Microbiological Assessment of Raw Milk Available in the Metropolitan City of Sindh, Karachi, Pakistan

Currently, milk quality is judge on its health and hygienic parameters equally as its composition. Raw milk is a rich medium for the growth and proliferation of different pathogenic microorganisms such food-safety hazard may incorporate into the dairy chain, not only affect its safety and quality but also causing various milk borne diseases. Objective: To evaluate the microbiological assessment of raw milk accessible in Karachi with the intention to develop risk tracking strategies and its mitigation plan in the future. Methods: Total 270 raw milk samples were collected from different sites throughout the dairy supply chains in each district of the city. Microbiological assessment of raw milk was carried out by following the bacteriological analytical manual (BAM, FDA) protocol. Results: The raw milk safety and quality at the dairy farms were satis�ed, except raw milk storage tanks samples. The bacterial count boosted in almost all the samples collected during its transportation, higher aerobic and pathogenic load was observed in the retail shop's samples however, maximum counts were noticed in the selling point milk samples. None of the milk samples contained other pathogens like Listeria or Salmonella . Conclusions: The milk quality of the supply chain, retail shops and storage tanks at dairy farms were un-satised based on different microbiological parameters.

Currently, the milk safety and hygienic parameters are equally judged as its composition due, to the present trends in consumer preferences to use naturally pure or minimally processed raw milk [1,2]. Normally, raw milk gets contaminated by direct transfer from the blood to the milk through an udder infection called mastitis and post milking contamination occurs during its handling. According to literature review, enterotoxin-producing Staphylococcus aureus, human pathogenic verocytotoxin-producing Escherichia coli (VTEC), human pathogenic, Listeria monocytogenes, Staphylococcus aureus, Pseudomonas aeruginosa, Leptospira spp. Salmonella spp. etc. are deemed the main microbiological hazards related to raw milk consumption [1]. Milk is a signi cant source of staphylococcal food poisoning which leads to septicemia, pneumonia, gastroenteritis and dermatitis in humans [3]. Salmonella causes illness in human through fecal contamination of food or water [4]. The main source of For the evaluation of the microbiological assessment the dairy supply chains were studied in the ve districts of Karachi as shown in gure 1. Total 9 sampling spots were selected throughout the milk supply chain, as speci ed in the table 2.

M E T H O D S
Copyright © 2022. PJHS, Published by Crosslinks International Publishers human illness is milk and milk products contaminated with Salmonella species, that have been considered responsible for causing typhoid fever, enteritis and bacteremia [5,6]. E. coli, a fecal coliform, is an indicator bacterium of unhygienic handling of food. E. coli is responsible for a wide range of infections like mild diarrhea, gastroenteritis, septicemia and typhoid fever [7]. Listeria monocytogenes is usually present in the dairy farm's soil, manure, plants, water and food chain environment [8]. It can thrive in harsh environment and even in raw milk that has been refrigerated. It can cause mastitis in cow and can be shed in milk of healthy cows [4,9]. Additionally, improper milk handling, storage and transportation from the farm to the table increases the risk of pathogenic microbial contamination, which has a negative impact on the milk's quality and makes it unhealthy for human consumption [10]. Contaminated or open raw milk is responsible for many zoonotic diseases like hepatitis, typhoid, animal contact disease, in uenza, and aerosolized dust illnesses are common in Pakistan due to absence of suitable food standards, unhygienic conditions, poor sanitation, poverty and illiteracy are the main factors contributing to the rise of food-borne illnesses [11,12]. The inadequate monitoring and ineffective law enforcement, is substantially worse in developing and underdeveloped nations [13]. Therefore, maintaining and control milk quality is one of the big challenges in the dairy sector. Implementing Good Veterinary Practices (GVP), Good Management Practices (GMP), and Good Hygienic Practices (GHP) is crucial to reducing or eliminating the risks [14]. Therefore, this study was designed to evaluate the microbiological assessment of raw milk available in Karachi city with the intentions to develop risk tracking strategies and its mitigation plan in future.
Raw milk and their complete supply chain within the city were studied to assesses their quality and safety attributes according to different Microbiological Standards as indicated in table 1.   Four sampling points were chosen from dairy farms cites, 2 spots were selected during supply chain while, 3 venues were selected for sampling from retail shops. Three samples from each sampling point were collected. For sample collection, sterile, clean polythene plastic bags were used. The sample units were quickly and aseptically transferred to the lab in a clean, chilled container after being properly sealed. Most samples were examined for bacteriological examination as soon as they arrived or within 24 hours after being held at 0-4°C.   8.5x10 CFU/mL, Coliforms 240 CFU/mL; E. coli 90 CFU/mL, Staph. aureus 77 CFU/mL) its high number might be linked to the milk being collected in an unsanitary manner and being handled carelessly during transportation. Moreover, coliforms contaminated water in milk during transportation could be possible reason of its high count [15]. Although, the overall milk quality at the retail shops were unacceptable as it strongly exceeded the microbiological parameters of both national and international standards.

D I S C U S S I O N
Raw milk is a perfect medium to support the growth and proliferation of different bacteria [15]. Milk samples collected from direct animals were almost free of microorganism (average TAPC; 2 CFU/mL) this indicates that there is no inherent danger of bacterial contamination in dairy farm animals [16]. The majority of the dairy farms milk samples collected from storage tank showed 5 exceeded microbiological limits (average 2.1x10 CFU/mL APC, 8 CFU/mL Coliforms, 5 CFU/mL Staph. aureus) due to lack of cooling systems, non-implementation of good management practices (GMP) and good hygiene practices [14,17]. Likewise, the leading microbial ora associated with raw milk samples in and around were in the order of a e r o b i c c o u n t > C o l i fo r m s > E s c h e r i c h i a c o l i > Staphylococcus aureus among the isolated pathogens. The existence of these bacteria in milk re ects the various sources of contamination such as animal, human, environment, utensils etc. [18]. The majority of the milk supplied to the city is transported mainly from Bhains Colony [15]. The delivery of milk from a great distance at ambient temperature encourages the growth and proliferation of bacteria. According to reports, lack of refrigeration and lengthy transportation lead to contamination in the milk supply chain [19]. The milk samples taken from bulk milk supply cans had a high 6 bacterial counts (average APC; 5.8x10 CFU/mL, Coliforms 85 CFU/mL; E. coli 25 CFU/mL; Staph. aureus 19 CFU/mL). These high counts are related to improper milk handling practices, contamination from animal bedding, mixing of normal milk with milk taken from an animal with an infected udder, etc. Total bacterial, Coliform, E. coli and Staph. aureus count in milk samples collected from supply chain were beyond the acceptable limits [15]. The overall bacterial count in milk storage tanks without refrigeration and with refrigeration (-4°C) at uncontrolled temperature 7 at various retail stores were high (average APC; 7.8x10

C O N C L U S I O N S
It could be concluded that the raw milk sold in Karachi at retail stores is of poor microbiological quality and is unsafe for human consumption because it contains pathogenic bacteria, which are responsible for a number of food-borne illnesses. A possible risk to consumer health is indicated by the high bacterial count and the presence of several pathogenic microorganisms. Overall, Karachi's raw milk is of poor quality for human consumption. It is therefore, signi cantly important to ensure high quality raw milk production under good hygienic conditions, beside this an effective sanitary and hygienic measures must be implement during milk handling, transportation and marketing to ensure its safety.

C o n  i c t s o f I n t e r e s t
The authors declare no con ict of interest S o u r c e o f F u n d i n g The project was partially funded by a grant from the Dean, Faculty of Science, University of Karachi, Pakistan (AZN).