Prevalence of Saprophytic Staphylococci in Medical Laboratories

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Huda Abdel Rahim Mohamed Abdel Karim, Abdel Karim
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A survey was carried out in five diagnostic and research laboratories. These were the microbiology and preventive medicine laboratories at the Faculty of Veterinary Science., U. of K., Bacteriology laboratory at the Animal Research Centre of the Animal Resources Research Corporation, Soba, Bacteriology Laboratory at the National Medical Laboratory, Microbiology Laboratory at the Faculty of Pharmacy, U. of K. Examination of 167 samples for Staphylococci was done to detect saprophytic staphylococcal species that cause contamination. Prevalence of different species in these laboratories greatly differed according to the samples presented in each laboratory, and the different sanitary measures. Out of the 167 samples, 25 yielded different species of Staphylococci which were divided into three main groups i.e. Coagulase-positive Staphylococci, Coagulase-negative novobiocin-resistant species and Coagulase-negative Novobiocin-sensitive species. In the Microbiology Laboratory of the Faculty of Veterinary Science, 19 species were identified from 87 isolates of Staphylococci and were grouped into four coagulase-positive species viz: Staph. aureus, Staph. intermedius, Staph. hyicus, Staph. delphini, six coagulase negative Novobiocin-resistant species viz Staph. sciuri, Staph. equorum, Staph. kloosii, Staph. saprophyticus, Staph. cohni, Staph. lentus and one Staph. cohnii subsp. urealyticus, and eight coagulase negative novobiocin-sensitive species viz: Staph. caseolyticus, Staph. warneri, Staph. simians, Staph. auricularis, Staph. carnosus, Staph. simulans, Staph capitis and Staph. lugdunensis. In the Preventive Medicine Laboratory, 16 species were identified out of 35 Staphylococci isolates and these were two coagulase-positive species Staph. aureus and Staph. hyicus, three coagulase-negative Novobiocin-resistant species Staph. sciuri, Staph. kloosii, Staph. saprophyticus and one Staph. cohnii subspecies urealyticus, five coagulase-negative Novobiocin-sensitive species Staph. caseolyticus, Staph. warneri, Staph. schleiferi, Staph. capitis, Staph. epidermidis and one Staph. capitis subsp. ureolyticus. In the National Medical Laboratory, six species were identified from 10 isolates, one coagulase-positive species Staph. hyicus. There were no coagulase negative Novobiocin-resistant species identified. There were five coagulase-positive Novobiocin-sensitive species viz: Staph. caseolyticus, Staph. warneri, Staph. simians, Staph. capitis and Staph. chromogenes. In the Pharmacy Laboratory, six species of Staphylococci were identified out of 10 isolates, no coagulase-positive species were identified. Two coagulase-negative Novobiocin-resistant Staph. sciuri and Staph. kloosii, 3 coagulase-negative Novobiocin viz. Staph. caseolyticus, Staph. simians, Staph. epidermidis. and Staph. capitis. There were no coagulase-positive species identified. All the species isolated were grown on Staphylococcus medium number 110 and on Baird-Parker medium to study the ability of growth in each medium. Few species failed to grow a fact that does not agree with the general idea that these two media support Staphylococcal growth. Staph. lugdunensis could not grow on Staph. Medium No 110, while Staph. chromogenes and Staph. capitis subspecies clureolyticus could not grow on Baird-Parker, but they play an important role in pathogenicity. Staphylococci which were not isolated in this study were Staph. aureus subsp anaerobius, Staph. arlettae, Staph. xylosus, Staph. haemolyticus and Staph. hominis. All the species were grown microaerophilically and preserved at 4oC in the refrigerator for further study of the morphological, biochemical and growth characteristics. All of them could grow aerobically. Microscopically, the organisms were Gram-positive, occurring singly, in pairs or in clusters. Most of them enlarged cells, after incubation microaerophilically on blood agar for 24 hours colonies were low convex, circular, entire, glistening or opaque. Most of the pigmented, and on further preservation the colonies were enlarged. All species studied were catalase-positive, oxidase-negative except Staph. caseolyticus and Staph. sciuri which were oxidase-positive. Srapliylococci were either coagulase-positive or negative. However, Staph. hyicus was coagulase variable i.e. coagulase-positive and coagulase-negative forms. Sugar fermentation and urease production were often late. The percentage of contamination in all laboratories was generally caused by the coagulase-negative novobiocin-sensitive species whereas the coagulase-positive species showed low percentage. Staph. hyicus was an exception as it was more prevalent in the Microbiology Laboratory at the Faculty of Veterinary Science. The Preventive Medicine Laboratory was highly contaminated in comparison with the two other laboratories.
Prevalence of Saprophytic Staphylococci in Medical Laboratories