Methicillin-resistant Organisms Research Articles

Optimizing Detection of MEC-Mediated Methicillin Resistance in Coagulase Negative Staphylococcus Species

Abstract Introduction/Objective Parenteral therapy for invasive staphylococcal infections often comprises lipo/glycopeptides for methicillin resistant (MR) organisms, with extended spectrum penicillins reserved for those confirmed as methicillin susceptible (MS). While phenotypic antimicrobial susceptibility testing (AST) using cefoxitin has high accuracy for differentiating MR/MS for S. aureus, the same, simple approach does not reliably distinguish resistance among all coagulase negative Staphylococcus species (CoNS). As such, clinicians may work under an assumption that MS CoNS cannot be reliably predicted by laboratories, leading to lipo/glycopeptide therapeutic use for invasive infections caused by both MR and MS isolates. To better inform laboratory practice, this study aimed to establish the accuracy of multiple phenotypic and genotypic tests for differentiation of MR/MS among commonly recovered CoNS species producing invasive infections. Methods/Case Report A convenience sample of 155 unique invasive CoNS isolates with historic Vitek 2 and/or disc diffusion (DD) AST results (~50% MR) were retrieved from frozen storage and tested by: (1) cefoxitin and oxacillin DD, (2) a lateral flow immunoassay for PBP2a without beta-lactam induction, and (3) a lab-developed PCR for mecA. A commercial real-time PCR for mecA/C was also employed for a subset of isolates. Results (if a Case Study enter NA) A total of 144 isolates belonging to 11 taxa were evaluated by all tests after accounting for missing, non-viable, and incorrectly cataloged isolates. Using PCR mecA/C detection as the reference standard, categorical agreement for MR/MS status was 95.5% (127/133) for original Vitek GP75 results, 98.6% (142/144) for DD interpreted using updated, species-specific CLSI guidelines, and 100% (144/144) for the lateral flow PBP2a assay. Six MR isolates from five different taxa that were repeatedly mecA-negative by lab-developed PCR confirmed as mecA/C-positive by a commercial assay. Conclusion Although all methods evaluated distinguish MR/MS CoNS with sufficient accuracy, definitive determination is best achieved using off-label/lab-developed PCR for mec or lateral flow immunoassay for PBP2a.

Dealing with Hidden Threats: The Antimicrobial Effect of the Embalming Process.

Individuals naturally carry bacteria and other microbes as part of their natural flora, with some being opportunistic pathogens. Approximately 30% of the population is known to carry Staphylococcus aureus in their nasal cavity, an organism that causes infections ranging from soft tissue abscesses to toxic shock syndrome. This problem is compounded by the presence of antibiotic-resistant strains such as Methicillin-Resistant Staphylococcus aureus (MRSA). Commensal bacteria present on cadavers pose a risk to those who handle the body. As a Medical School Anatomy laboratory that performs hands-on cadaveric dissection, we wanted to know whether the embalming process is sufficient to kill all commensal bacteria that pose a risk to staff and students. Even if these strains do not cause disease in these individuals, secondary transmission could occur to friends and family, who may be at higher risk of acquiring an infection. Embalming is assumed to eliminate all microbial contamination on the body. However, there are limited studies to confirm this. This study characterises the incidence of antibiotic sensitive and resistant bacteria in cadavers donated for medical teaching and research. We have screened for Methicillin-Resistant Organisms (MRO) and Extended-Spectrum Beta-Lactamase (ESBL) producing bacteria. In this study group of cadavers, approximately 46% (16/35) carry an MRO, while 51% (18/35) carry an ESBL positive organism prior to embalming. By determining the organisms' presence pre- and post-embalming, we can evaluate the embalming procedure's effectiveness. Our results show embalming eliminates detectable microbes in about 51% (18/35) of the cadavers. MRO dropped by 75% (16 to 4 positive cadavers), while ESBL organisms went down by almost 95% (from 18 to 1 positive cadaver). There was a further decrease in the number of positive cadavers after storage at 4 °C to 6% (2/32). Thus, although the embalming process does not immediately sterilise all the cadavers, prolonged storage at 4 °C can further reduce the number of viable bacteria.

Potent, specific MEPicides for treatment of zoonotic staphylococci.

Coagulase-positive staphylococci, which frequently colonize the mucosal surfaces of animals, also cause a spectrum of opportunistic infections including skin and soft tissue infections, urinary tract infections, pneumonia, and bacteremia. However, recent advances in bacterial identification have revealed that these common veterinary pathogens are in fact zoonoses that cause serious infections in human patients. The global spread of multidrug-resistant zoonotic staphylococci, in particular the emergence of methicillin-resistant organisms, is now a serious threat to both animal and human welfare. Accordingly, new therapeutic targets that can be exploited to combat staphylococcal infections are urgently needed. Enzymes of the methylerythritol phosphate pathway (MEP) of isoprenoid biosynthesis represent potential targets for treating zoonotic staphylococci. Here we demonstrate that fosmidomycin (FSM) inhibits the first step of the isoprenoid biosynthetic pathway catalyzed by deoxyxylulose phosphate reductoisomerase (DXR) in staphylococci. In addition, we have both enzymatically and structurally determined the mechanism by which FSM elicits its effect. Using a forward genetic screen, the glycerol-3-phosphate transporter GlpT that facilitates FSM uptake was identified in two zoonotic staphylococci, Staphylococcus schleiferi and Staphylococcus pseudintermedius. A series of lipophilic ester prodrugs (termed MEPicides) structurally related to FSM were synthesized, and data indicate that the presence of the prodrug moiety not only substantially increased potency of the inhibitors against staphylococci but also bypassed the need for GlpT-mediated cellular transport. Collectively, our data indicate that the prodrug MEPicides selectively and robustly inhibit DXR in zoonotic staphylococci, and further, that DXR represents a promising, druggable target for future development.

Comparison of bacterial culture results collected via direct corneal ulcer vs conjunctival fornix sampling in canine eyes with presumed bacterial ulcerative keratitis.

To compare aerobic bacterial culture results between samples obtained from the corneal ulcer versus lower conjunctival fornix in eyes with presumed bacterial ulcerative keratitis. Fifty five client-owned dogs diagnosed with ulcerative keratitis. Ophthalmic examinations were performed on each dog including slit-lamp biomicroscopy and indirect ophthalmoscopy. Microbial swabs were collected by direct sampling of the infected corneal ulcer as well as the lower conjunctival fornix, of the same eye, using a sterile rayon-tipped swab. Samples were submitted to an outside reference laboratory for aerobic bacterial culture and sensitivity. One hundred twelve samples were obtained from 56 eyes (55 dogs). Sixty-eight samples yielded bacterial growth. Positive growth from both sites was obtained in 31 eyes (55%). Six eyes yielded bacterial growth from the conjunctival fornix but not from the cornea. No bacterial growth was obtained from either sampling site in 19 eyes. Overall, 31/56 (55%) corneal samples were positive and 37/56 (66%) conjunctival fornix samples were positive. Comparison of organisms isolated from the two collection sites of the same eye revealed an exact correlation in 42/56 (75%) eyes and differed in 14/56 (25%) eyes. Twenty different bacterial isolates were obtained from 68 positive samples. Gram-positive (71%) organisms were more common than Gram-negative (29%). The most commonly isolated organisms were Staphylococcus pseudintermedius (25%), beta-hemolytic Streptococcus spp. (23%), and Pseudomonas aeruginosa (12%). Methicillin-resistant organisms were isolated in 9% of samples. Sampling from the conjunctival fornix may be a suitable alternative to direct ulcer sampling in eyes with compromised corneal structural integrity.

Prevention of Arrhythmia Device Infection Trial: The PADIT Trial

BackgroundInfection of implanted medical devices has catastrophic consequences. For cardiac rhythm devices, pre-procedural cefazolin is standard prophylaxis but does not protect against methicillin-resistant gram-positive organisms, which are common pathogens in device infections. ObjectiveThis study tested the clinical effectiveness of incremental perioperative antibiotics to reduce device infection. MethodsThe authors performed a cluster randomized crossover trial with 4 randomly assigned 6-month periods, during which centers used either conventional or incremental periprocedural antibiotics for all cardiac implantable electronic device procedures as standard procedure. Conventional treatment was pre-procedural cefazolin infusion. Incremental treatment was pre-procedural cefazolin plus vancomycin, intraprocedural bacitracin pocket wash, and 2-day post-procedural oral cephalexin. The primary outcome was 1-year hospitalization for device infection in the high-risk group, analyzed by hierarchical logistic regression modeling, adjusting for random cluster and cluster-period effects. ResultsDevice procedures were performed in 28 centers in 19,603 patients, of whom 12,842 were high risk. Infection occurred in 99 patients (1.03%) receiving conventional treatment, and in 78 (0.78%) receiving incremental treatment (odds ratio: 0.77; 95% confidence interval: 0.56 to 1.05; p = 0.10). In high-risk patients, hospitalization for infection occurred in 77 patients (1.23%) receiving conventional antibiotics and in 66 (1.01%) receiving incremental antibiotics (odds ratio: 0.82; 95% confidence interval: 0.59 to 1.15; p = 0.26). Subgroup analysis did not identify relevant patient or site characteristics with significant benefit from incremental therapy. ConclusionsThe cluster crossover design efficiently tested clinical effectiveness of incremental antibiotics to reduce device infection. Device infection rates were low. The observed difference in infection rates was not statistically significant. (Prevention of Arrhythmia Device Infection Trial [PADIT Pilot] [PADIT]; NCT01002911)

Safety and Efficacy of Antibacterial Prophylaxis After Craniotomy: A Decision Model Analysis.

Antibiotic prophylaxis has revolutionized the safety of neurosurgical procedures in the last century. Today, the clinician's drug of choice before surgery often is based on the antibiotic's resistance profile and drug-induced complications. A decision tree model was developed to compare cefazolin (cephalosporin), vancomycin, or theircombination on 90-day mortality postcraniotomy. Wemodeled the infection type (methicillin-sensitive, methicillin-resistant, or other organisms), antibiotic-related complications that could affect mortality (e.g., renal injury), and Clostridium difficile infections. Parameters' values were extracted from published sources. One-way sensitivity analysis was used to examine results' robustness to plausible variations in input parameter values. The expected value (EV) of 90-day survival was the greatest among patients on cefazolin (EV= 0.9145), followed by patients on vancomycin (EV= 0.8898), and patients on the combination (EV= 0.8886). Cefazolin was the preferred strategy in most one-way sensitivity analyses, except for a few cases in which other options could be preferred based on expected survival. Vancomycin was preferred if kidney injury risk was ≤0.056 conditional on vancomycin intake or ≥12% conditional on cefazolin intake. The combination was preferred if kidney injury conditional risk was ≤0.083 or that for kidney injury-mortality was ≤4.7%. Varying other risks (e.g.,postsurgical-site infections (methicillin-resistant Staphylococcus aureus, methicillin-sensitive Staphylococcus aureus, or other); Clostridium difficile infections' risks conditional on each antibiotic) did not change the preferred strategy. According to this decision analysis, patients undergoing a craniotomy who had cefazolin as prophylaxis had a slightly greater expected survival compared with other strategies. These results were sensitive to changes in kidney injury development risk and kidney failure-associated death.

Infectious agents after liver transplant: etiology, timeline and patients' cell-mediated immunity responses.

Infections continue to be one of the leading causes of morbidity and mortality in liver transplant recipients. We retrospectively reviewed the symptomatic infectious episodes that occurred during the first year post-transplant to determine time of onset, causative pathogens and cell-mediated immunity response patterns. Ninety-eight of the 202 (48.5%) recipients enrolled developed at least one infectious episode. The total number of infectious episodes was 135: 77 (57.1%) bacterial, 45 (33.3%) viral and 13 (9.6%) fungal. The most frequently isolated bacteria were Escherichia coli (21 isolates) and Klebsiella pneumoniae (19 isolates). Overall, extended-spectrum beta lactamase-producing and methicillin-resistant organisms were responsible for 29 (29/77; 37.7%) infectious episodes. Members of the herpes virus group, in particular cytomegalovirus (34/45 viral infections, 75.5%), were detected. Candida species (9 isolates) followed by Aspergillus species (4 isolates) were isolated. The majority of infections (63%) occurred during the early post-transplant phase (<1month), whereas only 8/135 episodes (5.9%) were detected after the sixth month (late phase). Significantly lower median ImmuKnow® intracellular ATP values in patients who developed bacterial and fungal infections compared to infection-free patients were observed (P<0.0001 and P=0.0016, respectively), whereas patients who developed a viral infection had a median intracellular ATP level not statistically different compared to uninfected patients (P=0.4). Our findings confirm that bacteria are responsible for the majority of symptomatic infections and occur more frequently during the first month post-transplant. The ImmuKnow® measurements can be a useful tool for identifying patients at high risk of developing infection, particularly of fungal and bacterial etiology.

A Comparison between Methicillin Resistant Organism and Non- Methicillin Resistant Organism in 2-Stage Reimplantation of Periprosthetic Hip Infection

Background: The prevalence of resistant organisms has increased in periprosthetic hip infection. The purpose of this study is to evaluate the effectiveness of staged reimplantation for the treatment of periprosthetic hip infection caused by methicillin resistant microorganisms. Methods: We performed a retrospective case-control study on 25 consecutive patient (15 men, 10 women) who had periprosthetic hip infection treated using a 2-stage reimplantation. Results: 13 patients infected by methicillin resistant microorganisms were compared with 12 patients infected by non-methicillin resistant microorganisms. The 2-stage reimplantation was possible in all patients. At a mean follow-up of 4.8 years, no significant differences were found between 2 groups with age, sex, body mass index, diabetes, primary diagnosis and kind of primary hip arthroplasty. But methicillin resistant group had much longer period with intravenous antibiotics and oral antibiotics. Erythrocyte sedimentation rate (ESR) and C-reactive protein (CRP) was much higher in methicillin resistant group after 2-stage reimpantation. Harris Hip Score was lower in methicillin resistant group after 2-stage reimplantation. There were 3 recurrent infections after 2-stage reimplantation in methicillin resistant group. But there was no recurrent infection in non-methicillin resistant group. Conclusion: Periprosthetic hip infection caused by methicillin resistant bacterial strain need cautious care of operation and infection control.

Methicillin-resistant Staphylococcal periprosthetic joint infections can be effectively controlled by systemic and local daptomycin.

BackgroundMethicillin-resistant Staphylococcus remains a serious problem in the treatment of periprosthetic joint infection (PJI). Higher failure rates were reported when vancomycin was used in 2-stage exchange arthroplasty. Therefore a better therapeutic drug is needed to treat PJI caused by methicillin-resistant organisms. The purpose of the study was to evaluate the safety and efficacy of daptomycin when administered in bone cement combined with systemic use for methicillin-resistant Staphylococci PJI.MethodsWe conducted a retrospective study from January 2010 to December 2012. Twenty-two patients (10 knees and 12 hips) with PJI caused by methicillin-resistant Staphylococcus species underwent 2-stage revision arthroplasty. In the first stage, 10 % daptomycin (weight daptomycin per weight bone cement) was incorporated into polymethylmethacrylate bone cement, and systemic daptomycin (6 mg/kg) was administered postoperatively for 14 days. In the second stage, 2.5 % w/w daptomycin was used in the bone cement. The minimum follow-up was 2 years or until recurrence of infection.ResultsThe infecting organisms included methicillin-resistant Staphylococcus aureus in 10 patients, methicillin-resistant Staphylococcus epidermidis in 8 patients and methicillin-resistant coagulase-negative Staphylococci in 4 patients. The mean follow-up duration was 33.7 months (range, 24–51 months). The treatment success rate was 100 %. Only one patient developed asymptomatic transient elevation of the creatine phosphokinase level. No patient experienced any adverse effects related to daptomycin such as myositis, rhabdomyolysis, peripheral neuropathy, derangement of liver function, or eosinophilic pneumonia.ConclusionsIn this series, no serious adverse events occurred. Our protocol, using daptomycin-impregnated cement combined with short duration of systemic daptomycin, appears to be an effective and safe treatment for methicillin-resistant Staphylococcus PJI.

Treatment of 50 Deep Infections After Total Knee Arthroplasty.

The prevalence of infections caused by methicillin-resistant organisms has increased, causing difficulty in the treatment of prosthetic joint infection. A multicenter study was performed to review 50 patients with deep infections with or without a resistant organism, such as methicillin-resistant Staphylococcus aureus, at the site of total knee arthroplasty. A group of 13 patients with early deep infections and 4 patients with acute hematogenous infections underwent treatment with debridement, antibiotic therapy, and retention of the prosthesis with revision of the polyethylene insert. Thirty-three patients with late chronic infections were treated with challenging prosthesis retention for prostheses that had not loosened or 2-stage exchange arthroplasty for prostheses that had loosened. Mean duration of follow-up was 4.7±1.8 years. No significant differences in resultant functional knees and mean number of operations were observed between 7 patients with resistant early deep infections and 6 patients with nonresistant early deep infections. However, 24 patients with nonresistant chronic infections showed significant improvement in resultant functional knees (24 of 24; 100%) and fewer mean operations (2.8 times) compared with 9 patients with resistant chronic infections (1 of 9, 11%, and 4.3 times, respectively). The remaining 8 patients with resistant chronic infections (89%) had arthrodesis (3 patients) or underwent above-the-knee amputation (1 patient) or spacer arthroplasty (4 patients). Although patients with resistant early postoperative deep infections showed good results that were similar to those in patients with nonresistant early infections, those with resistant late chronic infections had a significantly inferior success rate compared with those who had nonresistant late chronic infections.

Factors influencing the outcome of deep infection following total knee arthroplasty

BackgroundWhereas clinical studies have revealed a number of important risk factors for postoperative infection following total knee arthroplasty (TKA), it is unclear which factor influences clinical results. A multicenter study was therefore performed by reviewing 51 patients with deep infection after TKA and seeking for the factors related to clinical outcomes. MethodsFifty-one deep infections after TKA were treated from 2000 to 2011 at the multicenter including a university or three arthroplasty centers. Among them, two clinical outcome measures including retention of prosthesis at initial treatment and functional prosthetic knee were assessed for several factors such as age, sex, primary diagnosis, onset time after primary TKA, type of hospital where the primary TKA was performed and the organism's resistance to methicillin using the logistic regression analysis model. ResultsAmong the factors, type of hospital where the primary TKA was performed and onset time after primary TKA had higher multivariable-adjusted odds ratios (ORs) for retention of primary prosthesis (ORs 35.21 and 11.69, respectively.). The cases which primary surgery were performed in arthroplasty centers had higher multivariable-adjusted ORs for functional prosthetic knee (OR 4.9). Thirty-one infection cases with non-methicillin-resistant organisms were all able to keep functional prosthetic knee after the operation, whereas 13 out of 20 infection cases with methicillin-resistant organisms lost their knee function after the operation. ConclusionsOnset time after primary TKA, type of hospital where the primary surgery was performed and the organism's resistance to methicillin are important factors influencing the clinical outcomes after infected TKA. Level of EvidenceLevel 3. Retrospective comparative study.

Short communication: Prevalence of methicillin resistance in coagulase-negative staphylococci and Staphylococcus aureus isolated from bulk milk on organic and conventional dairy farms in the United States

The objective of this study was to evaluate the presence of methicillin-resistant Staphylococcus aureus and coagulase-negative Staphylococcus spp. in bulk tank milk samples from 288 organic and conventional dairy farms located in New York, Wisconsin, and Oregon from March 2009 to May 2011. Due to recent publications reporting the presence mecC (a mecA homolog not detected by traditional mecA-based PCR methods), a combination of genotypic and phenotypic approaches was used to enhance the recovery of methicillin-resistant organisms from bulk tank milk. In total, 13 isolates were identified as methicillin resistant: Staph. aureus (n=1), Staphylococcus sciuri (n=5), Staphylococcus chromogenes (n=2), Staphylococcus saprophyticus (n=3), Staphylococcus agnetis (n=1), and Macrococcus caseolyticus (n=1). The single methicillin-resistant Staph. aureus isolate was identified from an organic farm in New York, for an observed 0.3% prevalence at the farm level. The methicillin-resistant coagulase-negative staphylococci prevalence was 2% in the organic population and 5% in the conventional population. We did not identify mecC in any of the isolates from our population. Of interest was the relatively high number of methicillin-resistant Staph. sciuri recovered, as the number of isolates from our study was considerably higher than those recovered from other recent studies that also assessed milk samples. Our research suggests that the presence of a potential methicillin-resistant Staphylococcus reservoir in milk, and likely the dairy farm population in the United States, is independent of the organic or conventional production system.

Incidence and susceptibility pattern of methicillin resistant coagulase-negative staphylococci isolated from a tertiary care hospital of pakistan.

Background:Methicillin resistant coagulase-negative Staphylococci are resistant organisms causing infections associated with high morbidity and mortality. Methicillin resistant Staphylococcus epidermidis (MRSE), is especially important with respect to admitted patients with indwelling catheters and other installed invasive devices where these organisms are known to be found. As a result, such lifesaving measures may prove fatal from subsequent infection and sepsis by these pathogens. Therefore, to limit such conditions in patients, the spread of MRSE and related organisms in the hospitals have to be effectively controlled.Objectives:This study was carried out to determine the frequency of methicillin resistant organisms among all isolated coagulase negative Staphylococci (CoNS) and to find effective antibiotics against these microorganisms.Patients and Methods:All samples sent to the lab were routinely processed according to standard microbiological procedures and the cultures yielding growth of CoNS were selected for the study. All samples containing CoNS collected over a 2 year-period, were included irrespective of patients' age and gender. The antibiogram of the organisms was recorded according to CLSI guidelines and the ratio of methicillin resistant organisms determined.Results:From a total of 299 isolated coagulase negative Staphylococci (CoNS), 40.1% were methicillin resistant. A high proportion of these organisms (more than 50%) were resistant to cephalosporins, aminoglycosides and quinolones while only a small number were found to show resistance to linezolid, minocycline, chloramphenicol and rifampicin. There were no resistant organisms against vancomycin.Conclusions:A considerable amount of methicillin resistant organisms found among CoNS in our region. The above stated antibiotics would prove effective in limiting these infections. Clinicians should keep these facts in mind while treating their patients.

Perioperative Skin Preparation

Liaison: Anthony T Tokarski BS Leaders: David Blaha MD (US), Michael A. Mont MD (US), Parag Sancheti MS, DNB, MCh (International) Delegates: Lyssette Cardona MD, MPH, MHA, AAHIVS, FIDSA, Gilberto Lara Cotacio MD, Mark Froimson MD, Bhaveen Kapadia MD, James Kuderna MD, PhD, Juan Carlos Lopez MD, Wadih Y Matar MD, MSc, FRCSC, Joseph McCarthy MD, Rhidian Morgan-Jones MB BCh, FRCS, Michael Patzakis MD, Ran Schwarzkopf MD, Gholam Hossain Shahcheraghi MD, Xifu Shang MD, Petri Virolainen MD, PhD, Montri D. Wongworawat MD, Adolph Yates Jr, MD

Surgical Site Infections in Spine Surgery

Retrospective analysis. The objective of this study was to describe the microbiology of surgical site infection (SSI) in spine surgery and relationship with surgical management characteristics. SSI is an important complication of spine surgery that results in significant morbidity. A comprehensive and contemporary understanding of the microbiology of postoperative spine infections is valuable to direct empiric antimicrobial treatment and prophylaxis and other infection prevention strategies. All cases of spinal surgery associated with SSI between July 2005 and November 2010 were identified by the hospital infection control surveillance program using Centers for Disease Control National Health Safety Network criteria. Surgical characteristics and microbiologic data for each case were gathered by direct medical record review. Of 7529 operative spine cases performed between July 2005 and November 2010, 239 cases of SSI were identified. The most commonly isolated pathogen was Staphylococcus aureus (45.2%), followed by Staphylococcus epidermidis (31.4%). Methicillin-resistant organisms accounted for 34.3% of all SSIs and were more common in revision than in primary surgical procedures (47.4% vs. 28.0%, P = 0.003). Gram-negative organisms were identified in 30.5% of the cases. Spine surgical procedures involving the sacrum were significantly associated with gram-negative organisms (P < 0.001) and polymicrobial infections (P = 0.020). Infections due to gram-negative organisms (P = 0.002) and Enterococcus spp. (P = 0.038) were less common in surgical procedures involving the cervical spine. Cefazolin-resistant gram-negative organisms accounted for 61.6% of all gram-negative infections and 18.8% of all SSIs. Although gram-positive organisms predominated, gram-negative organisms accounted for a sizeable portion of SSI, particularly among lower lumbar and sacral spine surgical procedures. Nearly half of infections in revision surgery were due to a methicillin-resistant organism. These findings may help guide choice of empiric antibiotics while awaiting culture data and antimicrobial prophylaxis strategies in specific spine surgical procedures. 3.

Targeted Use of Vancomycin as Perioperative Prophylaxis Reduces Periprosthetic Joint Infection in Revision TKA

The role of vancomycin in surgical antimicrobial prophylaxis and high-risk patients who are most likely to benefit remains unclear. We determined the impact of targeted use of vancomycin on (1) the incidence of periprosthetic joint infection (PJI); and (2) the incidence of PJI from methicillin-resistant organisms in patients undergoing revision total knee arthroplasty (TKA) at our institution. In an effort to reduce PJI rates, we added vancomycin to cefazolin as surgical antimicrobial prophylaxis for patients undergoing revision TKA in October 2010. Internal data indicated a high rate of PJI in revision TKA and in particular PJI resulting from methicillin-resistant organisms, including methicillin-resistant Staphylococcus aureus (MRSA) and methicillin-resistant Staphylococcus epidermidis (MRSE). We retrospectively reviewed infection control surveillance data on 414 revision TKAs performed between July 2008 and June 2012 (fiscal years 2009-2012). The overall rate of PJI in fiscal years 2009-2010 among 190 patients undergoing revision TKA was 7.89%. After the change in surgical antimicrobial prophylaxis, there was a significant reduction in PJI among patients undergoing revision TKA in fiscal years 2011-2012 to 3.13% (p = 0.046). In particular, we observed a reduction in PJI resulting from methicillin-resistant organisms over this same time period, from 4.21% to 0.89% (p = 0.049). Targeted use of vancomycin in patients undergoing revision TKA was effective in reducing the rate of PJI and PJI resulting from methicillin-resistant organisms in an institution with a high baseline rate of PJI due to MRSA and MRSE. Identification of high-risk subgroups of patients within a surgical population can help target infection prevention strategies to those who are most likely to benefit and thus minimize potential risks (eg, selection of resistant organisms, adverse drug events) associated with broader application of such an intervention.

Peristomal infection after percutaneous endoscopic gastrostomy: a 7-year surveillance of 297 patients

Healthcare-associated infection represents the most frequent adverse event during care delivery. Medical advances like percutaneous endoscopic gastrostomy have brought improvement on quality of life to patients but an increased risk of healthcare-associated infection. Predictive risk factors for peristomal wound infection are largely unknown but evidence suggests that antibiotic prophylaxis and preventive strategies related to infection control may reduce infection rates. The primary aim was to evaluate the global prevalence rate of peristomal infection. Secondary objectives were to characterise the positive culture results, to evaluate the prophylactic antibiotic protocol and to identify potential risk factors for peristomal infection. Retrospective study of 297 patients with percutaneous endoscopic gastrostomy performed at a general hospital between January 2004 and September 2010. Patients received prophylactic cefazolin before the endoscopic gastrostomy procedure. Medical records were reviewed for demographic data, underling disease conditions to percutaneous endoscopic gastrostomy and patient potential intrinsic risk factors. Statistical analysis was made with the statistical program SPSS 17.0. A total of 297 percutaneous endoscopic gastrostomy tubes were inserted. Wound infection occurred in 36 patients (12.1%). Staphylococcus aureus methicillin resistant was the most frequently isolated microorganism (33.3%) followed by Pseudomonas aeruginosa (30.6%). The incidence rate had been rising each year and differ from 4.65% in 2004/2007 to 17.9% in 2008/2010. This finding was consistent with the increasing of prevalence global infection rates of the hospital. Most of the infections (55.6%) were detected in the first 10 days post procedure. There was no significant difference in age, body mass index values, mean survival time and duration of percutaneous endoscopic gastrostomy feeding between patients with and without periostomal infection. Institutional factors, namely global prevalence infection rates and the endemic character of Staphylococcus aureus methicillin resistant, play an important role in peristomal infection rates. Traditional antibiotic prophylaxis with cefazolin is not adequate due to the prevalence of resistant organisms. Peristomal infection is a frequent problem with clinical impact in percutaneous endoscopic gastrostomy patients and should be considered a healthcare associated infection. The antimicrobial prophylaxis regimens using cephalosporins are not adequate and need to be reviewed due to the high prevalence of Staphylococcus aureus methicillin resistant and other resistant organisms in hospitals and nursing homes.

Incidence and antibiotic susceptibility of methicillin resistant Staphylococcus aureus in pus samples of patients of Bastar region, Central India

Increasing prevalence of methicillin resistant S. aureus (MRSA) and resistanceto multiple antibiotic classes is a global issue. Regional surveillance of antibiotic susceptibility of the organism is a necessary step to overcome the issues of antimicrobial resistance and treatment failure in MRSA infections. The study was conducted to find the pattern of antibiotic susceptibility in MRSA isolated from the pus samples of patients attending a tertiary care hospital in Bastar tribal region in Central India. The study was performed on 215 MRSA isolates cultured from pus samples of patients over a period of two years and five months. In the methicillin resistant organisms selected by oxacillin screen agar test and cefoxitin disk diffusion test, antibiotic susceptibility was determined by Kirby Baur disk diffusion test with CLSI guide lines. Of the total S. aureus isolates, the incidence of MRSA was 34.1% of which 82.8% were resistant to co‐trimoxazole, 77.2% to tetracycline, 68.8% to gentamycin, 66% to erythromycin, 64.2% to ciprofloxacin, 1.4% to vancomycin, and 0.9% to linezolid. All these isolates were resistant to the ß‐lactam antibiotics tested. Emergence of linezolid resistance and relatively higher vancomycin resistance in the MRSA isolates is a worrisome finding of this study. The antibiotic prescribing must rely on both initial empirical therapy and microbiological antibiotic susceptibility result.

Articulating antibiotic impregnated spacers in two-stage revision of infected total knee arthroplasty

Antibiotic impregnated articulating spacers are used in two-stage revision total knee arthroplasty to deliver local antibiotic therapy while preserving function. We have observed infection control in greater than 95% of cases with functional outcomes approaching those seen in revision for aseptic loosening. Higher failure has been observed with methicillin resistant organisms.

Shifting Trends in Bacterial Keratitis in Toronto: An 11-Year Review

To review the distribution, current trends, and resistance patterns of bacterial keratitis isolates in Toronto over the last 11 years. Retrospective, observational, case series. Microbiology records of suspected bacterial keratitis cases that underwent a diagnostic corneal scraping and cultures from January 1, 2000, through December 31, 2010, were reviewed. Culture results and antibiotic sensitivity profiles were reviewed and analyzed. Distribution of the main isolated pathogens as well as in vitro laboratory minimum inhibitory concentration testing results to identify resistance patterns. A total of 1701 consecutive corneal scrapings were taken during the 11 years of the study. A pathogen was recovered in 977 samples (57.4%), with bacterial keratitis accounting for 897 of the positive cultures (91.8%). The total number of Gram-positive and Gram-negative isolates was 684 and 213, respectively. We identified a decreasing trend in Gram-positive isolates (P = 0.016). The most common isolate overall was coagulase-negative Staphylococcus (CNS) and the most common Gram-negative bacteria isolated was Pseudomonas aeruginosa. Methicillin-resistant Staphylococcus aureus (MRSA) was present in 1.3% of the S aureus isolates, whereas methicillin-resistant CNS (MRCNS) was present in 43.1% of the CNS isolates. There was a trend toward increasing laboratory resistance to methicillin from 28% during the first 4 years of the study to 38.8% for the last 3 years (P = 0.133). When analyzing the sensitivities of MRSA and MRCNS isolates to other antibiotics, there was resistance to cefazolin and sensitivity to vancomycin in all isolates, whereas resistance to other antibiotics was variable. There was a significant decrease in the percentage of Gram-positive microorganisms over time. The sensitivity of Gram-negative isolates to tested antimicrobials was >97% response for all the reported antibiotics; this was not the case for Gram-positive isolates, in which resistance to the antibiotics was more common. Methicillin-resistant organisms accounted for 29.1% of all Gram-positive cultures in our series, suggesting that the empiric use of vancomycin in the setting of severe suspected bacterial keratitis may be justified.