Biofilm-Based Infections in Long-term Care Facilities

Gianfranco Donelli; Claudia Vuotto


Future Microbiol. 2014;9(2):175-188. 

In This Article

Infected Pressure Ulcers

Bedridden patients transferred from general hospitals to LTCFs are very often affected by pressure ulcers. In fact, incidence rates are reported to reach up to 38% for hospitals, 24% for LTCFs and 17% for home care.[119] Pressure ulcers require a prompt and efficacious treatment, especially to avoid wound-related infections and the establishment of a microbial colonization that delays the wound healing.[120–122] Otherwise, infected pressure ulcers can give rise to deep soft-tissue infections that, when not adequately treated, may cause osteomyelitis and secondary bacteremic infections associated with a 50% mortality rate.[120–123]

According to a study performed on patients admitted to our hospital in Rome from 2007 to 2009, a large number of different antibiotic-resistant microorganisms were collected from pressure ulcers at stage III and IV using the irrigation–aspiration technique (Figure 4).[124] The most frequently isolated species were MRSA (32%), P. aeruginosa (21%), E. coli (23%) and Proteus spp. (17%).[125]

Figure 4.

Collection by the irrigation–aspiration procedure of a clinical sample from a grade IV-infected pressure ulcer of a patient transferred to the Fondazione Santa Lucia from a general hospital.

Our results are in agreement with the high rates of MRSA carriage, ranging between 8.8 and 23%, reported in the literature for other LTCFs.[126–129]

The loss of the innate barrier function of the skin facilitates the colonization of wounds by pathogens and promotes biofilm development. Bacterial biofilms are implicated not only in the failure of wound healing but also in the occurrence of chronic inflammation by the EPS matrix-mediated evasion of the immune response and induction of a nonhealing inflammatory phase. Direct evidence of biofilm presence in wounds, especially in chronic ones, has been provided by James and coworkers, who investigated biopsies from acute and chronic wounds by light microscopy and SEM.[130] Results demonstrated a very lower prevalence of biofilm in acute wounds in comparison with chronic wounds (6 vs 60%) and the polymicrobial nature of chronic wound biofilms, constituted by several species, including Staphylococcus (65%), Enterococcus (62%), Pseudomonas (35%), Proteus (24%), Escherichia (14%), Klebsiella (5%) and Acinetobacter (5%).

Pressure ulcers of grade III and IV can also be infected by strict Gram-positive anaerobes, including Finegoldia spp., Clostridium spp. and Veillonella spp., and it is noteworthy that these species have been recently demonstrated to be able to grow as single- (Figure 5A & B) or multi- (Figure 5C) species biofilm.[131]

Figure 5.

Field emission scanning electron microscopy micrographs of biofilms grown in vitro by anaerobic clinical strains. (A) Clostridium difficile biofilm; (B) Veillonella spp. biofilm, and (C) dual biofilm constituted by the above-mentioned species.

The recovery of biofilm from an infected pressure ulcer represents a difficult challenge, since a fully satisfactory sampling method has not yet been defined. In fact, there are no experimental data on the reliability of the noninvasive aspiration–irrigation procedure[124] compared with the use of swabs or tissue biopsies.[122] Anyway, SEM has been used to observe the presence of biofilms within wound tissues, while confocal laser scanning microscopy has provided information on the tridimensional structure of biofilm and EPS matrix by resorting to a range of staining and molecular techniques, including FISH.[132–134]