hospital mortality was also recorded.

Statistical analysis

Data were analysed using SPSS version 16 (IBM Corp., Armonk, NY, USA). Normality was assessed with the Shapiro-Wilk test. Quantitative data were expressed as means ± SDs, or medians (ranges), and compared using Student's t-test or Mann-Whitney test as appropriate. Qualitative variables were presented as numbers and percentages, with comparisons made using the chi-square test or Fisher’s exact test. Multivariate logistic regression was performed to identify risk factors for bacteriologically confirmed cholangitis. A p-value < 0.05 was considered significant.

Results

Characteristics of the study patients

This study analysed 105 patients undergoing biliary intervention for acute cholangitis. The mean age was 58.5 ± 17 years, with 64.8% females. Malignant obstruction was the leading cause (46.7%), followed by calculi obstruction (36.2%). Comorbidities were present in 61%, mainly hypertension (28.6%) and diabetes (25.7%). Only five patients had received antibiotics in the past three months (Table 1).

Table 1.

Baseline data of patients with clinically suspected acute cholangitis

	Patients with acute cholangitis			P
	Total (n= 105)	Negative culture (n= 55)	Positive culture (n= 50)
Age (years, Range)	58.5 ± 17 (18 - 90)	54.4 ± 17.5	62.9 ± 15.4	0.01
Sex; Male/ Female	37/68 (35.2/64.8)	7/48 (12.7/87.3)	30/20 (60/40)	< 0.001
Smoking	22 (21)	7 (12.7)	15 (30)	0.02
Comorbid diseases	64 (61)	26 (47.3)	27 (54)	0.31
Previous attack of cholangitis	1 (0.01)	0	1 (2)	0.47
Previous use of antibiotics	5 (4.8)	4 (7.3)	1 (2)	0.21
Previous hospitalization	11 (10.5)	6 (10.9)	5 (10)	0.57
Causes of obstruction Stones Malignant cause Biliary stenting Biliary stricture	38 (36.2) 49 (46.7) 4 (3.8) 14 (13.3)	22 (40) 15 (27.3) 4 (7.3) 14 (25.5)	16 (32) 34 (68) 0 0	0.001
Serum bilirubin (µmol/L)	98 (9 - 570)	58 (9 - 214)	183 (32 - 570)	< 0.001
Serum albumin (g/L)	36.4 ± 9.2	42.3 ± 5.7	29.9 ± 8	< 0.001
Aspartate transaminase (U/L)	98 (14 - 201)	89 (14 - 197)	115.5 (43 - 201)	0.56
Alanine transaminase (U/L)	55 (17 - 275)	36 (17 - 275)	70 (35 - 128)	0.009
Alkaline phosphatase (U/L)	245 (74 - 2000)	167 (74 - 327)	372 (135 - 2000)	< 0.001
INR	1.1 ± 0.3	1 ± 0.1	1.2 ± 0.4	< 0.001
Leukocytes (x109/L)	11.7 ± 5.7	8.1 ± 1.2	15.6 ± 5.1	< 0.001
Hemoglobin (g/dL)	11.5 ± 2.3	12.3 ± 1.7	10.8 ± 2.6	< 0.001
Platelets (x109/L)	333.2 ± 122.8	388.2 ± 89.4	272.7 ± 126.9	< 0.001
Neutrophil (x109/L)	8.8 ± 5.1	5.4 ± 0.8	12.5 ± 5.5	< 0.001
Serum creatinine (µmol/L)	89 (38-234)	80 (53 - 178)	109 (38 - 234)	< 0.001
Serum C-reactive protein (mg/dL)	91.3 ± 23.5	38.6 ± 17.6	149.3 ± 34.9	< 0.001
SOFA score	9.2 ± 2.6	4.6 ± 1.6	10 ± 2.3	< 0.001

Data expressed as frequency (percentage), mean (SD) or median (range). P value was significant if < 0.05

INR: international randomized ratio; SOFA: sequential organ failure assessment

Among 105 patients with acute cholangitis, 50 (47.6%) cases (20 females and 30 males; mean age of 62.9 ± 15.4 years) were confirmed bacteriologically via bile cultures, with microorganism concentrations exceeding 10,000/mL. The remaining 55 patients (48 females and 7 males; mean age, 54.4 ± 17.5 years) had negative cultures. Further clinical and laboratory data for both groups are summarized in Table 1.

Determination of risk factors for bacteriologically confirmed cholangitis

Culture-positive patients were more likely to be male (P< 0.001), older (P 0.01), smokers (P 0.02), and have malignant obstructions (P< 0.001) compared to culture-negative patients. Univariate analysis also revealed significant associations between positive cultures and elevated bilirubin, ALT, ALP, INR, creatinine, leukocytes, neutrophils, CRP, and SOFA scores, as well as lower albumin, hemoglobin, and platelet counts (Table 1).

Multivariate analysis identified malignant obstruction (P = 0.01) and SOFA score (P < 0.001) as independent predictors of bacteriologically confirmed cholangitis (Table 2).

Table 2.

Predictors of bacteriologically-confirmed acute cholangitis

Predictors	Odd’s ratio	95% CI	P
Age	0.98	0.45 - 1.76	0.53
Gender (male)	1.23	0.97 - 1.56	0.09
Smoking	0.65	0.33 - 1.09	0.10
Malignant obstruction	1.91	1.30 - 3.65	0.01
Serum albumin	1.13	0.84 - 1.52	0.42
Alanine transaminase	1.01	0.95-1.45	0.24
Alkaline phosphatase	1.22	0.89-2.44	0.54
INR	0.49	0.29 - 1.15	0.08
Leukocytes	1.34	0.89 - 2.56	0.43
Hemoglobin	1.12	0.90-2.22	0.08
Neutrophil	1.56	0.91-2.87	0.22
Serum C-reactive protein	1.22	0.67-2.45	0.20
SOFA score*	2.76	2.22-4.56	< 0.001

CI: confidence interval; INR: international randomized ratio; SOFA: sequential organ failure assessment

*Each of creatinine, bilirubin and platelets were excluded from the regression analysis because they were components in the SOFA score.

Distribution of microorganisms

Bile cultures revealed 77% gram-negative bacteria, 14.8% gram-positive bacteria, and 8.2% fungi, with 16% polymicrobial infections. The most common gram-negative organisms were Klebsiella (K.) pneumoniae (44.7%), Escherichia (E.) coli (23.4%), Acinetobacter (A.) baumannii (19.1%), and Pseudomonas (P.) aeruginosa (12.8%). Among gram-positives, Staphylococcus aureus was the predominant species (55.6%). Candida (C.) albicans was the only fungal species isolated (n= 5) (Table 3).

Table 3.

Frequency and distribution of microorganisms according to causes of biliary obstruction

	Bile culture			Blood culture
	Total	Malignant (n= 34)	Calcular (n= 16)	Total	Malignant (n= 34)	Calcular (n= 16)
Microorganism number	61	44	17	33	23	10
Gram-negative bacteria	47 (77)	30 (68.2)	17 (100)	28 (84.8)	18 (78.2)	10 (100)
Klebsiella pneumoniae	21 (44.7)	12	9	10 (30.3)	3	7
Escherichia coli	11 (23.4)	11	0	11 (39.3)	11	0
Acinetobacter baumannii	9 (19.1)	6	3	5 (15.2)	4	1
Pseudomonas aeruginosa	6 (12.8)	1	5	2 (6.1)	0	2
Gram-positive bacteria	9 (14.8)	9 (20.5)	0	0	5 (21.7)	0
CoNs	4 (44.4)	4	0	0	4	0
Staphylococcus aureus	5 (55.6)	5	0	0	1	0
Fungi	5 (8.2)	5 (11.4)	0	0	0	0
Candida albicans	5 (100)	5	0	0	0	0

Data expressed as frequency (percentage). CoNs: coagulase-negative Staphylococci

Of the 50 patients with positive bile cultures, 33 had concurrent positive blood cultures. All were monomicrobial and predominantly gram-negative (84.8%), with E. coli (33.3%) and K. pneumoniae (30.3%) being the most common. Blood culture isolates matched those from bile cultures.

Microorganism distribution differed between malignant and calculous biliary obstructions. Malignant cases presented diverse profiles in bile cultures (68.2% gram-negative, 20.5% gram-positive, and 11.4% fungal) and blood cultures (78.2% gram-negative and 21.7% gram-positive). In contrast, calculi yielded exclusively gram-negative bacteria in both bile and blood cultures. E. coli was found only in malignant cases, whereas P. aeruginosa was more common in calculi obstructions. Detailed distributions of microorganisms are shown in Table 3.

Antimicrobial resistance

Sensitivity tests showed variable antimicrobial resistance, with 51.8% of isolates classified as MDROs. Among Staphylococci, 77.8% were methicillin-resistant. Among gram-negative isolates, 53.2% were extended-spectrum β-lactamase (ESBL) producers (90.9% of E. coli and 71.4% of K. pneumoniae), and 46.8% were carbapenem-resistant (77.8% of A. baumannii, 50% of P. aeruginosa, 38.1% of K. pneumoniae, and 36.4% of E. coli). Detailed resistance patterns are presented in Table 4.

Table 4.

Percentages of antimicrobial resistance of isolated organisms

For isolated bacteria
		K. pneumoniae (n= 21)		E. coli (n= 11)		A. baumannii (n= 9)		P. aeruginosa (n= 6)		Staphylococci (n= 9)
Penicillin		100		90.9		-		-		88.9
Ampicillin		100		100		-		-		88.9
Amoxicillin-Clavulanic acid		66.7		72.7		88.9		-		55.6
Ampicillin-sulbactam		95.2		81.8		77.8		-		-
Piperacillin-Tazobactam		47.6		27.3		88.9		50		-
Oxacillin		-		-		-		-		77.8
Cefoxitin		47.6		45.5		-		-		77.8
Ceftazidime		66.7		90.9		77.8		66.7		-
Cefepime		38.1		54.5		88.9		33.3		-
Ciprofloxacin		42.9		63.6		66.7		50		55.6
Levofloxacin		66.7		72.7		66.7		66.7		70.4
Moxifloxacin		14.3		54.5		44.4		-		11.1
Imipenem		19.1		27.3		66.7		50		-
Meropenem		23.8		18.2		77.8		33.3		11.1
Amikacin		42.9		9.1		44.4		50		44.4
Gentamicin		33.3		18.2		55.6		66.7		77.8
Tobramycin		66.7		27.3		66.7		-		88.9
TS.SMT SXT		61.9		72.7		-		-		33.3
Tigecycline		4.8		0		11.1		-		11.1
Vancomycin		-		-		-		-		11.1
Linezolid		-		-		-		-		0
Clindamycin		-		-		-		-		22.2
For isolated fungi
	Fluconazole		Voriconazole		Caspofungin		Micafungin		Amphotericin B		Flucytosine
C. albicans (n= 5)	60		20		20		20		20		60

Data expressed as percentage.

A. baumannii: Acinetobacter baumannii; E. coli: Escherichia coli; K. pneumoniae: Klebsiella pneumoniae; P. aeruginosa: Pseudomonas aeruginosa; TS.SMT: trimethoprim-sulfamethoxazole

Follow-up

All culture-negative patients underwent ERCP for biliary drainage. Among those with positive cultures, 30 (60%) had ERCP, 8 (16%) underwent PTD, and 12 (24%) received both. All patients initially received empiric cefoperazone, with 13 switching to adjusted antibiotic therapy based on susceptibility results.

After biliary drainage, clinical manifestations (jaundice, fever, gastrointestinal bleeding, itching, and abdominal pain) remained more frequent in culture-positive patients who also had more extended hospital stays. Also, post-drainage laboratory results revealed significantly higher bilirubin, ALT, ALP, INR, leukocytes, neutrophils, CRP, and SOFA scores in these patients (Table 5).

Table 5.

Follow-up data among patients after biliary drainage

	Patients with acute cholangitis		P
	Negative culture (n= 55)	Positive culture (n= 50)
Fever	0	13 (26)	< 0.001
Jaundice	17 (30.9)	45 (90)	< 0.001
Bleeding	0	3 (6)	0.10
Itching	3 (5.5)	26 (52)	< 0.001
Abdominal pain	19 (34.5)	34 (68)	< 0.001
Serum bilirubin (µmol/L)	29 (6 - 158)	106 (17 - 292)	< 0.001
Serum albumin (g/L)	40.9 ± 4.3	27.6 ± 8	< 0.001
Aspartate transaminase (U/L)	70 (14 - 156)	103 (24 - 145)	0.07
Alanine transaminase (U/L)	27 (15 - 189)	39 (15 - 96)	0.02
Alkaline phosphatase (U/L)	134 (69 - 198)	271 (99 - 721)	< 0.001
INR	0.9 ± 0.2	1.1 ± 0.2	< 0.001
Leukocytes (x109/L)	7 ± 0.9	10.6 ± 4.3	< 0.001
Hemoglobin (g/dL)	12.2 ± 1.6	10.3 ± 1.8	0.03
Platelets (x109/L)	377.6 ± 64.2	288.9 ± 123.5	< 0.001
Neutrophil (x109/L)	4.6 ± 0.6	13.3 ± 6.5	< 0.001
Serum creatinine (µmol/L)	65 (49 - 150)	73 (45 - 156)	0.08
Serum C-reactive protein (mg/dL)	17.3 ± 7.6	63.8 ± 20.5	< 0.001
SOFA score	2.5 ± 0.6	4.26 ± 1	< 0.001
Methods of biliary drainage ERCP/ PTD/Both	55/0/0 (100/0/0)	30/8/12 (60/16/24)	< 0.001
Post-intervention complications	2 (3.6)	6 (12)	0.107
In-hospital mortality	0	5 (10)	0.016
Hospital stay (days)	6.9 ± 0.2	9.6 ± 2.9	< 0.001

Data expressed as frequency (percentage), mean (SD) or median (range). P value was significant if < 0.05

ERCP: Endoscopic retrograde cholangiopancreatography; INR: international randomized ratio; PTD: percutaneous transhepatic drainage; SOFA: sequential organ failure assessment

Eight patients developed post-intervention complications during hospitalization, including two with negative bile cultures and six with positive cultures. Among the culture-negative group, acute pancreatitis occurred in two patients. In the culture-positive group, complications included acute pancreatitis (n= 1), acute kidney injury (n= 2), hepatic encephalopathy (n= 5), bleeding (n= 3), and septic shock (n= 2). In-hospital mortality was significantly higher in culture-positive patients, at 10% (five cases). All nonsurvivors had malignant biliary obstructions and positive gram-negative cultures in bile with or without corresponding blood cultures (Table 6).

Table 6.

Characteristics of non-survivors

Characteristics	Non-survivors
	No.1		No.2	No.3	No.4	No.5
Sex, Age (years)	Male, 50		Male, 61	Male, 87	Male, 60	Male, 72
Smoking	No		No	No	Yes	Yes
Comorbid disease	Diabetes mellitus			Systemic hypertension		Cirrhosis
Cause of biliary obstruction	Malignant
Fever	Persistent			Developed
Hospital stay (days)	17	10		11	15	12
Serum bilirubin (µmol/L)	516	400		520	250	194
Serum albumin (g/L)	25	27.5		22.2	19.1	20
Aspartate transaminase (U/L)	90	101		122	49	50
Alanine transaminase (U/L)	70	90		88	40	35
Alkaline phosphatase (U/L)	340	311		560	412	642
INR	1.5	1.4		1.3	1.8	1.8
Leukocytes (x109/L)	11	17		16	29	32
Hemoglobin (g/dL)	12.6	12.3		11.8	8.9	7.8
Platelets (x109/L)	211	189		190	101	53
Neutrophil (x109/L)	9.9	12.2		10.1	22	23.3
Serum creatinine (µmol/L)	212	187		199	101	90
Serum C-reactive protein (mg/dL)	100	132		101	90	67
baseline SOFA	12	11		12	14	13
Biliary drainage	PTD	PTD		PTD	ERCP	ERCP
Post-drainage complications	AKI, HE	Pancreatitis, HE		AKI, HE	Bleeding, HE, Septic shock
Blood/Bile culture	No/klebsiella	No/Klebsiella		No/klebsiella	E. coli/E. coli	E. coli/E. coli

AKI: acute kidney injury; DM: diabetes mellitus; E. coli: Escherichia. coli; ERCP: Endoscopic retrograde cholangiopancreatography; HE: hepatic encephalopathy; INR: international randomized ratio; PTD: percutaneous transhepatic drainage.

Discussion

Acute cholangitis (AC) is a potentially fatal illness often stemming from bile duct obstruction, leading to cholestasis, bacterial translocation, and inflammation (6). This study provides insights into the microbiological profile, risk factors, antibiotic resistance patterns, and outcomes of AC in 105 patients undergoing biliary intervention.

In this cohort study, pathogens were identified in 47.6% of bile cultures, consistent with previously reported positivity rates (~50%) (14, 15). However, this rate was lower than that reported in some studies (60–100%) (16-18), and higher than in earlier studies (6–38%) (19, 20), reflecting variations in region, population characteristics, etiology, and diagnostic techniques.

Our results revealed that elderly males and smokers with malignant biliary obstruction were predominantly seen among patients with positive bile cultures, consistent with previous studies (21–25). These factors are associated with and an increased risk of infection due to altered biliary anatomy and impaired immunity (25–28). The high malignancy rate likely reflects our hospital’s role as a tertiary referral center managing advanced cases. Moreover, systemic inflammatory responses may be less apparent, leading to delayed diagnosis and intervention (24), which could explain the relatively higher proportion of malignant cases in this cohort.

Consistent with several studies (22, 29–31), we found significantly higher inflammatory markers (leukocytes, neutrophils, and CRP) and worsened liver function (abnormal INR, high bilirubin, low albumin, and elevated enzymes) in culture-positive patients. These factors, which may serve as potential predictors of bactibilia, bacteremia, or cholangitis, indicate greater disease severity and organ failure (29, 32).

Malignant obstruction and high SOFA scores were key predictors of bacteriologically confirmed AC in this study, consistent with earlier reports showing higher bactibilia and cholangitis rates in malignant biliary disease and linking AC to increased stent occlusion in malignancy (22, 33). In addition, immunosuppression may allow colonized biliary bacteria to become pathogenic, and frequent biliary interventions in these patients further increase infection risk, particularly MDROs (22, 27, 33, 34). Higher SOFA scores, which reflect disease severity and organ dysfunction in culture-positive patients, are likely driven by NF-κB–mediated cytokine release, causing neutrophil overactivation and organ failure (35), underscoring the importance of early intervention.

Identifying the causative organisms among widely variable bacteriological profiles and high-risk patients is essential for administering prophylactic and effective antibiotics before intervention. (14–16, 36). Consistent with previous reports (18, 37–39), we found that gram-negative bacteria, particularly Enterobacteriaceae (K. pneumoniae and E. coli) were the predominant isolates, (77%), followed by gram-positive bacteria (14.8%) and fungi (8.2%), reflecting endogenous ascending infections from intestinal flora (16, 39–41). A. baumannii and P. aeruginosa were also common, suggesting healthcare-associated infections or local epidemiological patterns (42, 43). We observed that Staphylococci were the predominant Gram-positive isolates, similar to the findings of Shafagh et al. (44), but unlike earlier studies that reported Enterococcus as the predominant species (5, 19, 41).

Fungal isolates, mainly Candida species, were detected in bile (8.2%) at rates comparable to previous reports (7–10%) (14, 19, 45). Their clinical relevance remains uncertain, particularly in distinguishing actual infection from contamination. All fungal-positive cases occurred in patients with malignant obstruction, aligning with established risk factors for this condition. Although bacterial infections predominate, fungal cholangitis can worsen prognosis (45). Although antifungal therapy is controversial, it may be warranted in high-risk or persistently symptomatic patients, while others recommend reserving treatment for confirmed invasive infections (46, 47). These findings underscore the importance of recognizing fungal pathogens in immunocompromised patients and refining treatment guidelines.

Polymicrobial growth was observed in 16% of our samples, which is lower than previously reported rates (17, 18), possibly due to the lack of anaerobic cultures and the widespread use of antimicrobials. While staphylococci were predominantly gram-positive pathogens, the overall microbial profile has remained stable over recent decades (37–41).

One-third of patients had positive blood cultures, mainly with gram-negative bacteria (84.8%), which matched the bile isolates, supporting the diagnosis of bacteremia and ascending cholangitis (25). Zhao et al. (16) reported a higher blood culture positivity rate (65.9%), with E. coli, K. pneumoniae, and E. faecalis being the most common organisms. The lower culture yield in our cohort may be due to prior antibiotic use.

The role of bile cultures alongside blood cultures in AC remains debated. Where some studies support bile cultures for targeted therapy as organisms in positive bile cultures often match those in blood (48, 49), others recommend routine blood cultures in all emergency department patients, citing high bacteremia rates even in mild cases or those not meeting TG18 criteria (50). Conversely, some advocate routine bile sampling during biliary drainage due to higher detection of polymicrobial and drug-resistant organisms, as Pseudomonas, that can be missed in blood cultures (16, 51).

Consistent with previous studies (9, 18, 52), we found that gram-negative isolates showed high resistance to ampicillin, penicillins, fluoroquinolones, and third-generation cephalosporins (50–100%), but remained susceptible to carbapenems (except A. baumannii) and tigecycline. Gram-positive isolates, Staphylococci, exhibited high resistance to β-lactams, fluoroquinolones, and tobramycin (88.9%), yet remained sensitive to vancomycin and linezolid, reflecting rising methicillin-resistant Staphylococcus rates as reported by Hao et al. (5).

In our study, the detection of MDR pathogens (51.8%) exceeded earlier reports (7.2–42%) (18, 35, 49), but was lower than others (59–79.5%) (30, 53), possibly due to the use of the Vitek system or the use of an inappropriate antibiotic. Notably, methicillin-resistant Staphylococci (77.8%) were frequent than in earlier research (32). Among gram-negative isolates, ESBL production (74.5%; primarily in E. coli (63.6%) and K. pneumoniae (76.2%)) and carbapenem resistance (48.9%; primarily in A. baumannii (86.2%) and P. aeruginosa (50%)) exceeded previous reports (18, 32, 54, 55). A Singaporean study linked empirical carbapenem use to increased MDRO and fungal infections (56), emphasizing the need for antibiotic stewardship and local resistance monitoring.

In our study, patients underwent biliary decompression and received empirical cefoperazone according to the Tokyo Guidelines, which was later adjusted per susceptibility results in those with persistent symptoms (13). However, the high rates of ESBL and carbapenem resistance raise concerns about the adequacy of cefoperazone, as inappropriate empirical therapy has been linked to higher complication rates, prolonged hospitalization, and increased mortality (48, 57, 58). Ongoing resistance surveillance and antibiotic stewardship are therefore crucial to guide empirical therapy. In settings with high MDRO prevalence, carbapenems or β-lactam/β-lactamase inhibitor combinations may offer better initial coverage (13, 57). Tailoring empiric antibiotics to local susceptibility data is essential to improve outcomes and limit further resistance development.

Following cholangitis management, culture-positive patients experienced ongoing complaints, longer hospital stays, persistent liver dysfunction, higher SOFA scores, and more complications, including hepatic encephalopathy (10%), gastrointestinal bleeding (6%), septic shock (4%), acute kidney injury (4%), and pancreatitis (2%). These complications were comparably documented in other studies (3, 13).

In this study, the mortality rate was significantly higher among culture-positive patients with gram-negative infections and malignant obstruction (10%), consistent with previous reports (30, 58, 59). Malignant obstruction is linked to increased mortality due to MDROs such as E. coli and Klebsiella (60), aligning with our findings. Early biliary drainage can reduce mortality from 50% to below 10% (28), whereas delayed ERCP in malignant cases is associated with poorer outcomes (24), emphasizing the importance of early intervention and targeted therapy guided by local resistance patterns.

This single-center study's small sample size may limit generalizability. The lack of molecular typing and the exclusion of unreliable anaerobic cultures due to technical limitations may have underestimated pathogen diversity; however, as most causative organisms in acute cholangitis are aerobic, our findings remain broadly representative and clinically relevant. Short-term follow-up limits insight into long-term outcomes. Larger multicenter studies using advanced microbiological techniques and extended follow-up are needed to confirm these findings and assess regional variations, long-term outcomes, and recurrence rates.

Conclusions

This study highlights evolving microbiological trends in acute cholangitis and the growing challenge of multidrug resistance. Awareness of local resistance patterns and microbiological sampling are essential for guiding empiric therapy, particularly in high-risk patients with malignant obstruction. Carbapenems or tigecycline are recommended for Enterobacteriaceae, and vancomycin or linezolid is recommended for staphylococci. Continuous antibiotic stewardship, resistance surveillance, and timely biliary drainage remain key in improving outcomes.

Conflict of interests

There is no conflict of interest for authors of this article.