Potential role of pet animals in household transmission of methicillin-resistant Staphylococcus aureus: a narrative review

In this narrative review, we found numerous reports suggesting that dogs and cats may play a role in household methicillin-resistant Staphylococcus aureus (MRSA) transmission and recurrent MRSA infection in human contacts. Future work should emphasize elucidating more clearly the prevalence of MRSA in household pets and characterize transmission dynamics of MRSA humans and pet animals.     

Sample collection and handling considerations for peptidomic studies in whole saliva; implications for biomarker discovery

BackgroundProteomic studies in saliva have demonstrated its potential as a diagnostic biofluid, however the salivary peptidome is less studied. Here we study the effects of several sample collection and handling factors on salivary peptide abundance levels.MethodsSalivary peptides were isolated using an ultrafiltration device and analyzed by tandem mass spectrometry. A panel of 41 peptides common after various treatments were quantified and normalized. We evaluated the effects of freezing rate of the samples, nutritional status of the donors (fed vs. fasted), and room-temperature sample degradation on peptide abundance levels. Repeatability of our sample processing method and our instrumental analysis method were investigated.ResultsIncreased sample freezing rate produced higher levels of peptides. Donor nutritional status had no influence on the levels of measured peptides. No significant difference was detected in donors' saliva following 5, 10 and 15 min of room-temperature degradation. Sample processing and instrumental variability were relatively small, with median CVs of 9.6 and 6.6.ConclusionsPeptide abundance levels in saliva are rather forgiving towards variations in sample handling and donor nutritional status. Differences in freezing methods may affect peptide abundance, so consistency in freezing samples is preferred. Our results are valuable for standardizing sample collection and handling methods for peptidomic-based biomarker studies in saliva.     

Serotype emergence and genotype distribution among macrolide-resistant invasive Streptococcus pneumoniae isolates in the postconjugate vaccine (PCV-7) era

We conducted population-based surveillance for pneumococcal bacteremia within a 5-county region surrounding Philadelphia from October 2001 through September 2008, the period following introduction of the seven-valent pneumococcal conjugate vaccine. Erythromycin resistance increased from 14.7% in 2001-2002 to 20.3% in 2007-2008, while the resistance rate to penicillin (MIC, ≥2 μg/ml) decreased from 7.2% to 4.2% during the same period. The most predominant serotypes associated with erythromycin resistance in 2007-2008 included 19A (29.7%), 15A (29.2%), 6C (10.1%), 3 (5.6%), and 6A (4.5%). The molecular mechanisms for the increasing erythromycin resistance were mainly due to the growing presence of mef(A) negative erm(B)(+) and mef(A)(+) erm(B)(+) genotypes, which increased from 20.0% to 46.1% and from 1.8% to 19.1%, respectively, from 2001-2002 to 2007-2008. However, mef(A)-mediated erythromycin resistance decreased from 72.7% in 2001-2002 to 34.8% in 2007-2008. Serotypes related to the erm(B) gene were 15A (45.6%), 19A (20.9%), 3 (10.1%), and 6B (6.3%); serotypes related to the mef(A) gene were 6A (18.6%), 19A (15.0%), 6C (9.3%), and 14(8.4%); serotypes associated with the presence of both erm(B) and mef(A) were 19A (81.5%), 15A (7.7%), and 19F (6.2%). Pulsed-field gel electrophoresis analysis demonstrated that erythromycin-resistant isolates within the 19A serotype were genetically diverse and related to several circulating international clones. In contrast, erythromycin-resistant isolates within the 15A serotype consisted of clonally identical or closely related isolates.     

Effect of Reduced Vancomycin Susceptibility on Clinical and Economic Outcomes in Staphylococcus aureus Bacteremia

Reduced vancomycin susceptibility (RVS) may lead to poor clinical outcomes in Staphylococcus aureus bacteremia. The objective of this study was to evaluate the clinical and economic impact of RVS in patients with bacteremia due to S. aureus. A cohort study of patients who were hospitalized from December 2007 to May 2009 with S. aureus bacteremia was conducted within a university health system. Multivariable logistic regression and zero-truncated negative binomial regression models were developed to evaluate the association of RVS with 30-day in-hospital mortality, length of stay, and hospital charges. One hundred thirty-four (34.2%) of a total of 392 patients had bacteremia due to S. aureus with RVS as defined by a vancomycin Etest MIC of >1.0 μg/ml. Adjusted risk factors for 30-day in-hospital mortality included the all patient refined-diagnosis related group (APRDRG) risk-of-mortality score (odds ratio [OR], 7.11; 95% confidence interval [CI], 3.04 to 16.6), neutropenia (OR, 13.4; 95% CI, 2.46 to 73.1), white blood cell count (OR, 1.05; 95% CI, 1.01 to 1.09), immunosuppression (OR, 6.31; 95% CI, 1.74 to 22.9), and intensive care unit location (OR, 3.51; 95% CI, 1.65 to 7.49). In multivariable analyses, RVS was significantly associated with increased mortality in patients with S. aureus bacteremia as a result of methicillin-susceptible (OR, 3.90; 95% CI, 1.07 to 14.2) but not methicillin-resistant (OR, 0.53; 95% CI, 0.19 to 1.46) isolates. RVS was associated with greater 30-day in-hospital mortality in patients with bacteremia due to methicillin-susceptible S. aureus but not methicillin-resistant S. aureus. Further research is needed to identify optimal treatment strategies to reduce mortality associated with RVS in S. aureus bacteremia.     

Risk Factors for Infection or Colonization with CTX-M Extended-Spectrum-β-Lactamase-Positive Escherichia coli

There has been a significant increase in the prevalence of Enterobacteriaceae that produce CTX-M-type extended-spectrum β-lactamases. The objective of this study was to evaluate risk factors for infection or colonization with CTX-M-positive Escherichia coli. A case-control study was conducted within a university system from 1 January 2007 to 31 December 2008. All patients with clinical cultures with E. coli demonstrating resistance to extended-spectrum cephalosporins were included. Case patients were designated as those with cultures positive for CTX-M-positive E. coli, and control patients were designated as those with non-CTX-M-producing E. coli. Multivariable logistic regression analyses were performed to evaluate risk factors for CTX-M-positive isolates. A total of 83 (56.8%) of a total of 146 patients had cultures with CTX-M-positive E. coli. On multivariable analyses, there was a significant association between infection or colonization with CTX-M-type β-lactamase-positive E. coli and receipt of piperacillin-tazobactam in the 30 days prior to the culture date (odds ratio [OR], 7.36; 95% confidence interval [CI], 1.61 to 33.8; P = 0.01) and a urinary culture source (OR, 0.36; 95% CI, 0.17 to 0.77; P = 0.008). The rates of resistance to fluoroquinolones were significantly higher in isolates from case patients than in isolates from control patients (90.4 and 50.8%, respectively; P < 0.001). We found that nonurinary sources of clinical cultures and the recent use of piperacillin-tazobactam conferred an increased risk of colonization or infection with CTX-M-positive E. coli. Future studies will need to focus on outcomes associated with infections due to CTX-M-positive E. coli, as well as infection control strategies to limit the spread of these increasingly common organisms.     

Fluoroquinolone-resistant Escherichia coli in the long-term care setting

Background

Prior studies have found fluoroquinolone exposure to be a risk factor for infection with fluoroquinolone-resistant gram-negative rods in the acute care setting. However, risk factors may be different in the long-term care setting.

Methods

A case-control study design was used to determine whether fluoroquinolone exposure is a risk factor for fluoroquinolone-resistant Escherichia coli urinary tract infections in a long-term care center. Cases had fluoroquinolone-resistant E. coli urinary tract infections; 4 controls were selected for each case.

Results

Thirty-three case patients were eligible; 132 controls were then selected. In the multivariable analysis, fluoroquinolone-resistant E. coli urinary tract infection was more common with prior fluoroquinolone use (odds ratio 21.8, 95% confidence interval, 3.7-127.1).

Conclusions

Prior fluoroquinolone use is a strong risk factor for fluoroquinolone-resistant E. coli urinary tract infection in the long-term care setting. Further studies are needed to examine the effect of interventions to decrease fluoroquinolone-resistant infections in the long-term care setting, including studying the effect of decreasing fluoroquinolone use.     

Low prevalence of prior streptococcus pneumoniae vaccination among potential lung transplant candidates

INTRODUCTION: Appropriate vaccination status in the pre-solid organ transplant period is critically important. METHODS: To determine if lung transplant candidates are adequately vaccinated for Streptococcus pneumoniae, a cross-sectional study was performed. Electronic records of patients referred to our institution for transplantation evaluation between July 2002 and January 2004 were reviewed. RESULTS: Only 98 of 157 patients (62.4%; 95% confidence interval [CI], 54.8 to 70.1%) evaluated for lung transplantation reported prior receipt of S pneumoniae vaccine. COPD was the only factor significantly associated with vaccination. Patients with COPD were more likely to have received vaccination compared to patients with other diagnoses (odds ratio, 4.66; 95% CI, 2.26 to 9.60). CONCLUSIONS: S pneumoniae vaccination rates among potential lung transplant candidates fall substantially short of current recommendations for universal immunization. Transplant programs should thoroughly review vaccination status and develop strategies to ensure that candidates receive all appropriate vaccines before transplantation.     

Scaphoid fracture and scaphoid pseudarthrosis

Summary Careful diagnostic and early therapy are especially important in cases of scaphoid fractures. This is due to the patients being mostly young and the high number of non-unions of these carpal bones. Conservative and various operative treatments are therapeutical options. Out of the patients who underwent surgery from January 1993 to February 1999 42 patients with a scaphoid fracture and 88 patients with a scaphoid non-union were, in addition to standard X-ray examination, examined clinically and by MRI pre- and post-operatively. Fractures of the scaphoid were treated by Herbert screw fixtion. The operative treatment of non- unions of the scaphoid included the transplantation of an iliac crest graft and Herbert screw fixation. Post-operatively a cast-immobilisation was done. Subjective statements of the patients and clinical results were assessed. The classification of Herbert and Fisher (1984)/Filan and Herbert (1996) for X-rays was used. The signal intensities of the MRI in the fragments of the scaphoid were determined qualitatively and quantitatively by computer calculation, comparing the pre- and post-operative results with one another. Post-operative results of the scaphoid fractures were in most cases good and excellent. 67 patients with a scaphoid non-union and 11 with a scaphoid fracture showed a pre-operative diminishing of the signal in the proximal fragment. For these patients, the fusion rate was lower than in patients without pre-operative signal reduction. The examination shows that in most cases bony fusions with good clinical results could be achieved by Herbert screw fixation. The MRI seems to be able to complete the radiological classification of the fractures regarding a prognosis.      

Enterococcal bacteremia: risk factors for vancomycin resistance and predictors of mortality.

OBJECTIVE: To identify risk factors for vancomycin resistance and mortality in enterococcal bacteremia. DESIGN: Historical cohort study. SETTING: A large academic medical center with a high prevalence of vancomycin-resistant enterococci (VRE). PATIENTS: Two hundred sixty patients with enterococcal bacteremia, of whom 72 (28%) had VRE. RESULTS: Independent risk factors for infection with VRE were the mean number of antibiotic days (P<.001), renal insufficiency (P<.001), mean days of vancomycin use (P = .005), and neutropenia (P = .013). A trend toward a significant association between metronidazole use and VRE also was noted (P = .068). Mortality was attributable to the bacteremia in 96 patients (37%). Severity of illness (P<.001) and age (P = .020) were independent risk factors for mortality. Vancomycin resistance was not, however, an independent predictor of mortality. CONCLUSION: These results suggest that restrictions on antibiotic use, particularly in patients with renal insufficiency and neutropenia, may help to combat the rising incidence of VRE. Although patients with VRE bacteremia demonstrated higher mortality rates than patients with infection due to susceptible isolates, vancomycin resistance was not an independent predictor of mortality in these patients and likely serves more as a marker of underlying severity of illness.