New Delhi metallo-beta-lactamase-producing enterobacteriaceae in an Australian child who had not travelled overseas

To the Editor: The editorial by Looke and colleagues in the 18 March 2013 issue of the Journal highlighted the increasing threat of gram-negative resistance.1 Since its description in 2009,2 gram-negative bacteria carrying the gene for New Delhi metallo-beta-lactamase-1 (NDM-1) production have been observed globally. To date, a small number of cases have been reported in adults in Australia.3-5 In all cases, patients travelled to the Indian subcontinent; many required hospitalisation for their infection. We report the first case of NDM-1-producing Enterobacteriaceae in a young infant who had not travelled outside Australia.

An Australian-born 3-week-old boy presented to hospital in 2013 with a 4-day history of cough, rhinorrhoea and vomiting. His mother had visited Pakistan and Afghanistan in 2011 and 2012, respectively. The mother had no relevant medical history and had not attended hospitals in either country. She had lived in Australia exclusively during pregnancy.

Culture of a clean-catch urine sample grew more than 108 colony-forming units (CFU) per litre of Klebsiella pneumoniae (amoxycillin resistant, otherwise susceptible). The child was diagnosed with a urinary tract infection and treated with ceftriaxone and gentamicin followed by oral combined trimethoprim and sulfamethoxazole (co-trimoxazole). The child's symptoms resolved and imaging showed no structural anomaly.

The child re-presented at 5 weeks of age with irritability and vomiting. A urine sample was taken, and the culture grew > 108 CFU/L of Enterobacter cloacae. Susceptibility testing was performed using agar dilution, Vitek2 and Etests (bioMérieux). Using Clinical and Laboratory Standards Institute breakpoints, the isolate was resistant to all β-lactam antibiotics, including meropenem, aminoglycosides, quinolones, co-trimoxazole and nitrofurantoin. The minimum inhibitory concentration to colistin, tigecycline and fosfomycin were < 2 mg/L, < 4 mg/L and < 16 mg/L, respectively. Polymerase chain reaction-based investigation of β-lactamase production provided positive results for blaNDM-1 and blaCTX-M genes. The child was successfully treated with oral fosfomycin (100 mg/kg/day).

This case highlights the emerging impact of NDM-1-producing bacteria. Given that the likely source was the mother or another household contact, this is an example of vertical or horizontal transmission in a country with low community prevalence of NDM-1-producing bacteria. In addition to an increased risk for patients previously receiving medical care overseas or returning from countries where there is a high risk of infection with gram-negative bacteria producing NDM-1, their children and household contacts are also at increased risk.