Knowing what cancerous conditions lead to which kinds of bacterial infections can help doctors predict which patients are likely to benefit from pretreatment with certain kinds of antibiotics. A new study found that Escherichia coli and Klebsiella pneumoniae are especially prevalent in patients with lung and GI cancers, with more Klebsiella cases reported if the patients were previously treated with aminopenicillins.

“These are really dangerous infections. You think about Klebsiella–it can develop resistance really quickly. And these patients have generally been in and out of hospitals. If you can’t treat the infection early, it can quickly become a serious and life-threatening condition,” said Andrés Felipe Henao-Martínez, MD, of the University of Colorado Cancer Center and University of Colorado Hospital.

This study looked at 462 patients with bacterial bloodstream infections who were admitted to hospitals for treatment. Of these patients, 203 had cancer and 259 did not, so the clinical and microbiological differences between these populations were explored. Interestingly, the research team could show that most infections existing in cancer patients were contracted in hospital settings and not in the community, while  patients without cancer typically had community-acquired infections.

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“Normally every hospital has a spreadsheet, an antibiogram, listing the bacteria and their rate of antibiotic resistance they’ve found in their patient population. But if you can predict ahead of time what bacteria you’re likely to encounter, you can prescribe more targeted antibiotic therapy before infections create complications,” Henao-Martínez said.

For example, previous treatment with aminopenicillins, like amoxicillin, and the presence of cancer seemed to significantly increase the likelihood of Klebsiella infection.

Klebsiella pneumoniae is largely resistant to amoxicillin–with the immune system compromised by the cancer and by chemotherapy, and with other bacteria largely wiped away by the amoxicillin class of antibiotics it appears that Klebsiella is left to flourish with little competition in patients with cancer,” Henao-Martínez said. This study was published in the International Journal of Infectious Diseases (2013; doi:10.1016/j.ijid.2012.11.030).