Aims: Rosenow’s broth is an enriched liquid medium used at laboratory for culture of anaerobes. It has never been tested for transport and culture of bacteria, particularly those that are frequently involved in chronic prosthetic infections. This prospective study assessed these data. Methods: 154 intraoperative specimens and joint aspirations were harvested between 1998 and 2000 in 80 patients that had infected knee (24) or hip (56) prostheses. For each of the 154 specimens there was a standard and a Rosenow recipient. Culture obtained on agar medium was called “direct culture” (DC) and culture from any liquid medium was called after “enrichment” (AE). The similitude between bacteria isolated from different specimens was assessed. Results: A bacteria was isolated from DC in 59 specimens (38%) and after AE in 95 specimens (62%). Among the 59 positive DC there was agreement between standard and Rosenow in 87%, and no agreement in 13% [ Staphylococcus sp. (6), Pseudomonas sp.(1) Enterobacteriacae (1)]. Among the 95 cultures AE, Rosenow and standard cultures were in agreement in 41 (43,1%), only standard was positive in 13 (13,6%), but only Rosenow’s broth was positive in 41 (43,1%) with negative standard cultures [16 Staphylococcus sp(13 S. epidermidis), 5 Streptococcus sp., 2 Enterococcus sp., 1 Corynebacterium sp, 3 Enterobacteriacaeand 14 anaerobes]. Sensibility and predictive positive value of Rosenow were respectively 0.86 and 0.86. Conclusion: This study suggest the accuracy of the Rosenow’s broth for transport and culture as agreement was observed in 87% with the DC that is considered as the “gold standard”. When only cultures AE were positive, the Rosenow’s broth corrected the diagnosis in 43%, particularly for infections related to S. epidermidis-and anaerobes.

Purpose: The Rosenow enriched medium (RW) enables culture of anaerobic germs as well as slow-growing germs sometimes causing chronic infections on implanted material. The purpose of this work was to determine the usefulness of RW for the bacteriological diagnosis of infections on total hip arthroplasty (THA) and total knee arthroplasty (TKA°.

Material and methods: One hundred fifty-four pre- or intraoperative standard and RW samples were obtained in a prospective study of 80 consecutive patients (mean age 67.6 years) with an infected THA (n=56) or TKA (n=24) between January 1998 and June 2000. A bacteria was considered “infecting” if it grew on direct culture on at least two samples after enrichment. A single positive sample after enrichment was considered a contamination except for strict anaerobes for which direct culture could not be achieved. For these germs, growth after enrichment was thus considered significant.

Results: Among the 154 samples, 59 (38%) gave positive direct cultures and 95 (62%) positive enriched cultures. Among the 59 positive direct cultures, the RW culture was concordant in 87% of the cases. For the 13% of discordant cultures, the germs did not grow on standard medium: Staphylococcus (n=6), Pseudomonas (n=1), and enterobacteria (n=1). For the 95 positive enriched cultures, 41 (43.1%) of the RW cultures were condordant with the standard culture; the standard was positive in 13 (13.6%) and the RW negative (11 Staphylococcus including five aureus, one Pseudomonas, and one Corynebacterium), but in 41 cases, the RW was positive while the standard was negative (16 Staphylococcus, including 13 coagulase negative, five Streptococcus, two Entero-coccus, one Corynebacterium, three enterobacteria, and fourteen anaerobes). The infecting nature of the aerobic bacteria was retained because earlier or later samples were positive. The sensitivity and predictive value of a positive RW culture were 86% and 86% respectively.

Discussion: Using RW medium and standard samples is useful if germs grow after enrichment in order to confirm the infecting nature of the isolated germ (double culture). The reliability of RW medium was confirmed since it was concordant in 87% of the cases with a positive “gold standard” culture. For positive cultures after enrichment with a negative standard culture, RW allows correcting the diagnosis of infection in 43% of the cases. Its usefulness lies basically in the isolation of coagulase negative Staphylococcus and anaerobes (especially Propionibacterium spp. and Peptostreptococcus spp.).