Long-term faecal carriage in infants and intra-household transmission of CTX-M-15-producing Klebsiella pneumoniae following a nosocomial outbreak.

OBJECTIVES

To investigate the duration of faecal carriage of CTX-M-15-producing Klebsiella pneumoniae in infants colonized during a nosocomial neonatal intensive care unit (NICU) outbreak after discharge from hospital, possible risk factors for long-term colonization and transmission to household contacts (HCs).

METHODS

Fifty-one infants colonized with two unrelated clones of CTX-M-15 K. pneumoniae [sequence type (ST) 17 and ST485] during an NICU outbreak and 60 HCs provided faecal and rectal samples, respectively, every 1-3 months after hospital discharge. Extended-spectrum β-lactamase (ESBL)-producing strains of K. pneumoniae were identified on Chrom ID ESBL agar and examined by antimicrobial susceptibility testing. blaCTX-M-15 was detected by PCR and DNA sequencing. Clonal relationship was examined by PFGE.

RESULTS

The median carriage time in infants after discharge was 12.5 months (IQR 9.5-17.5). Stable antimicrobial susceptibility patterns in PFGE-related strains confirmed the intestinal persistence of both outbreak strains. Risk factors for prolonged faecal carriage in infants were delivery by caesarean section [hazard ratio (HR) 2.4, 95% CI 1.1-5.5, P = 0.029] and treatment with antibiotics during hospitalization (HR 4.5, 95% CI 1.6-12.6, P = 0.004). Transmission of CTX-M-15 K. pneumoniae was observed in 9/28 (32%) households. Median carriage length in parents was 2.5 months (IQR 1.0-5.0) (P < 0.001 compared with infants).

CONCLUSIONS

Infants may be long-term faecal carriers of ESBL-producing K. pneumoniae after colonization during hospitalization in the neonatal period. Delivery by caesarean section and antibiotic treatment during hospitalization are possible risk factors for prolonged carriage. Faecal ESBL carriage in infants represents a reservoir for intra-household spread of ESBL-producing K. pneumoniae.