The Journal of Hospital Infection - Supplement 1

Abstracts of FIS/HIS 2016

–

HIS Grants Abstracts

Evaluating the treatment of surgical site infection (SSI) in patients

undergoing surgery for spinal metastases

Ross A. Atkinson, Anna Jones, Benjamin M. Davies, Dmitri van Popta,

Karen J. Ousey, John Stephenson.

Connolly Hospital, Dublin

Background:

Surgical site infection (SSI) is a highly undesirable

complication of any surgical procedure. Spinal tumour patients, who

may have undergone chemo- and radiotherapy, are immunosuppres-

sed and nutritionally compromised, are at increased risk of SSI.

Understanding the risk to patients requiring surgery, and the costs

associated with this complication, is important for operative planning.

Aims:

The aims of this project were to retrospectively audit suitability

of patients with metastatic spinal tumours for surgery based on a

recognised prognostic tool; conduct a survival analysis of patients

experiencing SSI; characterise the management plan for spinal

metastatic tumour patients experiencing SSI; and calculate the costs

associated with SSI in this patient group.

Methods:

A retrospective case review study identified spinal meta-

static tumour patients both with and without SSI undergoing surgery

between January 2009 and December 2012. Eligibility for surgery

(using the Revised Tokuhashi Scoring [RTS] system) and fitness for

surgery (using the American Society of Anesthesiologists [ASA] grade)

were determined. Overall survival was assessed using the Kaplan-

Meier method. A semi-parametric Cox proportional hazards survival

(time-to-event) analysis was undertaken to assess the relationships

between covariates and survival. The management of those with SSI

was reviewed from existing clinical documentation, and the costs to

the service associated with SSI were calculated.

Results:

A total of 176 surgical procedures for metastatic spinal

tumours were undertaken in 152 patients (77 females and 75 males,

mean age 60.5 ± 12.9 years) over the four year study period. SSI

occurred following 17 procedures in 17 patients (SSI rate 11.2 per 100

patients; 9.7 per 100 procedures). As expected, better survival was

observed in patients with higher RTS scores and lower ASA grades.

Survival was substantively better in patients without SSI (median

276 days [95% CI 183

–

369 days]) when compared with those with SSI

(median 135 days [95% CI 62

–

208 days]) (P = 0.075). Costs were

significantly higher in patients with SSI when compared with a

random sample of patients without SSI (p = 0.019). In-patient hos-

pital stay and return to theatre were the main costs associated with

SSI. Return to theatre was the most expensive single intervention

employed to treat SSI.

Conclusions:

Both RTS and ASA can be used as indicators of patient

survival in those undergoing surgery for spinal metastases. SSI has a

negative impact on survival, but a larger study sample would be

needed to confirm this. SSI in this patient group significantly increases

healthcare costs, mainly due to prolonged hospitalisation and return

to theatre for wound management.

Do biocides increase antibiotic resistance in

Klebsiella pneumoniae

and

Escherichia coli

H. Herault

, K. Hopkins

, M. Sutton

, N. Woodford

, J.-Y. Maillard

School of Pharmacy and Pharmaceutical Sciences, Cardiff University,

Cardiff, Wales,

PHE Colindale, London,

PHE Porton Down, UK

Since the discovery of penicillin in 1929, antibiotics have been heavily

used and misused to treat bacterial infections. This resulted in an

increased number of multidrug resistant bacteria. Bacteria are

adapting faster to antibiotics than pharmaceutical companies are

able to introduce new ones on the market. Therefore, multi-drug

resistant organisms are becoming one of the most important concerns

worldwide. Without any new family of antibiotics developed within

the last decade, infection prevention and control measures are

predominant, relying on the efficiency of biocides to contain the

spread of

“

superbugs

”

. Biocides are now extensively used, questioning

their impact on the development and transfer of resistance mechan-

isms within bacteria. The selective pressure exerted by biocides could

lead to co-selection and cross-resistance mechanisms, enhancing the

maintenance and transfer of resistance genes.

As little is still known about the impact of biocides on antibiotic

resistance, this study aims to investigate four commonly used biocides,

including a quaternary ammonium compound (benzalkonium chlor-

ide), a biguanide (chlorhexidine digluconate) and two heavy metals

(copper sulfate and silver nitrate), on the maintenance and transfer

of carbapenem-resistance genes among

E. coli

and

K. pneumoniae

clinical isolates. Using microdilution broth method, minimum inhibi-

tory and bactericidal concentrations (MICs and MBCs) were deter-

mined for 210 clinical isolates. For each biocide, the distribution

presented a single modal value, except for copper where a bi-modal

distribution with two peaks was observed. Correlations studies were

performed using Spearman

’

s nonparametric test to detect potential

links between the susceptibility profiles to biocides and antibiotics.

Regardless of the bacterial species, weak to moderate but significant

correlations (p < 0.05 to p < 0.001) were found between the MICs of

benzalkonium chloride and chlorhexidine. For

K. pneumoniae

isolates,

correlations between elevated MICs and MBCs of benzalkonium

chloride or silver nitrate and elevated MICs of ertapenem were

observed. Furthermore high MICs/MBCs of chlorhexidine and clinical

resistance to imipenem, meropenem and ertapenem were identified.

Further studies are needed to investigate the reasons behind these

apparent correlations.

Pseudomonas aeruginosa

: contamination of tap outlet fittings

and consequential contamination of tap water

Chloe Hutchins.

University of Southampton and Public Health

England, UK

Recent neonatal deaths were linked to

Pseudomonas aeruginosa

and

the contamination of hospital tap water. Investigations demonstrated

that the tap outlet fittings (OFs) were heavily colonised by

aeruginosa

. Cross-contamination during cleaning has been implicated

in OF contamination.

To investigate the contamination of OFs via contaminated cleaning

cloths and the consequential contamination of water delivered from

both frequently and infrequently used taps.

Microfibre cloths contaminated with

P. aeruginosa

(10

CFU/mL) were

used towipe three different types of OF (A, B and C). OFs were inserted

into an experimental tap rig for up to 24-hours. Survival over time was

assessed by culture. Taps were used at high-and low-frequencies by

subjecting taps to single, and multiple flushes. Water was sampled via

membrane filtration.

The median number of

P. aeruginosa

transferred from cloths to OFs was

1.4 × 10

CFU.

P. aeruginosa

persisted on all OFs for 24-hours. However,

in comparison to OFA, significantly fewer organisms were recovered

from OFB and C after 8- and 12 h respectively.

At all time points and despite tap usage,

P. aeruginosa

was recovered

from water delivered from OFA at levels above the augmented care

alert level (i.e.

≥

10 CFU/100 mL). Water delivered from OFB did not

contain

P. aeruginosa

beyond the first flush.

Contamination of OFs via cleaning cloths is possible and can lead

to contaminated water being eluted from frequently- and infre-

quently-used taps. OF design, whilst not removing the potential

for retrograde contamination, may, in combination with a flushing

regimen, reduce the risk of persistent contaminant presence in the

water.