Susceptibility patterns of enterococci causing infections

Antimicrobial resistance profile of Enterococcus species isolated from intestinal tracts of hospitalized patients in Jimma, Ethiopia

Background

Multi-drug-resistant Enterococci colonizing the intestinal tract of hospitalized patients are the major source of infection as well as nosocomial spread. Despite worldwide increasing rate of multidrug resistant Enterococci colonization and infection among hospitalized patients, there is scarcity of data from resource limited setting. The present study aimed at determining the antimicrobial resistance profile of Enterococcus species from intestinal tracts of hospitalized patients in Jimma, Ethiopia.

Methods

The study was conducted among hospitalized patients at Jimma University Specialized Hospital, from January to July 2013. Fecal samples were collected and processed for bacterial isolation and susceptibility testing to antimicrobial agents. Stool samples were inoculated onto enterococcus selective media (Bile Esculin azide agar plate) with and without 6 µg/ml of vancomycin. The isolates were identified to genus and species level by cultural characteristics, Gram’s stain, catalase test, growth in 6.5% NaCl broth, growth at 45°C, motility test and by using API 20 Streptococcus system. Sensitivity testing was done using Kirby–Bauer disk diffusion method. Minimum inhibitory concentrations for vancomycin were determined using E-test strips.

Result

Overall, Enterococci were isolated from 114 (76%) of the study subjects. The isolates were Enterococcus faecium (35.1%) followed by Enterococcusfaecalis (29.8%), Enterococcus gallinarum (17.5%), Enterococcuscasseliflavus (8.8%) and Enterococcusdurans (8.8%). Among 114 tested Enterococci isolates, 41 (36%) were resistant to ampicillin, 62 (54.4%) to streptomycin and 39 (34.2%) to gentamycin. Other alternative antibiotics to treat mixed nosocomial infection caused by Enterococci also showed high rate of resistance in vitro: ciprofloxacin (50% of resistance), norfloxacin (49.1%), erythromycin (63.2%), tetracycline (64.9%), chloramphenicol (34.2%), and nitrofrantoin (32.4%). Multiple drug resistance was observed among 89.5% of E. faecium and E. faecalis. Vancomycin resistant Enterococci were observed in 5% of E. faecium isolates.

Conclusion

This study reveals high rate of fecal colonization by multidrug-resistant Enterococci and prevalence of vancomycin resistance strains. Thus periodic surveillance of antibacterial susceptibilities is recommended to detect emerging resistance and to prevent the spread of antibacterial-resistant strains.

Comparison of different doses of vancomycin andteicoplanin lock solutions in catheters colonized with Staphylococcus epidermidis: An in vitro, blinded, antibiotic lock study

BACKGROUND

The antibiotic lock (AL) technique is used for sterilization ofthe intraluminal surface of catheters. This technique consists of filling a catheter lumen with an antibiotic solution and allowing it to dwell for a time sufficient to sterilize the device. Glycopeptide antibiotics (vancomycin and teicoplanin) are commonly used agents for this purpose. But studies evaluating the different dosages of these antibiotics, their optimum concentrations, and duration in AL treatment are lacking.

OBJECTIVE

The aim of this study was to compare the efficacy of differentdoses of vancomycin/saline solution (VSS) and teicoplanin/saline solution (TSS) and to establish the optimal dosage and time needed to eliminate intraluminal methicillin-resistant Staphylococcus epidermidis colonization.

METHODS

This in vitro AL study was conducted at the Department of Infectious Diseases and Clinical Microbiology, Adnan Menderes University Medical Faculty, Aydin, Turkey. Catheters were divided into 2 groups those colonized with slime-forming S epidermidis, and those colonized with non-slime-forming S epidermidis. In each group, catheters were locked with VSS or TSS at 1-, 3-, and 5-mg/mL doses. Catheters instilled with saline solution were used as the control group. After 12 hours of incubation, the catheters were drained and filled with human plasma. Instillation of human plasma or AL solution was alternated every 12 hours to simulate clinical conditions. Every other day, catheters locked with each antibiotic dose or saline were cultured to determine colony count. These procedures were maintained until the catheters were sterile.

RESULTS

The baseline counts of slime-forming and non-slime-forming S epidermidisadhered to 1-cm segment catheters were 39 × 106 and 32 × 106 colony-forming units, respectively. The bacterial count was decreased significantly from baseline on the first day after the start of treatment (day 1) (P < 0.001). At the end of day 7, all catheters treated with antibiotics were sterile. The de creases in bacterial count were statistically similar in catheters treated with all doses of VSS and TSS. Also, the decrease in intraluminal colonization was statistically similar in catheters colonized with slime-forming S epidermidis and non-slime-forming S epidermidis.

CONCLUSION

In this in vitro, blinded AL study, the efficacy of vancomycin and teicoplanin lock solutions were similar and sterilized the catheters in 7 days, suggesting that the 2 antibiotics might be selected for shorter durations compared with those currently recommended for AL treatment in catheter-related infections due to methicillin-resistant staphylococci.

Elimination of Intraluminal Colonization by Antibiotic Lock in Catheters

Antibiotic lock (AL) technique for catheter related infection encompasses the filling of a catheter lumen with high concentrations of antibiotics for hours. The goal of AL therapy is to decontaminate the intraluminal surface of the catheter. However the duration of antibiotic therapy is not established. An in vitro model was designed to establish the time needed to eliminate intraluminal microbial colonization and to evaluate the efficacy of vancomycin in comparison with teicoplanin by using laboratory AL model. Human plasma was instilled into the catheters to allow deposition of fibrin and other products on the catheter wall. After 48 hours, the catheters were drained and inoculated with bacteria in tryptic soy broth. The catheters were then drained and filled with either (a) vancomycin saline solution (VSS) lock (b) teicoplanin saline solution (TSS) lock or (c) saline solution (SS) as the control and then incubated for 12 hours. After 12 hours incubation all the catheter were drained and filled with human plasma. Instillation of human plasma and AL was alternated every 12 hours to simulate clinical conditions. For each day three catheters, locked with VSS, TSS and SS were cultured for colony count. Microbial counts were expressed as total colony-forming units per longitudinal centimeters of catheter surface. A significant decrease in intraluminal catheter colonization started as early as day 1. At the end of 7th day catheters treated with VSS and TSS lock were completely sterile. The decrease of intraluminal colonization was similar in catheters treated with VSS and TSS lock. Also the decrease of intraluminal colonization were similar in catheter colonized with slime forming S. epidermidis and nonslime-forming S. epidermidis.