Christy Zalewski

Resistance to Antimalarials in Southeast Asia and Genetic Polymorphisms in pfmdr1

ABSTRACT Resistance to antimalarial drugs is a public health problem worldwide. Molecular markers for drug-resistant malaria, such as pfcrt and pfmdr1 polymorphisms, could serve as useful surveillance tools. To evaluate this possibility, sequence polymorphisms in pfcrt (position 76) and pfmdr1 (positions 86, 184, 1034, 1042, and 1246) and in vitro drug sensitivities were measured for 65 Plasmodium falciparum isolates from Thailand, Myanmar, Vietnam, and Bangladesh. The pfcrt Thr76 polymorphism was present in 97% of samples, consistent with observations that chloroquine resistance is well established in this region. Polymorphisms in pfmdr1 clustered into four specific patterns: the wild type (category I), a Tyr86 polymorphism only (category II), a Phe184 polymorphism only (category III), and Phe184 in combination with Cys1034 and/or Asp1042 (category IV). Isolates in categories I and III were more sensitive to chloroquine and more resistant to mefloquine, artesunate, and artemisinin than isolates in categories II and IV (P ≤ 0.01). Mefloquine resistance was significantly more common in category I and III isolates than in category II and IV isolates, with a prevalence ratio of 14.95 (95% confidence interval, 3.88 to 57.56). These categories identified mefloquine resistance with a sensitivity and a specificity of 94 and 91%, respectively. The pfmdr1 gene copy number was measured by real-time PCR as a ratio of the amount of pfmdr1 DNA to the amount of lactate dehydrogenase (ldh) DNA. Eight samples had pfmdr1 DNA/ldh DNA ratios ≥3. The isolates in all 8 samples fell into categories I and III and were significantly more resistant to mefloquine, quinine, artemisinin, and artesunate and more sensitive to chloroquine than the isolates in the 57 samples with <3 copies of the gene (P ≤ 0.001). Thus, measurement of pfmdr1 mutations and gene copy number may be useful for surveillance of mefloquine-resistant malaria in Southeast Asia.

Analysis of central line-associated bloodstream infections in the intensive care unit after implementation of central line bundles.

Central line-associated bloodstream infections (CLABSIs) have been reduced in number but not eliminated in our intensive care units with use of central line bundles. We performed an analysis of remaining CLABSIs. Many bloodstream infections that met the definition of CLABSI had sources other than central lines or represented contaminated blood samples.

Clonal Groups and the Spread of Resistance to Trimethoprim-Sulfamethoxazole in Uropathogenic Escherichia coli

BACKGROUND Antibiotic resistance is increasingly complicating the management of urinary tract infection. We investigated the extent to which a group of Escherichia coli called clonal group A (CGA), which is associated with resistance to trimethoprim-sulfamethoxazole (TMP-SMZ), accounted for TMP-SMZ resistance among a prospectively collected set of uropathogenic and rectal E. coli isolates from a university population in Michigan. METHODS Resistant and susceptible uropathogenic E. coli isolates (45 each) and 79 randomly selected rectal E. coli isolates were evaluated for CGA status by use of 2 definitions of this group-- the enterobacterial repetitive intergenic consensus sequence 2 (ERIC2)-polymerase chain reaction (PCR) pattern A fingerprint and the C288T single nucleotide polymorphism (SNP) in the fumC gene. We compared virulence gene profiles and molecular mechanisms of resistance to TMP-SMZ between isolates classified as CGA by both approaches to better characterize the relationship between isolates. RESULTS Of the 45 isolates that exhibited ERIC2-PCR pattern A, one-half (23 of 45) were resistant to TMP-SMZ, and 16 contained the C288T SNP. The pattern A isolates were diverse, exhibiting multiple mechanisms of resistance to TMP-SMZ and various combinations of virulence factors. C288T SNP isolates showed less variation, with 15 of 16 resistant to TMP-SMZ and a 1.8-kb class I integron bearing the dfrA17 gene present in 14 of 15 resistant isolates. Twelve of 16 exhibited the same combination of virulence genes. Pulsed-field gel electrophoresis patterns for these 12 isolates were unique. CONCLUSION CGA, as defined by the fumC C288T SNP, appears to be distantly clonal but is not an outbreak-related group. The widespread group has likely evolved through lateral transfer of genes conferring virulence and antibiotic resistance.

Catheter-Related vs. Catheter-Associated Blood Stream Infections in the Intensive Care Unit: Incidence, Microbiology, and Implications

BACKGROUND Catheter-associated blood stream infections (CA-BSI) and catheter-related blood stream infections (CR-BSIs) differ in the degree of proof required to show that the catheter is the cause of the infection. The U.S. Centers for Disease Control and Prevention (CDC) National Healthcare Safety Network (NHSN; formerly the National Nosocomial Infections Surveillance [NNIS] group) collects data regarding CA-BSI nationally. We hypothesized that there would be a significant difference in the rates reported according to the definition. METHODS Prospective surveillance of CA-BSI (defined as bacteremia with no extravascular source identified) is performed in all intensive care units (ICUs) at our institution and reported as the rate per 1,000 catheter-days. In January 2006, we initiated cultures of all catheter tips to evaluate for CR-BSI (defined as a catheter tip culture with >15 colony-forming units of the same microorganism(s) found in the blood culture) in the surgical, trauma-burn, and medical ICUs. RESULTS The CA-BSI rate across all ICUs for the 24-mo study period was 1.4/1,000 catheter-days. The CR-BSI rate was 0.4/1,000 catheter days, for a rate difference of 1.0 infections/1,000 catheter-days (p < 0.001 vs. CA-BSI). The pathogens identified in CA-BSI included many organisms that are not associated with catheter-related BSIs. CONCLUSIONS The CR-BSI rate is significantly lower than the CA-BSI rate. The organisms identified in CA-BSI surveillance often are not common in catheter-related infections. Reporting CR-BSI thus is a more accurate measure of complications of central venous catheter use, and this rate may be more sensitive to catheter-specific interventions designed to reduce rates of BSI in the ICU.

Intensive care unit core measures improve infectious complications in burn patients.

There are no data on the effects of the Joint Commission on the Accreditation of Healthcare Organizations intensive care unit (ICU) core measures for outcomes in the burn population. The impact of the ICU core measures on patients admitted to burn center was studied. The prospective outcomes measured were hospital length of stay, ventilator-associated pneumonia (VAP), catheter-related bloodstream infection (BSI) rates, and mortality for all burn patients admitted to the ICU. Protocols for the ICU core measures of deep venous thrombosis prophylaxis, stress ulcer prophylaxis, and daily weaning parameters, were in place before the start of the study period in 2005. Head-of-bed up at 30 degrees and glucose control, although variably practiced, were formally instituted in 2005. Enforcement of daily weaning parameters and sedation holidays were also implemented after 2005. The time period before institution of the core measures was 2003 to 2004 (pregroup), which was compared with the study time period of 2006 to 2008 (postgroup). There were no differences in the mean burn size, percent of inhalation injuries, or age between the two time periods. The VAP rate fell from 42/1000 to 13/1000 ventilator days, P = .0001. The BSI rate also declined from 12/1000 to 4/1000 line days, P = .05. Hospital and ICU lengths of stay and ventilator days did not change significantly between the periods. Risk-adjusted mortality for ICU patients improved from 13 to 7% (P = 0.01, odds ratio = 0.5 [0.29–0.85]). Although not specifically designed for the burn population, implementation of the proposed Joint Commission on the Accreditation of Healthcare Organizations ICU core measures for burn patients was associated with improvements in VAP and BSI rates, as well as a lower mortality.

Prevention of Catheter-Related Blood Stream Infection: Back to Basics?

BACKGROUND Central venous catheter (CVC)-related infections are a substantial problem in the intensive care unit (ICU). Our infection control team initiated the routine use of antiseptic-coated (chlorhexidine-silver sulfadiazine; Chx-SS) CVCs in our adult ICUs to reduce catheter-associated (CA) and catheter-related (CR) blood stream infection (BSI) as we implemented other educational and best practice standardization strategies. Prior randomized studies documented that the use of Chx-SS catheters reduces microbial colonization of the catheter compared with an uncoated standard (Std) CVC but does not reduce CR-BSI. We therefore implemented the routine use of uncoated Std CVCs in our surgical ICU (SICU) and examined the impact of this change. HYPOTHESIS The use of uncoated Std CVCs does not increase CR-BSI rate in an SICU. METHODS Prospective evaluation of universal use of uncoated Std CVCs, implemented November 2007 in the SICU. The incidences of CA-BSI and CR-BSI were compared during November 2006-October 2007 (universal use of Chx-SS CVCs) and November 2007-October 2008 (universal use of Std CVCs) by t-test. The definitions of the U.S. Centers for Disease Control and Prevention were used for CA-BSI and CR-BSI. Patient data were collected via a dedicated Acute Physiology and Chronic Health Evaluation (APACHE) III coordinator for the SICU. RESULTS Annual use of CVCs increased significantly in the last six years, from 3,543 (2001) to 5,799 (2006) total days. The APACHE III scores on day 1 increased from a mean of 54.4 in 2004 to 55.6 in 2008 (p = 0.0010; 95% confidence interval [CI] 1.29-5.13). The mean age of the patients was unchanged over this period, ranging from 58.2 to 59.6 years. The Chx-SS catheters were implemented in the SICU in 2002. Data regarding the specific incidence of CR-BSI were collected beginning at the end of 2005, with mandatory catheter tip cultures when CVCs were removed. Little difference was identified in the incidence of BSI between the interval with universal Chx-SS use and that with Std CVC use. (Total BSI 0.7 vs. 0.8 per 1,000 catheter days; CA-BSI 0.5 vs. 0.8 per 1,000 catheter days; CR-BSI 0.2 vs. 0 per 1,000 catheter days.) No difference was seen in the causative pathogens of CA-BSI or CR-BSI. CONCLUSION Eliminating the universal use of Chx-SS-coated CVCs in an SICU with a low background incidence of CR-BSIs did not result in an increase in the rate of CR-BSIs. This study documents the greater importance of adherence to standardization of the processes of care related to CVC placement than of coated CVC use in the reduction of CR-BSI.

Efficacy of Surveillance for 2009 H1N1 Pandemic within a Healthcare System

In the fall of 2009, our hospital introduced a surveillance system to monitor the increase in cases of H1N1 pandemic influenza A virus infection. The system involved tracking cases of influenza-like illness in the emergency department, the outpatient clinics, and the inpatient wards as well as specimens with positive polymerase chain reaction results reported by the microbiology laboratory. Our data correlated well with national and regional data.