ReseaRch PaPeR Journal of Agricultural and Marine Sciences 2021, 26(1): 21–26 DOI: 10.24200/jams.vol26iss1pp21-26 Reveived 06 July 2020 Accepted 01 Dec 2020 Subclinical Mastitis in Camels in Oman: A Pilot Study Muhammad Nadeem Asi, Waleed Al-Marzooqi, Yasmin ElTahir, Al Ghaly, Al Toobi, Sara Al Raisi, Haytham Ali, Elshafie I. Elshafie, Eugene H. Johnson Muhammad Nadeem Asi( ) asi@squ.edu.om, Assistant Professor, Department of Animal & Veterinary Sciences, College of Agricultural & Marine Sciences, Sultan Qaboos University, 123 Oman Introduction Camels are a mainstay of rural communities in Oman as elsewhere in arid and semi-arid zones in the Middle East and Africa, by virtue of their endurance and productive potential under such agro-ecological environments. In Oman, as in the Arab world, camel (Camelus dromedaries) is akin to culture and subsistence livelihood in rural areas where camel is an important source of milk (Barlowska et Al., 2011; Zibaee et al, 2015), which is generally acclaimed for its nutritive and health benefits (Mullaicharam, 2014). Moreover, camel’s milk has recently been gaining wider consumption and a place in the market of dairy products. Relevant to that is the relatively substantial population of camel in Oman, estimated at 273,000 (NCSI, 2019), with significant contributions to livelihood of the own- ers and economy. However, one of the major problems إلتهاب الضرع حتَت السَّريِريَّ يف اإلبل يف عمان: ِدراَسة ِإْرتَِياِديَّة حممد ندمي عاصي ، وليد املرزوقي ، ايمسني الطاهر ، الغالية الطويب ، سارة الرئيسي ، هيثم علي ، الشفيع إبراهيم الشفيع ، يوجني هاربر جونسون Abstract. Camels are important and multipurpose animals in many parts of the world including Middle East. Camel milk may harbor different bacteria. Centuries old tradition of consumption of raw camel milk is still a common prac- tice in Oman. This study was carried out to conduct a microbiological analysis of camel milk samples with subclinical mastitis in the region of Muscat, Sultanate of Oman. A total of 61 camel (Camelus dromedarius) milk samples were collected from various animal holdings in and around Muscat. Onsite California Mastitis Test (CMT) revealed 18 (29%) camels positive for subclinical mastitis. Positive milk samples were subjected to routine microbiological workup for bacterial isolation and identification. A total of 7 (47%) Enterobacter cloacae isolates, 4 (27%) Escherichia. coli, 3 (20%) coagulase negative Staphylococci spp. (CNS) and 1 (7%) Micrococcus spp. were identified out of 15 milk samples. Three milk samples did not yield any growth after two repeat attempts. Isolates belonging to Enterobacteriaceae were further subjected to antimicrobial sensitivity testing. All E. cloacae samples 7 (100%) were found to be resistant to penicillin, ampicillin, amoxicillin-clavulanic acid, first generation cephalosporins, and the macrolide group of antibiotics whereas 3 (43%) E. cloacae isolates were found to be intermediately resistant to the phenicol group of antibiotics. All four E. coli (100%) isolates were found resistant to penicillin, ampicillin, amoxicillin-clavulanic acid, first generation cephalospo- rins, and 2 (50%) showed resistance to macrolides, whereas 1 (25%) isolate was found to be resistant to tetracyclines. In this study, Enterobacteriaceae were the most common group of bacteria isolated from camels with subclinical mastitis. Enterobacter cloacae and E. coli were the predominant organisms. Keywords: Raw camel milk, Enterobacter cloacae, E. coli, resistance املســتخلص:تعترب اإلبــل حيــواانت مهمــة ومتعــددة األغــراض يف أجــزاء كثــرة مــن العــامل مبــا يف ذلــك الشــرق األوســط. قــد حيتــوي حليــب اإلبــل علــى أنــواع خمتلفــة مــن البكتــراي. ال يــزال تقليــد اســتهالك حليــب اإلبــل اخلــام ممارســة شــائعة يف عمــان منــذ قــرون. أجريــت هــذه الدراســة إلجــراء حتليــل ميكروبيولوجــي لعينــات حليــب اإلبــل املصابــة ابلتهــاب الضــرع حتــت السَّــريرِيَّ يف منطقــة مســقط ، ســلطنة عمــان. مت مجــع 61 عينــة مــن حليــب اإلبــل )Camelus dromedarius( مــن خمتلــف حيــازات احليــواانت يف مســقط وحوهلــا. أظهــر اختبــار كاليفورنيــا إللتهــاب الضــرع )CMT( أن 18 )29٪( مــن اإلبــل كانــت إجيابيــة لإلصابــة إبلتهــاب الضــرع حتــت الســريري. مت إخضــاع عينــات احلليــب املوجبــة للفحــص امليكروبيولوجــي الروتيــي لعــزل وتعريــف البكتــراي. أظهــرت النتائــج 7 )47٪( عــزالت مــن اأَلْمعائِيَّــُة َكيَــّـَرة مــن أصــل 15 عينــة ُ ْذَرِقيَّــة ، 4 )27٪( مــن اإِلْشــريِكيَُّة القولونِيَّــة ، 3 )20٪( مــن املكــورات العنقوديــة الســلبية املخثــرة و 1 )7٪( مــن جنــس البكــراي امل َ امل حليــب. ثــالث عينــات مــن احلليــب مل تســفر عــن أي منــو بكتــري بعــد حماولتــني متكررتــني. مت إجــراء إختبــار احلساســيه للعــزالت الــي تنتمــي إىل اأَلْمعائِيَّــات ملضــادات ْذَرِقيَّــة كانــت مقاومــة للبنســلني، األمبيســلني، محــض أموكسيســيلني-كالفوالنيك، اجليــل األول َ امليكــروابت. أظهــرت النتائــج أن مجيــع عينــات 7 )100٪( اأَلْمعائِيَّــُة امل ْذَرِقيَّــة ذات مقاومــة متوســطه جملموعــة الفينيكــول مــن َ مــن السيفالوســبورينات، وجمموعــة املاكروليــد مــن املضــادات احليويــة، بينمــا 3 )43٪( مــن عــزالت اأَلْمعائِيَّــُة امل املضــادات احليويــة. مت العثــور علــى عــزالت اإلشــريكية القولونيــة األربعــة )100٪( مقاومــة للبنســلني واألمبيســلني ومحــض أموكسيســيلني كالفوالنيــك واجليــل األول مــن السيفالوســبورين و 2 )50٪( مقاومــة للماكروليــدات ، بينمــا وجــدت عزلــة واحــدة )25٪( مقاومــة للتراســيكلني. يف هــذه الدراســة ، كانــت البكتــراي اأَلْمعائِيَّــُة هــي ْذَرِقيَّــة و اإِلْشــريِكيَُّة القولونِيَّــة هــي الســائدة. َ اجملموعــة األكثــر شــيوعا مــن البكتــراي املعزولــة مــن اإلبــل املصابــة إبلتهــاب الضــرع حتــت الســريري. كانــت بكــراي اأَلْمعائِيَّــُة امل ْذَرِقيَّة ، اإِلْشريِكيَُّة القولونِيَّة ، املقاومة. َ الكلمات املفتاحية: حليب اإلبل اخلام ، اأَلْمعائِيَُّة امل 22 SQU Journal of Agricultural and Marine Sciences, 2021, Volume 26, Issue 1 Subclinical Mastitis in Camels in Oman: A Pilot Study impacting camel milk production and health is masti- tis, though there is lack of reports in Oman. Mastitis, both clinical and subclinical, has been reported in Gulf countries neighboring Oman, UAE and Saudi Arabia, in addition to Iraq, Kuwait, Pakistan, India, Somalia, Su- dan, Kenya and more (Toroitich et al., 2017). Subclinical mastitis does not seem to show clear clinical signs but pathogenic microorganisms are harbored in intramam- mary tissue and are secreted in the milk. However, milk from an animal positive for subclinical mastitis may ap- pear normal with normal total somatic cell count. This does raise public health concern considering the tradi- tion of consumption of raw and unpasteurized milk in these regions, besides its bearing on camel health and losses in milk yield. However, unpasteurized milk is not recommended for its safety issue. Our literature search indicated that there is lack of studies on subclinical mas- titis in camels in Oman. Therefore, the aim of this study was to investigate the status of subclinical mastitis by conducting microbiological analysis of milk of camels to ascertain the extent of positive cases. A number of studies investigated subclinical mas- titis in camel with successful application of California Mastitis Test (CMT) (Saber et al., 2010, Ali et al., 2019). Assessment of milk samples by CMT and somatic cell count (SCC) was shown to tie significantly regarding the detection subclinical mastitis in camels (Abdulrahman, 1996), together with a good correlation of CMT to milk leukocyte count (Obeid, 1983). Applying CMT and SCC to screen for subclinical mastitis in a group of camels led to revealing the predominance of Gram-positive bacteria including streptococci spp. and staphylococci spp (Saleh, 2011). Moreover, a similar study in camels revealed the predominance of Enterobacterium spp., Staphylococcus spp. and Streptococcus spp. in cases of subclinical mastitis (Al-Sailihi, 2017). Diverse bacterial species were reported to be implicated in subclinical and clinical mastitis in camel. This is apparently related to a location as well as hygiene conditions and their manage- ment. A study of subclinical mastitis in camels in a dis- trict in Iraq showed that the main isolates involved were coagulase negative Staphylococci followed by Strepto- coccus spp. and E. coli and Micrococcus spp. were in a lesser extent (Al-Rammahi et al., 2018). In another loca- tion, Ali et al. (2019) investigated subclinical mastitis in the two districts in Pakistan and observed the high prev- alence of S. aureus. In a habitat with close resemblance to Oman, such as that of UAE, isolates from subclinical as well as clinical mastitis of camel were identified to be mainly Staphylococcus spp. trailed by Streptococcus spp. and Enterobacterium spp. (Al-Jaboori et al., 2013). Materials and Methods Study Area In this study, a total of 61 milk samples from healthy she-camels (Camelus dromedaries) located in various holdings in and around Muscat, Sultanate of Oman were considered. Ethics Statement In this study, verbal consent of camel’s owners was ob- tained prior to the collection of milk samples from their animals. Animals were used just once for milk collection by professional veterinary technologists at the Depart- ment of Animal & Veterinary Sciences. This work was not an experimental research on animals and hence ap- proval by the ethical committee at Sultan Qaboos Uni- versity was not obtained. Milk Samples Collection Milk sampling was done by hand stripping just prior to milking using sterile screw caped 50 ml Falcon tubes (Kartell S.p.A and Cellstar tubes, Germany). Milk sam- ple (10 mL) was collected from each quarter in a sterile tube and labeled as per guidelines. (National Mastitis Council., 1990). California Mastitis Test (CMT) Milk samples were subjected to onsite CMT test. CMT was carried out using the methods as described by Schalm and Noolander (1957). The CMT solution was obtained from ImmuCell (Portland, USA). Equal vol- ume of milk and CMT working solution were mixed in corresponding testing paddles. The mixture was gently rotated in horizontal position and results were record- ed as negative, weak positive (+), distinct positive (++) and strong positive (+++). Milk samples positive for on- site CMT test were transported to the laboratory in an ice box and processed for bacteriological examination within two hours of collection. Animals with history of mastitis or recent treatment with antimicrobials were excluded from this study. Bacteriological Examination Bacteriological examination of the samples was carried out following the standard methods as described by Quinn et al. (1999). For microbiological analysis, each milk sample (0.1 mL) was streaked on blood agar (Ox- oid, Basingstoke, England) and MacConkey’s agar (Ox- oid, Basingstoke, England) and subjected to incubation at 37oC for 24-48 hours in both aerobic and anaerobic conditions. In the case of no growth, corresponding milk sample was cultured again to obtain growth. The plates with growth were examined for growth colony morphol- ogy, hemolysis, and pigment production. 23Research Paper Asi, Al-Marzooqi, ElTahir, Al Ghaly, Al Toobi, Al Raisi, Haytham Ali, I. Elshafie, H. Johnson Identification of Bacterial Isolates All isolates were subjected to Gram staining, catalase, and oxidase tests. Micrococci spp. and Staphylococci spp. were identified using Mannitol Salt Agar (Oxoid), and co- agulase test using both slide and tube methods along with catalase and oxidase testing. All biochemical tests were done according to standard procedures (NCCLS, 2000). Analytical Profile Index Test Gram-negative isolates with oxidase negative and cat- alase positive reactions were subjected to API® 20E (Biomérieux, France) and were further confirmed us- ing Vitek2 Gram-negative (GN) test cards (Biomérieux, France) in an automated Vitek® 2 instrument. All iso- lates were kept in Viabank TM tubes at -70°C for further use. Gram-positive cocci isolates with positive catalase reactions were subjected to API® Staph (Biomérieux, France). Staphylococci isolates were subjected to Coagu- lase test using the tube coagulase method (Quin, 1998). Antimicrobial Sensitivity Test Antimicrobial susceptibility and minimum inhibitory concentrations (MICs) were determined using automat- ed Vitek® 2 instrument with AST cards (Biomérieux, France). Breakpoints used as recommended by the Na- tional Committee for Clinical Laboratory Standards (NCCLS, 2000). Results California Mastitis Test and Bacteriological Ex- amination Analysis A total of 61 camels were examined for subclinical mas- titis. Out of 61 animals, 18 (29%) camel milk samples were found to be positive for subclinical mastitis using California Mastitis Test (CMT), whereas only 15 isolates yielded growth during microbiological analysis. Three samples positive for CMT, did not yield any growth even after second culture. Out of 15 positive growths, 7 (47%) isolates were confirmed as E. cloacae, 4 (27%) E. coli whereas 3 (20%) coagulase negative staphylococci and 1 (7%) isolate was confirmed as Micrococcus spp. Antimicrobial Sensitivity Test Analysis Antimicrobial sensitivity analysis revealed that all E. cloacae (100%) isolates were resistant to penicillin, first generation cephalosporins, and macrolide group of an- tibiotics, whereas 3 isolates (43%) shown intermediate resistance to phenicols. All four E. coli (100%) isolates exhibited resistance to penicillin, ampicillin, and amox- icillin, 2 (50%) isolates were resistant to erythromycin and tylosin, 3(75%) were resistant to first generation cephalosporins whereas only 1 (25%) isolate was found resistant to tetracycline. Discussion The present study shows the presence of subclinical mas- titis in camels in Oman based on CMT and bacterial cul- ture of milk samples. They also reflect a high correlation between CMT and cultural isolates. Enterobacteriaceae E. cloacae and E. coli were found as the predominant bacteria with few coagulase negative Staphylococci and Micrococcus sp. E. cloacae isolated in this study belongs to the microbiota in the surrounding environment. This is a common commensal in animal digestive tract and is a common member of the human microbiome (Keller et al., 1998). Our results are in slight discrepancy with oth- er reports since we report Enterobacteriaceae E. cloacae and E. coli as dominant causative agents in subclinical mastitis in camels. Reports on isolates from camel cas- es from neighboring countries implicate Staphylococcus and Streptococcus spp. as dominant ones in clinical and subclinical mastitis (Al-Jaboori et al., 2013; Al-Ramma- hi, 2018), in agreement with other reports (Hadel et al., 2018). Though Al-Jaboori et al. (2013) identified Entero- bacterium spp. from subclinical mastitis in camels in the UAE, yet the dominant ones were Staphylococcus and Streptococcus spp. Considering rural management practice, it is likely that cross-infection was established in camels since management and the level of hygiene is not optimal. To best of our knowledge this is the initial investiga- tion to report subclinical mastitis in camels in Oman, and that the coliform is the dominant type. Not a single camel owner interviewed during sampling was aware of the concept of subclinical mastitis in camels or use of California Mastitis Test (CMT) screening. Camel milk is obtained via hand milking without any pre or post milk- ing dipping. It was even observed camel owners drink- ing milk right from camel teats using hands, although it is not recommended for safety. E. cloacae is a biofilm forming organism and this secretes a number of cytotoxins deemed important for its pathogenicity (Mezzatesta et al., 2012). More impor- tantly, due to expression of extended spectrum β-lact- amases (ESBL) and carbapenemases, it has turned into third broad spectrum Enterobacteriaceae specie causing nosocomial infections along with K. pneumoniae and E. coli (Potron et al., 2013). In last few decades, E. cloacae have been added to the list of most worrying microorganisms due to their ability to acquire resistance. In humans, E. cloacae are known to cause septic arthritis, endocarditis, and skin, urinary, respiratory and abdominal infections. It is contracted via skin and gastrointestinal tract (Sanders et al., 1997, Lee et al., 2002). Coliform mastitis is also the most common form of clinical mastitis in cattle in different parts of the world. Among coliforms, E. coli is most commonly iso- lated from animals with mastitis and primary source of these bacteria are cow feces, environment and infections via teat canal (Sumathi et al., 2008, Lipman et al., 1995). 24 SQU Journal of Agricultural and Marine Sciences, 2021, Volume 26, Issue 1 Subclinical Mastitis in Camels in Oman: A Pilot Study In the present study, Enterobacteriaceae was observed to be the predominant isolates from camels with subclin- ical mastitis. This is in line with other studies conducted in cows with mastitis (Bengtsson et al., 2009, Saidi et al., 2014). However, a study done in subclinical mastitis in camels in Saudi Arabia, Streptococcus spp., Staphylococ- cus aureus and other staphylococci spp. were found to be the predominant organism (77%) whereas only 12.9% isolates were identified as E. coli. (Saleh & Faye, 2011). In another study conducted on subclinical mastitis in camels, the authors found coagulase negative staphylo- cocci (CNS) to be the predominant isolates (35%) and only (10.72%) were confirmed as E. coli (Leyla et al., 2017). A study (Al-Rahmmahi et al., 2018) carried on in Al-Najaf on 82 camels, the researchers found Coagulase Negative Staphylococci to be the predominant (17.68%) followed by Streptococcus spp. (12.92%). The authors also reported Staphylococcus aureus (10.2%), E. coli (8.16%) and Micrococcus (4.08%). In our study we found 3 isolates (20%) of CNS and 1 isolate of Micrococcus. In the present study, all E. cloacae (100%) isolates were found to be resistant to penicillin, first generation cephalosporins, macrolides and 43% were intermediate- ly resistant to phenicols. Currently, there is a lack of con- sensus regarding exact definition of multidrug resistant organisms in veterinary medicine. In human medicine, for an organism to be reckon as multidrug resistant, it should be resistant to at least one agent in at least three antimicrobial classes. However, according to criteria for assessment of multidrug resistance in bacteria (food.gov. uk), these organisms cannot be considered multi-drug resistant as E. cloacae harbors intrinsic resistance to pen- icillin, first generation cephalosporins and cephamycins. In our study, all E. coli (100%) isolates were resis- tant to ampicillin, amoxicillin, 3 (75%) were resistant to the first generation cephalosporins, 2 (50%) resis- tant to macrolides whereas 1 (25%) were found re- sistant to tetracyclines. Similar trends have been re- ported in cows with mastitis (Saidi et al., 2014) and camels with subclinical mastitis (Saleh and Faye, 2011). Camel milk if consumed raw can be a source of in- fection for humans. A case of E. cloacae sepsis has been reported in a preterm infant feeding on mother’s milk. Same pathogen was cultured from milk samples obtained from mother over the period of 7 days. How- ever, mother’s milk could not be established as a direct cause of E. cloacae infection in infant as other sources of infection could not be ruled out (Weem et al., 2015). Further studies warranted to establish the link between consumption of raw camel milk and human infections. All of the isolates (100%) were found to be resistant to macrolide antibiotics including erythromycin and ty- losin. Macrolides have shown good activity especially against gram-positive cocci organisms. However, these antibiotics have limited efficacy against Enterobacte- riaceae in general. Enterobacteriaceae may acquire re- sistance against macrolide in a variety of mechanisms described elsewhere (Leclercq, 2002; Ojo et al., 2004) Identification of Enterobacter cloacae establish- es the fact that the organism is AmpC producer that yields the inducible chromosomal AmpC β-lactamase and therefore it is not necessary to detect AmpC pro- duction in these isolates (Gupta et al., 2014). Coagu- lase negative Staphylococci (CNS) are opportunistic pathogens that may cause infection due to improper teat disinfection. CNS are commonly isolated from bo- vine milk samples as these organisms are part of nor- mal skin flora and contamination of milk is common. However, infections are usually subclinical in nature. Raw milk contamination with Enterobacteriaceae can occur during milking process, contamination of milk with animal feces or mastitis (Dahmen et al., 2013). As camel milk is obtained exclusively by hand-milking, washing hands and udder of the animal, post milking teat dipping, pasteurization of milk and prevention of contamination during transport of camel milk can help in control of these organisms. The best way forward is the education of camel owners about dangers of drinking raw camel milk that can lead to infection with variety of bacteria and importance of pasteurization to avoid infections. Consumption of raw camel milk is commonly prac- ticed in Middle East including Oman; therefore, it is important to evaluate the microbiological quality of the camel milk. More number of camels could not be includ- ed in the study due to various factors including overall low camel population in the study area as compared to other parts of Oman, noncompliance of camel owners to provide milk samples, small holdings (one or two camels commonly kept along with other livestock animals), and non-availability of camels for sampling at holdings due to long overall grazing time period. It is concluded that camel owner education programs are required to im- prove the udder health of the camels, regular screening of camels for subclinical mastitis using CMT, and edu- cate them regarding hazards of using raw camel milk. Conclusion and Recommendation This is the initial investigation to report subclinical mas- titis in camels in Oman, and that the coliform is the dom- inant type. In the present study, Enterobacteriaceae was observed to be the predominant isolates from camels with subclinical mastitis. This is the initial report of iso- lation of E. cloacae and E. coli from camel milk samples positive for subclinical mastitis in Oman. In the pres- ent study, all E. cloacae (100%) isolates were found to be resistant to penicillin, first generation cephalosporins, macrolides and 43% were also intermediately resistant to phenicols. In this study, we could conclude that camel owner education programs are required to improve the udder health of the camels, regular screening of camels for subclinical mastitis using CMT, and educate them regarding hazards of using raw camel milk. 25Research Paper Asi, Al-Marzooqi, ElTahir, Al Ghaly, Al Toobi, Al Raisi, Haytham Ali, I. Elshafie, H. Johnson Acknowledgement This work was supported by Deanship Research Fund, project number: RF/AGR/ANVS/18/01. Special thanks go to the Ministry of Agriculture & fisheries camel own- ers’ community for facilitating the sample collection and cooperating with the team during sample collection. All authors declare no conflict of interest. References Al-Rammahi HM, Hatem AA, Al-Atabi AC (2018). Di- agnostic study of she camel subclinical mastitis in Al-Hyadia district – Al-Najaf province. Advances in Animal and Veterinary Sciences 6(6): 1-3. Al-Salihi, KA, Sahab A, Lifta A, Habib L. (2017). Epi- demiological study of clinical and subclinical mastitis in she-camel in Samawah desert - Al Muthanna gov- ernorate. Mirror of Research in Veterinary Sciences and Animals 6: 11-24. Barłowska J, Szwajkowska M, Litwińczuk Z, Król J. (2011). Nutritional value and technological suitabil- ity of milk from various animal species used for dairy production. Comprehensive Reviews in Food Science and Food Safety 10: 291– 302. Bengtsson B, Unnerstad HE, Ekman T, Artursson K, Nilsson-Ost M, Waller KP. (2009). Antimicrobial susceptibility of udder pathogens from cases of acute clinical mastitis in dairy cows. Veterinary Microbiol- ogy 136: 142-149. Dahmen S, Métayer V, Gay E, Madec JY, Haenni M. (2013). Characterization of extended-spectrum be- ta-lactamase (ESBL)-carrying plasmids and clones of Enterobacteriaceae causing cattle mastitis in France. Veterinary Microbiology 162(2-4): 793–99. Gupta G, Tak V, Mathur P. (2014). Detection of AmpC β lactamases in Gram-negative Bacteria. Journal of Laboratory Physicians 6(1): 1-6. Hoffmann H, Roggenkamp A. (2003). Population genet- ics of the nomenspecies Enterobacter cloacae. Applied and Environmental Microbiology 69: 5306–5318. Keller R, Pedroso MZ, Ritchmann R, Silva RM. (1998). Occurrence of virulence-associated properties in Enterobacter cloacae. Infection and Immunity 66: 645–649. Leclercq R. (2002). Mechanisms of resistance to macro- lides and lincosamides: nature of the resistance ele- ments and their clinical implications. Clinical Infec- tious Diseases 34: 482–92. Lee SO, Kim YS, Kim BN, Kim MN, Woo JH, Ryu J. (2002). Impact of previous use of antibiotics on de- velopment of resistance to extended-spectrum ceph- alosporins in patients with enterobacter bacteremia. European Journal of Clinical Microbiology and Infec- tious Diseases 8: 577–581. Leyla H, Aggad H, Hamad B. (2017). Bacterial caus- ative agents with subclinical mastitis in Dromedary She-Camels in Southeaster Algeria. Jordan journal of biological sciences 11: 209-214. Lipman LJA, de Nijs A, Lam TJGM, Gaastra, T. (1995). Identification of Eschericia coli strains from cows with clinical mastitis by serotyping and DNA poly- morphism patterns with REP and ERIC primers. Vet- erinary Microbiology 43:13-19. Lj T. (1965). Role of milk and milk products in nutrition in tropical and subtropical countries. Journal of Dairy Science 48: 1547– 50. Mezzatesta ML, Gona F, Stefani S. (2012). Enterobacte- rcloacae complex: clinicalimpactandemergingantibi- oticresistance. Future Microbiology 7: 887–902. National Center for Statistics & Information (NCSI), Ministry of Oman, Oman (2019). https://data.gov. om/search?query=camel&pageIndex=&scope=&ter- m=&correct= (accessed: 1 March 2020). National Committee for Clinical Laboratory Standards. (2000). Methods for Disk Susceptibility Tests for Bac- teria that Grow Aerobically, 7th ed. NCCLS docu- ment M2-A7. Wayne, USA. National Mastitis Council (1990). Microbiological Pro- cedures for the Diagnosis of Bovine Udder Infection. National Mastitis Council, Arlington, VA, USA. Table 1. Percentage resistance of 11 Enterobacteriaceae species from camel positive for subclinical mastitis. En- tero- bacte- riace strains To - tal Number of resistant isolates (percentage resistance) PEN. CET AMP AMC. TIM STR. ENR. ERY. TYL. TET. FFC. CFP. FUR. IPM. GEN. NEO. FLU. ENR. MAR. SXT. LEX. E. cloacae 7 7(100) 7(100) 7(100) 0(0) 0(0) 0(0) 7(100) 7(100) 0(0) 3(43) 0(0) 0(0) 0(0) 0(0) 0(0) 0(0) 0(0) 0(0) 7(100) 7(100) E. coli 4 4(100) 4(100) 4(100) 0(0) 0(0) 0(0) 2(50) 2(50) 1(25) 0(0) 0(0) 0(0) 0(0) 0(0) 0(0) 0(0) 0(0) 0(0) 3(75) 3(75) Total 11 11(100) 11(100) 11(100) 0(0) 0(0) 0(0) 9(82) 9(82) 1(9) 3(27) 0(0) 0(0) 0(0) 0(0) 0(0) 0(0) 0(0) 0(0) 10(90) 10(90) PEN: Penicillin; AMP: Ampicillin; AMC: Amoxicillin + Clavulanic acid; TIM: Ticarcillin/Clavulanic acid; STR: Streptomycin; ENR: Enrofloxacin; ERY: Erythromycin; TYL: Tylosin; TET: Tetracycline; FFC: Florfenicol; CFP: Cefoparazone; FUR: Ceftiofur ; IMP: Imipenem ; GEN: Gentamicin; NEO: Neomycin; FLU: Flumequine ; ENR: Enrofloxacin ; MAR: Marbofloxacin ; SXT: Trimethoprim/Sulfamethoxazole; LEX: Cefalexin; CET: Cefalotin; 26 SQU Journal of Agricultural and Marine Sciences, 2021, Volume 26, Issue 1 Subclinical Mastitis in Camels in Oman: A Pilot Study Obeid AI, Bagadi HO. (1996). Mastitis in Camelus dromedarius and the somatic cell count of camel’s milk. Research in Veterinary Science 61: 55-58. Ojo KK, Ulep C, Van Kirk N, Luis H, Bernardo M, Leitao J. (2004). The mef(A) gene predominates among sev- en macrolide resistance genes identified in gram-neg- ative strains representing 13 genera, isolated from healthy Portuguese children. Antimicrob Agents Chemotherapy 48: 3451–3456. Potron A, Poirel L, Rondinaud E, Nordmann P. (2013). Intercontinental spread of OXA-48 beta-lactamase producing Enterobacteriace over a 11-year period, 2001 to 2011. Eurosurveillance 18(31): 1-14 (Article 20549). Quinn PJ, Carter ME, Markey B, Carter GR. (1999). Clinical Veterinary Microbiology Wolf publishing, London, England. p. 327. Quinn PJ, Carter ME, Markey BK, Carter GR. (1998). Clinical Veterinary Microbiology. 2nd ed. Mosby Publishing, London, UK. Saber K, Mohammed S, Ahmed A. (2010). Sanitary conditions of lactating dromedary she-camel envi- ronment with special reference to milk quality and subclinical mastitis monitoring. Emirates Journal of Food and Agriculture 22(3): 207-215. Saleh SK, Faye B. (2011). Detection of subclinical masti- tis in dromedary camels (Camelus dromedaries) us- ing somatic cell counts, California mastitis test and udder pathogen. Emirates Journal of Food and Agri- culture 23(1): 48-58. Sanders WE Jr, Sanders CC. (1997). Enterobacter spp. Pathogens poised to flourish at the turn of the centu- ry. Clinical Microbiology Reviews 10: 220–241. Schalm OW, Noorlander DD. (1957). Experiments and observations leading to development of California Mastitis Test. Journal of the American Veterinary Medical Association 130: 199–204. Sumathi BR, Veeregowda BM, Amitha GR. (2008). Prev- alence and antimicrobial profile of bacterial isolates from clinical mastitis. Veterinary World 1: 237-238. Weem MF, Dereddy NR, Arnold SR. (2015). Mother’s milk as a source of Enterobacter cloacae sepsis in a preterm infant. Breastfeeding Medicine 10(10): 503-504. Zibaee S, Hosseini SM, Yousefi M, Taghipour A, Kiani MA, Noras MR. (2015). Nutritional and therapeutic characteristics of camel milk in children: a systematic review. Electronic Physician 7: 1523–1528.