The effect of different antibiotic combinations in calcium sulfate cement on the growth of Cutibacterium acnes and Staphylococcus periprosthetic shoulder infection isolates

BACKGROUND

Periprosthetic joint infections (PJI) of the shoulder are a devastating complication of shoulder arthroplasty and are commonly caused by Staphylococcus and Cutibacterium acnes. Absorbable calcium sulfate (CS) beads are sometimes used for delivering antibiotics in PJI. This study evaluates the in vitro effect of different combinations of gentamicin, vancomycin, and ertapenem in beads made from CS cement on the growth of C acnes and coagulase-negative Staphylococcus (CNS) strains.

METHODS

Three strains of C acnes and 5 strains of CNS from clinically proven shoulder PJI were cultured and plated with CS beads containing combinations of vancomycin, gentamicin, and ertapenem. Plates with C acnes were incubated anaerobically while plates with Staphylococcus were incubated aerobically at 37 °C. Zones of inhibition were measured at intervals of 3 and 7 days using a modified Kirby Bauer technique, and beads were moved to plates containing freshly streaked bacteria every seventh day. This process was run in triplicate over the course of 56 days. Statistical analysis was conducted using SPSS v. 28 with repeated measures analysis of variance (ANOVA) and pairwise comparisons with Tukey correction.

RESULTS

In experiments with C acnes, beads containing ertapenem + vancomycin and vancomycin alone formed the largest zones of inhibition over time (P < .001). In experiments with Staphylococcus, beads containing vancomycin alone formed the largest zones of inhibition over time for all 5 strains (P < .001). Zones of inhibition were 1.4x larger for C acnes than for Staphylococcus with beads containing vancomycin alone. For both C acnes and Staphylococcus, beads containing ertapenem had the strongest initial effect, preventing all bacterial growth in C acnes and almost all growth for Staphylococcus during the first week but dropping substantially by the second week. Beads containing gentamicin alone consistently created smaller zones of inhibition than beads containing vancomycin alone, with vancomycin producing zones 5.3x larger than gentamicin in C acnes and 1.3x larger in Staphylococcus (P < .001).

DISCUSSION

These data suggest that for both C acnes and Staphylococcal species, CS beads impregnated with vancomycin were most effective at producing a robust antibiotic effect. Additionally, ertapenem may be a viable supplement in order to create a more potent initial antibiotic effect but is not as effective as vancomycin when used alone. Gentamicin alone was not effective in maintaining consistent and long-term antibiotic effects. These results indicate that amongst the antibiotics currently commercially available to be used with CS, vancomycin is consistently superior to gentamicin in the setting of C. acnes and CNS.

Coagulase-Negative Staphylococci as an Etiologic Agent of Ovine Mastitis, with a Focus on Subclinical Forms

The objective of this review is to investigate the distribution and the characteristics of coagulase-negative Staphylococci (CoNS) implicated in ovine mastitis, and especially in subclinical cases, in order to provide a global perspective of the current research data and analyze specific critical aspects of the issue. PRISMA guidelines were implemented in the search of the last 20 years of the related literature in two databases. In total, 139 studies were included in this review. Relevant data were tracked down, assembled, and compared. Regarding the geographical distribution, most studies originated from Europe (68), followed by South America (33). Lacaune was the most examined breed, while S. epidermidis was the predominantly identified species, representing approximately 39% of the obtained isolates. Antibiotic resistance in the relevant bacteria was documented mostly for Penicillin (32.8%) and Amoxicillin (32.1%), while biofilm- and toxin-associated genes were encountered in variable rates because significant inequalities were observed between different articles. Significantly higher rates of antimicrobial resistance were detected in Asia and South America compared to Europe. Finally, the diagnostic procedures carried out in the respective studies were evaluated. Conventional culture and biochemical tests were mostly performed for simple strain identification; therefore, further molecular investigation of isolates should be pursued in future studies, as this will provide important data regarding specific aspects of the implication of CoNS in ovine mastitis.

The first reported case of Staphylococcus pettenkoferi prosthetic joint infection

Staphylococcus aureus and Staphylococcus epidermidis are among the most frequent causes of prosthetic joint infections (PJIs). Staphylococcus pettenkoferi, a coagulase-negative Staphylococcal species first described in 2002, has been detected in fewer than 20 patients with true infection (15 cases of bacteremia and 1 case of osteomyelitis). This organism has never been implicated in a PJI, likely owing in part to the difficulty in identification via biochemical methods. S. pettenkoferi is almost universally reported to be a contaminant when detected. We report the first case of a PJI caused by S. pettenkoferi, highlighting its infectious potential in specific patient populations.

Antibacterial and Anti-Biofilm Activity of Omega-3 Polyunsaturated Fatty Acids against Periprosthetic Joint Infections-Isolated Multi-Drug Resistant Strains

Background: Implantable medical devices, such as prosthetics, catheters, and several other devices, have revolutionized medicine, but they increase the infection risk. In previous decades, commercially available antibiotics lost their activity against coagulase-negative Staphylococci (CoNS) and several other microorganisms. Docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are the two major omega-3 polyunsaturated fatty acids (ω-3 PUFAs) with antimicrobial properties. Materials and Methods: In this study, we tested the EPA and the DHA for its antibacterial and anti-biofilm activity in vitro against Staphylococcus epidermidis, Staphylococcus aureus, and different CoNS as reference strains and isolated from patients undergoing orthopedic treatment for implant infections. The tests were carried out with the strains in planktonic and biofilm form. Cytotoxicity assay was carried out with EPA and DHA using human gingival fibroblasts HGF-1. Results: The highest concentration of EPA and DHA promoted the complete killing of S. epidermidis 1457 and S. aureus ATCC 25923 in planktonic form. The fatty acids showed low activity against P. aeruginosa. EPA and DHA completely killed or significantly reduced the count of planktonic bacteria of the patient isolated strains. When incubated with media enriched with EPA and DHA, the biofilm formation was significantly reduced on S. epidermidis 1457 and not present on S. aureus ATCC 25923. The reduction or complete killing were also observed with the clinical isolates. The pre-formed biofilms showed reduction of the cell counting after treatment with EPA and DHA. Conclusion: In this study, the ω-3 PUFAs EPA and DHA showed antimicrobial and anti-biofilm activity in vitro against S. aureus, S. epidermidis, and P. aeruginosa, as well as against multi-drug resistant S. aureus and CoNS strains isolated from patients undergoing periprosthetic joint infections (PJI) treatment. Higher concentrations of the fatty acids showed killing activity on planktonic cells and inhibitory activity of biofilm formation. Although both substances showed antimicrobial activity, EPA showed better results in comparison with DHA. In addition, when applied on human gingival fibroblasts in vitro, EPA and DHA showed a possible protective effect on cells cultured in medium enriched with ethanol. Further studies are required to confirm the antimicrobial activity of EPA and DHA against multi-drug resistant strains and pan-drug resistant strains.

Reduction in the processing of possible blood culture contaminants by the application of a selection criterion

Possible blood culture (BC) contaminants are generally considered to be skin flora species including coagulase-negative Staphylococci (CNS), Corynebacterium species, Micrococcus species, Bacillus species and Propionibacterium acnes. Prior to October 1, 2016 all possible BC contaminants were fully processed (identification, susceptibility testing) in our laboratory. In order to reduce the laboratory workload from October 1, 2016 a possible contaminant was only processed if it was present in more than one BC pair drawn from the same patient within the same day. The two-year study period was divided in two periods namely period A from January 1, 2016 to September 30, 2016 (first 9 months) and period B from October 1, 2016 to December 31, 2017 (last 15 months). A series of indices (INs) were calculated including among others the Working Rate IN (WR) defined as the total isolates divided to the total number of BCs submitted per month and the CNS Rate (CNSR) defined as the total number of CNS processed divided to the total number of BCs submitted per month. A 23.08% reduction in the CNSR was noted (from 3.51% in period A to 2.70% in period B) whereas the overall WR was reduced from 7.19% in period A to 6.84% in period B. Furthermore, the total number of contaminants processed per month divided to the total number of isolates processed per month was reduced from 54.50% in period A to 42.41% in period B. The reduction in the INs recorded is of great value since it was achieved by the implementation of a simple criterion easily applicable and without any cost.

Prevalence of and risk factors for intravenous catheter infection in hospitalized cattle, goats, and sheep

BACKGROUND

Intravenous catheter (IVC) use in hospitalized ruminants is a common procedure. Limited information is available describing complications associated with IVCs.

HYPOTHESES

Prevalence of IVC infections in hospitalized ruminants is >50%. Intravenous catheters maintained for >5 days are more likely to be infected than those maintained for <5 days. Intravenous catheters placed non-aseptically have a higher risk for infection than those placed aseptically.

ANIMALS

Thirty-four cattle, 39 goats, and 33 sheep were hospitalized in a university teaching hospital.

METHODS

Prospective observational study. The IVCs from cattle, goats, and sheep admitted for medical and surgical procedures were randomly selected and submitted for bacteriological culture and susceptibility testing.

RESULTS

Prevalence values (95% confidence interval) of infected catheters were 61.8 (45.5, 78.1), 51.3 (35.3, 66.7), and 42.4% (25.2, 58.8) in cattle, goats, and sheep, respectively. Coagulase-negative Staphylococcus spp was the most frequently isolated bacterium. Catheter type/placement technique was a significant (P = .03) predictor of IVC infection in goats but not in cattle (P = .65) and sheep (P = .47). Antibiotic use and reason for catheter placement were not significant predictors of IVC infection in all species. Catheters maintained for >4 days had a higher likelihood of being infected than those maintained for <4 days in all species.

CONCLUSIONS AND CLINICAL IMPORTANCE

Clinicians should consider replacing catheters maintained for >4 days to reduce IVC infection.

Higher proportion of low-virulence anaerobic bacterial infection in young patients with intervertebral disc herniation

Intervertebral disc (IVD) degeneration caused by the latent infection of low-virulence anaerobic bacteria (LVAB) is a hot research topic. The present study analyzed and compared the positive rate of LVAB within IVDs of patients of different ages. IVD samples were intraoperatively retrieved from 176zpatients with disc herniation and subjected to microbiological culture. Subsequently, all the patients were classified into 3 groups based on their ages as follows: Group A (age <30 years), group B (age from 30 to 50 years) and group C (age >50 years) and the positive rates of LVAB were compared among the three groups. The severity of IVD degeneration was also assessed by measuring intervertebral height. Of the 176 cultured discs, 39 samples had bacterial growth, while 6 of them were suspiciously contaminated. Follwoing the exclusion of the 6 suspicious samples, 31 samples were Propionibacterium acnes and 2 samples were coagulase-negative Staphylococci of the remaining 33 samples, The bacterial positive rates were significantly higher in younger patients, with 34.4% (11/32), 25.5% (13/51) and 10.3% (9/87) in group A, B and C, respectively. More importantly, the bacterial-positive samples had a significantly lower disc height compared with the negative samples in groups A and B. Therefore, it can be reasonably concluded that younger patients have a much higher prevalence of LVAB infection in herniated IVDs and a greater severity of IVD degeneration when infected by bacteria. The LVAB may have a strong association with IVD degeneration, particularly in young patients.

Prevalence and bacterial etiology of subclinical mastitis in goats reared in organized farms

Aim:

Assessment of the status of subclinical mastitis (SCM) in Jamunapari and Barbari goats in Indian organized farms, the involvement of bacterial pathogens and their sensitivity to antibiotics.

Materials and Methods:

A total of 181 composite milk samples were aseptically collected from the apparently healthy Barbari (n=95) and Jamunapari (n=86) goats. The California mastitis test (CMT) and somatic cell count (SCC) were used to diagnose SCM. The milk samples with CMT scores of 0 and +1 were considered as negative, while the samples with the score of +2 or +3 were taken as positive, and further, the positive samples were used for the bacteriological examination. An antibiotic sensitivity test was performed by disk diffusion method using seven commercially available antibiotic discs.

Results:

All the samples having CMT score of +2 or +3 demonstrated SCC more than 1 million. Overall, the prevalence of SCM in the goats was assessed as 19.89% (36/181). The prevalence of SCM in Barbari and Jamunapari goats was found as 24.21% (23/95) and 15.12% (13/86), respectively. Out of 11 isolates of Staphylococci, 9 isolates were identified as coagulase-negative Staphylococci (CNS), whereas 2 isolates were found as Staphylococcus aureus. The identified bacterial isolates (n=30) did not show antibiotic resistance.

Conclusion:

The current investigation showed the considerable prevalence of SCM among Jamunapari and Barbari goats which may have a negative impact on quantity and quality of the milk. CNS was found as the most prevalent cause of SCM in the goats. Negligible antibiotic resistance was found among the identified udder pathogens.

Surgical site infections following instrumented stabilization of the spine

Background

Implant-associated infections are still a feared complication in the field of orthopedics. Bacteria attach to the implant surface and form so-called biofilm colonies that are often difficult to diagnose and treat. Since the majority of studies focus on prosthetic joint infections (PJIs) of the hip and knee, current treatment options (eg, antibiotic prophylaxis) of implant-associated infections have mostly been adapted according to these results.

Objective

The aim of this study was to evaluate patients with surgical site infections following instrumented stabilization of the spine with regard to detected bacteria species and the course of the disease.

Patients and methods

We performed a retrospective single-center analysis of implant-associated infections of the spine from 2010 to 2014. A total of 138 patients were included in the study. The following parameters were evaluated: C-reactive protein serum concentration, microbiological evaluation of tissue samples, the time course of the disease, indication for instrumented stabilization of the spine, localization of the infection, and the number of revision surgeries required until cessation of symptoms.

Results

Coagulase-negative Staphylococcus spp. were most commonly detected (n=69, 50%), followed by fecal bacteria (n=46, 33.3%). In 23.2% of cases, no bacteria were detected despite clinical suspicion of an infection. Most patients suffered from degenerative spine disorders (44.9%), followed by spinal fractures (23.9%), non-degenerative scoliosis (20.3%), and spinal tumors (10.1%). Surgical site infections occurred predominantly within 3 months (64.5%), late infections after 2 years were rare (4.3%), in particular when compared with PJIs. Most cases were successfully treated after 1 revision surgery (60.9%), but there were significant differences between bacteria species. Fecal bacteria were more difficult to treat and often required more than 1 revision surgery.

Conclusion

In summary, we were able to demonstrate significant differences between spinal implant-associated infections and PJIs. These aspects should be considered early on in the treatment of surgical site infections following instrumented stabilization of the spine.

Increased Resistance of Skin Flora to Antimicrobial Prophylaxis in Patients Undergoing Hip Revision Arthroplasty

BACKGROUND/AIM

Prosthetic joint infection (PJI) remains a major complication after total joint replacement and is the primary indication for revision arthroplasty. Specifically, coagulase-negative Staphylococci (CNS) can cause low-grade infections. Despite the use of cephalosporin-based antimicrobial prophylaxis (AMP) and antiseptic treatment at the surgical site, evidence suggests that a significant number of cases of dermal CNS results in low-grade PJI. Thus, this study examined the bacterial colonization and resistance patterns at the surgical site. We hypothesized that the bacteria developed resistance to antibiotics that are frequently used in primary and revision total hip arthroplasty (THA) procedures.

PATIENTS AND METHODS

Ninety patients, including 63 primary and 27 revision THA patients, were enrolled in this study. For each patient, a single swab of the skin at the surgical site was subjected to clinical microbiology to assess bacterial colonization. Furthermore, resistance to a sentinel panel of antibiotics (benzylpenicillin, erythromycin, tetracycline, oxacillin, fusidic acid, clindamycin, gentamicin, levofloxacin/moxifloxacin, rifampicin, linezolid and vancomycin) was tested.

RESULTS

In 96.7% of the patients, at least one bacterial strain was identified at the surgical site, with CNS strains comprising 93.1% of the total. The sentinel panel showed that 30.7% of the CNS strains exhibited maximal resistance to oxacillin, a commonly used cephalosporin. Additionally, oxacillin resistance increased 1.9-fold (p=0.042) between primary and revision THA. Notably, 8.1% of the CNS stains found on patients undergoing primary THA were resistant to gentamicin, an aminoglycoside, and this rate increased 4.7-fold (p=0.001) for patients undergoing revision THA.

CONCLUSION

CNS strains have significant resistance to standard AMP, particularly in individuals undergoing revision THA.