Francisca Sanz

Clinical Significance of Donor-Unrecognized Bacteremia in the Outcome of Solid-Organ Transplant Recipients

We evaluated the clinical significance of unrecognized bacteremia in the organ donor (i.e., blood culture results that were reported to be positive after transplantation) on the outcome of transplant recipients. Twenty-nine of 569 liver and heart donors (5%) had bacteremia at the time of organ procurement, but there were no documented instances of transmission of the isolated bacteria from the donor to the recipient. Unrecognized bacteremia in the donor does not have a negative clinical impact on the outcome of organ transplant recipients.

Nosocomial Spread of Colistin-Only-Sensitive Sequence Type 235 Pseudomonas aeruginosa Isolates Producing the Extended-Spectrum β-Lactamases GES-1 and GES-5 in Spain

ABSTRACT The mechanisms responsible for the increasing prevalence of colistin-only-sensitive (COS) Pseudomonas aeruginosa isolates in a Spanish hospital were investigated. Pulsed-field gel electrophoresis revealed that 24 (50%) of the studied isolates belonged to the same clone, identified as the internationally spread sequence type 235 (ST235) through multilocus sequence typing. In addition to several mutational resistance mechanisms, an integron containing seven resistance determinants was detected. Remarkably, the extended-spectrum β-lactamase GES-1 and its Gly170Ser carbapenem-hydrolyzing derivative GES-5 were first documented to be encoded in a single integron. This work is the first to describe GES enzymes in Spain and adds them to the growing list of β-lactamases of concern (PER, VIM, and OXA) detected in ST235 clone isolates.

OXA-24 Carbapenemase Gene Flanked by XerC/XerD-Like Recombination Sites in Different Plasmids from Different Acinetobacter Species Isolated during a Nosocomial Outbreak

ABSTRACT A clinical strain of Acinetobacter calcoaceticus resistant to carbapenems was isolated from a blood culture sample from an inpatient in a hospital in Madrid (Spain) during a large outbreak of infection (affecting more than 300 inpatients), caused by a multidrug-resistant Acinetobacter baumannii clone. The carbapenem resistance in both the A. calcoaceticus and A. baumannii clones was due to a blaOXA-24 gene harbored in different plasmids. The plasmids were fully sequenced, revealing the presence of site-specific recombination binding sites putatively involved in mobilization of the blaOXA-24 gene. Comparison of plasmids contained in the two strains revealed possible horizontal transmission of resistance genes between the Acinetobacter species.

Nosocomial spread of colistin-only-sensitive (COS) ST235 Pseudomonas aeruginosa producing the extended-spectrum β-lactamases GES-1 and GES-5 in Spain

ABSTRACT The mechanisms responsible for the increasing prevalence of colistin-only-sensitive (COS) Pseudomonas aeruginosa isolates in a Spanish hospital were investigated. Pulsed-field gel electrophoresis revealed that 24 (50%) of the studied isolates belonged to the same clone, identified as the internationally spread sequence type 235 (ST235) through multilocus sequence typing. In addition to several mutational resistance mechanisms, an integron containing seven resistance determinants was detected. Remarkably, the extended-spectrum β-lactamase GES-1 and its Gly170Ser carbapenem-hydrolyzing derivative GES-5 were first documented to be encoded in a single integron. This work is the first to describe GES enzymes in Spain and adds them to the growing list of β-lactamases of concern (PER, VIM, and OXA) detected in ST235 clone isolates.

High Vancomycin MIC and Complicated Methicillin-Susceptible Staphylococcus aureus Bacteremia

We conducted a retrospective study of 99 patients with methicillin-suseptible Staphylococcus aureus catheter-related bacteremia in which vancomycin MIC was determined by Etest. High vancomycin MIC (>1.5 μg/mL) was the only independent risk factor for development of complicated bacteremia caused by methicillin-susceptible S. aureus (odds ratio 22.9, 95% confidence interval 6.7–78.1).

VIM-2-producing multidrug-resistant Pseudomonas aeruginosa ST175 clone, Spain.

This clone is a major public health problem because it limits antimicrobial drug therapy.

Multidrug-resistant Acinetobacter baumannii Harboring OXA-24 carbapenemase, Spain.

In February 2006, a patient colonized with a multidrug-resistant sequence type 56 Acinetobacter baumannii strain was admitted to a hospital in Madrid, Spain. This strain spread rapidly and caused a large outbreak in the hospital. Clinicians should be alert for this strain because its spread would have serious health consequences.

Clinical and Molecular Characteristics of Infections with CO2-Dependent Small-Colony Variants of Staphylococcus aureus

ABSTRACT Most Staphylococcus aureus small-colony variants (SCVs) are auxotrophs for menadione, hemin, or thymidine but rarely for CO2. We conducted a prospective investigation of all clinical cases of CO2-dependent S. aureus during a 3-year period. We found 14 CO2-dependent isolates of S. aureus from 14 patients that fulfilled all requirements to be considered SCVs, 9 of which were methicillin resistant. The clinical presentations included four cases of catheter-related bacteremia, one complicated by endocarditis; two deep infections (mediastinitis and spondylodiscitis); four wound infections; two respiratory infections; and two cases of nasal colonization. Pulsed-field gel electrophoresis typing showed that the 14 isolates were distributed into 4 types corresponding to sequence types ST125-agr group II (agrII), ST30-agrIII, ST34-agrIII, and ST45-agrI. An array hybridization technique performed on the 14 CO2-dependent isolates and 20 S. aureus isolates with normal phenotype and representing the same sequence types showed that all possessed the enterotoxin gene cluster egc, as well as the genes for α-hemolysin and δ-hemolysin; biofilm genes icaA, icaC, and icaD; several microbial surface components recognizing adhesive matrix molecules (MSCRAMM) genes (clfA, clfB, ebh, eno, fib, ebpS, sdrC, and vw); and the isaB gene. Our study confirms the importance of CO2-dependent SCVs of S. aureus as significant pathogens. Clinical microbiologists should be aware of this kind of auxotrophy because recovery and identification are challenging and not routine. Further studies are necessary to determine the incidence of CO2 auxotrophs of S. aureus, the factors that select these strains in the host, and the genetic basis of this type of auxotrophy.

Nosocomial spread of linezolid-resistant Staphylococcus haemolyticus infections in an intensive care unit.

This report documents the nosocomial spread for an 18-month period of a single clone of linezolid- and teicoplanin-resistant Staphylococcus haemolyticus associated primarily with catheter-related bacteremia in intensive care unit patients. All linezolid-resistant isolates had the same G2576T mutation in at least 1 copy of the 23S rRNA gene.

Endoluminal colonization as a risk factor for coagulase-negative staphylococcal catheter-related bloodstream infections in haemodialysis patients

BACKGROUND Approximately 25% of haemodialysis (HD) patients use catheters as vascular access. Catheter-related bloodstream infections (CRBSI) are a major risk in this population. The objective of our study was to determine whether endoluminal catheter colonization (ECC) predicts CRBSI. METHODS We followed up a cohort of HD patients in our institution who underwent HD with tunnelled cuffed central venous catheters (TCC) between December 2006 and June 2008. Colonization of the inner catheter lumen was assessed every 15 days immediately before HD by culture of blood-heparin mixture and the time to positivity (TTP) was recorded by the BacT/Alert automated system. CRBSI was confirmed by differential TTP (> 2 h) between TCC and peripheral blood cultures. RESULTS We studied 51 patients who required 64 TCC. The incidence of CRBSI was 1.65 episodes per 1000 catheter-days, with Staphylococcus epidermidis being the most common cause of infection (76.2%). ECC was more frequent in the CRSBI group than in the non-CRBSI group (100 vs 5.4%, P < 0.001). For S. epidermidis CRBSIs, the median time from ECC to CRBSI was 31.5 days (interquartile range, 27.0-79.0). The sensitivity, specificity and negative and positive predictive values of arterial lumen cultures for S. epidermidis CRBSIs were 100, 96.3, 92.3 and 100%, respectively, while for venous culture, these values were 92.3, 96.3, 92.3 and 96.3%, respectively. For predicting S. epidermidis CRBSI, endoluminal cultures with a TTP of ≤ 14 h had sensitivity and specificity of 52.1 and 97.7%, respectively. CONCLUSIONS This study shows that ECC may predict the risk of developing CRSBI. Surveillance cultures could, therefore, be used to triage individual HD patients who might benefit from specific intervention measures.