Blinded comparison of repetitive-sequence PCR and multilocus sequence typing for genotyping methicillin-resistant Staphylococcus aureus isolates from a children's hospital in St. Louis, Missouri

Inhibition of Staphylococcus aureus cocktail using the synergies of oregano and rosemary essential oils or carvacrol and 1,8-cineole

This study assessed the inhibitory effects of the essential oils (EOs) from Origanum vulgare L. (OVEO) and Rosmarinus officinalis L. (ROEO), as well as of the its majority individual constituents (ICs) carvacrol (CAR) and 1,8-cineole (CIN), respectively, combined at subinhibitory concentrations against a cocktail of Staphylococcus aureus. The Minimum inhibitory Concentration (MIC) of both OVEO and CAR against S. aureus cocktail was 1.25 μL/mL, while for ROEO and CIN the MIC value was 10 μL/mL. The Fractional Inhibitory Concentration Index of the combined EOs or ICs was ≤0.5 indicating a synergic interaction. The incorporation of OVEO and ROEO or CAR and CIN at different combinations in cheese and meat broths caused a decrease (p ≤ 0.05) of initial counts of S. aureus. Combined application of 1/8 MIC OVEO and 1/4 MIC ROEO or 1/4 MIC CAR and 1/4 MIC CIN in meat and cheese samples reduced (p ≤ 0.05) the viable cells counts and caused morphological changes in S. aureus cells, such as cell shrinkage and appearance of blebbing-like structures on cell surfaces. However, in cheese and meat samples the decrease in viable cell counts was smaller (p ≤ 0.05) than that observed in cheese and meat broths. These findings reinforce the potential of the use of OVEO and ROEO or CAR and CIN in combination to control S. aureus in cheese and meat matrices.

Treatment and clinical outcomes of urinary tract infections caused by KPC-producing Enterobacteriaceae in a retrospective cohort

BACKGROUND

Optimal treatment regimens for infections caused by Klebsiella pneumoniae carbapenemase (KPC)-producing Enterobacteriaceae are not well-defined.

OBJECTIVES

This study describes the treatment and outcomes in patients with urinary tract infection (UTI) caused by KPC-producing Enterobacteriaceae.

METHODS

This retrospective cohort study analyzed data from adult inpatients with bacteriuria caused by KPC-positive organisms treated at Barnes-Jewish Hospital from June 1, 2006, to February 1, 2008. KPC-positive isolates were identified utilizing disk-diffusion susceptibility testing and confirmed to contain bla(KPC) via molecular methods.

RESULTS

Twenty-one patients met the inclusion criteria and all were classified as having symptomatic UTI. The majority of patients were female (15/21 [71%]), and the mean (SD) age was 62.4 (15.2) years. Successful clinical and microbiologic responses were observed in 16 patients (76%) for both outcomes. Patients with urinary catheters had them removed or replaced in 9 of 15 cases (60%). Antibiotics active against the isolated pathogen were provided in 14 of 21 cases (67%), often after considerable delay (median, 72.5 hours [range, 4-312 hours]). All 7 patients receiving aminoglycoside therapy had successful clinical and microbiologic responses, and in vitro testing of an extended antibiotic panel revealed high susceptibility rates for tigecycline (28/29 [97%]), minocycline (22/29 [76%]), and fosfomycin (25/29 [86%]) against the KPC-positive isolates.

CONCLUSIONS

Although receipt of appropriate therapy was delayed in many cases, clinical outcomes investigated revealed [corrected] high rates of successful response in this defined group of patients Aminoglycosides and tetracycline derivatives suggested therapeutic promise in the treatment of KPC-producing Enterobacteriaceae UTI.

Carriage frequency, phenotypic and genotypic characteristics of Staphylococcus aureus isolated from dialysis and kidney tranplant patients at a hosptial in northern paraná

The objective of the present study was to determine the frequency of Staphylococcus aureus nasal carriage among dialysis and kidney transplant patients, to identify the antimicrobial resistance profile of these strains and to verify their genetic profiles with the RW3A primer. The study included 159 individuals, comprising 111 dialysis and 48 kidney transplant patients. Of the 48 transplant patients, 75% were positive for S. aureus, whereas 49% of the 111 dialysis patients were carriers. Two samples yielded conflicting results for oxacillin sensitivity between the disk diffusion and minimum inhibitory concentration (MIC) assays: both were sensitive by the disk diffusion assay and resistant by MIC (4 μg/ml). In the antibiogram by disk diffusion, ten samples were resistant to cefoxitin, among which eight were also resistant to oxacillin. The resistance of the ten samples to cefoxitin by the disk diffusion assay was confirmed by MIC. Of the ten oxacillin-resistant samples, eight harbored the mecA gene. All samples were sensitive to vancomycin, and most were resistant to penicillin and demonstrated high rates of resistance to the other antimicrobials tested. The samples from dialysis patients exhibited a more homogenous genetic profile. Among the samples with a high percent similarity, no correlation with sensitivity or resistance to oxacillin was observed. According to the results of this study, the implementation of prevention and control measures, such as increased restrictions on prescriptions for antimicrobial drugs and nasal decontamination prior to high-risk procedures, is recommended.

contribution of genetically restricted, methicillin-susceptible strains to the ongoing epidemic of community-acquired Staphylococcus aureus infections

BACKGROUND

Within the current worldwide epidemic of community-acquired Staphylococcus aureus infections, attention has focused on the role of methicillin-resistant strains. We characterize methicillin-susceptible strains that also contribute to this epidemic.

METHODS

We tracked cultures from abscess specimens submitted to the microbiology laboratory at St. Louis Children's Hospital and examined Panton-Valentine leukocidin (PVL) genes in methicillin-susceptible S. aureus (MSSA) isolates. We further characterized some isolates by multilocus sequence typing, pulsed-field gel electrophoresis, antibiotic susceptibility, accessory gene regulator (agr) allele, and presence of the arcA gene of the arginine catabolic mobile element.

RESULTS

From 1999 to 2007, we detected a 250-fold increase in cultures of abscesses yielding methicillin-resistant S. aureus (MRSA) and a 5-fold increase in abscess cultures yielding MSSA. MSSA isolates from abscesses and wounds were more likely to encode PVL than isolates from other sources. In contrast to PVL-negative isolates of MSSA, which were genetically diverse, PVL-positive isolates were predominantly multilocus sequence typing type 8 and agr type 1. More than half of PVL-positive MSSA isolates were resistant to erythromycin and susceptible to clindamycin with the absence of inducible resistance, a pattern uncommon in PVL-negative MSSA but frequent in the USA300 clone of MRSA. In addition, pulsed-field gel electrophoresis of PVL-positive MSSA strains revealed the USA300 pattern.

CONCLUSIONS

In addition to methicillin-resistant strains, the current epidemic of S. aureus infections includes infections caused by methicillin-susceptible strains that are closely related genetically and share phenotypic characteristics other than susceptibility to methicillin. These findings suggest that factors other than methicillin resistance are driving the epidemic.

Education of the PhD in laboratory medicine

Throughout the history of laboratory medicine, the PhD scientist has played a role in developing new methods and algorithms that have contributed significantly to the field. Although the number of formally trained PhDs in laboratory medicine is currently small, they continue to play an important role in large, primarily academic, clinical laboratories and departments and in the in vitro diagnostics industry. This article discusses the importance of the formally trained PhD in today's laboratory medicine environment and the necessary training process, and approach for training PhDs at the postdoctoral level to have successful careers in laboratory medicine.