To evaluate the efficacy of a new monochloramine generation system for control of Legionella in a hospital hot water distribution system

A 495-bed tertiary care hospital in Pittsburgh, Pennsylvania. The hospital has 12 floors covering approximately 78,000 m2.

The hospital hot water system was monitored for a total of 29 months, including a 5-month baseline sampling period prior to installation of the monochloramine system and 24 months of surveillance after system installation (postdisinfection period). Water samples were collected for microbiological analysis (Legionella species, Pseudomonas aeruginosa, Stenotrophomonas maltophilia, Acinetobacter species, nitrifying bacteria, heterotrophic plate count [HPC] bacteria, and nontuberculous mycobacteria). Chemical parameters monitored during the investigation included monochloramine, chlorine (free and total), nitrate, nitrite, total ammonia, copper, silver, lead, and pH.

A significant reduction in Legionella distal site positivity was observed between the pre- and postdisinfection periods, with positivity decreasing from an average of 53% (baseline) to an average of 9% after monochloramine application (P > .05). Although geometric mean HPC concentrations decreased by approximately 2 log colony-forming units per milliliter during monochloramine treatment, we did not observe significant changes in other microbial populations.

This is the first evaluation in the United States of a commercially available monochloramine system installed on a hospital hot water system for Legionella disinfection, and it demonstrated a significant reduction in Legionella colonization. Significant increases in microbial populations or other negative effects previously associated with monochloramine use in large municipal cold water systems were not observed.

Infect Control Hosp Epidemiol 2014;35(11):1356–1363

Methicillin-resistant Staphylococcus aureus (MRSA) is a major pathogen in hospital-acquired infections. MRSA-colonized inpatients who may benefit from undergoing decolonization have not been identified.

To identify risk factors for MRSA infection among patients who are colonized with MRSA at hospital admission.

A case-control study.

A 146-bed Veterans Affairs hospital.

Case patients were those patients admitted from January 2003 to August 2011 who were found to be colonized with MRSA on admission and then developed MRSA infection. Control subjects were those patients admitted during the same period who were found to be colonized with MRSA on admission but who did not develop MRSA infection.

A retrospective review.

A total of 75 case patients and 150 control subjects were identified. A stay in the intensive care unit (ICU) was the significant risk factor in univariate analysis (P<.001). Prior history of MRSA (P = .03), transfer from a nursing home (P = .002), experiencing respiratory failure (P<.001), and receipt of transfusion (P = .001) remained significant variables in multivariate analysis. Prior history of MRSA colonization or infection (P = .02), difficulty swallowing (P = .04), presence of an open wound (P = .002), and placement of a central line (P = .02) were identified as risk factors for developing MRSA infection for patients in the ICU. Duration of hospitalization, readmission rate, and mortality rate were significantly higher in case patients than in control subjects (P< .001, .001, and <.001, respectively).

MRSA-colonized patients admitted to the ICU or admitted from nursing homes have a high risk of developing MRSA infection. These patients may benefit from undergoing decolonization.

Hospital-acquired Legionella pneumonia has a fatality rate of 28%, and the source is the water distribution system. Two prevention strategies have been advocated. One approach to prevention is clinical surveillance for disease without routine environmental monitoring. Another approach recommends environmental monitoring even in the absence of known cases of Legionella pneumonia. We determined the Legionella colonization status of water systems in hospitals to establish whether the results of environmental surveillance correlated with discovery of disease. None of these hospitals had previously experienced endemic hospital-acquired Legionella pneumonia.

Cohort study.

Twenty US hospitals in 13 states.

Hospitals performed clinical and environmental surveillance for Legionella from 2000 through 2002. All specimens were shipped to the Special Pathogens Laboratory at the Veterans Affairs Pittsburgh Medical Center.

Legionella pneumophila and Legionella anisa were isolated from 14 (70%) of 20 hospital water systems. Of 676 environmental samples, 198 (29%) were positive for Legionella species. High-level colonization of the water system (30% or more of the distal outlets were positive for L. pneumophila) was demonstrated for 6 (43%) of the 14 hospitals with positive findings. L. pneumophila serogroup 1 was detected in 5 of these 6 hospitals, whereas 1 hospital was colonized with L. pneumophila serogroup 5. A total of 633 patients were evaluated for Legionella pneumonia from 12 (60%) of the 20 hospitals: 377 by urinary antigen testing and 577 by sputum culture. Hospital-acquired Legionella pneumonia was identified in 4 hospitals, all of which were hospitals with L. pneumophila serogroup 1 found in 30% or more of the distal outlets. No cases of disease due to other serogroups or species (L. anisa) were identified.

Environmental monitoring followed by clinical surveillance was successful in uncovering previously unrecognized cases of hospital-acquired Legionella pneumonia.

Methicillin-resistant Staphylococcus aureus has emerged as a leading pathogen in transplant recipients and has become endemic in many institutions where transplantation is performed. The role of active surveillance programs based on the detection of colonization in the prevention of S. aureus infection in liver transplant recipients has not been defined.

A total of 47 consecutive patients who underwent liver transplantation during 1996-1999 were compared with 97 patients who received a liver transplant during 2000-2004 after implementation of an intensive intervention program that included use of surveillance cultures to detect nasal and rectal colonization, use of cohorting and contact isolation precautions, and decolonization with intranasal mupirocin therapy.

The rate of new acquisition of S. aureus colonization of nares after transplantation decreased from 45.6% (21 of 46 patients) during the preintervention period to 9.9% (9 of 91 patients) during the postintervention period (P< .001). An increased length of hospital stay (odds ratio, 1.03; 95% confidence interval, 1.01-1.05; P < .002) was associated with new carriage acquisition, and transplantation during the postintervention period (odds ratio, 0.21; 95% confidence interval, 0.08-0.51; P<.001) was independently protective against new carriage. The rate of infection due to S. aureus decreased from 40.4% (19 of 47 patients) during the preintervention period to 4.1% (4 of 97 patients) during the postintervention period (P<.001), and the rate of bacteremia decreased from 25.5% (12 of 47 patients) to 4.1% (4 of 97 patients), respectively (P< .001). Overall, S. aureus infections occurred more frequently among patients with new carriage than among patients who were carriers at the time of transplantation (P< .001) or patients who were noncarriers (P< .001).

Use of active surveillance cultures to detect colonization and implementation of targeted infection control interventions proved to be effective in curtailing new acquisition of S. aureus colonization and in decreasing the rate of S. aureus infection that was endemic in our population of liver transplant recipients.

The role of rectal carriage of Staphylococcus aureus as a risk factor for nosocomial S. aureus infections in critically ill patients has not been fully discerned.

Nasal and rectal swabs for S. aureus were obtained on admission and weekly thereafter until discharge or death from 204 consecutive patients admitted to the surgical intensive care unit and liver transplant unit.

Overall, 49.5% (101 of 204) of the patients never harbored S. aureus, 21.6% (44 of 204) were nasal carriers only, 3.4% (7 of 204) were rectal carriers only, and 25.5% (52 of 204) were both nasal and rectal carriers. Infections due to S. aureus developed in 15.7% (32 of 204) of the patients; these included 3% (3 of 101) of the non-carriers, 18.2% (8 of 44) of the nasal carriers only, 0% (0 of 7) of the rectal carriers only, and 40.4% (21 of 52) of the patients who were both nasal and rectal carriers (P = .001). Patients with both rectal and nasal carriage were significantly more likely to develop S. aureus infection than were those with nasal carriage only (odds ratio, 3.9; 95% confidence interval, 1.18 to 7.85; P = .025). By pulsed-field gel electrophoresis, the infecting rectal and nasal isolates were clonally identical in 82% (14 of 17) of the patients with S. aureus infections.

Rectal carriage represents an underappreciated reservoir for S. aureus in patients in the intensive care unit and liver transplant recipients. Rectal plus nasal carriage may portend a greater risk for S. aureus infections in these patients than currently realized.

To determine the influence of catheter site and type (single- vs triple-lumen) on infection rates associated with central venous catheterization.

Prospective observational study of all nontunneled central venous catheters over a 28-month period. Data collected included patient characteristics, insertion site, catheter type, and receipt of parenteral nutrition. End points were clinical infection (bacteremia or site infection) and catheter contamination (clinical infection or colonization with >15 colonies on semiquantitative culture).

Medical-surgical wards of Veterans' Affairs hospital.

Three hundred catheters were inserted into 204 patients. Seventy percent were inserted into upper-body sites, and 30% were inserted into the femoral vein. Forty-five percent were triple-lumen catheters. Bacteremia occurred in 2.7% of catheter insertions; insertion-site infections developed in 1.3%, and catheter colonization developed in 12%. Catheter contamination was associated with emergent insertion (odds ratio [OR], 6.2; 95% confidence interval [CI95], 1.1-36.7; P=.04) by logistic regression and with femoral location (hazard, 4.2; CI95, 2.0-8.8; P=.0001) and history of transplantation (hazard, 2.8; CI95, 1.1-6.7; P=.024) by Cox regression. Clinical infection was not associated with any of the risk factors evaluated, although there was a trend for association with femoral location by Cox regression (hazard, 4.7; CI95, 0.82-26; P=.08). We did not identify an association between infection and use of triple-lumen catheters or parenteral nutrition.

Our data support an association between intravenous catheter contamination and insertion at a femoral site.

To determine the relation between prior exposure to specific antimicrobials and acquisition of gram-negative bacilli resistant to multiple ß-lactam and aminoglycoside antibiotics among long-term-care patients.

Case-control study. Cases were patients from whom multiply resistant Enterobacteriaceae or Pseudomonas aeruginosa were isolated; controls were patients from whom nonresistant bacteria of the same species were isolated. Prospectively defined risk factors included underlying illness, activity level, presence of decu-bitus ulcers, presence of indwelling devices, and prior exposure to specific antimicrobial agents. Resistant and control isolates of P aeruginosa were compared using pulsed-field gel electrophoresis (PFGE) of genomic DNA after digestion with XbaI.

390-bed long-term Veterans' Affairs facility.

We identified 35 patients with multiply resistant Enterobacteriaceae and 24 patients with multiply resistant P aeruginosa. Of the resistant Enterobacteriaceae, 87% of isolates were resistant to piperacillin, 55% to ceftazidime, and 90% to gentamicin. Acquisition of multiply resistant Enterobacteriaceae was associated with presence of decubitus ulcers (odds ratio [OR], 12.2; 95% confidence interval [CI95], 3.3-44.2; P=.0002) and prior receipt of ampicillm (OR, 13.7; CI95, 2.2-84; P=.005). Of resistant isolates of P aeruginosa, 88% were resistant to piperacillin, 25% to ceftazidime, 42% to imipenem, and 67% to ciprofloxacin. Isolation of a multiply resistant P aeruginosa was associated with total days of antimicrobial exposure (OR, 1.07; CI95, 1.01-1.12; P=.011) and not with prior receipt of any individual agent. Eleven multiply resistant isolates shared a common PFGE pattern.

In our long-term-care facility, acquisition of multiply resistant Enterobacteriaceae was associated with the presence of decubitus ulcers and prior exposure to ampicillin. Acquisition of resistant P aeruginosa was associated with total antibiotic exposure. Molecular typing of P aeruginosa isolates implicated patient-to-patient transmission of a limited number of resistant strains.