Letters
Infectious diseases
Volume 194 - Issue 1

A risk for returned travellers: the “post-antibiotic era”

Authors:  Subhash C Arya and Nirmala Agarwal

Med J Aust 2011; 194 (1): 55-56. || doi: 10.5694/j.1326-5377.2011.tb04162.x
Published online: 3 January 2011
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To the Editor: We share the concern of Fernando and colleagues about the recent emergence of multidrug-resistant bacteria via travellers returning to Australia and the resulting reduction of therapeutic options for such patients, who may have entered a “post-antibiotic era”.1

In countries such as India that lack an integrated laboratory network, the precise magnitude of the threat of plasmids encoding blaNDM1 type metallo-β-lactamases is unknown. Molecular testing for the NDM-1 type of β-lactamases might be available at only two or three national laboratories, and most hospitals will have no such testing facilities.

During replication of multidrug-resistant bacteria carrying blaNDM1 type metallo-β-lactamases, susceptibility to some older antimicrobial agents might be retained. This was evident in two multidrug-resistant Enterobacteriaceae isolates that were identified at the Sant Parmanand Hospital (a 140-bed tertiary-care, multidisciplinary hospital that serves the population of Delhi and two adjoining townships), at which blaNDM1 metallo-β-lactamase testing is not available.

From March to August 2009, 509 Enterobacteriaceae isolates were identified — Klebsiella pneumoniae (368), Escherichia coli (112), Salmonella enterica serotypes Typhi, Paratyphi A, and Paratyphi B (20) and Proteus species (nine). Bacteria were identified by morphological, biochemical and serological characteristics. Antimicrobial susceptibility was tested by the disk diffusion method, according to the United States Clinical and Laboratory Standards Institute guidelines.

Two of the K. pneumoniae isolates were resistant to meropenem, piperacillin–tazobactam, cefepime, amoxicillin–clavulanic acid, amikacin, gentamicin, ciprofloxacin and tigecycline. One had been isolated from the pulmonary secretions of a 45-year-old woman in March 2009; it was susceptible to ofloxacin and chloramphenicol. The other had been isolated from the urine of a 55-year-old woman in July 2009; it was susceptible to chloramphenicol and nitrofurantoin.

Among all the K. pneumoniae isolates, there were 53 resistant to meropenem, 113 resistant to ceftriaxone, 82 resistant to gentamicin and 111 resistant to ciprofloxacin. Among all the E. coli isolates, there were three resistant to meropenem, 38 resistant to ceftriaxone, nine resistant to gentamicin and 35 resistant to ciprofloxacin. The proportion of meropenem- and gentamicin-resistant isolates was significantly higher for K. pneumoniae compared with E. coli (Fisher exact test, P < 0.001).

Older antimicrobial agents such as ofloxacin, chloramphenicol and nitrofurantoin, developed in the 1940s and 1950s, would not be the initial choice for today’s clinicians managing patients with severe multidrug-resistant infections. However, they should be considered before declaring that the post-antibiotic era has arrived.

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