Worldwide Prevalence of Antibiotic Resistance in the Bacteria Klebsiella pneumoniae

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The summary below is from the full report titled "International Prospective Study of Klebsiella pneumoniae Bacteremia: Implications of Extended-Spectrum ß-Lactamase Production in Nosocomial Infections." It is in the 6 January 2004 issue of Annals of Internal Medicine (volume 140, pages 26-32). The authors are D.L. Paterson, W.-C. Ko, A. Von Gottberg, S. Mohapatra, J.M. Casellas, H. Goossens, L. Mulazimoglu, G. Trenholme, K.P. Klugman, R.A. Bonomo, L.B. Rice, M.M. Wagener, J.G. McCormack, and V.L. Yu.

What is the problem and what is known about it so far?

Infections are caused by bacteria that invade various tissues of the body or grow in the bloodstream. For about the past 80 years, doctors have used antibiotics to kill bacteria and cure infections. But millions (and sometimes billions) of bacteria are often present at any one time, and individual bacterial organisms may vary slightly with regard to their genetic makeup. These genetic differences allow some bacteria to produce chemicals that destroy the antibiotic that is being used to treat the infection. Overuse of antibiotics has been linked to the emergence of antibiotic resistance when the bacteria are able to adapt to the presence of these medicines by altering their genetic makeup. The resistant bacteria can eventually multiply and become more common in the environment. Researchers have responded to this threat by developing new antibiotics that are able to avoid being destroyed by the bacterial chemicals. Recently, a new and dangerous threat to successful antibiotic treatment has been identified: Researchers have found that bacteria can exchange among themselves packets of genetic material that make them resistant to antibiotics. Using this mechanism of exchange, some bacteria that are not usually resistant to antibiotics, such as Klebsiella pneumoniae, have developed strains that are resistant to several antibiotics at the same time. These strains are known as extended-spectrum ß-lactamase (ESBL)–producing K. pneumoniae.

Why did the researchers do this particular study?

They wanted to find out what proportion of bloodstream infections with K. pneumoniae were caused by ESBL-producing organisms, whether there were any factors that increased the risks for being infected with an ESBL-producing organism, and what could be done to decrease these risks.

Who was studied?

455 consecutive patients at 12 hospitals in the United States, Taiwan, Australia, South Africa, Turkey, Belgium, and Argentina who had bloodstream infections with K. pneumoniae.

How was the study done?

Bacterial cultures from these patients were tested for ESBL production, and the clinical circumstances of acquiring the infection were noted.

What did the researchers find?

Almost 20% of all K. pneumoniae bloodstream infections were found to be caused by ESBL-producing bacteria. Thirty percent of such infections acquired during hospitalization and 43% of infections acquired in the intensive care unit were ESBL-producing. Other tests showed that there was person-to-person spread of these antibiotic-resistant bacteria. There was also a suggestion that previous treatment with certain types of antibiotics increased the risk for infection with ESBL-producing bacteria.

What were the limitations of the study?

Since the researchers did not take part in any treatment decisions on these patients and the number of ESBL-producing infections was relatively small, the study could not determine with certainty whether treatment with particular antibiotics was a true risk factor for these infections.

What are the implications of this study?

Multi-antibiotic–resistant bacteria are relatively common in hospitalized patients and can be spread from person to person. Strict isolation of infected patients and careful management of antibiotic therapy may help reduce their occurrence.