Clostridium difficile infections (CDI) in hospitalized patients are known to be closely related to antibiotic exposure. Although several substances can cause CDI, the risk differs between individual agents. In Vienna and other eastern parts of Austria, CDI ribotype 027 is currently highly prevalent. This ribotype has the characteristic of intrinsic moxifloxacin resistance. Therefore, we hypothesized that moxifloxacin restriction can decrease the number of CDI cases in hospitalized patients. Our antibiotic stewardship (ABS) group applied an information campaign on CDI and formal restriction of moxifloxacin in Wilhelminenspital (Vienna, Austria), a 1,000-bed tertiary care hospital. The preintervention period (period 1) was January through May 2013, and the intervention period (period 2) was June through December 2013. We recorded the defined daily doses (DDD) of moxifloxacin and the number of CDI patients/month. Moxifloxacin use was reduced from a mean (؎ standard error of the mean [SEM]) of 1,038 ؎ 109 DDD per month (period 1) to 42 ؎ 10 DDD per month (period 2) (P ‫؍‬ 0.0045). Total antibiotic use was not affected. The mean (؎SEM) numbers of CDI cases in period 1 were 59 ؎ 3 per month and in period 2 were 32 ؎ 3 per month (46% reduction; P ‫؍‬ 0.0044). Reducing moxifloxacin use in combination with providing structured information on CDI was associated with an immediate decrease in CDI rates in this large community teaching hospital.C lostridium difficile infection (CDI) is a common side effect of antimicrobial therapy, and C. difficile is endemic in hospitals due to health care-associated transmissions. CDI is associated with increased mortality rates and economic burden (1, 2). Although several substances can cause CDI, the risk differs between individual antibiotics. A recent meta-analysis of community-associated CDI comprising 30,184 patients (3) showed that the risk for CDI was greatest with clindamycin (odds ratio [OR], 20.43; 95% confidence interval [CI], 8.50 to 49.09), followed by fluoroquinolones (OR, 5.65; 95% CI, 4.38 to 7.28).

Background: Yersiniabactin, a siderophore with a high affinity to iron, has been described as a potential virulence factor in Enterobacteriaceae. Klebsiella aerogenes is a Gram-negative rod known to cause invasive infection in very low birth weight infants but is an unusual pathogen to cause outbreaks in neonatal intensive care units (NICU). Methods: We performed a retrospective analysis of all patients colonized with K. aerogenes in our NICU from September to December 2018. Each infant with an occurrence of K. aerogenes in any microbiological culture was defined as a case. Clinical data were taken from medical charts. K. aerogenes isolates were genotyped using whole-genome sequencing combined with core genome multilocus sequencing type analysis. Yersiniabactin production was evaluated by luciferase assay. Results: In total 16 patients were colonized with K. aerogenes over the 3-month period and 13 patients remained asymptomatic or developed late-onset neonatal sepsis from another pathogen. Three patients developed necrotizing enterocolitis, 2 complicated by sepsis and 1 of them died. All symptomatic patients were premature infants with low birth weight. Genetic sequencing confirmed an outbreak with the same strain, all samples expressed the high-pathogenicity island, necessary for the production of yersiniabactin. Six exemplary cases were proven to produce yersiniabactin in vitro. Conclusion: This is the first report of an outbreak of a yersiniabactin-producing K. aerogenes strain causing invasive infection in preterm infants. We hypothesize that, due to improved iron uptake, this strain was associated with higher virulence than non-yersiniabactin-producing strains. Extended search for virulence factors and genetic sequencing could be pivotal in the management of NICU outbreaks in the future.