Narelle George

Carbapenem Resistance in Klebsiella pneumoniae Due to the New Delhi Metallo-β-lactamase

Carbapenem resistance in Klebsiella pneumoniae is most notably due to the K. pneumoniae carbapenemase (KPC) β-lactamase. In this report, we describe the occurrence of a newly described mechanism of carbapenem resistance, the NDM-1 β-lactamase, in a patient who received medical attention (but was not hospitalized) in India.

A prospective, randomized trial of rifampicin-minocycline-coated and silver-platinum-carbon-impregnated central venous catheters

Objective:Central venous catheters are the predominant cause of nosocomial bacteremia; however, the effectiveness of different antimicrobial central venous catheters remains uncertain. We compared the infection rate of silver-platinum-carbon (SPC)-impregnated catheters with rifampicin-minocycline (RM)-coated catheters. Design:A large, single-center, prospective randomized study. Setting:Twenty-two-bed adult general intensive care unit in a large tertiary metropolitan hospital in Brisbane, Australia (2000–2001). Patients:Consecutive series of all central venous catheterizations in intensive care unit patients. Interventions:Randomization, concealment, and blinding were carefully performed. Catheter insertion and care were performed according to published guidelines. Blood cultures were taken at central venous catheter removal, and catheter-tip cultures were performed by both roll-plate and sonication techniques. Pulsed field gel electrophoresis was used to establish shared clonal origin for matched isolates. Measurements and Main Results:Central venous catheter colonization and catheter-related bloodstream infection were determined with a blinded technique using the evaluation of the extensive microbiological and clinical data collected and a rigorous classification system. Six hundred forty-six central venous catheters (RM 319, SPC 327) were inserted, and 574 (89%) were microbiologically evaluable. Colonization rates were lower for the RM catheters than SPC catheters (25 of 280, 8.9%; 43 of 294, 14.6%; p = .039). A Kaplan-Meier analysis that included catheter time in situ did not quite achieve statistical significance (p = .055). Catheter-related bloodstream infection was infrequent for both catheter-types (RM 4, 1.4%; SPC 5, 1.7%). Conclusions:The SPC catheter is a clinically effective antimicrobial catheter; however, the RM catheter had a lower colonization rate. Both catheter types had low rates of catheter-related bloodstream infection. These results indicate that future studies will require similar rigorous methodology and thousands of central venous catheters to demonstrate differences in catheter-related bloodstream infection rates.

Clinical utility of hygroscopic heat and moisture exchangers in intensive care patients.

OBJECTIVE To compare the degree of bacterial circuit colonization, frequency of ventilator-associated pneumonia (VAP), character of respiratory secretions, rewarming of hypothermic patients, disposable costs, and air flow resistance in intensive care patients ventilated using either a heat and moisture exchanger (HME) or hot water (HW) humidifier circuit. DESIGN A prospective, randomized blinded trial of patients in the intensive care unit undergoing mechanical ventilation. SETTING A metropolitan teaching hospital. PATIENTS One hundred sixteen patients undergoing mechanical ventilation for a minimum period of 48 hrs were enrolled. INTERVENTIONS Patients were randomized to three ventilation groups using a) an HW circuit with a 2-day circuit change (n = 41); or b) a bacterial-viral filtering HME in the circuit, with either a 2-day (n = 42); or c) a 4-day circuit change (n = 33). MEASUREMENTS AND MAIN RESULTS Circuit colonization was assessed using quantitative culture of washings taken from the circuit tubing and semiquantitative culture of swabs from the Y connectors. Sixty-seven percent of HW circuits became contaminated compared with 12% in the two HME groups (p < .0001). Median colony counts were lower in the HME groups (p < .0001). If circuits at first circuit change were contaminated in the HW group, 89% of subsequent circuit changes became contaminated compared with 0% and 25% for the 2- and 4-day HME groups, respectively. The frequency of VAP, the time to resolution of admission hypothermia, and the volume and fluidity of secretions were similar for all groups. The resistance of the HME after 24 hrs of use was < 0.025 cm H2O/L at gas flows of 40 L/min. HME use resulted in a cost reduction of

Comparison of the immediate, residual, and cumulative antibacterial effects of Novaderm R, Novascrub R, Betadine Surgical Scrub, Hibiclens, and liquid soap☆☆☆★★★

1.48 (Australian)/day. CONCLUSIONS Circuits with a bacterial-viral filtering HME are less readily colonized by bacteria. Contamination is a random event. Humidification technique has no influence on the frequency rate of VAP, the effectiveness of rewarming, nor the character of the respiratory secretions. Breathing resistance is generally low and disposable costs are reduced when an HME is used.

Double-heater-wire circuits and heat-and-moisture exchangers and the risk of ventilator-associated pneumonia

BACKGROUND Triclosan (Irgasan), an antibacterial active against staphylococci and coliform bacteria, has been formulated for use as a handwash. There has been only one previous report of the use of the glove juice test to determine the immediate, residual, and cumulative effects of a 1% triclosan-based handwash product. There have been no previous studies on the use of 1% triclosan combined with povidone-iodine (PI) in a handwash product. METHODS The glove juice technique was used to document and compare the immediate, 3-hour residual, and 5-day cumulative effects on the mean log10 bacterial counts of 1% triclosan-based handwash product and 1% triclosan with 5% PI. A standardized surgical handwashing technique was used before sample collection. These results and the identity and type of the aerobic bacteria cultured from the samples were compared with the results of standardized washing and glove juice sampling with 4% weight/volume chlorhexidine gluconate (CHG), 7.5% PI, and a nonantimicrobial liquid soap. RESULTS All five tested products showed significant log10 reduction from baseline on day 1, hour 0 (p < 0.05). There was no significant difference between the mean log10 bacterial count when 7.5% PI, 4% CHG, and 1% triclosan with 5% PI were compared with each other immediately after washing (p > 0.05). There was a significant difference between 1% triclosan and the liquid soap when they were each compared with 4% CHG, 7.5% PI, and 1% triclosan with 5% PI. There was no statistically significant difference between the 1% triclosan product and the liquid soap (p > 0.20). All products were effective at reducing the immediate bacterial count from the baseline level. All formulations except the liquid soap showed significant cumulative effect (p < 0.05) after multiple washes, with no significant difference between the cumulative effects of the liquid soap and 1% triclosan (p > 0.05). Both products differed significantly (p < 0.05) from the CHG, PI, and triclosan with PI. CHG, PI, and triclosan with PI showed effects significantly different from each other (p < 0.05). CONCLUSIONS Triclosan combined with PI resulted in the prevention of bacterial regrowth at 3 hours such as occurred when PI alone was used. Triclosan-containing products have a small cumulative effect, although not as great as that produced by CHG. The triclosan-based products did not appear to select for gram-negative bacterial overgrowth, although the study period may have been too short to detect such an effect.

Rapid Detection of Staphylococcus aureus Panton-Valentine Leukocidin in Clinical Specimens by Enzyme-Linked Immunosorbent Assay and Immunochromatographic Tests

Objective:To compare the incidence of ventilator-associated pneumonia (VAP) in patients ventilated in intensive care by means of circuits humidified with a hygroscopic heat-and-moisture exchanger with a bacterial viral filter (HME) or hot-water humidification with a heater wire in both inspiratory and expiratory circuit limbs (DHW) or the inspiratory limb only (SHW). Design:A prospective, randomized trial. Setting:A metropolitan teaching hospitals general intensive care unit. Patients:Three hundred eighty-one patients requiring a minimum period of mechanical ventilation of 48 hrs. Interventions:Patients were randomized to humidification with use of an HME (n = 190), SHW (n = 94), or DHW (n = 97). Measurements and Main Results:Study end points were VAP diagnosed on the basis of Clinical Pulmonary Infection Score (CPIS) (1), HME resistance after 24 hrs of use, endotracheal tube resistance, and HME use per patient. VAP occurred with similar frequency in all groups (13%, HME; 14%, DHW; 10%, SHW; p = 0.61) and was predicted only by current smoking (adjusted odds ratio [AOR], 2.1; 95% confidence interval [CI], 1.1–3.9; p = .03) and ventilation days (AOR, 1.05; 95% CI, 1.0–1.2; p = .001); VAP was less likely for patients with an admission diagnosis of pneumonia (AOR, 0.40; 95% CI, 0.4–0.2; p = .04). HME resistance after 24 hrs of use measured at a gas flow of 50 L/min was 0.9 cm H2O (0.4–2.9). Endotracheal tube resistance was similar for all three groups (16–19 cm H2O min/L; p = .2), as were suction frequency, secretion thickness, and blood on suctioning (p = .32, p = .06, and p = .34, respectively). The HME use per patient per day was 1.13. Conclusions:Humidification technique does not influence either VAP incidence or secretion characteristics, but HMEs may have air-flow resistance higher than manufacturer specifications after 24 hrs of use.

Dominance of IMP-4-Producing Enterobacter cloacae among Carbapenemase-Producing Enterobacteriaceae in Australia

ABSTRACT Staphylococcus aureus strains producing Panton-Valentine leukocidin (PVL) have been epidemiologically linked to specific human infections. To evaluate immunological tests that may be used to diagnose infections with PVL-producing strains, we prospectively collected pus, respiratory tract specimens, and joint fluid specimens from which S. aureus had been isolated in clinical laboratories in six countries. An enzyme-linked immunosorbent assay (ELISA) and an immunochromatographic test (ICT) targeting LukS-PV were performed directly with clinical samples for the detection of PVL. The same tests were applied to S. aureus culture supernatants. The corresponding S. aureus isolates were characterized by PCR for the presence of the PVL locus (lukS-PV and lukF-PV) and the mec A gene. A total of 185 samples from 144 skin infections, 23 bone and joint infections, and 18 lower respiratory tract infections were analyzed. By PCR, 72/185 S. aureus isolates were PVL locus positive (PVL+); 28 of these were also mecA positive. PVL was detected in the supernatants of all PVL+ strains by both ELISA and an ICT, while no signal was observed with PVL-negative strains. The PVL concentrations in human clinical samples that grew PVL+ strains ranged from 0 to 399 μg/ml by ELISA. By the use of 0.015 μg/ml of PVL as a cutoff value, PVL was detected in 65/72 (90%) of the clinical samples by ELISA. The sensitivity and specificity of the ELISA test were 90% and 100%, respectively. By the ICT, PVL was detected in 57/72 (79%) of the samples, and the sensitivity and specificity of ICT were 79% and 100%, respectively. PVL is expressed by S. aureus during human infection, and a PVL-specific ELISA and ICT could be reliable tests for the diagnosis of infections caused by PVL-producing strains.

Comparison of the antibacterial efficacy of 4% chlorhexidine gluconate and 1% triclosan handwash products in an acute clinical ward

ABSTRACT The prevalence of carbapenemase-producing Enterobacteriaceae (CPE) has been increasing worldwide. blaIMP has been reported to be the predominant carbapenemase-encoding gene within Enterobacteriaceae in Australia. However, there are limited data currently available on CPE from Queensland, Australia. A total of 58 CPE isolates were isolated between July 2009 and March 2014 from Queensland hospitals. The clonality of isolates was determined by Diversilab repetitive sequence-based PCR. The isolates were investigated for the resistance mechanisms carbapenemase, extended-spectrum β-lactamase, and AmpC β-lactamase and for aminoglycoside resistance and plasmid-mediated quinolone resistance genes by PCR. The plasmid types associated with carbapenemase-encoding genes were characterized. The majority of the CPE were Enterobacter cloacae (n = 29). The majority of Queensland CPE isolates were IMP producers and comprised 11 species (n = 48). Nine NDM-producing Enterobacteriaceae were identified. One NDM-producing Klebsiella pneumoniae isolate coproduced OXA-48. One K. pneumoniae isolate was an OXA-181 producer. The incidence of IMP producers increased significantly in 2013. blaIMP-4 was found in all IMP-producing isolates. blaTEM, qnrB, and aacA4 were common among IMP-4 producers. The HI2 (67%) and L/M (21%) replicons were associated with blaIMP-4. All HI2 plasmids were of sequence type 1 (ST1). All but one of the NDM producers possessed blaCTX-M-15. The 16S rRNA methylase genes found among NDM producers were armA, rmtB, rmtC, and rmtF. The substantial increase in the prevalence of CPE in Queensland has been associated mainly with the emergence E. cloacae strains possessing HI2 plasmids carrying blaIMP-4 over the past 2 years. The importation of NDM producers and/or OXA-48-like producers in patients also contributed to the increased emergence of CPE.

Pseudomonas aeruginosa genotypes acquired by children with cystic fibrosis by age 5-years.

The antibacterial efficacy of 4% chlorhexidine gluconate (CHG) and 1% triclosan as handwash antiseptics is well established. Few published studies have identified hand bacteria found in glove juice samples, and most studies have used nonclinical study subjects. We report a longitudinal comparative study to determine the effect of 4% CHG and 1% triclosan on the composition of the hand bacterial flora of clinical staff in a specialist surgical unit. Prehandwash and posthandwash samples were collected on 3 separate occasions throughout each day by using the glove juice method and a supervised handwashing technique. Total bacterial counts were determined as well as counts for specific pathogens including methicillin-resistant Staphylococcus aureus and coliforms. Both 4% CHG and 1% triclosan were found to effectively reduce the total hand bacterial count preduty (P =.0001). Four percent CHG also was consistently more effective at reducing the total count than was 1% triclosan. However, 1% triclosan eliminated methicillin-resistant S aureus, whereas 4% CHG failed to do so (P =.0001). Gram-negative bacteria were more likely to be eliminated after the use of 4% CHG compared with 1% triclosan. This study is the first to report the effects of 1% triclosan on the bacterial flora present on the hands of clinical staff and demonstrates the ability of 1% triclosan to eliminate methicillin-resistant S aureus.

Control of an Outbreak of Carbapenem- Resistant Acinetobacter baumannii in Australia after Introduction of Environmental Cleaning with a Commercial Oxidizing Disinfectant

BACKGROUND We describe Pseudomonas aeruginosa acquisitions in children with cystic fibrosis (CF) aged ≤5-years, eradication treatment efficacy, and genotypic relationships between upper and lower airway isolates and strains from non-CF sources. METHODS Of 168 CF children aged ≤5-years in a bronchoalveolar lavage (BAL)-directed therapy trial, 155 had detailed microbiological results. Overall, 201/271 (74%) P. aeruginosa isolates from BAL and oropharyngeal cultures were available for genotyping, including those collected before and after eradication therapy. RESULTS Eighty-two (53%) subjects acquired P. aeruginosa, of which most were unique strains. Initial eradication success rate was 90%, but 36 (44%) reacquired P. aeruginosa, with genotypic substitutions more common in BAL (12/14) than oropharyngeal (3/11) cultures. Moreover, oropharyngeal cultures did not predict BAL genotypes reliably. CONCLUSIONS CF children acquire environmental P. aeruginosa strains frequently. However, discordance between BAL and oropharyngeal strains raises questions over upper airway reservoirs and how to best determine eradication in non-expectorating children.