Antibiotic Resistant Bacteria Frequently Transmitted Between Intensive Care Patients

Intensive care patients are especially vulnerable to picking up infections in hospital, due to their poor health. Researchers from the Karolinska Institutet in Sweden found that 70% of intensive care patients studied were colonized with bacteria from other patients in the unit.

The researchers investigated the transmission of several strains of Staphylococcus bacteria, called CoNS. These strains are the primary cause of circulatory infections picked up in hospitals, and the third most common cause of all hospital infections. "These species have the ability to survive in the ICU surroundings on medical devices and equipment for weeks up to months," say the researchers. "They are specifically prone to causing catheter-related infections."

The team, led by Professor Charlotta Edlund, took swabs from the upper and lower airways of 20 intensive care patients that had required mechanical ventilation for at least three days. The researchers cultured the bacteria from these swabs and analysed the genetic fingerprints of Staphylococcus strains to identify bacteria that were identical or closely related. They could then assess the transmission rates of bacteria between patients, by seeing which patients harboured the same bacterial strains.

17 of the patients were colonised by CoNS during their hospital stay. In six of these cases, the bacteria had colonised the lower airways after the patient was ventilated, suggesting that the procedure itself had introduced the bacteria. 14 of the patients had either passed on a bacterial strain to another patient or received a bacterial strain from another patient. Worryingly, one patient passed on bacteria to a patient they had never met, having being discharged about three weeks prior to the other's arrival. This implies that the strain had survived in the ward during this period, perhaps on staff or on additional patients.

"Local guidelines for antibiotic use, close cooperation with infectious diseases specialists and restrictions with invasive treatment are strategies that can improve infection control and lower the incidence of hospital infections," write the authors. "Hand hygiene among hospital staff is [also] an important factor for preventing these infections."

The antibiotic resistance of the bacterial strains was analysed. 95% were resistant to penicillin, 86% to oxacillin, 48% to erythromycin, 42% to clindamycin, 54% to gentamicin, and 66% to ciprofloxacin. None were resistant to vancomycin, which is currently used to treat MRSA and other infections caused by other antibiotic-resistant bacteria.

Resistance to multiple antibiotics was commonly seen. 21% of the bacterial strains were resistant to six, 34% to at least five, and 59% to at least four of the tested antibiotics. "This multi-resistance will lead to higher consumption of broadspectrum antibiotics such as vancomycin, promoting the development of antibiotic resistance."

CoNS normally live on our skin without causing us any harm, but they can colonise airways or invasive devises (such as tubes used in mechanical ventilation), especially in people with weak immune systems. Although these bacteria do not always cause disease, colonisation is a risk factor for infection with other, more dangerous, antibiotic resistant bacterial strains.

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This press release is based on the following article:

Multiresistant Coagulase-negative staphylococci disseminate frequently between intubated patients at a multidisciplinary ICUChristina Agvald-Öhman, Bodil Lund and Charlotta EdlundCritical Care 2004, 8:R42-R47Published 22 December 2003

Upon publication this article will be available online free of charge, according to Critical Care's open access policy at: http://ccforum.com/content/8/1/R42

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