Epidemiological investigation of a nosocomial outbreak of multidrug-resistant Corynebacterium striatum at one Belgian university hospital

During an 8-month period, 24 Corynebacterium striatum isolates recovered from lower respiratory tract specimens of 10 hospitalized patients were characterized. The organisms were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) and by 16S rRNA gene sequencing. The cluster of C. striatum exclusively affected patients who had been admitted to an intensive care unit and/or subsequently transferred to one medium-size respiratory care unit. Prolonged duration of hospitalization, advanced stage of chronic obstructive pulmonary disease, recent administration of antibiotics and exposure to an invasive diagnostic procedure were the most commonly found risk factors in these patients. Seven patients were colonized and three infected. All strains displayed a similar broad spectrum resistance to antimicrobial agents, remaining susceptible to vancomycin only. Typing analysis by MALDI-TOF MS and by semi-automated repetitive sequence-based PCR (DiversiLab typing) showed that all outbreak-associated C. striatum isolates clustered together in one single type while they differed markedly from epidemiologically unrelated C. striatum isolates. Pulsed-field gel electrophoresis (PFGE) profiles revealed three distinct PFGE types among the C. striatum isolates associated with the outbreak while all external strains except one belonged to a distinct type. We conclude that C. striatum is an opportunistic nosocomial pathogen in long-term hospitalized patients and can be at the origin of major outbreaks. The routine use of MALDI-TOF MS greatly facilitated the recognition/identification of this organism in clinical samples and this technique could also offer the potential to be used as an easy and rapid epidemiological typing tool for outbreak investigation.     

Monitoring of nosocomial invasive aspergillosis and early evidence of an outbreak using cumulative sum tests (CUSUM)

In order to provide a statistically based evaluation of the incidence of invasive aspergillosis (IA) over time, we applied the cumulative sums (CUSUM) methodology, which was developed for quality control and has already been applied for the surveillance of hospital-acquired infections. Cases of IA were recorded during a 5-year period. Incidence rates of cases assumed to be hospital-acquired, i.e. nosocomial IA (NIA), were analysed using CUSUM tests. Relationships between NIA, fungal contamination and construction or renovation work were tested using time-series methods. Between January 2002 and December 2006, 81 cases of NIA were recorded. CUSUM analysis of NIA incidence showed no significant deviation from the expected monthly number of cases until August 2005, and then the CUSUM crossed the decision limit, i.e. identified a significant increase in NIA as compared with the reference period (January 2002 to December 2004). Up to April 2006, the learning-curve CUSUM stayed over its limit, supporting an ongoing outbreak involving 24 patients, and then it significantly decreased in May 2006. Follow-up after May 2006 indicated no out-of-control situation, supporting a return to the baseline situation. In haematology wards, significant links were found between NIA incidence and fungal contamination of several sites at each ward (mainly unprotected common sites). An environmental source of contamination could be suspected, but no significant relationship was found between NIA incidence and ongoing construction or renovation. In conclusion, the CUSUM test proved to be well suited for real-time monitoring of NIA and for early identification and follow-up of an outbreak.     

Co-circulation of human metapneumovirus and SARS-associated coronavirus during a major nosocomial SARS outbreak in Hong Kong

BACKGROUND: The clinico-epidemiological significance of human metapneumovirus (hMPV) detected during the SARS outbreak is unknown. OBJECTIVES: To characterize a nosocomial hMPV outbreak during the 2003 SARS epidemic. STUDY DESIGN AND METHODS: All available nasopharyngeal aspirate (NPA) collected from confirmed patients during the first 8 weeks of the SARS outbreak in 2003 were tested for hMPV by a nested RT-PCR assay targeting the F-gene. Clinico-epidemiological information was used to analyze the relationship of hMPV co-infection to specific risk factors (demographics/symptoms/outcomes; status as health-care workers (HCWs)/patients; history of exposure/contact; ward location). Multivariate logistic regression analysis was performed to determine independent risk factors. RESULTS: An hMPV outbreak occurred during 6-16 March 2003 (first week of the Hong Kong SARS epidemic). hMPV RNA was detected in 31 of 155 (20%) NPAs from SARS patients. HCW status (OR 2.72, 95% CI 1.11-6.68; p=0.029) or epidemiological linkage to the SARS outbreak ward (OR 3.59, 95% CI 1.42-9.05; p=0.007) were independent factors associated with hMPV infection. Symptoms of cough and coryza were more common in co-infected individuals (22.6% vs. 15.9%) but this was not statistically significant. Other clinical manifestations and outcomes were not different in co-infected patients. CONCLUSIONS: A major nosocomial hMPV outbreak involving HCWs occurred during the early SARS epidemic. Patients with dual hMPV and SARS infection were not sicker than those with SARS infection only.     

First nosocomial outbreak of VIM-16-producing Serratia marcescens in Argentina

Seven metallo-β-lactamase-positive isolates of Serratia marcescens were recovered from three patients hospitalized in a neonatal ward in an Argentinean hospital during the period July–September 2011. All the isolates were multidrug-resistant, they belonged to a single clone, and carried a bla_VIM-16-containing class I integron structure. This represents the first nosocomial outbreak of metallo-β-lactamase in Enterobacteriaceae in Argentina.     

Emergence and control of an outbreak of infections due to Panton-Valentine leukocidin positive,ST22 methicillin-resistant Staphylococcus aureus in a neonatal intensive care unit

Methicillin resistant Staphylococcus aureus (MRSA) infection can cause significant morbidity and mortality in neonates. We investigated a nosocomial MRSA outbreak in a neonatal intensive care unit (NICU), using a novel typing method. Following two fatal cases, in May 2011, a prospective outbreak investigation was conducted, involving neonates, mothers and healthcare workers in a large tertiary NICU in Sydney. MRSA isolates were characterized by antimicrobial susceptibility testing, a multiplex PCR-based reverse line blot (mPCR/RLB) binary typing system and other molecular typing methods. Over 7 months, 14 neonates were colonized with MRSA and six infected: three with superficial lesions and three with life-threatening disease, including the two index cases, who died despite empirical treatment with vancomycin. Isolates from 15 neonates were indistinguishable by RLB typing and identified as a PVL-producing ST22 SCCmec IV MRSA strain, which was resistant to gentamicin and trimethoprim-sulphamethoxazole. The outbreak strain was also isolated from one healthcare worker, one environmental swab and one father, but the source remained obscure. During the same period several different non-multiresistant and multiresistant MRSA strains were isolated from five neonates, five mothers (including two whose infants were colonized with the outbreak strain), one father, three healthcare workers and two environmental swabs. Rapid turnaround time of typing results allowed us to recognize and define the outbreak and implement targeted infection control interventions. PVL-producing ST22 SCCmec IV MRSA appears to be a virulent and highly transmissible pathogen in the NICU, which was difficult to control.     

An outbreak of hepatitis A on a hospital ward

An outbreak of hepatitis A has been recognised on a medical ward of a district general hospital. Eleven nurses and one patient were reported to have hepatitis over a period of 18 days in October, 1984. Specific tests for hepatitis A IgM were positive in all cases. Following extensive investigations, the outbreak was traced to a female patient who had recently returned from India and who was incontinent. Her serum, when tested subsequently, showed evidence of recent hepatitis A infection. The implications of this outbreak are discussed.     

O148 Shiga toxin-producing Escherichia coli outbreak: microbiological investigation as a useful complement to epidemiological investigation

An outbreak of Shiga toxin-producing Escherichia coli (STEC) O148 infection occurred among wedding attendees in France in June 2002. A retrospective cohort study was performed and ten cases were identified, including two adults with haemolytic uraemic syndrome (HUS). The analytical study revealed that > 80% of affected individuals had eaten lightly roasted mutton and poultry paté, but only the consumption of paté tended to be associated with illness (relative risk 3.4; 95% CI 0.8-14.4). Left-overs (cooked mutton and raw offal) and processed foods (paté) from the same batches as served at the party were sampled. Human, food and environmental samples were examined for the Shiga toxin (stx) gene and virulence traits by PCR. Stx-positive samples were cultured for STEC. HUS cases were tested for serum antibodies against 26 major STEC serogroups. An STEC O26 strain (stx1, eae, ehxA) was isolated from one case with diarrhoea, and an STEC O148 strain (stx2c) from one case of HUS. Serum antibodies against O26 were not detected in either of these patients; antibodies against O148 were not tested. Three STEC strains were isolated from the mutton and the offal (stx2c, O148), and two from the paté (stx2c, O-X and O-Y). The isolates from the mutton were indistinguishable from the human stx2c isolate, whereas the paté isolates differed. Although four different STEC strains were identified in patients and foods, the results of molecular subtyping, in conjunction with analysis of food consumption patterns, strongly suggested that this outbreak was caused by mutton contaminated with STEC O148.     

Phylogenetic analysis of hepatitis B virus full-length genomes reveals evidence for a large nosocomial outbreak in Belgium

BackgroundHepatitis B virus (HBV) is primarily transmitted from mother to child, by sexual contact, intravenous drug abuse, or unsafe health care-related injection practices. Despite increased safety efforts, nosocomial acquired hepatitis B infection remains problematic.ObjectivesA large HBV outbreak was investigated comprising 36 patients with acute HBV infection in a primary care physician's practice.Study designIn a retrospective study (2003–2008), 36 serum samples from patients with acute HBV infection were collected. They had received several injections by the same physician at least 3 months before the onset of clinical symptoms. As a control group, sera were collected from HBV patients from other physicians from the same province. Full-length HBV genomes were amplified and were phylogenetically analysed.ResultsHBV complete genomes of 32 patients were successfully amplified and sequenced, and clustered together with the reference genotype A, subgenotype A2 strains. We also analysed 26 control HBV genotype A samples. All 32 HBV strains from the patient group clustered in a monophyletic branch with a bootstrap value of 100, whereas the control samples branched separately in another clade. The genetic distance value showed small differences within the patients group, whereas the rate within the control group was seven times higher. These observations confirm that the source of transmission was clearly different in both groups.ConclusionMaximum likelihood analysis and genetic distance calculations based on the full-length genomes of HBV strains isolated from patients and controls provided strong evidence for a common nosocomial source of infection for all 32 patient cases.     

PCR-based DNA fingerprinting (REP-PCR, AP-PCR) and pulsed-field gel electrophoresis characterization of a nosocomial outbreak caused by imipenem- and meropenem-resistant Acinetobacter baumannii

Objective   To demonstrate the usefulness of REP-PCR and AP-PCR on molecular typing of A. baumannii isolates.
Method   From February to November 1997, 29 inpatients at Ramón y Cajal Hospital, Madrid—23 in five intensive care units (ICUs) and six at two different medical departments—were either colonized or infected with imipenem- and meropenem-resistant Acinetobacter baumannii (IMRAB) strains (MICs of 64–256 mg/L). A wide antibiotic multiresistance profile was observed with IMRAB strains, and only tobramycin, sulbactam and colistin displayed valuable activity. For typing IMRAB isolates, repetitive extragenic palindromic sequence-based polymerase chain reaction (REP-PCR) and arbitrary primer sequence-based polymerase chain reaction (AP-PCR) methods were used and compared with pulsed-field gel electrophoresis (PFGE) as reference technique. For comparative purposes, 30 imipenem- and meropenem-susceptible A. baumannii (IMSAB) strains isolated before, during and after the outbreak were included in this study.
Results   The molecular typing results showed that the outbreak was caused by a single IMRAB strain (genotype 1). On the other hand, seven different genotypes were observed in the pre-, at- and post-outbreak strains tested by REP-PCR. Regarding AP-PCR, three of four at-outbreak IMSAB strains were indistinguishable from the IMRAB profile. Thus, with AP-PCR, only six genotypes were obtained, apart from the IMRAB genotype.
Conclusion   Under our experimental conditions, REP-PCR had a higher discriminatory power than AP-PCR, with PFGE as reference technique. The REP-PCR technique is a useful and expeditious method for the epidemiologic characterization of A. baumannii nosocomial outbreaks, the results being comparable to those obtained with the PFGE technique.     

A nosocomial outbreak of KPC-2-producing Klebsiella pneumoniae in a Chinese hospital: dissemination of ST11 and emergence of ST37, ST392 and ST395

In China, Klebsiella pneumoniae carbapenemase (KPC) -producing K. pneumoniae isolates have been identified. However, little is known about the spread and outbreak of KPC-producing enterobacterial pathogens. In this study, 48 non-duplicated KPC-producing isolates were analysed for genetic relatedness by pulsed-field gel electrophoresis (PFGE), antimicrobial susceptibility by E-test, and sequence type (ST) by multilocus sequence typing. S1-PFGE and Southern blot were used for plasmid profiling, and PCR and subsequent sequencing were performed to determine the effects of genetic background on the blaKPC gene. From December 2011 to June 2012, an outbreak of the KPC-2-producing K. pneumoniae was observed. The 48 isolates of K. pneumoniae are categorized into eight PFGE types (A1, A2, A3, A4, B, C, D and E). The predominant pathogens of the outbreak were strains with PFGE types A1, A2 and A3, which all belong to ST11. Furthermore, ST37, ST392 and ST395 KPC-2-producing K. pneumoniae isolates have also been sporadically identified. The blaKPC-2-carrying plasmids vary in size from 30 to 220 kb. The genetic environments of the blaKPC-2 gene for most strains were consistent with the genetic structure of blaKPC-2 on the plasmid pKP048. In conclusion, the dissemination and outbreak of KPC-2-producing K. pneumoniae isolates in this study appeared to be clonal, and ST11 K. pneumoniae was the predominant clone attributed to the outbreak. This is the first study to report the emergence and spread of KPC-producing K. pneumoniae ST392 and ST395 worldwide. Our findings suggest that horizontal transfer of Tn3-based transposons might mediate the spread of blaKPC-2 gene between different K. pneumoniae clones in China.     

Use of sequence-based typing and multiplex PCR to identify clonal lineages of outbreak strains of Acinetobacter baumannii

Representatives (n = 31) of outbreak strains of Acinetobacter baumannii from five countries fell into three clear groups, designated Groups 1-3, based on their ompA (outer-membrane protein A), csuE (part of a pilus assembly system required for biofilm formation) and bla(OXA-51-like) (the intrinsic carbapenemase gene in A. baumannii) gene sequences. With the exception of the closely related alleles within the Group 1 clonal complex, alleles at each locus were highly distinct from each other, with a minimum of 14 nucleotide differences between any two alleles. Isolates within a group shared the same combination of alleles at the three loci, providing compelling evidence that the outbreak strains investigated belonged to three clonal lineages. These corresponded to the previously identified European clones I-III. Sequence differences among the alleles were used to design multiplex PCRs to rapidly assign isolates belonging to particular genotypes to sequence groups. In the UK, genotypes belonging to the Group 1 clonal complex have been particularly successful, accounting for the vast majority of isolates referred from hospitals experiencing problems with Acinetobacter.     

一起小学流行性腮腺炎爆发的调查分析

目的核实疫情,确定某小学流行性腮腺炎（简称流腮）暴发的存在并描述疫情三间分布特征和流行强度,探讨发病危险因素。结论按照病例定义,开展病例搜索,描述其三间分布后,结合现场流行病学调查情况,形成假设,再采用病例对照研究方法验证假设。结果某小学2009年5月1日至6月18日搜索到符合病例定义的病例共33例。首例病例5月21日发病,6月14-17日出现发病高峰。二（3）班罹患率最高,为28%。男生罹患率为12%,女生罹患率为9%。病例对照研究表明,在校就餐是危险因素;吃午饭前洗手、平时洗手时使用肥皂是保护因素。结论根据病例临床表现、三间分布特征,确定某小学存在流行性腮腺炎暴发;建议校方减少学生在教室就餐的机会,加强宣传教育,提高学生自我保护意识,养成良好的洗手习惯。     

An outbreak of carbapenem-resistant Pseudomonas aeruginosa in a urology ward

Objective  To investigate an outbreak of carbapenem-resistant Pseudomonas aeruginosa (CRPA) in a urology ward.
Methods  Patients infected or colonized with CRPA were prospectively identified by daily laboratory surveillance. Routine infection-control measures were reinforced, disinfection protocols were revised, and a surveillance program was set up, analyzing cross-transmission in the nursing ward and environment cultures from urology wards and the operating theater. CRPA isolates from clinical and environment samples were studied by pulsed-field gel electrophoresis (PFGE), following Xba I and Spe I restriction.
Results  From February 1998 to September 2000, 59 adult urology patients were colonized or infected by CRPA. All patients had been operated on prior to identification of the CRPA isolate and 79% of these procedures were performed in the same cystoscopy room. No patients had received prior carbapenem therapy. No cross-transmission was detected, and environment cultures from the urology ward and theater were negative except for five samples collected in the cystoscopy room. PFGE identified a single clone in the isolates from different patients and the environment samples.
Conclusions  The PFGE analysis indicated that the CRPA outbreak resulted from the contamination of the cystoscopy room via an unsealed drain. The outbreak ended when the drain was sealed.     

Use of random amplified microsatellites to type isolates from an outbreak of nosocomial aspergillosis in a general medical ward.

Numerous patients were diagnosed with aspergillosis in a nosocomial outbreak caused by Aspergillus fumigatus and Aspergillus flavus. Thirty-three isolates of the former and 28 isolates of the latter were collected from the hospital environment and from the patients and studied for genetic relatedness by random amplified microsatellites (RAMS) analysis, in which two polymorphic regions were tested. Twenty-eight genotypes of A. fumigatus and 23 genotypes of A. flavus were identified. Four patients were infected by two isolates with the same genotype as the environmental isolates. One clinical genotype was shared by three patients and another was shared by two patients. We found that RAMS was useful for fingerprinting Aspergillus spp.     

深圳市某小学一起水痘暴发疫情的现场流行病学调查

目的调查深圳市某小学一起水痘疫情的流行特征,探讨其危险因素。方法按照病例定义搜索病例,描述疾病的三间分布并开展危险因素现场调查分析。结果 2012年11月30日至2013年1月9日共搜索到符合病例定义的病例22例,首例病例发病时间为11月15日,未隔离;疫情报告日期和发病高峰为11月30日;对新发病例严格执行隔离措施,末例病例为12月19日。17例病例为一年级（6）班学生,该班罹患率为33.3%（17/51）,另有4例其它班级病例与该班首发病例在同一午托室休息。一年级（6）班未接种组的罹患率为100%（4/4）,接种组为33.3%（13/39）,水痘疫苗的4年保护率为66.7%。结论未尽早隔离首发病例、及时报告是此次疫情的主要危险因素,及时发现新发病例、严格执行隔离措施可有效控制疫情。疫苗保护效果还需深入开展评价。     

Application of microsatellite typing for the investigation of a cluster of cases of Candida albicans candidaemia

A cluster of cases of Candida albicans candidaemia in a surgical intensive care unit was investigated. The probability of such a cluster during a single month was highly significant compared with the frequency of candidaemia in the previous year. A molecular typing method, based on length analysis of three (EF3, CDC3, HIS3) microsatellite-containing regions, was used to investigate isolates from patients in and outside the ward. This demonstrated the involvement of different strains, indicating the absence of cross-transmission among patients. Results of microsatellite typing can be obtained almost in real-time, which is particularly useful in an outbreak context.     

Institutional outbreak of rubella in a healthcare center in Chandigarh,North India

Rubella is traditionally considered a childhood disease but it has the potential to cause outbreaks in closed communities when a susceptible population accumulates. The present study reports an outbreak of rubella among healthcare workers in the pediatric center of a tertiary care North Indian hospital. The cases of rubella were identified by clinical features and confirmed by the detection of anti‐rubella IgM antibodies in blood by enzyme linked immunosorbent assay. A total of 23 cases of rubella occurred over a period of one and a half month, out of which 9 (39%) were males. All the patients were in the age group of 21–35 years. None of the patients gave a history of rubella vaccination. This outbreak of rubella occurred due to the accumulation of a susceptible population in a closed hospital environment. There is need for the introduction of rubella vaccination in healthcare workers to prevent outbreaks at work place. J. Med. Virol. 82:341–344, 2010. © 2009 Wiley‐Liss, Inc.     

重庆市一起学校麻疹爆发疫情的调查分析

目的调查重庆市潼南县一所小学的麻疹爆发疫情,进行爆发流行病学和疾病传播模式描述,研究爆发危险因素和控制措施。方法对所有疑似病例开展流行病学调查和采集血、咽拭子标本进行实验室检测,同时隔离治疗病例和采取应急接种措施控制疫情蔓延。对收集的数据进行爆发流行病学描述。结果此次爆发中该小学共28名学生罹患麻疹,罹患率为1．7％,病例分布于新校区10个班级,首发病例所在班级幼儿园大三班发病数最多,罹患率10．26％。所有病例均住院隔离治疗,无重症和死亡病例。16名病例无麻疹类疫苗免疫史,首个病例发病后未及时诊断和隔离,导致疫情在学校内蔓延。该小学完成校区全部应急接种,实种2734人,接种率97．79％。塘坝镇与相邻乡镇目标儿童摸底共计12005人,实种11867人,接种率98．85％,无接种异常反应报告。结论降低麻疹发病率和防止学校等集体单位麻疹爆发疫情需保证儿童高质量2剂次含麻疹类疫苗接种率和严格执行入托、入学查验接种证制度,同时应加强疫情预警和提高对爆发疫情的应对能力。     

Molecular epidemiology of nosocomial invasive aspergillosis.

Moderately repeated DNA sequences were used to fingerprint strains of Aspergillus fumigatus isolated from patients with invasive aspergillosis and their hospital environment. Most strains sampled from the environment displayed different Southern blot hybridization patterns. A temporal survey of air contaminants showed that some strains can persist in the same environment for at least 6 months. Patients with invasive aspergillosis were infected by a single strain. In two patients, a nosocomial origin of infection was suggested.