Comparative study of antibiotic resistance of staphylococcus species isolated from clinical and environmental samples

Comparative Study of Antibiotic Resistance of Staphylococcus
Species Isolated from Clinical and Environmental Samples
Obasola Ezekiel Fagade, Cajethan Onyebuchi Ezeamagu,
Abolade Abioye Oyelade and Adeniyi Adewale Ogunjobi
Environmental Microbiology and Biotechnology Unit
Department of Botany and Microbiology, University of Ibadan, Ibadan, Nigeria
E-mail: <;;;>
Comparative study of antibiotic resistance patterns of one hundred Staphylococci isolates comprising of fifty from clinical and fifty from environmental samples were evaluated. The isolates were identified to species level by use of both classical and API-Staph identification kit, screened for beta-lactamase production and their antibiograms determined using agar diffusion technique. Five species of Staphylococcus aureus, S. haemolyticus, S. cohnni, S. xyloses and S. scuiri were identified. The 50 isolates from the environment showed multiple antibiotic resistance to selected antibiotics tested, 13(26.0%) were resistant to augumentin, 19(38.0%) to amoxicillin, 30(60.0%) to both cloxacillin and cotrimoxazole, 38(76.0%) to chloramphenicol, 43(86.0%) to erythromycin, 44(88.0%) to tetracycline and 48(96.0%) to gentamicin. The multiple antibiotic patterns of the clinical samples showed that 29(58.0 %) were resistant to augumentin, 39(78.0%) to chloramphenicol, and erythromycin while 42(84.0%) were resistant to cloxacillin, 45(90.0%) to amoxicillin, 48(96.0%) to gentamicin, and tetracycline, while all the isolates were resistant to cotrimaxazole, 50(100.0%). Only 8.0% of the environmental strains and 24.0% of the clinical strains had detectable beta-lactam enzyme activity. The results showed that S. xyloses had a wider range of antibiotic resistance activities when compared to other coagulase negative Staphylococci. This result showed the consequences of antibiotic resistance patterns in the environment and the need for urgent management. Keywords: Antibiotics, Coagulase negative, Resistance, Staphylococcus aureus.
Staphylococcus aureus (MRSA) and now Infections caused by Staphylococcus account for more than 50% of S. aureus aureus poses serious threat in health care recovered from patients in intensive care units institutions. (Panlilio et al. 1992; and NNIS and about 40% of S. aureus isolated from non 2001, 2004). It is one of the most widely spread and virulent nosocomial pathogen and is usually resistant to multiple antibiotics making methicillin resistance has been questioned in infections difficult to treat (Cooper et al. 2004). It appears to add to the total burden of Staphylococcus infections in the hospitals, MRSA. It has emerged as a significant cause of rather than replacing sensitive S. aureus, and is associated with sharp risk in mortality infections. Recent report of strains of MRSA attributable to Staphylococcal infection isolated from children in the community has (Crowcroft & Catchpole 2002). Staphylococcus led to speculation that the epidemiology of S. aureus strains continue to be a major problem aureus is changing (CDC 1999; and Boyce in many healthcare institutions especially with 1998). Traditionally, MRSA infections have been acquired almost exclusively in hospitals, Materials and Methods
long-term care facilities or similar institutional settings (Thompson et al. 1982). Health-care Bacterial Isolates
bacteremia and endocarditis, pneumonia, soft- February 2007 and June 2007 from patients tissue infections and urinary tract infections. admitted to University College Hospital, Ibadan. Of the 50 clinical samples, 8(16.0%) associated MRSA (CA-MRSA) infections is of major concern to both public health officials and clinicians. The first report of CA-MRSA infection occurred among Australian samples, 9(18.0%), 7(14.0%), 3(6.0%) were aboriginals and Native Americans in Canada in isolated from ear, skin and nose respectively of the early 1990s (Boyce 2003). The earliest apparently healthy individuals while 31(62.0%) reported cases of CA-MRSA infection in the United States occurred in children with little or no recognized contact with the hospitals or other health care institutions (Herold et al. 1998). Coagulase negative Staphylococci 1991; and Holt et al. 1994). Also, API-Staph (CNS) belong to the group of opportunistic pathogens since they are found as normal flora of the skin and mucus membranes in different part of the body (Einsenstein and Schaechter Detection of Beta-lactamase
1994). For this reason, CNS are often reported without further specification, assuming that they are contaminating clinical samples but are was employed, as described by Adeleke and Odelola (2007). Bacterial cell suspension However, there is mounting evidence that equivalent to 109cells/ml was prepared for each these bacteria may be responsible for primary strain from overnight nutrient agar plate infections as a result of increased use of culture, in 0.5ml of freshly prepared phosphate briefly in a vortex mixer. Ordinary penicillin G Bannerman 1994). Methicillin resistance phosphate buffer served as control. All test among CNS is particularly important due to cross resistance to virtually al B-lactam agents temperature for minimum of 1h.Thereafter, two and other antimicrobial classes. As a result, drops of freshly prepared 1% aqueous starch therapeutic approaches are restricted to solution was added to suspension, without glycopetide and new antimicrobial agents as shaking. The mixtures were allowed to stand Linezolid (Woods et al. 2002). Therefore, an for 10minutes, for a possible colour change accurate analysis of resistance between clinical and community strains may allow the provision of better antimicrobial therapy. Besides, the Susceptibility Test
importance for patient care the detection also has implications for the validity of antibiotic resistance surveillance. Hence the purpose of according Kirby-Bauer method, as described in this study is to isolate Staphylococcus species the guidelines of the National Committee for Clinical Laboratory Standards (NCCLS 2000, samples and to determine the antibiogram of 2002), using discs (Abterk) containing 10µg the isolates against some selected commercial (COT), 30 µg Chloramphenicol (CHL), 30 µg Augumentin (AUG), 25 µg Amoxacillin 42(84.0%) cloxacillin, 45(90.0%), amoxicillin (AMX), 5 µg Erythromicin (ERY), 10 µg 48(96.0%), gentamicin, and tetracycline, while Tetracycline (TET) and 5 µg Cloxacillin all the isolates were resistant to cotrimaxazole, difference in resistance patterns between the clinical and community strains were evaluated using Chi-square analysis and statistical significance was set at α = 0.05. showed multiple antibiotic resistance activities antibiotic resistance pattern amongst isolates to selected antibiotics tested, 13(26.0%) were resistant to augumentin, 19(38.0%) to gentamicin, chloramphenicol, erythromycin, amoxicillin, 30(60.0%) to both cloxacillin and and tetracycline. (p > 0.05). However, there are cotrimoxazole, 38(76.0%) to chloramphinicol significant difference in antibiotic resistance pattern amongst isolates from clinical and tetracycline and 48(96.0%) to gentamicin. The multiple antibiotic patterns of the clinical samples were augumentin 29(58.0 %), tetracycline (p < 0.05). 39(78.0%) chloramphenicol, and erythromycin, Table: 1 Comparison of antibiotic sensitivity and resistance of Community and Clinical strains of Staphylococcus species. Chloramphenicol 38 76.0 12 24.0 39 78.0 11 22.0 0.056 1 0.812 Augumentin 13 26.0 37 74.0 29 58.0 21 42.0 10.500 1 0.001* Key: n = number of isolates; level of significance = 0.05; * = significant. Staphylococcus as etiologic agents of infections Discussion
(Schnitzler et al. 1997; and Bannerman 2003) especially with infections associated with Coagulase negative Staphylococci were medical devices and in immunocompromised mostly encountered in this study. This is in patients. Boagdo et al. (2001) reported that the conformity with previous work of Bannerman incidence of resistant CNS to antimicrobial (2003) and Kwok and Chow (2003). agents are high and this is similar to the Staphylococcus xylosus, S. scuiri, and S. findings of other authors (Hedin 1996; and haemolyticus were isolated from eye swab and Martínez et al. 1997) especially with respect to wound swab while S. aureus was only isolated from eye swab. Although, the most reported therapeutic and economic problems raised by CNS of clinical importance are S. saprophyticus and S. haemolyticus (Kloos and The occurrence of S. xylosus from wound Wolfshohl 1982; and Sewell et al. 1982). The and eye infections and its predominance over isolation of S. xylosus and S. scuiri were in any other CNS encountered in this study raises accord with the more recently reports which the question to whether this is the most virulent implicated a much wider range of species of species or simply the most predominant on the References
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Adam W. Van Wynsberghe1063 Science CenterVisiting Assistant Research Scientist (Sabbatical Leave from Hamilton College)University of California-San DiegoDepartment of Chemistry and BiochemistryAssistant ProfessorHamilton College, Clinton, NYDepartment of ChemistryNIH Post-Doctoral FellowUniversity of California-San DiegoDepartment of Chemistry and BiochemistryAdvisor: Dr. J. Andrew McCammonAss

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