Biofilm-Based Infections in Long-term Care Facilities

Gianfranco Donelli; Claudia Vuotto

Disclosures

Future Microbiol. 2014;9(2):175-188. 

In This Article

Background of Long-term Care Facilities & Biofilm-Based Infections

Long-term care facilities (LTCFs) are a heterogeneous group of institutions, ranging from rehabilitation centers to those providing chronic care for the sick and elderly. These clinical settings provide healthcare to a broad spectrum of patients of all classes of age, their institutionalization lasting for a long period of rehabilitation or for a shorter period before returning to the community or being admitted to another health facility.[1]

Infections among patients admitted to LTCFs often exhibit a frequency comparable with that observed in acute care facilities; this is also because the host susceptibility as well as the transfer of patients from an acute care to a long-term care setting adds significant risk factors to the transmission and acquisition of healthcare-associated infections (HAIs).[2] A great deal of information has been published concerning infections in the LTCFs, and specific infection control programs to prevent and detect HAIs in these facilities in a timely fashion have been widely developed in all industrialized countries.[3] However, in recent years, the patient profile was modified due to changes in the healthcare systems of most of these countries, mainly because of the earlier discharge of patients from acute care hospitals to LTCFs and the increasing use of invasive medical devices. In fact, most LTCF patients affected by HAIs are elderly, suffer from a severe underlying disease, exhibit poor functional status, sometimes have wounds in different areas of their body and frequently are in need of an indwelling medical device. However, data reporting the infection occurrence and risk factors in patients bearing medical devices, including urinary catheters or urethral stents, central venous catheters, or percutaneous or nasogastric feeding tubes, are still underestimated and poorly documented.

In particular, urinary, respiratory and GI tract infections, as well as those involving skin and soft tissues, and the implant of medical devices, are the most commonly occurring among these patients, and outbreaks are frequent.[4] As is well known, most HAIs are preventable through good hand hygiene at the right time and in the right way; according to the recent WHO Guidelines on Hand Hygiene in Health Care,[5] the person-to-person transmission via the hands of healthcare workers appears to be the most effective way to spread HAIs. It has been estimated that approximately 70% of HAIs are caused by multidrug-resistant (MDR) pathogens that may enter an LTCF when a colonized patient is transferred from an acute care hospital or they can be the result of a mutation or gene transfer in bacterial strains already present in the LTCF. It is also well known that MDR bacteria often arise from antibiotic overuse, erroneous drug selection or inappropriate antimicrobial treatment duration.[6,7] It has been estimated that up to 70% of patients admitted to a LTCF receive at least one course of an antimicrobial drug per year of hospitalization.[8] Once patients or environmental surfaces of the setting have been colonized by resistant strains, they can persist, rapidly disseminate and become endemic. Thus, antimicrobial stewardship consisting of better clinical management of patients by promoting the singling out of optimal drug regimen, dose, route of administration and duration of therapy has been recommended in the most recent infection control guidelines.[9] However, it should be here emphasized that persistence of MDR bacteria in the hospital environment as well as in the infected patients and healthcare workers is worsened by the ability of the great majority of them to strongly adhere to biotic (mucosal and soft tissues) or abiotic (medical devices and instruments, trolleys for dressing, and so on) surfaces, and to grow in sessile mode to form a biofilm. Microbial life within these multicellular communities encased in a hydrated matrix of extracellular polymeric substances (EPS) provides microbes with greater protection from host immune response and chemical attacks, easier gene transfer among cells and higher resistance to antimicrobials.

Biofilms have been implicated in a large number of acute and chronic infections, as well as in the failure of indwelling medical devices. The establishment of bacterial biofilm communities on the tissues of susceptible hosts or surfaces of medical devices is believed to inhibit the effectiveness of antibiotic treatment, bypass host defense mechanisms and facilitate bacterial communication, leading to expression of virulence determinants. It is well known that growth as biofilm of many opportunistic bacteria involved in the above-mentioned infections can have a great influence on the success of antibiotic therapies, biofilm-growing bacteria being less susceptible to antibiotics (Figure 1).[10]

Figure 1.

Field emission scanning electron microscopy micrographs of in vitro biofilms obtained from clinical strains belonging to the indicated species and isolated from explanted urinary or intravascular catheters, or infected pressure ulcers.

In fact, biofilm-forming bacteria have altered phenotypes despite the corresponding planktonic bacteria and this phenomenon has significant consequences. Antibiotic resistance of biofilm-growing bacteria may be 100–1000-fold higher than planktonic bacteria. This reduced susceptibility seems to be multifactorial, including:

  • The mechanical barrier of the EPS matrix;[11]

  • The low level of metabolic activity and slow or no growth in the deeper layers of biofilm (persister cells);[12]

  • The increase in mutation frequency;[13]

  • The increase in horizontal gene transfer.[14,15]

All these acquired resistance factors are to be added to the intrinsic antibiotic resistance of the MDR clinical strains belonging to the different species involved in HAIs.

The state of the field of the most common biofilm-based infections occurring in patients admitted to LTCFs will be reviewed here, also with reference to our experience at the Santa Lucia Foundation research hospital in Rome (Italy), which is one of the largest long-term care settings for neuromotor rehabilitation in Italy.

Particularly, the involvement of biofilms and its relevance in diagnosis and treatment of catheter-associated urinary tract infections (CAUTIs), catheter-related bloodstream infections (CRBSIs) and infected pressure ulcers will be illustrated and discussed.

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