A microbiological analysis of BioClad in a food preparation environment.

A microbiological analysis of BioClad in a food preparation environment.

A microbiological analysis of BioCote-treated BioClad® PVC wall cladding installed in a food preparation environment.

Date of study: October 2012

Study conducted and report written by Dr Richard Hastings, Microbiologist, Affiliate Microbiology Department, Life Sciences Department, University of Warwick, CV4 7AL. Study and report reviewed and audited by Dr Pamela Simpson, Independent Consultant Microbiologist, Whitewater Technologies Ltd, DY8 2GB.

Study Aim

This study aimed to compare levels of bacterial contamination isolated from surfaces in a busy kitchen situated in a UK care home. The study’s main objective was to compare bacterial contamination on the antimicrobial wall cladding with other surfaces in the kitchen. The care home kitchen had been fitted with BioClad® PVC wall cladding (Advanced Hygienic Cladding Ltd, Harrogate, UK) at the time of construction in 2011. All walls in the rectangular-shaped room were fitted with BioClad® from ceiling to floor. The antimicrobial performance of the wall cladding was to be appraised according to the findings of the study.

Methods

Transport medium swabs were collected from various surfaces situated in a working kitchen (Fig. 1) of a recently commissioned (2011) care home for the elderly located in the UK. Swabbing was performed by rubbing an object’s surface area of 25cm2 (typically 5cm by 5cm) with the cotton tip of a pre-moistened bacterial transport swab. Objects swabbed from the kitchen are identified in Figure 1. Swabs were transported to the microbiology laboratory for processing but kept at 4oC during transport. Bacteria collected on the swabs were transferred to two types of solid growth media; plate count agar and brain heart infusion agar containing 5% horse blood. Cultures were incubated in an aerobic environment at 36oC for 48 hours. After incubation, the amount of bacterial growth isolated from each swab was quantified by colony counting and the diversity of growth estimated by inspection of colony types. Isolates presenting a colonial appearance suggestive of a pathogen were Gram stained and presumptively identified.

Kitchen Plan

Fig. 1: Floor plan of kitchen swabbed in study. Numbers indicate approximate positions of swabbing points and correspond with Swab No listed in Table 1.

Results

Table 1: Comparison of abundance and diversity of bacteria isolated from surfaces in a working kitchen located in a UK care home.

Swab No

Kitchen surface swabbed

Bacterial count

Bacterial diversity

Presumptive bacterial identification

1

BioClad® wall cladding position 1 north wall

0

2

BioClad® wall cladding position 2 north wall

0

3

BioClad® wall cladding position 3 north wall

0

4

BioClad® wall cladding position 1 east wall

0

5

BioClad® wall cladding position 2 east wall

0

6

BioClad® wall cladding position 3 east wall

0

7

BioClad® wall cladding position 1 south wall

0

8

BioClad® wall cladding position 2 south wall

0

9

BioClad® wall cladding position 3 south wall

0

10

BioClad® wall cladding position 1 west wall

0

11

BioClad® wall cladding position 2 west wall

0

12

BioClad® wall cladding position 3 west wall

0

13

Rubberised flooring 1

51

4 different colony types

CNS, Bacillus, 2 unidentified species

14

Rubberised flooring 2

12

1 colony type

Unidentified species

15

Rubberised flooring 3

83

6 different colony types

CNS x2, Bacillus, coliform-like, 2 unidentified species

16

Rubberised flooring 4

107

4 different colony types

CPS, CNS x2, 1 unidentified species

17

Suspended plastic ceiling tile 1

8

2 different colony types

Unidentified species

18

Suspended plastic ceiling tile 2

1

1 colony type

Unidentified species

19

Suspended plastic ceiling tile 3

3

1 colony type

Bacillus

20

Suspended plastic ceiling tile 4

0

21

Stainless steel work surface 1

17

2 different colony types

CNS, unidentified species

22

Stainless steel work surface 2

3

2 different colony types

CNS, unidentified species

23

Stainless steel work surface 3

10

3 different colony types

Bacillus, fungus, unidentified species

24

Stainless steel work surface 4

1

1 colony type

Bacillus

25

Stainless steel handle, door 1

16

3 different colony types

CNS x2, unidentified species

26

Stainless steel handle, door 2

2

2 different colony types

CNS x2

27

Stainless steel handle, door 3

237

>6 different colony types

CPS, Pseudomonas, CNS x2, fungus, >2 unidentified species

28

Grilling machine plastic handle

14

3 different colony types

CNS x2, unidentified species

29

Water heater dispensing plastic handle

60

4 different colony types

CPS, CNS x2, 1 unidentified species

30

Liquid hand soap dispenser plastic casing

9

2 different colony types

CNS x2

31

Food warning trolley plastic handle

31

4 different colony types

CNS, Bacillus, 2 unidentified species

32

Waste collection unit casing

>1000

>4 different colony types

Pseudomonas, >3 unidentified species

33

Plastic refuse bin lid

28

3 different colony types

CPS, CNS, unidentified species

34

Plastic refuse bin pedal

375

>6 different colony types

CNS x3, Bacillus, fungus, >1 unidentified species

35

Plastic oven handle

2

I colony type

CNS

 

Key:         CPS = Coagulase positive Staphylococcus sp.

CNS = Coagulase negative Staphylococcus sp.

 

 

 Bacteria Growth

Fig. 2 & 3: Bacterial isolates from swabs taken from surfaces in kitchen used for study.

 Concluding statement

This study revealed a variety of bacterial counts on different kitchen surfaces. Numbers of bacteria isolated from the surfaces ranged from none (zero) detected to over 1000 colony forming units from 25cm2 sampling area. Only two surface types did not produce bacterial growth upon swab culture – BioClad® wall cladding and a suspended plastic ceiling tile. It does not follow that these surfaces were sterile (i.e. totally free from microorganisms), as bacteria may have been present on these surfaces that were not able to grow as colonies on the media used in this study, or the bacteria were present in such low numbers per unit surface area that the sensitivity limit of the isolation techniques used was exceeded. Given the ease of demonstrating the presence of diverse bacteria from all other surfaces examined in the kitchen, it is reasonable to suppose those surfaces that yielded no bacterial growth on culture were not solely contaminated by non-cultivable bacteria rather numbers of bacteria on them were very low or, indeed, were absent. Thirteen swabs yielded no bacterial growth. Twelve of the thirteen surfaces swabbed were BioClad® wall cladding. A strong explanation for this observation must be the activity of BioClad’s® antimicrobial feature. Previous laboratory analysis of BioCote® treated BioClad® wall cladding according to the ISO22196:2011 protocol (Measurement of antibacterial activity on plastics and other non-porous surfaces) demonstrated this material to possess a potent antimicrobial property under laboratory conditions. This study suggests BioClad’s® antimicrobial efficacy is transferable to the working environment.

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