TEMPORAL PATTERN AND CONTROL OF AN OUTBREAK OF EXTENSIVELY DRUG RESISTANT ACINETOBACTER BAUMANNII IN AN ICU.
Objective: Acinetobacter baumannii is (XDR AB) an important human pathogen causing many noso-comial infections. Once introduced into the hospital, it may become difficult to get rid of it. It can cause a range of infections, which are difficult to treat because the organism is usually resistant to many classes of antibiotics. We describe the temporal pattern of a cohort of cases which alerted the infection control committee for action to prevent these infections.
Methods: Spread over a four months period,nine cases of XDR-AB admitted in the ICU, were diagnosed by appropriate cultures. Extensive environmental sampling was done to find a niche for the causative organism. Infection Control Committee compiled and implemented the disinfection protocols and other infection prevention strategies. Close surveillance for any additional cases was instituted.
Results: XDR AB from all nine cases had similar antibiogram. We identified the index case and deter-mined the temporal pattern of all subsequent cases. The environmental cultures did not yield a growth of XDR AB. The high level disinfection and observance of standard precautions led to disappearance of new cases for the three months period of follow-up.
Conclusion: An effective infection control program can control the outbreak situation in a hospital, pro-vided all the members of the hospital team (administration, treating physicians and surgeons, microbio-logy laboratory and infection control committee) work in harmony and follow the standard operating protocols.
Key Words: Acinetobacter, Acinetobacter baumannii, Acinetobacter infections, Infection Control, Pneu-monia Ventilator Associated, Outbreak Control.
Acinetobacter baumannii has become increasingly im-portant as a human pathogen over the last 2 decades.1 A saprophytic bacillus normally present in soil and water and in the hospital environment is now conside-red an important organism responsible for many noso-comial infections.2 It may be isolated from colonized or infected patients or from hospital staff, and is predo-minantly present on the hands.3 As an opportunistic organism it can cause pneumonia, blood stream infect-ions, urinary tract infection, central nervous system in-fections and soft tissue (wound) infections.4 In hospi-tal settings, Acinetobacter baumannii has been associ-ated with about one third of ventilator associated pne-umonias (VAP).5 These infections may often be diffi-cult to treat because of multiple or complete resistance to different classes of antibiotics.3
In the present study conducted at Shalamar Tea-ching Hospital, the Infection Control Committee (ICC) was alerted to the increasing incidence of cases of XDR AB in ICU over a period of 14 weeks. This pro-mpted the ICC to constitute an Outbreak Control team to investigate the issue resulting in this report that describes the temporal pattern of the outbreak and ex-tensive infection control efforts.
MATERIALS AND METHODS
1. Inclusion Criteria
All those patients who were admitted in ICU for more than 48 hours and from whom XDR AB was isolated from at least one site between September 2013 and January 2014 were included in the study.
2. Patient Sample Collection / Processing
The specimens from these patients included High Vag-inal Swab (HVS), Tracheal Aspirate, Sputum, Wound Swab / Aspirate and Blood. All the specimens were col-lected and processed as per standard policies and pro-cedures.6 The moderate to heavy growths for speci-mens with normal flora (HVS and Sputum) and a pure isolate for other specimens was interpreted as signifi-cant and processed further. Because we use a manual blood culture system, the subcultures were done after 24 hours incubation. The subcultures were made on Blood Agar, Chocolate Agar and McConkey's Agar.
Acinetobacter baumannii was identified by using Non-Lactose fermenting colonies on McConkey's Agar, Gram Stain morphology and Oxidase reaction. Final identification was done by using API 20E system after 24 48 hours incubation at 37C.7 Sensitivity test was done by Kirby Bauer disc diffusion method. The zo-nes of inhibition against selected antibiotics discs were interpreted using CLSI 2012 criteria.8
3. Environmental Sample Collection / Processing
An extensive environmental sampling was done towa-rds the end of January 2014. Altogether 120 samples were collected from the environment of the nine bed-ded ICU as part of exploratory study. The specimens were obtained from ICU as detailed in table 1. The air samples were collected by settle plates (10 minutes ex-posure time).
After the environmental sampling, the ICU was closed to new admissions over the weekend to perform the high level disinfection and admissions were resu-med after 48 hours.
4. High Level Disinfection
A highlevel disinfection protocol9-11 was rigorously fol-lowed and all ICU surfaces were cleaned with freshly prepared 1% solution of Polyhexamethylenebiguanide-hydrochloride (Alpha GuardTM) as per manufacturer's instructions, allowing 30 minutes contact time. ICU had 85 items in equipment category which were disin-fected.
5. Contact Isolation and Standard Precautions
These were strictly implemented and importance of hand washing before, after and between patients care was stressed to all categories of healthcare staff.
Patients admitted after high level disinfection were closely monitored for a period of 12 weeks from 1st February 2014 to 30th April 2014.
Description of the Outbreak
1. The Index case: The Index case in this outbreak was a 21 year old female with history of drowsi-ness, high fever and fits for few hours before her admission to the hospital through Emergency. She had a Caesarean section at a hospital in Gujran-wala district a few hours prior to admission in Sha-lamar Hospital. Her initial CBC revealed a total leukocyte count (TLC) of 16,000 / mm3. A high va-ginal swab obtained for culture and sensitivity on the 1st day of admission, grew XDR AB that was sensitive to Colistin only. This was the only case from where XDR AB was grown on Day 1 of ad-mission in the hospital. She stayed in the ICU for 7 days out of which she was mechanically ventilated for last 5 days.
After the Index case, we identified 8 patients who got admitted in the ICU over a period of 14 weeks who fulfilled the inclusion criterion, to be categorized as part of an outbreak. Depending on the time frame ove-rlap, four clusters were identified that constituted this outbreak of XDR-AB.
2. Grouping of cases as Outbreak Clusters
We decided to put patients in clusters or groups based on the fact that each cluster had patients overlapping for their stay in the ICU. If the gap was of more than 48 hours, we considered that as a separate cluster. The eligible patients were placed in four groups, for the purpose of temporal description.
The collective temporal relationship of the index case and remaining 8 cases in the outbreak is summa-rized in Fig 1. A brief description of these clusters is given below.
The Index case and two other cases were placed in this Cluster. The second patient was admitted to the ICU a day after the index case expired. She stayed in ICU for 16 days and was not on Ventilator at any time. The thi-rd patient had an overlap of 6 days stay in ICU with the second patient. He was on the Ventilator for 6 days during his stay in ICU.
There was only one case in this cluster and there was a gap of 45 days between this and the last patient in Clu-ster 1. This patient was in ICU for 10 days and was on the Ventilator all the time during her stay.
This cluster comprised of two cases. The first in this group was admitted 14 days after the fourth patient. This patient was on Ventilator for 14 days, overlapped by sixth patient for a period of 7 days. The latter case was on Ventilator support for 8 days.
There were 3 cases in this cluster and there was a gap of 5 days from patients in Cluster 3, all overlapped seq-uentially. The seventh patient was in the ICU for a per-iod of 20 days without Ventilator support. The eighth patient was on Ventilator for 6 days. The last (9th) case was admitted with sepsis and was on Ventilator for 15 days.
3. Environmental Sampling
Altogether 120 samples from the ICU were obtained as part of this exploratory study. There was no growth in all specimens except three (table 1). However, we did not grow XDR-AB in any of the samples.
Acinetobacter baumanniiis considered to be a major nosocomial pathogen, associated with significant morbidity and mortality in hospitalized patients and once introduced into the hospital environment; it takes exh- austive infection control efforts to prevent continuing transmission.12
An outbreak of XDR AB that consis- ted of four sequential clusters in the ICU of a tertiary care hospital is described. It see- ms plausible to suggest that the Index case introduced this pathogen into the ICU as no such cases were identified prior to Septem- ber 2013. Four clusters were identified with similar antibiograms. However, the com-mon source origin could not be verified as the isolates were not available for genotypic studies. Bahador et al, from Iran used amp-lified length polymorphism (AFLP) for gen-otype profiling of multi drug resistant isola-tes of Acinetobacter baumannii from ICUs in Tehran and they were able to report so-me novel variants on this basis.13 It would be of interest to use molecular methods to type our strains in future, for comparison with other centers.
In the cases in our study, it was obser-ved that the time between each cluster sho-rtened considerably towards the later part of the outbreak (Fig. 1). There was a gap of six weeks between thepatients in first and second cluster, which reduced to two weeks between cluster 2 and 3 and barely 3 days between the last two clusters.
Acinetobacter baumannii has been kn-own to become persistent in the hospital environment and, once introduced, is diffi-cult to eradicate.12 It is possible that after introduction into the unit, it finds a favor-able niche to survive and then colonizes and / or infects critically ill or immunocom-promized patients.
Ray et al, have reported that patients colonized or infected with XDR AB conta-minate the environment on first or subsequent admission. Acinetobacter baumannii was found in 8% of their environmental samples, including pati-ent rooms and a wound care cart.14 In our study, in spi-te of exhaustive efforts, we did not find any XDR AB from more than one hundred environmental samples from within the ICU. However, we did grow Pseudomonas and Staphylococci from some areas.
Table 1: Microbiological Screening of ICU Environment.
###Area / Source of###No. of Samples
###Growth of Organism
###Sample###(n = 120)
Bed Side Rails###03
###(in one rail)
Equipment Trolley###01###No Growth
Side Railing###08###No Growth
###(on one table)
Food Table###03###No Growth
Expiratory Valve###05###No Growth
Inspiratory Valve###05###No Growth
Equipment Trolley###05###No Growth
Suction Jars###08###Fungus (in one jar)
Suction Points###08###No Growth
###epidermidis (in one point)
I/V Stands###08###No Growth
Door Handles###05###No Growth
Air Conditioning Units
A.C Filters###05###No Growth
Counter Desk###02###No Growth
PC / Keyboard###02###No Growth
Telephone Set###01###No Growth
At the time when samples were taken, all the patients in the out-break had critical illnesses and all were taking more than one class of antibiotics as part of therapy. Except two, all the cases were on Ventilator and had pneumo-nitis. As VAP is a serious nosocomial infection, exhaustive efforts were mounted to investigate the source of XDR AB for outbreak investigation. We were unable to isolate XDR AB from any samples obtained from outside surfaces or tubing components of the five Ven-tilators.
The inaccessible parts of the Ventilators were not sampled in our study.
We found a mortality rate of 78% in our patients which is in agreement with other studies that have re-ported mortality rates between 30 75% who had nos-ocomial VAP caused by Acinetobacter baumannii.15,16 In a recent study, Ozgur et al concluded that VAP cau-sed by Acinetobacter baumannii was the cause of high mortality independent of its sensitivity / resistance profile.16
The presence of clustered cases has been reported by Tsiatsiou et al in a neonatal intensive care unit, as part of an outbreak that lasted for 2 months in the unit. They reported 8 neonates who developed infect-ions due to Carbapenem resistant Acinetobacter bau-mannii; all isolates harbored blaOXA 58 and intrin-sic chromosomal blaOXA 51 carbapenemase genes. Active surveillance and infection control efforts contai-ned this outbreak.17
Another study has shown that inadequate concent-ration of sodium hypochlorite used for environmental cleaning resulted in an outbreak that lasted for 5 mon-ths in an ICU.18 Use of infection control measures as described by CDC has also been associated with reduc-tion in infection rates and interruption in transmission of XDR AB.19
Many researchers have published internationally and from Pakistan, highlighting molecular aspects of Acinetobacter baumannii isolates from different clini-cal areas of the hospitals including intensive care units in prevalence studies.13,17,20,21 However, an outbreak in-vestigation to link the rise of cases in a unit to the ad-mission of a particular case at a particular time has not been reported so far from Pakistan. We have shown in our study that the ICU of a hospital can become a ni-che for dissemination of XDR AB to susceptible pati-ents even after a gap of 45 days. In a recent study from Iran by Alfandri et al, who investigated an outbreak of carbapenem resistant Acinetobacter baumannii in an ICU, it was shown that although the Index patient was admitted in ICU under strict isolation precautions, it still led to an outbreak 2 months after the patient was discharged.
This outbreak persisted despite isolation precautions, patient and staff cohorting, environmen-tal decontamination, terminal disinfection and hydro-gen peroxide treatment of the unit. The source of this outbreak was suspected to be the Velcro of blood pres-sure cuffs. The use of cuffs submersible in a disinfec-tant stopped this outbreak.22
The actions taken to reduce the burden of XDR AB in our setup included closure of the ICU to new ad-missions over a weekend and high level disinfection based on published protocols of HICPAC with some customization to cater for local needs.9-11 Infection Co-ntrol Team and Outbreak Control Team were institu-ted under the Infection Control Committee, that took the responsibility of looking into different aspects of the outbreak so that such incidences could be preven-ted or minimized. Infection Control Nurse was made responsible for an on-going microbiological surveilla-nce of all high risk areas of the hospital. These measu-res led to complete control of XDR AB infections in the three months follow up period, highlighting the importance of concerted infection control efforts.
It is concluded that the presence of unusual nu-mber of XDR AB in patients in ICU of a tertiary care hospital, over a four months period, was linked to the admission of a patient from a peripheral hospital. This outbreak was controlled by using high level disinfect-ion and strict hand washing protocol. In the post-out-break period, no XDR AB was isolated from any pat-ient highlighting the effectiveness of stringent infect-ion control measures in outbreak situations. Regular microbiological surveillance of high risk areas in a bu-sy hospital setting is the cornerstone of infection con-trol and prevention thus reducing the morbidity and mortality in already seriously sick and immunocom-promized patients.
We wish to thank members of SMDC Research and Grant Review Committee headed by Professor Abdul Wajid, Department of Orthopaedic surgery at Shala-mar Teaching Hospital (STH) for prompt approval of the project. We would also to thank Mr. Waqas Sad-dique of Marketing Department for his contribution in preparation of Fig. 1 and Mr. Mudassar Ahmad for technical support in Microbiology Laboratory of STH.
The work was carried out in the Intensive Care Unit of Shalamar Teaching Hospital and Infection Control Se-ction of the Department of Pathology Shalamar Medi-cal and Dental College Lahore.
Source(s) of Support: None.
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