Application of multilocus enzyme electrophoresis to epidemiologic investigations of Xanthomonas maltophilia

OBJECTIVE: To test the utility of a newly developed multilocus enzyme electrophoresis typing method for Xanthomonas maltophilia. DESIGN: Isolates were first screened by slide agglutination, which served as the standard to characterize the outbreak strains. All isolates were then subjected to multilocus enzyme electrophoresis and the results analyzed based on epidemiological data. SETTING: This outbreak occurred in a shock-trauma intensive care unit of a large general community hospital. PATIENTS: Patients admitted to the shock-trauma intensive care unit who had X maltophilia isolated from any site greater than or equal to 24 hours after admission met the case definition. Specimens from patients who fit the case definition were characterized, as were specimens from other patients that were used as controls for nonoutbreak isolates. Environmental samples were also evaluated for X maltophilia. RESULTS: Most of the 64 isolates received during this outbreak were serotype 10, and when they were subjected to multilocus enzyme electrophoresis, one electrophoretic type predominated and correlated to most outbreak isolates. Unrelated isolates of serotype 10 from other institutions all exhibited unique electrophoretic types. CONCLUSION: Application of multilocus enzyme electrophoresis to X maltophilia outbreaks is a valuable addition to the characterization of suspected outbreak strains.     

Acquisition and spread of Acinetobacter baumannii and Stenotrophomonas maltophilia in intensive care patients

Acinetobacter baumannii and Stenotrophomonas maltophilia are increasingly important pathogens, especially in the intensive care units (ICUs). This study was designed to investigate the clonality, the mode of transmission and the patients' risk profile for acquisition of A. baumannii and S. maltophilia at the ICU of an Italian Hospital. Patterns of A. baumannii and S. maltophilia acquisition in the ICU during the period of the survey were carriage, colonization and infection. Characterization of A. baumannii was performed by ARDRA and genotyping of both pathogens by PFGE. Our study provided evidence for the occurrence of an outbreak sustained by the two organisms in study involving 27.3% of patients enrolled into the surveillance. The spread of a unique A. baumannii epidemic clone was demonstrated. A major clone of S. maltophilia was responsible for the epidemic spread of S. maltophilia (55.5% of isolates), thus confirming A. baumannii cross-transmission and showing--among few published reports--the clonal spread of S. maltophilia. Outliers analysis suggested colonized patients as the probable epidemic sources. Mechanical ventilation was confirmed as risk factor for infection (OR 8.4; 95%C.I.: 2.6-27.5). A multimodal intervention program was introduced, followed in later months with a drastic restriction of infection and colonization due to A. baumannii and S. maltophilia and subsequently with the successful control of the outbreak. Active surveillance of infection and colonization by high-risk clones, together with implementation of control strategies, including strict hand hygiene, proved to be effective to reduce the epidemic spread of both alert pathogens in our ICU.     

Electronic ventilator temperature sensors as a potential source of respiratory tract colonization withStenotrophomonas maltophilia

Stenotrophomonas maltophilia (S. maltophilia) is an important cause of nosocomial infection among ventilated and immunocompromised patients, and among patients receiving broad-spectrum antimicrobials. We report a cluster of patients in a surgical intensive care unit who were colonized or infected with S. maltophilia. An epidemiological investigation was initiated after surveillance data revealed that eight patients were culture-positive from sputum for S. maltophilia in the preceding month. Review of respiratory care procedures revealed that when mechanical ventilators were serviced between patients, the electronic temperature probes used with servo-controlled humidifiers were wiped with inadequate disinfection. We collected cultures of case-patient room surfaces, sinks and ventilator equipment. S. maltophilia was recovered from room surfaces, ventilator expiratory circuits and a temperature sensor which had been kept in ambient air after disinfection. Patients and environmental isolates were examined by RAPD-PCR. Three clinical isolates and one environmental isolate had the same profile, which suggests cross-contamination or common source exposure. The outbreak was controlled by adequate disinfection of the temperature sensors. No single epidemic strain was identified but several observations support the conclusion that the temperature probes contributed to the outbreak.     

Hospital outbreak of multi-resistant Acinetobacter anitratus: an airborne mode of spread?

During a 10-month period, from October 1984 to July 1985, a multi-resistant strain of Acinetobacter anitratus was isolated from 36 patients in three neurosurgical wards, one medical ward and the intensive care unit of a district general hospital, and from two patients in the intensive care unit of a hospital in another district. Fourteen patients developed significant infection including pneumonia (10), meningitis (2), septicaemia (2) and wound infection (4). The majority of cases (28) involved the respiratory tract of ventilated patients, although respiratory equipment was not implicated as a source of the infection. The epidemic strain was recovered from the skin, nose, mouth and rectum of colonized patients and from the hands of personnel. However, extensive air and environmental contamination in the vicinity of colonized patients was also demonstrated. This is the first outbreak of infection with Acinetobacter, of which we are aware, where airborne spread has been observed.     

Outbreak of Serratia marcescens colonization and infection traced to a healthcare worker with long-term carriage on the hands.

OBJECTIVE: To reveal the source of a nosocomial outbreak of colonization and infection with a strain of Serratia marcescens positive for Guiana extended-spectrum beta-lactamase 1 (GES-1) that occurred among patients in a neurosurgical intensive care unit (ICU) in a Dutch university medical center from May 2002 through March 2003. METHODS: Samples from the environment and from the hands of healthcare workers (HCWs) were cultured. A retrospective case-control study was carried out. RESULTS: Fifteen neurosurgical ICU patients who had 1 or more cultures that yielded the epidemic strain of S. marcescens from May 2002 through March 2003 were defined as case patients and matched with 30 control patients. Environmental cultures did not reveal a prominent source of S. marcescens. Cultures of specimens from the hands of 100 HCWs revealed colonization of a single HCW with the epidemic strain. Although this HCW instantly went on leave, serial cultures detected prolonged carriage of the epidemic strain on the hands of the HCW for 3 months. The skin of the HCW's hands was psoriatic. The epidemic abruptly ended after the colonized HCW went on leave. Retrospective case-control analysis showed that the patients colonized or infected with S. marcescens received significantly more nursing care from the colonized HCW than did control patients (P<.05). From February 2004 through October 2004, a second cluster of 3 patients was detected with the epidemic strain of S. marcescens. In October 2004, the formerly colonized HCW appeared to have carriage of the epidemic strain on the hands again. CONCLUSIONS: A single HCW with the epidemic strain of S. marcescens on the hands was considered the source of this outbreak.     

Rapid inter-strain comparison by pyrolysis mass spectrometry in nosocomial infection with Xanthomonas maltophilia.

Seventeen strains of Xanthomonas maltophilia and one strain of Pseudomonas cepacia were examined by pyrolysis mass spectrometry (PYMS). The Xanthomonas strains comprised 11 clinical and environmental isolates from a suspected outbreak of colonization and infection on a heart-lung transplant intensive care unit, two strains from patients elsewhere in the same hospital and four strains from a national reference collection. The single isolate of Pseudomonas cepacia was from a sink in the same affected intensive care unit. A series of discriminant analyses performed on the PYMS-derived data showed that, whereas six strains of Xanthomonas from the respiratory tract, blood and ventilatory equipment of one of the affected patients were indistinguishable, all the other isolates were distinct. The results of PYMS rapid inter-strain comparison were in accord with those of an epidemiological investigation which suggested that the episode was due to unauthorized reuse of disposable nebulizers and not to cross-infection between patients. Pyrolysis mass spectrometry with rapid data analysis is a potentially useful technique for the investigation of nosocomial infections due to organisms such as X. maltophilia.     

重症监护病房鲍曼不动杆菌感染现场调查及风险管理研究

目的对重症监护病房泛耐药鲍曼不动杆菌（PDR-AB）所致的院内感染进行确认和流行病学调查,探讨风险管理机制在控制院内感染中的应用,保护患者和医务工作者的健康。方法 针对2007年3月在重症监护病房中的7例鲍曼不动杆菌感染的患者进行现场流行病学调查,同时对医院重症监护病房医务人员手及环境进行细菌采样与培养,识别并评估院内感染风险,制订风险控制措施并验证其可行性。结果重症监护病房环境中存在PDR-AB定植,严格执行消毒程序,能够彻底清除环境中的PDR-AB。本次调查中该病房院内感染的风险管理关键点包括规章制度,医护人员尤其是护工和保洁员的相关知识培训和院内感染的管理策略及技术等三方面。结论重症监护病房需进行严格的清洁与消毒,及时进行现场流行病学调查的同时将风险管理机制应用于院内感染的全程防控是减少院内感染的发生、暴发或流行的有效措施。     

Epidemiology and susceptibility of serratia marcescens in a large general hospital over an 8-year period

Over the 8 year period 1988-1995, 1367 isolates of Serratia marcescens were isolated from 582 patients on 12 different wards of a large Dublin hospital and were particularly associated with the surgical intensive care unit. The annual incidence was over 200 isolates from 1990 to 1992 but fell to below 100 following the opening in April 1992 of a replacement surgical hospital incorporating a new intensive care unit on the same site. The most common source of S. marcescens was sputum from patients. Strain identities were determined by serotyping and phage typing at least one isolate from each of 311 of the 582 patients. The results showed that a single epidemic strain of serotype O14:K14 was present in 69% of these patients, and persisted throughout the hospital for the whole of the eight-year period. This strain was recovered from a variety of clinical specimens, including blood cultures. A minor outbreak involving a serotype O16:K28 strain also occurred and this strain also persisted from at least 1989 to 1994. Extensive surveillance failed to reveal an environmental source or faecal carriage. The likely mode of transmission appears to have been via staff hands from both symptomatic and asymptomatic patients acting as reservoirs of the organism, as has commonly been reported for this species.     

Outbreak of extended spectrum beta-lactamase-producing Klebsiella pneumoniae in an intensive care unit (Brest)

Introduction

We had for aim to describe control and investigation of an outbreak caused by a strain of Extended spectrum beta-lactamase producing Klebsiella pneumoniae in intensive care units of the Brest teaching hospital.

Patients and method

The case definition was a patient infected by or carrying the epidemic strain. Control measures and investigations are presented. A case-control study was conducted in the surgical intensive care unit. Each case was matched with two controls based on admission times in the unit. The study focused on diagnostic and therapeutic procedures, and potential contacts with healthcare workers, in this context of cross transmission.

Results

Between February and May 2011, nine cases were reported in the surgical ICU and two in the medical ICU. Eighteen controls were matched with the nine surgical ICU cases. Several factors were found to be statistically associated with infection or colonization by the epidemic strain: the surgical block in which patients had been operated and the ward of first hospitalization; the number of trans-esophageal and trans-thoracic echocardiographies, of central venous catheter insertions, and of surgical operations; intubation. The total number of invasive procedures was also found to be statistically higher among cases.

Conclusion

This study identified factors associated with colonization or infection by the epidemic strain. These factors might have been involved in the transmission tree, and be vulnerable elements for the prevention of nosocomial infections and colonisations, and their epidemic spread.     

MRSA医院获得性肺部感染流行趋势

目的研究MRSA院内获得性肺部感染流行趋势和防治对策。方法对重症监护病房患者MRSA肺部感染及传播因素进行监测。结果金黄色葡萄球菌中MRSA占的比例逐年升高，尤其重症监护病房肺部感染的患者痰中MRSA检出率为75％；医护人员工作中手、呼吸机管道MRSA阳性率为40％～50％，水龙头、拖布MRSA阳性率为50％～100％；通过环境消毒，物表未检出MRSA。结论MRSA是医院获得性感染重要致病菌，在重症监护病房引起肺部感染流行，医务人员的手是感染的重要媒介。     

Molecular investigation of Stenotrophomonas maltophilia isolates exhibiting rapid emergence of ticarcillin-clavulanate resistance

The prevalence of Stenotrophomonas maltophilia resistance to ticarcillin-clavulanate has dramatically increased in our hospital over the past few years. Sixty-six clinical isolates, collected from 61 patients, were tested for antibiotic susceptibility and genotyped by two different enterobacterial repetitive intergenic consensus-PCR (ERIC-PCR) systems. Although two small outbreaks were identified in the medical intensive care unit, the remaining 58 strains generated 48 different PCR patterns. The rapid emergence of resistance in S. maltophilia occured in absence of an epidemic and was probably influenced by increasing-b-lactam use in our hospital.     

Risk factors for infection and molecular typing in patients in the intensive care unit colonized with nosocomial Enterobacter aerogenes.

OBJECTIVES: To determine the frequency of colonization by Enterobacter aerogenes in patients in the intensive care unit (ICU) for more than 48 hours and to evaluate the risk factors for infection in patients colonized by this bacteria. DESIGN: An 8-month prospective study. SETTING: A 12-bed medical-surgical ICU in a 450-bed, university-affiliated, tertiary-care hospital in Belgium. METHOD: Pulsed-field gel electrophoresis was used to determine the genotypes of E. aerogenes isolates. RESULTS: We observed two major clones of E. aerogenes in the ICU. Interestingly, 87.5% of infected patients had the same genomic profile for colonization and infection. Risk factors for infection in this particular population included younger age, prolonged hospital stay, mechanical ventilation, and bronchoscopy. CONCLUSIONS: Colonization is a major prerequisite for infection. The identification of risk factors for infection in colonized patients can optimize the quality of treatment in the ICU.     

Colonization with methicillin-resistant Staphylococcus aureus in ICU patients: morbidity, mortality, and glycopeptide use.

OBJECTIVE: To determine the impact of methicillin-resistant Staphylococcus aureus (MRSA) colonization on the occurrence of S. aureus infections (methicillin-resistant and methicillin-susceptible), the use of glycopeptides, and outcome among intensive care unit (CU) patients. DESIGN: Prospective observational cohort survey. SETTING: A medical-surgical ICU with 10 single-bed rooms in a 460-bed, tertiary-care, university-affiliated hospital. PATIENTS: A total of 1,044 ICU patients were followed for the detection of MRSA colonization from July 1, 1995, to July, 1 1998. METHODS: MRSA colonization was detected using nasal samples in all patients plus wound samples in surgical patients within 48 hours of admission or within the first 48 hours of ICU stay and weekly thereafter. MRSA infections were defined using Centers for Disease Control and Prevention standard definitions, except for ventilator-associated pneumonia and catheter-related infections, which were defined by quantitative distal culture samples. RESULTS: One thousand forty-four patients (70% medical patients) were included in the analysis. Mean age was 61+/-18 years; mean Simplified Acute Physiologic Score (SAPS) II was 36.4+/-20; and median ICU stay was 4 (range, 1-193) days. Two hundred thirty-one patients (22%) died in the ICU. Fifty-four patients (5.1%) were colonized with MRSA on admission, and 52 (4.9%) of 1,044 acquired MRSA colonization in the ICU. Thirty-five patients developed a total of 42 S. aureus infections (32 MRSA, 10 methicillin-susceptible). After factors associated with the development of an S. aureus infection were adjusted for in a multivariate Cox model (SAPS II >36: hazard ratio [HR], 1.64; P=.09; male gender: HR, 2.2; P=.05), MRSA colonization increased the risk of S. aureus infection (HR, 3.84; P=.0003). MRSA colonization did not influence ICU mortality (HR, 1.01; P=.94). Glycopeptides were used in 11.4% of the patients (119/1,044) for a median duration of 5 days. For patients with no colonization, MRSA colonization on admission, and ICU-acquired MRSA colonization, respectively, glycopeptide use per 1,000 hospital days was 37.7, 235.2, and 118.3 days. MRSA colonization per se increased by 3.3-fold the use of glycopeptides in MRSA-colonized patients, even when an MRSA infection was not demonstrated, compared to non-colonized patients. CONCLUSIONS: In our unit, MRSA colonization greatly increased the risk of S. aureus infection and of glycopeptide use in colonized and non-colonized patients, without influencing ICU mortality. MRSA colonization influenced glycopeptide use even if an MRSA infection was not demonstrated; thus, an MRSA control program is warranted to decrease vancomycin use and to limit glycopeptide resistance in gram-positive cocci.     

Nosocomial infection caused by Xanthomonas maltophilia: a case-control study of predisposing factors

Factors predisposing to clinically significant nosocomial infection with Xanthomonas maltophilia were examined in a matched case-control study using multivariate techniques. Sixteen cases occurred among cancer patients in a six-month period, including an apparent cluster of three cases in an intensive care unit. These infections were unusually serious; eight patients had disseminated infection caused by X maltophilia and six died as a result of their infections. Among the 64 factors that were examined, therapy with broad-spectrum antibiotics and central venous catheterization were found to significantly increase susceptibility to infection. Therapy with imipenem was more than ten times more frequent among cases than among controls (p less than .001). All fatal infections occurred in patients who had received imipenem, including two patients who died before the organism could be identified and appropriate therapy instituted. Infection with X maltophilia should be suspected in patients who develop superinfection while receiving imipenem, and prompt therapy should be instituted to improve chances of survival. Because a common environmental source of X maltophilia was not identified, further study is necessary to determine specific preventive measures.     

外科重症监护病房系统化医院感染管理

目的 提高外科重症监护病房医院感染的管理水平，有效地降低医院感染发病率。方法 通过对1997年1月～2004年12月医院感染监测项目进行比较，评价外科重症监护病房实施系统化管理的效果。结果 外科重症监护病房进行系统化管理后感染率显著降低，消毒灭菌质量监测合格率有不同程度提高。结论 加强系统化管理是降低外科重症监护病房医院感染的有效措施。     

Control measures against Serratia marcescens colonization at the neonatal intensive care unit of UOEH hospital

In September 2001, twelve neonatal intensive care unit (NICU) patients were found to be colonized with pigment-producing strains of Serratia marcescens. The UOEH Infection Control Group (ICG) committee investigated the source of this epidemic and carried out several remedial measures. Immediate investigation of both the environment and the hands of health care workers were enforced. The most likely means of transmission was thought to be from the hands contaminated with S. marcescens that was found on antiseptic cotton, kept in shared stainless steel canisters, used for wiping the patients' buttocks. Therefore, we suggested the following interventions: 1) abolish the stainless steel canisters, and prepare antiseptic cottons for each patient, 2) monitor cultures with some specimens for all patients in the NICU, 3) periodically investigate the environment, 4) enforce workers to wash and disinfect their hands before and after patient care, 5) use new gloves for each treatment, 6) re-examine and modify the caring procedures for inpatients by the nursing staff. In January 2002, this nosocomial colonization came to an end without any serious infection. One of the key points of this success was the quick response by the clinical staff and ICG committee members to the laboratory results of bacteriological examinations. Furthermore, the early investigation of reservoir and good communication between the clinical staff and ICG committee members mostly prevented this nosocomial colonization from becoming worse.     

重症监护病房感染流行菌及其耐药性

目的 研究重症监护病房(ICU)感染流行菌株及其耐药性，为合理使用抗生素提供依据。方法对ICU人住患者各种标本分离菌株进行统计分析。结果 所有病原菌中鲍氏不动杆菌占21．3％、铜绿假单胞菌20．7％、嗜麦芽寡养单胞菌12．0％，药敏显示各菌耐药水平较高。结论 G^-菌中上述3种是ICU主要致病菌；治疗时铜绿假单胞菌可选用阿米卡星，鲍氏不动杆菌首选亚胺培南，其次为头孢哌酮／舒巴坦和阿米卡星；嗜麦芽寡养单胞菌可选用头孢哌酮／舒巴坦和喹喏酮类。     

A risk index for sternal surgical wound infection after cardiovascular surgery.

OBJECTIVES: To identify factors that increase the risk of sternal surgical wound infection after cardiovascular surgery and to develop a bedside clinical risk index using these factors. DESIGN: A risk index was developed using clinical data collected from a cohort of 11,508 cardiac surgery patients and validated using three independent subsets of the data. With two of these subsets, we derived a logistic regression equation and then modified the scoring algorithm to simplify the calculation of patient risk scores by clinicians. The final subset was used to validate the index. The area under the receiver operating characteristic (aROC) curve was the primary measure of goodness of fit. SETTING: Toronto General Hospital, a teaching hospital and the largest center for cardiac surgery in Ontario, Canada. PATIENTS: Cardiac surgery patients receiving cardiopulmonary bypass between April 1, 1990, and December 31, 1995, who survived at least 6 days after surgery. RESULTS: Variables that were used to construct the risk index included reoperation due to complication (odds ratio, 4.3; range, 1.9 to 8.5), diabetes (odds ratio, 2.4; range, 1.5 to 3.7), more than 3 days in the intensive care unit (odds ratio, 5.4; range, 3.2 to 8.7), and use of the internal mammary artery for revascularization (odds ratio, 3.2; range, 1.7 to 5.8). Validation showed that the index had an aROC curve of 0.64. CONCLUSIONS: The risk index described in this article allows clinicians to quickly stratify patients into four risk groups associated with an increasing risk of sternal surgical wound infection. It may be used perioperatively or as part of a wound infection surveillance system.