Clostridioides difficile infection after antibiotics: risk by drug class, prevention and outcomes

What it is

Clostridioides difficile is a spore-forming bacterium that can expand in a gut whose normal community has been disturbed by antibiotics, causing diarrhoea and colitis. It is among the leading causes of healthcare-associated diarrhoeal death. Risk differs sharply between antibiotic classes.

What the research says

Pooled observational data show large differences in risk by drug class, with clindamycin, fluoroquinolones and cephalosporin-type drugs carrying the highest odds and tetracyclines showing no increase. Probiotics taken alongside antibiotics were associated with fewer cases of C. difficile-associated diarrhoea in Cochrane's pooled trials, but the evidence is low certainty, absolute risk reduction is small and stool carriage was not significantly reduced.

Evidence grade: Well established.

What goes wrong

Community antibiotic exposure was associated with sharply different odds of C. difficile infection depending on class, with clindamycin highest. (Source 1)

• Meta-analysis, Low certainty.
• Size: 7 observational studies identified from 465 screened articles.
• Who: non-hospitalised populations.
• How long: varied by study.
• Result: Clindamycin OR 16.80 (95% CI 7.48 to 37.76); fluoroquinolones OR 5.50 (4.26 to 7.11); cephalosporins, monobactams and carbapenems OR 5.68 (2.12 to 15.23); penicillins OR 2.71 (1.75 to 4.21); macrolides OR 2.65 (1.92 to 3.64); sulfonamides and trimethoprim OR 1.81 (1.34 to 2.43)
• Funding: not stated.

clindamycin (OR = 16.80; 95% confidence interval [95% CI], 7.48 to 37.76), fluoroquinolones (OR = 5.50; 95% CI, 4.26 to 7.11), and cephalosporins, monobactams, and carbapenems (CMCs) (OR = 5.68; 95% CI, 2.12 to 15.23) had the largest effects

Modelled Global Burden of Disease estimates show deaths attributed to C. difficile infection in European countries rising steadily over three decades. (Source 2)

• Survey study, Very low certainty.
• Size: Global Burden of Disease estimates for Central, Eastern and Western Europe, 1990-2019.
• Who: European populations.
• How long: 30 years.
• Result: Mortality attributable to CDI increased by +2.1% per year in males and +2.8% per year in females; about 76% of 2019 deaths were in the Western European sub-region.
• Funding: not stated.

A significantly increasing trend in mortality attributable to Clostridioides difficile infection from 1990 to 2019 was recorded both in males (by +2.1% per year) and females (by +2.8% per year).

In a national cohort of people with recorded C. difficile infection, short-term mortality was high and higher still in people with cancer. (Source 3)

• Cohort study, Low certainty.
• Size: 43,150 individuals with recorded CDI in Sweden, 2006-2019.
• Who: all people with a recorded CDI diagnosis.
• How long: 8 weeks after diagnosis for mortality.
• Result: 8-week all-cause mortality: ongoing cancer OR 1.58 (95% CI 1.43 to 1.74); cancer history OR 1.45 (1.36 to 1.55) versus no cancer.
• Funding: not stated.

There was an increased 8-week all-cause mortality (Ongoing cancer: OR =1.58, 95% CI 1.43–1.74; Cancer history: OR =1.45, 95% CI 1.36–1.55) compared to those without cancer.

What the evidence supports

Probiotics given with antibiotics were associated with fewer cases of C. difficile-associated diarrhoea, on low-certainty evidence and a small absolute difference. (Source 4)

• Systematic review, Low certainty.
• Size: 13,179 participants across 38 trials.
• Who: adults and children receiving antibiotics for any reason.
• How long: trial durations varied.
• Result: CDAD 1.6% (110/6787) with probiotics versus 3.2% (203/6392) with control; RR 0.50, 95% CI 0.38 to 0.64; absolute risk reduction 1.6%; NNTB 65 (95% CI 48 to 97)
• Funding: no funding for the review update; 28 included studies had probiotic-company affiliation or support.

Limit of this finding: This particular result is internally consistent, but two other results in the same Cochrane abstract are not: the passages on C. difficile carriage and on antibiotic-associated diarrhoea each state an absolute risk reduction that does not match their own percentages. Figures taken from elsewhere in this abstract should be judged by the risk ratios and confidence intervals rather than by the absolute percentages printed beside them.

and a relative risk reduction (RRR) of 50% (RR 0.50, 95% CI 0.38 to 0.64; P < 0.001; low-certainty evidence) in incidence of CDAD

What the evidence does not support

Tetracyclines were not associated with increased odds of community-associated C. difficile infection. (Source 1)

• Meta-analysis, Low certainty.
• Size: 7 observational studies.
• Who: non-hospitalised populations.
• How long: varied by study.
• Result: Tetracyclines OR 0.92, 95% CI 0.61 to 1.40.
• Funding: not stated.

We noted no effect of tetracyclines on CDI risk (OR = 0.92; 95% CI, 0.61 to 1.40).

The same review found no significant reduction in C. difficile carriage in stool without symptoms. (Source 4)

• Systematic review, Low certainty.
• Size: 1,302 participants across 16 trials.
• Who: adults and children receiving antibiotics.
• How long: trial durations varied.
• Result: Colonization 14.9% versus 16.2%; RR 0.87, 95% CI 0.68 to 1.11; P = 0.27.
• Funding: no funding for the review update.

Limit of this finding: The Cochrane abstract's own arithmetic does not hold together for this result. It calls it an absolute risk reduction of 2.1%, but the two figures it gives, 14.9% and 16.2%, differ by 1.3 percentage points, and it prints the same numerator, 101, over two different denominators (101/677 and 101/625). Read the risk ratio instead: 0.87, with a confidence interval from 0.68 to 1.11 that crosses 1, meaning no difference was shown. You should conclude that probiotics were not shown to reduce carriage of C. difficile; you should not treat the 2.1% figure or the paired counts as reliable numbers.

Pooled results from 16 trials (1302 participants) suggest that probiotics may result in a small absolute reduction in C difficile in stool (i.e. colonization in absence of symptoms) (ARR 2.1%; incidence of 14.9% [101/677] in the probiotic group versus 16.2% [101/625] in the control group; RR 0.87, 95% CI 0.68 to 1.11; P = 0.27; low-certainty evidence).

Around 30% of the trials in the Cochrane review lacked a published protocol or registration, and 28 had probiotic-company involvement. (Source 5)

• Systematic review, Low certainty.
• Size: 47 trials, 15,260 participants.
• Who: adults and children receiving antibiotics.
• How long: review searched to March 2025.
• Result: High risk of bias for sequence generation or allocation concealment in individual studies; about 30% without protocol or registration.
• Funding: 28 studies with author affiliation to, or financial support from, probiotic companies.

We noted authors' affiliation with a probiotic company and financial support received from probiotic companies in 28 studies.

A common belief, and what the research shows

The belief: Any antibiotic is as likely as any other to give you C. difficile.

What the research shows: Pooled observational data show large differences between classes: "We noted no effect of tetracyclines on CDI risk (OR = 0.92; 95% CI, 0.61 to 1.40)." while clindamycin carried by far the highest odds.

Questions and answers

Clostridioides difficile is a bacterium that can take hold when antibiotics disturb the normal gut community, producing diarrhoea and colitis. It is one of the main causes of death from healthcare-associated diarrhoea. (Source 2)

Antibiotics reduce the gut community's resistance to colonisation, which is the mechanism Cochrane gives for why C. difficile can expand after a course. The clinical result is C. difficile-associated diarrhoea, which occurred in 3.2% of control-arm participants in the pooled prevention trials. (Source 6)

Harmful. Beyond the diarrhoea itself, a national cohort of 43,150 people with recorded infection found substantial eight-week mortality, higher in people with cancer, and European mortality attributed to the infection has been rising. (Source 3)

Does not apply: nobody seeks more C. difficile. What increases the chance of acquiring it is antibiotic exposure, and the pooled observational data show how much that varies by class. (Source 1)

What the retrieved evidence covers is prevention rather than treatment: in pooled trials, probiotics taken with antibiotics were associated with one case prevented for every 65 people treated, on low-certainty evidence. We did not retrieve trial evidence on vancomycin, fidaxomicin or faecal transplantation for established infection. (Source 7)

We searched: Crossref and Europe PMC searches for C. difficile treatment and faecal microbiota transplantation trials; only low-quality reviews and a preprint were retrieved within the fetch budget, so treatment evidence is not reported here.

Read as who is at risk: the odds of community-associated infection rose most after clindamycin, fluoroquinolones and cephalosporin-type drugs, and least after tetracyclines. These are observational associations, not experiments. (Source 1)

We found no trial of any whole food that changed C. difficile risk. The nearest retrieved evidence is a cross-sectional analysis of fibre intake and gut bacteria after antibiotics, which did not measure infection. (Source 8)

We searched: Crossref and Europe PMC searches for diet, fibre and fermented foods in relation to C. difficile infection; no dietary trial with infection endpoints was retrieved.

Read as what happens if the infection is present and untreated or recurrent: eight-week all-cause mortality in a whole-country cohort was substantial, and attributable mortality across Europe rose by about 2 to 3 percent a year between 1990 and 2019. (Source 2)

Stool testing distinguishes poorly between infection and harmless carriage: PCR detects the organism's genes while toxin immunoassay detects the toxin, and patients who are PCR positive but toxin negative are difficult to classify. Cochrane treated stool detection without symptoms as colonisation, a separate outcome from disease. The 50% figure quoted here comes from a single-centre conference abstract that does not name the prior studies behind it, so it is a rough working estimate rather than an established one. (Source 9)

References

1. Antimicrobial Agents and Chemotherapy. Meta-Analysis of Antibiotics and the Risk of Community-Associated Clostridium difficile Infection. 2013. DOI 10.1128/aac.02176-12. Read the source
2. Medicina. Mortality Attributable to Clostridioides difficile Infection: The Rising Burden of Disease in European Countries. 2024. DOI 10.3390/medicina60081222. Read the source
3. Infection. Clostridioides difficile recurrence in individuals with and without cancer: a Swedish population-based cohort study. 2024. DOI 10.1007/s15010-024-02193-1. Read the source
4. Cochrane Database of Systematic Reviews. Probiotics for the prevention of Clostridioides difficile-associated diarrhea in adults and children.. 2025. PMID 40931979, DOI 10.1002/14651858.cd006095.pub5. Read the source
5. Cochrane Database of Systematic Reviews. Probiotics for the prevention of Clostridioides difficile-associated diarrhea in adults and children.. 2025. PMID 40931979, DOI 10.1002/14651858.cd006095.pub5. Read the source
6. Cochrane Database of Systematic Reviews. Probiotics for the prevention of Clostridioides difficile-associated diarrhea in adults and children.. 2025. PMID 40931979, DOI 10.1002/14651858.cd006095.pub5. Read the source
7. Cochrane Database of Systematic Reviews. Probiotics for the prevention of Clostridioides difficile-associated diarrhea in adults and children.. 2025. PMID 40931979, DOI 10.1002/14651858.cd006095.pub5. Read the source
8. BMC Research Notes. Re-evaluating gut microbiome signatures of post-antibiotic dietary fiber intake in a large adult cohort. 2026. DOI 10.1186/s13104-026-07708-7. Read the source
9. Open Forum Infectious Diseases (conference abstract). P-209. Evaluation of Hospitalized Clostridioides difficile (C. difficile) Polymerase Chain Reaction (PCR) Positive/Enzyme Immunoassay (EIA) Negative Patients. 2025. DOI 10.1093/ofid/ofae631.413. Read the source