**3.6.1 Culture media**

444 Recent Advances in Arthroplasty

Automated incubation and fluorometric detection of bacterial growth improves sensitivity compared with conventional liquid culture broths (Font-Vizcarra et al., 2010; Levine & Evans, 2001). However, there are potential drawbacks. Firstly, the possibility to determine leukocyte counts is lost if no native material is saved. Secondly, if the sample volume falls short of three milliliters, standard aerobic and anaerobic blood culture bottles may lack sensitivity. Pediatric vials are optimized for culture of lower sample volumes, but it is possible that some anaerobic bacteria are missed due to the composition of the medium

Sonication of explanted prosthesis components to disrupt bacterial biofilms has been assessed by several authors (Achermann et al., 2010; Kobayashi et al., 2006; Trampuz et al., 2003, 2007; Tunney et al., 1998). Culture of the sonication fluid appears to be more sensitive than native sample processing. However, it is cumbersome and not suitable for high-throughput analysis. The possible destruction of planktonic bacteria is an issue that has not been raised systematically to date, but may be of importance in cases of prosthetic infection caused by bacteria which do not establish classical biofilms (Sampedro et al., 2010). There also may be an increased risk of contamination (Holinka et al., 2011;

The bacterial yield using a bead mill is probably enhanced due to facilitated tissue disruption (Roux et al., 2011). However, careful evaluation of conditions for different bacterial species is necessary in order to avoid overheating of samples and mechanical disruption of planktonic bacteria. At present it cannot be decided whether bead mill

Direct gram staining of periprosthetic samples is insensitive and therefore not recommended as a routine test (Banit et al., 2002; Parvizi et al., 2006; Spangehl et al., 1999). However, it can be useful in certain cases of early infection, where prompt treatment of agents which show characteristic morphology (e. g. *Clostridium perfringens*) is enabled. Classic microbiologic culture confirms the presence of viable bacteria and permits testing for

Universal bacterial detection by PCR-based amplification of the 16S rRNA gene allows the identification of bacteria or fungi which are not viable by conventional culture methods. The overall sensitivity may be higher compared with culture (Bergin et al., 2010; Dempsey et al., 2007; Ince et al., 2004; Levine et al., 1995; Panousis et al., 2005; Tunney et al., 1999). On the other hand, singular specific PCR assays (Kobayashi et al., 2009; Piper et al., 2009; Tarkin et al., 2003) or multiplex assays (Achermann et al., 2010) are sensitive but limited to the

**3.4.2 Blood culture vials** 

(Morello et al., 1991).

Trampuz et al., 2006).

antibiotic susceptibility.

**3.5.2 PCR strategies** 

**3.4.4 Bead mill processing of tissue biopsies** 

processing offers significant advantages.

**3.5 Identification of infectious agents** 

organisms included in the test panel.

**3.5.1 Conventional microbiological detection** 

**3.4.3 Sonication of explants** 

A combination of solid (usually blood agar, chocolate agar, and Schaedler agar) and liquid media (e. g. brain-heart infusion broth and Schaedler broth) is used by standard for aerobic and anaerobic cultivation. Solid media alone lack sensitivity to detect low-grade infections because because the medium eventually dries out. On the other hand, infections involving more than one agent can be overlooked if only broth media are utilized because slowergrowing organisms may be inhibited in the presence of fast-growing bacteria.
