J.K.A.U.: Sci., vol. 2, pp. 45-52 (1410 A.H./I990 A.D.

Effect of Natural Falling and Dipping of House Fly(Musca domestica) on the Microbial Contamination of

Water and Milk

N.A. BAESHIN, M.J. SEJINY, M. ZAKI AND A.M. ABDEL-HAFEZ

Department of Biological Sciences, Faculty of Science,King Abdulaziz University, leddah, Saudi Arabia; andDepartment of Microbiology, Faculty of Agriculture,

Ain Shams University, Cairo, Egypt.

ABSTRACf. The effect of n~ural falling and dipping of house flies on thedegree of contamination of sterile water and milk was investigated. Thestudy was made on sterile tap water and also on sterile water at pH 4, whichrepresents the reaction of stOOlach fluids.

It was found that the total microbial flora showed progressing drop intheir counts after 60 minutes incubation. Dipping treatments of house fliesgave lower microbial contamination of water at pH 4 than at neutral pH.This trend was also observed for non-haemolytic and haemolytic microfloradetermined on blood agar medium. Dipping the house flies three times gen-erally resulted in lower microbial count than natural falling and dippingonce treatments.

It was also found that complete dipping of fly in milk reduced the initialmicrobial contamination and retarded their growth. This paradoxial resultis quite interesting since the logical condition, if the microbial load is only amatter of contamination without the influence of any other factor. is thatdipping treatment would give higher figures than natural falling. All theseobservations suggest the presence of antimicrobial factors on the houseflies.

Introduction

It is well known fact that house fly (Musca domestica) is one of the most importantand transmitors of many pathogenic microorganisms. Smith[!], Frobisher et at. [2] andNester et at.[3] indicated that house fly is able to transmit virus diseases, such aspoliomyelitis and coxsakie viruses, bacteri'al diseases such as enteric fever, bacillary

45

46 N.A. Baeshin el 01.

dysentery, typhoid and paratyphoid, strepto- and staphylococcal infections, and pro-tozoan diseases including cysts of trophoxoites, trypanosomes and amoebic dysentrytogether with many other parasites.

Our Holy Prophet Mohammad (peace be upon him) declared that if a house flyhappened to fall in anyone's pot, it should be dipped completely in the food and thenthrow it away because it harbours the disease on one side and remedy on the other.According to this Holy Prophet, the flies carry microorganisms either pathogenic ornon-pathogenic, and in the same time they may carry some factors that are an-tagonistic to these microorganisms, an enzymatic factors that cause lysis topathogenic microorganisms, presence of organisms producing bacteriocius whichare lethal to other microorganisms, ...etc. This condition is believed to be a kind ofh~lp from the Merciful God of human beings. Therefore, it was worthwhile to inves-tigate these points.

The words given by our Prophet about the house fly attracted the attention ofmany religious specialists as well as muslim scientists and was a subject of a lot of ar-guments. The present study was carried out to find any difference of microbial countsbetween falling house flies in sterile water and milk without dipping the flies and fal-ling house flies followed by dipping them in sterile water at pH 7 and 4. The study wasmade using a large number of replicates to be more confident and to reduce thenatural variations in microbial load between different insects.

Material and Methods

1. House Fly Samples

Samples of house fly (Musca domestica) were collected from Jeddah and Makkahregions and transferred directly to the laboratory for microbiological analysis.

2. Effect of Natural Falling and Dipping of the same House Fly on MicrobialContamination of Water

The collected house flies were dropped one by one in sterile test tubes packed toabout 2/3 of their volume with sterile cotton to reduce the depth.

To determine the effect of natural falling of house flies on the microbial load ofsterile tap water ,each tube containing the fly was opened opposite to another largertube containing 10 ml sterile water. The fly reached the surface of the water and wasleft over it for 20 seconds, then removed. The microbial load was determined by plat-ing on different media. .

To determine the effect of complete dipping of house flies on the degree of micro-bial contamination of water, the tubes containing the same fly was opened againstanother containing 10 ml sterile tap water. After the fly reaches the water, it wascompletely dipped in it with the help of a special sterile inoculating needle. Dippingwas made by two methods. In the first, the fly was dipped once for 20 seconds. In thesecond, the fly was dipped three times, 20 seconds each. In the last case, the corres-ponding natural falling was left for 60 seconds.

47Effect of Natural Falling and Dipping of House Fly.

This experiment was made in natural sterile tap water (pH about 7), and in sterilewater at pH 4. The microbial load of the contaminated water was determined directlyafter falling or dipping, then after 15, 30, 45 and 60 minutes from incubation of waterat room temperature. The total microbial flora was determined on nutrient agar, andthe non-haemolytic and haemolytic microflora were determined on blood agar[4].

3. Natural Falling and Dipping of Separate House Flies

The above mentioned technique described in the previous study was applied here.The only difference was that different house flies were used in natural falling and dip-

ping treatments.

4. Effect of Natural Falling and Dipping to House Fly on MicrobialContamination of Milk

In another series of experiments, sterile milk was subjected to natural falling anddipping of the house flies. The microbial10ad of the milk was determined after its in-cubation at room temperature for 3 hours.

Results and Discussion

1. El1ect of Natural Falling and Dipping of the same House Fly on MicrobialLoad of Water

It is clear from data presented in Table 1 that total microbial flora, non-haemolyticand haemolytic microorganisms showed a progressive sharp decline during 60 mi-nutes incubation at room temperature. This reduction in count was, however, moreevident on water at pH 4.0 than at pH 7.0.

It was also evident that most cases of dipping treatments, showed lower microbialdensities than their corresponding natural falling treatments. Although dipping of flyin water is expected to result in higher contamination than natural falling, yet thepresent results showed a reverse data. This indicates that there are some antimicro-bial factors released from the insect in the water, during dipping treatments. The col-lected flies could carry microbial flora which varied widely from insect to anotherboth qualitatively and quantitatively. Some of them may resist the antimicrobial fac-tors which is expec~ed to be present on the flies. This may explain the higher countsobserved in some dipping treatments.2. EtTect of Natural Falling and Dipping of Separate House Flies on the

Microbial Load of WaterIn the previous group of experiments, natural falling and dipping treatments were

made on the same house fly. A considerable number of the microbial flora on the in-sect surface is washed off during falling on the surface of the water. Thus, when thesame fly was tested by dipping it will carry less amount of microbial flora. In addition,if the fly carries antimicrobial factors on its surface a part of this factor is released inthe water during natural falling treatment. This depends on how much the insectstruggled, and on the period of dipping. Thus, the amount of the antimicrobial fac-tors released in dipping treatment of the same insect, is expected to be unstable.

48 N.A. Baeshin eta/.

TABLE Effect of natural falling and dipping of house fly in sterile water on counts of total bacterial flora. non-haemolytic and haemolytic microorganisms (counts/ml)*.

;lncuballonI pH ofI

Period waler

(min)

015

3(1

45W

7.0(Natural)

015

})

45

00

4.0

.Mean of five replicates.Time of nalural falling and dipping onee is 20 seconds.Time Qr natural railing and dipping three times is 60 seconds

Therefore, in the following study two separate house flies were used for natural fal-ling and dipping.

It is clear from the data presented in Table 2 that the total microflora non-haemolytic and haemolytic microorganisms showed progressive decline in all treat~ments after the incubation of the contaminated water for 60 min at room tempera-ture. As previously mentioned, this sharp drop is an indication of the presence of anantimicrobial factor. It is also clear from these data that dipping once in water atneutral pH did not show any reduction in the microbial load. The total microbialcounts were higher in dipping once treatments as compared to those of natural fal-ling. However, when the microflora was determined after dipping three times andcompared to those of natural falling and dipping once treatments, the results showedthat the microbial loads in dipping 3 times treatments were considerably lower thanthose for natural falling and dipping for one time. This unexpected result may sup-port the hypothesis of antimicrobial factor, which assumes that dipping three timesensures the " release of high amount of this factor in the water.

In the case of water at pH 4.0, on the other hand, both dipping once and dippingthree times treatments gave lower counts than natural falling treatments with onlyfew exceptions. This may also indicate that the antimicrobial factor is more effectiveat pH 4.0.

When this study was made using a large number of replicates to be more confidentand to reduce the natural variation in microbial load between different insects, re-sults in Tables 3 and 4 indicated that the microbial load either non-pathogenic orpathogenic microorganisms showed a considerable calculation from fly to anothereither after falling or dipping in sterile water. It is also evident from data that thesemicroflora are affected by dipping treatments, where dipping treatment gave lower

Effect of Natural Falling and Dipping of House Fly. 4Q

TABLE 2. Effect of natural falling and dipping of separate house flies in sterile water on counts of totalmicrobial flora, non-haemolytic and haemolytic microorganisms (Countlml)*.

Total microbial flora Non-haemolytic bacteria Haemolytic bacteriaIncubation

Period

(min)

pHofwater NaturalI DippingIDippingI Natural I DippingI DippingI NaturalI DippingI Dipping

~ling once" t~e falling o~ three falli~~ once three

~51224019284

13401112450450232

510376969630

34016821610442

no592234348148

180240%1610

4079308

10

1103242522

8064888

0153045(i)

7.0(Natural)

2700 4996(X)

351624273

0153045(XI

33W~9273039864

2100208920895919I)Q

36W3168121529281377

210011m912

1440

24W127513681248850

94<; 949439417

4&)

4,()

117714711507

342639259

'Mean of five replicates.Time of natural falling and dipping once is 20 seconds.Time of dipping three times is ~ seconds.

counts than those reported for natural falling samples.. It may denote that althoughdipping has an inhibitory effect on the microbial flora as a whole, yet is probable thatpathogenic microorganisms are more liable to this retarding effect. This is in har-mony with the saying of the Holy Prophet of Islam concerning the effect of completedipping of house fly on antagonising the disease.

TABLE 3. Changes in total microbial fl~, non-haemolytic and haemolytic microorganisms counts as in-fluenced by natural falling and dipping of house flies in sterile water at natural pH 7.

Mean count of

(Counts/ml)SampleNo. Total microbial flora Non-haemolytic bacteria Haemolytic bacteria

I Falling I Dipping I % of change

~

218.3

173.3

2162.5

75.0

86.6

15.0

I216.6

196.6

193.3

400.0

688.3

35.051.6

11137.5

153.3

901.6

Dipping I % of change ~ Falling I Dipping i % of change I

413.3100.0

1240.070.0

228.083.0

228.0361.6258.3131.6593.338;33.6

38.361.6

893.3

70.08.0

277.556.661.6

123.368.0

181.6391.676.0

170.0191.6

6.648.386.6

823.3

-83.1-91.7-77.6-19.1-73.0+48.0-70.1-49.8+~.6-46.8-71.3

+403.4+83.3+26.1+40.6

-7.8

35.048.3

305.043.330.030.0.125.0188.3225.0

65.0186.6300.010.0

175.0153.0821.6

-79.4-72.1-85.9-42.3-65.4

+ 100.0-42.5-4.2

+11.2-83.7-72.9

-757.1-80.6+27.3

08.0

36.6

16.6

41.6

11.&5.03.38.3

13.3

11.6

108.3

93.3

6.6

16.0

00

115.0

3.33.3

25.03.31.63.33.3

18.321.610.045.033.31.6

10.026.6

126.6

-90.9-80.1-39.9-71.6~.o

0-W.2+37.6+46.3-90.7-51.8

+404.50+

10.0

123456789

10111213141516

50 N.A. Baeshin etal

TABLE 4. Changes in total microbial flora, non-haemolytic and haemolytic microorganisms counts as in-fluenced by natural falling and dipping of house flies in sterile water at pH 4.0.

Mean count of

(Counts/ml)

SampleNo. Total microbial flora Non-haemolytic bacteria Haemolytic bacteria

,

Falling I Dipping% change Falling I Dipping % change Falling I Dipping I % change

233.3275.0853.3293.3578.3713.3

268.3111.3858.3200.3543.3690.0

+20.2-59.4+0.5-31.8-6.1

-2.5

460.0325.02%.6198.3180.0413.3

503.388.3

126.685.0

126.6340.0

+9.4-78.9-57.3-57.1-29.7-17.7

71..625.0

105.056.640.080.0

78.333.348.016.635.036.6

+ 9.3+33.2-61.9-70.0-12.6-54.2

123456

3. Effect of Natural Falling and Dipping on Microbial Flora of Milk.

It is clear from the data presented in Table 5 that natural falling of house fly insterile milk resulted generally in a higher level of contamination of milk with diffe-rent microorganisms compared to complete dipping of insects. It is expected that indipping treatments, higher numbers of microorganisms are washed out from the in-sect surface than in natural falling treatments, and, consequently, higher levels ofmicrobial densities would be recorded in dipping treatment. This was in contrast toour results. This suggests that the house fly may contain some antimicrobial factor orfactors.

TABLE 5. Counts of total microbial flora, non-haemolytic and haemolytic microorganisms as influencedby falling and dipping of house flies in sterile milk, countslml (17 samples).

4. Effect of Natural Falling and Dipping of House Flies in Milk on the Growth ofContaminated Microorgani~ms

The previous data suggest the probability of the presence of antimicrobial factorson the house flies. Thus, it was thought that the incubation of contaminated milkfrom the flies for a reasonable time at room temperature may take the effect of thisfactor more clear. In this experiment, the contaminated milk, after natural fallingand dipping treatments, was incubated at room temperature and the microbial florawas counted after 0, 1,2, and 3 hours incubation.

Effect of Natural Falling and Dipping of House Fly. 51

From data presented in Table 6, several points can be observed. Firstly, the meansof bacterial counts after falling and dipping treatments at different incubationperiods showed that dipping treatments gave considerably lower value. Secondly, al-though milk is well-known to be an excellent medium for the proliferation of manymicroorganisms, yet many samples of contaminated milk, either after falling or dip-ping treatment, showed progressive decline in counts. These observations supportthe suggestions of the presence of antimicrobial factors on the house fly.

TABLE 6. Effect of incubation period on the counts of different microorganisms in contaminated milkwith natural falling and dipping house flies (counts/ml).

DippingFalling

Microflora Incubation period (hr) Incubation period (hr)

0 2

'3

0 2 :1

Total microflora1 -Total2-Mean

3660366

4620462

5200520

8420842

2640264

2200220

3800380

5840584

Non-haemolytic bacteriaI-Total2-Mean

3520352

3620362

4640464

3020302

2740 I 3600

274 360

3360336

4180418

Haemolytic bacteria1 -Total2-Mean

1520152

1080108

80080

72070

2480248

1360136

44044

64064

References

[1] Smith, K.G. V., Insuts and Other Arthropods of Medical Importance, Trustees of the British Museurr(Natural History), London, p. 263 (1973). .

[2] Frobisher, M., Hinsdill, R.D., Crabtree, K. T. and Goodheart, C.R., Fundamentals of Microbiology,9th ed., W.B. Sounders Co., Philadelphia, p. 351 (1974).

[3] Nester, E.W., Roberts, C.E., Pearsall, N.H. and McCarthy, B.J., Microbiology, 2nd ed., HoltRinehart and Winston, N. Y., New York (1978).

[4] Cruickshank, R., Duguide,J.P., Harmion, B.P. and Swain, R.H.A., Medical Microbiology, the Practice of Medical Microbiology, 20th ed., Vol. II. Churchill, Living Store, New York, p. 113 (1975).

N.A. Baeshin eta/.52

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