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The Discovery of a Multi-resistant Staphylococcus haemolyticus Clone in the Hospital and Community Environment in South Western Nigeria
Coagulase negative staphylococci (CNS) are resident bacteria in the human skin, nasal cavities, and oral mucosa.1
They are among the most frequently isolated bacteria in the clinical microbiology laboratory and their importance as major nosocomial pathogens is mainly due to the increasing use of prosthetic devices and other invasive technologies in medical institutions.2 Among the clinically significant isolates of CNS, Staphylococcus haemolyticus is ranked second after Staphylococcus epidermidis.3,4 It has been associated with septicemia in neonates and various infections in individuals with compromised host defenses and implanted foreign bodies.5,6 Methicillin-resistant Staphylococcus aureus (MRSA) is typically viewed as a hospital pathogen, but recent studies suggest that the epidemiology of MRSA may be changing with the presence of hospital MRSA clones in the community.7-9 Furthermore, reports on distinct community MRSA clones associated with skin and soft tissue infections (SSTIs) in patients without predisposing risk factors have been established.10-12 Staphylococcus haemolyticus is one of the main CNS species associated with multiple drug resistance, a trend that is evident in MRSA. However, the understanding of the dissemination of multi-resistant S. haemolyticus is not as clear as MRSA. Moreover, little information on the possible spread of hospital CNS clones into the community is available.
Microbiological Analysis and Clonal Relationship
Clinical observation. A single clone of multi-resistant S. haemolyticus was identified during a study on patients with SSTIs at two different local health clinics and a staphylococcal nasal carriage surveillance program. The latter was conducted among 60 randomly selected medical personnel and students at the Obafemi Awolowo University Teaching Hospitals Complex (OAUTHC) in Ile-Ife, South Western Nigeria. This hospital is a major referral center for more than 1 million people living within a 40 km radius from Ile-Ife. The clinical and epidemiological information of the non-hospitalized individuals have been described.13
Culturing procedure. Samples were streaked on blood and mannitol salt agar and incubated at 37oC for 24 hours and 48 hours, respectively. Staphylococcal isolates were identified based on cultural characteristics on growth media, Gram reaction (Gram positive cocci in clumps), catalase, coagulase (tube method using rabbit plasma), and DNase tests. Susceptibility testing was performed using the agar disk diffusion technique following the recommendations given in the National Committee for Clinical Laboratory Standards.14 Isolates were screened for intermediate resistance to vancomycin as previously described.13 Minimum inhibitory concentration (MIC) was determined using the macrodilution E-test method.15 An inoculum equivalent to 2 MacFarland was swabbed onto Brain Heart Infusion Agar (BHIA) before placement of vancomycin and teicoplanin E test strips and incubated at 35oC. Minimum inhibitory concentration readings were taken at 24 and 48 hours, respectively.
Molecular identification was performed by polymerase chain reaction (PCR) amplification of the 16S-23S rRNA intergenic spacer region — rRNA spacer length polymorphism analysis — as previously described.13 The patterns of the PCR products were visually compared with NCTC species reference strains. Genetic relatedness using pulsed field gel electrophoresis (PFGE) typing of SmaI digested DNA was carried out by a modification of the protocol previously published by Bannerman et al.16
Findings
One strain (S3-2) in this clone was recovered from the nasal culture of a medical staff member at OAUTHC and two (strain numbers 14 and 34) from wound swabs of outpatients with SSTIs. The strains were identified as S. haemolyticus by rRNA spacer length polymorphism analysis. Antibiotic susceptibility profile (resistant to penicillin, ampicillin, methicillin, streptomycin, gentamicin, tetracycline, and ciprofloxacin but sensitive to fusidic acid, mupirocin, and novobiocin) and PFGE analysis of SmaI digested chromosomal DNA revealed that the strains were identical (see Figure 1). One of the patients with SSTIs was a resident of Ile-Ife and received treatment at a local health clinic located 5 km from OAUTHC. The second patient received treatment at the local health clinic in Ipetumodu, 25 km from OAUTHC. The two local health institutions are situated 20 km from each other. Both patients had no record of hospitalization or antibiotic medication before sample collection.13 Confluent growth was observed on the vancomycin screen plates after 48 hours incubation. Minimum inhibitory concentration values (E-test) for vancomycin were 8 µg/mL, 6 µg/mL, and 4 µg/mL while teicoplanin MICs were 8 µg/mL, 6 µg/mL, and 8µg/mL for strains 14, 34, and S3-2 respectively, after 48 hours.
Discussion
Little is known about the epidemiology of S. haemolyticus in Nigeria because many clinical microbiology laboratories do not identify coagulase negative staphylococci to the species level. During the investigation of staphylococcal nasal carriage at OAUTHC, 11 S. haemolyticus isolates were recovered from 60 medical staff members and students, of which five were mecA positive (unpublished results). This trend indicates that healthcare workers (HCWs) could serve as important reservoirs for strains capable of colonization and spread from medical personnel to patients. Extensive nasal colonization and cross-infection of CNS from HCWs to patients and the existence of S. haemolyticus in the hospital environment and on the hands of HCWs have been established in several studies.17-21 The findings in this study suggest that the multi-resistant S. haemolyticus clone could be widespread in the hospital and community of this region or is a hospital clone that was transmitted via medical personnel or discharged patients to outpatients. To the authors’ knowledge, this is the first report of what appears to be a hospital-acquired and transmitted S. haemolyticus clone in South Western Nigeria.
A connection between medical personnel and the local health centers could not be ascertained. Furthermore, nasal carriage of methicillin-resistant S. haemolyticus among medical personnel in the two local health clinics and intrafamilial spread were not investigated.
Conclusion
The MIC values for vancomycin and teicoplanin in the multi-resistant S. haemolyticus strains from outpatients in Ile-Ife and Ipetumodu could be of great concern. Glycopeptides are not frequently prescribed to patients in the referral hospital or available over-the-counter in pharmacy outlets in South Western Nigeria. The clonal and multi-resistant nature of these strains from the hospital and community environment could have serious public health implications.
Community-acquired staphylococcal infections could be caused by the dissemination of strains from patients discharged from the hospital or via medical personnel. Unfortunately, treatment of patients in many outpatient departments is not always guided by microbiological analysis. Studies on the epidemiology of CNS infection in hospital and community settings are urgently needed to determine the role of human reservoirs in transmission and subsequent infection. Careful infection control practice including judicious use of antibiotics is important; hand washing, hand disinfection techniques, and the use of gloves must be promoted to limit the spread of such strains from healthcare institutions into the community. Furthermore, the need for strain typing (using phenotypic and genotypic methods) is essential if the clinical and epidemiological data indicate that identification of specific strains is necessary to understanding their epidemiology.
Acknowledgments
The National Research Foundation, Republic of South Africa, supported the project. The authors thank Bongi Sigwebela, University of Zululand, for assistance in the acquisition of research articles; and Dr. Edet Udo for the kind donation of E-test strips for MIC determination.
1. Patrick CC. Coagulase-negative staphylococci: pathogens with increasing clinical significance. J Paediatrics. 1990;116:497–507.
2. von Eiff C, Peters G, Heilmann C. Pathogenesis of infections due to coagulase-negative staphylococci. Lancet Infect Dis. 2002;2:677–685.
3. Kloos WE, Bannerman TL. Staphylococcus and micrococcus. In: Murray PR, Baron EJ, Pfaller MA, Tenover FC, Yolken RH, eds. Manual of Clinical Microbiology, 6th ed. Washington, DC: ASM Press;1995:282–298.
4. De Paulis AN, Predari SC, Chazaretta CD, Santoianni JE. Five-test scheme for species-level identification of clinically significant coagulase-negative staphylococci. J Clin Microbiol. 2003;41:1219–1224.
5. Mehta G, Singh S, Kumari S. Observations on coagulase-negative staphylococci in a neonatal unit in India. J Hosp Infect. 1991;19:273–281.
6. Mehta G, Kumari S. Multi-resistant Staphylococcus haemolyticus in a neonatal ward in New Delhi. Ann Trop Paediatr. 1997;17:15-20.
7. Cookson B. Methicillin-resistant Staphylococcus aureus in the community: new battlefronts, or are the battles lost? Infect Control Hosp Epidemiol. 2000;21:398-403.
8. Eady EA, Cove JH. Staphylococcal resistance revisited: community-acquired methicillin-resistant Staphylococcus aureus — an emerging problem for the management of skin and soft tissue infections. Curr Opin Infect Dis. 2003;16:103–124.
9. Saiman L, O’Keefe M, Graham III PL, et al. Hospital transmission of community-acquired methicillin-resistant Staphylococcus aureus among postpartum women. Clin Infect Dis. 2003;37:1313–1319.
10. Naimi TS, LeDell KH, Boxrud DJ, et al. Epidemiology and clonality of community-acquired methicillin-resistant Staphylococcus aureus in Minnesota, 1996-1998. Clin Infect Dis. 2001;33:990–996.
11. Dufour P, Gillet Y, Bes M, et al. Community-acquired methicillin-resistant Staphylococcus aureus infections in France: emergence of a single clone that produces Panton-Valentine leukocidin. Clin Infect Dis. 2002;35:819–824.
12. Wu KC, Chiu HH, Wang JH, et al. Characteristics of community-acquired methicillin-resistant Staphylococcus aureus in infants and children without known risk factors. J Microbiol Immunol Infect. 2002;35:53-56.
13. Shittu AO, Lin J, Morrison D, Kolawole DO. Isolation and molecular characterization of multi-resistant Staphylococcus sciuri and Staphylococcus haemolyticus associated with skin and soft-tissue infections. J Med Microbiol. 2004;53:51–55.
14. NCCLS. Performance standards for antimicrobial disk susceptibility tests. NCCLS document M2-A7. Wayne, Pa.: National Committee for Clinical Laboratory Standards, 2000.
15. Walsh TTR, Bolmstrom A, Qwarnstrom A, et al. Evaluation of current methods for detection of staphylococci with reduced susceptibility to glycopeptides. J Clin Microbiol. 2001;39:2439-2444.
16. Bannerman TL, Hancock GA, Tenover FC, Miller JM. Pulsed-field gel electrophoresis as a replacement for bacteriophage typing of Staphylococcus aureus. J Clin Microbiol. 1995;33:551–555.
17. Lee YL, Cesario T, Tran C, Stone G, Thrupp L. Nasal colonization by methicillin resistant coagulase negative staphylococci in community skilled nursing facility patients. Am J Infect Control. 2000;28:269–272.
18. Sousa M, Ferro ML, Sanches IS, de Lencastre H. Epidemiological study of staphylococcal colonization and cross-infection in two West African Hospitals. Microb Drug Resist. 2000;6:133–141.
19. Tabe Y, Nakamura A, Oguri T, Igari J. Molecular characterization of epidemic multi-resistant Staphylococcus haemolyticus isolates. Diagn Microbiol Infect Dis. 1998;32:177–183.
20. Perdreau-Remington F, Stefanik D, Peters G, Ruckdeschel G, Wenzel R, Pulverer G. Methicillin-resistant Staphylococcus haemolyticus on the hands of health care workers: a route of transmission or a source? J Hosp Infect. 1995;31:195–203.
21. Kitao T. Survey of methicillin-resistant coagulase-negative staphylococci isolated from the fingers of nursing students. J Infect Chemother. 2003;9:30–34.
