Can humidifier reservoir bacteria colonize the circuit during mechanical ventilation: An in vitro study.

BACKGROUND: Although the circuit condensate, an ideal bacterial reservoir during mechanical ventilation, may flow into the humidifier reservoir, no studies have investigated if humidifier reservoir colonized bacteria colonize other circuit locations with airflow. AIM: We aimed to prove whether the humidifier reservoir colonized bacteria colonize other circuit locations with airflow and provide some advice on the disposal of condensate in the clinical setting. STUDY DESIGN: An in vitro experiment was conducted. Mechanical ventilation simulators (n = 90) were divided into sterile water group (n = 30) and broth group (n = 60). In the sterile water group, sterile water was used for humidification, either Acinetobacter baumannii or Pseudomonas aeruginosa were inoculated to humidifier water in the humidifier reservoir, each accounted for 50% of the simulators. The broth group was performed the same as the sterile water group except for the addition of broth into the humidified water. After 24, 72, and 168 h of continuous ventilation, the humidifier water and different locations of the circuits were sampled for bacterial culture. RESULTS: All bacterial culture results of the sterile water group were negative. Bacteria in the humidifier water continued to proliferate in the broth group. With prolonged ventilation, the bacteria at the humidifier reservoir outlet increased. The bacteria at the humidifier reservoir outlet were much more in the Pseudomonas aeruginosa subgroup than in the Acinetobacter baumannii subgroup and the difference was statistically significant (p < .05). During continuous ventilation, no bacterial growth occurred at 10 cm from the humidifier reservoir outlet and the Y-piece of the ventilator circuits. CONCLUSIONS: Sterile water in the humidifier reservoir was not conducive to bacterial growth. Even if bacteria grew in the humidifier reservoir and could reach the humidifier reservoir outlet, colonization of further circuit locations with the airflow was unlikely. During a certain mechanical ventilation time, the amount of bacteria reaching the outlet of the humidifier reservoir varied due to different mobility of bacteria. RELEVANCE TO CLINICAL PRACTICE: In a clinical setting, nurses should not worry about a small amount of condensate backflow into the humidifier reservoir. Draining condensate into the humidifier reservoir can be used as a low risk and convenient method in clinical practice.

High index of suspicion for brucellosis in a highly cosmopolitan city in southern China.

BACKGROUND: Brucellosis is one of the most widespread zoonosis in the world. In China, 90% of human brucellosis occurs in six northern agricultural provinces. However, there is a recent increase in the trend of human brucellosis in southern provinces with limited cases reported in the literature. Our study aims to describe the clinical features and epidemiology of brucellosis in a tertiary hospital in southern China. METHODS: A retrospective case series of brucellosis was conducted between January 1, 2014 and October 31. 2018. Cases were identified based on positive Brucella serology by tube agglutination test, or positive culture from clinical specimen identified by Vitek 2 and MALDL-TOF MS. Clinical details of brucellosis including patients' occupation, risk factors, and complications were analyzed. Clinical characteristics between patients from Guangdong and other provinces were also compared. RESULTS: A total of 13 cases of laboratory-confirmed brucellosis were identified. 7 (53.8%) of the patients were male, 6 (46.2%) were female, with age ranging from 29 to 73 years old (median age: 51 years). 5 patients (38.5%) were from Guangdong province, while the remaining patients (61.5%) were from other provinces. The commonest risk factors of acquisition were consumption of undercooked meat and goat placenta. Patients from Guangdong province were found to be more likely to have prior placenta consumption. The commonest clinical presentations were fever, osteoarticular pain, urinary symptoms, splenomegaly, and lymphadenopathy. Spondylodiscitis/ peripheral joint arthritis (5 patients, 38.5%) was the most prevalent complication, while extra-osteoarticular complications including abdominal aortitis, hepatosplenic abscess, chest wall abscess, and epididymo-orchitis were observed in 4 other patients. Furthermore, it was demonstrated that MALDI-TOF MS is reliable in Brucella identification after additional of reference spectra with standard Brucella strain. CONCLUSIONS: Brucellosis, previously thought to be only found in northern China, is now increasingly seen in highly cosmopolitan part of southern China. MALDI-TOF MS in hospitals in China should include reference spectra with standard Brucella strain to aid bacterial identification in routine clinical practice. In addition to tuberculosis, typhoid fever and typhus, brucellosis should be considered in patients with fever of unknown origin in this locality.

Nosocomial transmission of chickenpox and varicella zoster virus seroprevalence rate amongst healthcare workers in a teaching hospital in China.

BACKGROUND: Varicella zoster virus (VZV) is a highly contagious herpesvirus with potential for nosocomial transmission. However, the importance of nosocomial chickenpox outbreak in China has often been ignored. With the increasing immunocompromised population in China, a thorough review of issues related to nosocomial transmission and the seroprevalence rate of VZV among healthcare workers is necessary. METHODS: Retrospective case finding for nosocomial transmission of chickenpox was conducted between January 1, 2013 and December 31, 2017. Cases were identified based on clinical features compatible with chickenpox. A cross-sectional study on the seroprevalence rate of VZV among healthcare workers (HCWs) was conducted between January 1, 2014 and December 31, 2017. The serum VZV antibodies of 1804 HCWs were measured by enzyme-linked immunosorbent assay (ELISA). The seroprevalence rate of VZV antibodies, the positive predictive value and negative predictive value of self-reported history of varicella were analyzed. The economic impact associated with nosocomial transmission of VZV was also assessed. RESULTS: A total of 8 cases of chickenpox were identified in three nosocomial transmissions, including 4 HCWs who were infected nosocomially. The overall seroprevalence rate of VZV was 88.4%, which significantly increased with age (P < 0.01). The seroprevalence rates of HCWs with different genders and occupations showed no statistically significant differences. The positive and negative predictive values of a self-reported history of varicella were 80.8 and 10.6% respectively. An estimation of 163.3 person-days of work were lost in each nosocomial transmission and 86.7 infection control unit person-hours were required for each outbreak investigation. The cost of VZV IgG ELISA screening was estimated to be 83 USD per nosocomial transmission. CONCLUSIONS: Nosocomial transmission of VZV occurred repeatedly in the hospital setting. An alarming 11.6% of HCWs were seronegative for VZV, which might increase the risk of nosocomial infection and outbreak for other susceptible co-workers and patients. This is especially important in the setting of a teaching hospital where many immunocompromised patients were managed. Furthermore, the positive predictive value of self-reported varicella on seroprevalence rate in our study was lower than those reported in other countries, therefore serological testing of VZV antibodies with subsequent vaccination for all non-immune HCWs should be considered.