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Indian Journal of Medical Microbiology, Vol. 23, No. 3, July-September, 2005, pp. 186-188 Brief Communications Survey of Staphylococcus isolates among hospital personnel, environment and their antibiogram with special emphasis on methicillin resistance Shobha K.L., Rao P.S., Thomas J. Department of Microbiology, Melaka Manipal Medical College, Manipal-576 104, Karnataka Date of Submission: 28-Sep-2004 Code Number: mb05054 ABSTRACT The objective of this study was to find the prevalence of Staphylococcus spp. carriage among hospital personnel and hospital environment and their antibiogram with special emphasis on methicillin resistance. A total of 205 samples from hospital personnel and environment were collected from casualty, oncology and multidisciplinary cardiac unit ward of Kasturba Medical College Hospital, Manipal. Samples were collected using sterile cotton wool swabs and inoculated into brain heart infusion broth. Subcultures were done onto blood agar and MacConkey's agar. Isolates were identified by standard methods up to species level. Antimicrobial susceptibility test was performed according to standardized disc diffusion Kirby-Bauer method. Each of the isolates was screened for methicillin resistance using oxacillin disc on Mueller Hinton agar plate followed by MIC for methicillin and cefoxitin susceptibility test by disc diffusion method. Sixty five out of 205 strains (31.7%) were Staphylococcus spp. and all of them were coagulase negative. Most of the strains belonged to S.epidermidis 49.23%(32/65) followed by S. saprophyticus 26.15%(17/65). Maximum isolates of S.epidermidis were from anterior nares 28.12%(9/32 strains of S.epidermidis ). Highest number of methicillin resistant coagulase negative strains (3/9, 33.33%) were isolated from stethoscope of multidisciplinary cardiac unit ward followed by carriers in the anterior nares (2/9, 22.22%). Methicillin resistant coagulase negative staphylococci are prevalent in anterior nares of hospital personnel and in the hospital environment thereby providing a definite source for hospital acquired infection. All isolates were sensitive to vancomycin, ciprofloxacin and amikacin.Keywords: Methicillin resistance, coagulase negative Staphylococcus species, stethoscope, anterior nares Multidrug resistant Staphylococcus isolates in hospitals have been recognized as one of the major challenges in the hospital infection control.[1] Isolation of coagulase negative S taphylococcus and antibiotic sensitivity patterns are regarded with all seriousness in clinical practice and clinical epidemiology.[2] These strains are not only resistant to multiple antibiotics, but also act as a reservoir for drug resistance gene.[3] Higher percentage of methicillin resistant Staphylococcus among carriers can serve as a focus of nosocomial spread of multidrug resistant Staphylococcus in tertiary hospitals and cause problems to hospital infection control programs.[1] In India, the study on the prevalence of Staphylococcus species among hospital personnel is much lacking.[4] Here we report the prevalence of Staphylococcus spp. isolated from hospital personnel and hospital wards and their antibiogram. We especially determined methicillin resistance among these isolates. MATERIALS AND METHODS A total of 205 samples were collected from casualty, oncology and multidisciplinary cardiac unit (MICU) wards of Kasturba Medical College Hospital, Manipal from December 2002 to February 2003. The specimens included swabs from floor, sink, tap, door handles of the wards and swabs from stethoscopes. Other samples included hospital staff ′s fingernails, skin swab, scalp hair, nasal swabs and urine from catheteterized patients admitted to these wards.Sterile cotton wool swabs, moistened with sterile normal saline were used to collect the specimen. Urine was collected by aspiration from the catheter using a sterile needle and syringe. Specimens were inoculated into brain heart infusion broth (BHI) immediately. Subcultures were done from BHI broth on to blood agar and MacConkey′s plate. Staphylococcus species were identified up to species level as per the scheme described by Baird-Parker [5] The antimicrobial susceptibility test was performed according to standardized disc diffusion Kirby-Bauer method.[6] Each of the isolates was screened for methicillin resistance by disc diffusion method. Four of five colonies picked from overnight growth were inoculated into 4 to 5 mL of peptone water which was incubated at 35 °C until turbid to 0.5 McFarland standard. The methicillin susceptibility was tested using 1 µg Oxacillin discs (Hi-Media, Mumbai, India). The diameter of the clear zone around the disk was measured and the results were interpreted as susceptible or resistant.[1] Drug free plates were also inoculated for growth control. Methicillin Sensitivity was further confirmed by minimum inhibitory concentration at 0.2 mg/mL to 0.8 mg/mL and susceptibility to cefoxitin was tested by disc diffusion method. The zone size of 24 mm or less for cefoxitin was considered as resistant.[7] RESULTS Out of 205 samples screened 65 (31.7%) samples yielded Staphylococcus spp. and all of them were coagulase negative (CoNS). Resistance to oxacillin was 13.84% (9/65). Highest percentage of oxacillin resistant coagulase negative Staphylococcus strains (MR-CoNS) were isolated from the stethoscope 33.33% (3/9) followed by carriers in the anterior nares 22.22% (2/9) of hospital personnel [Table - 1]. As shown in [Table - 2], 32 out of 65 (49.23%) staphylococcal species belonged to S.epidermidis followed by S.saprophyticus 17/65 (26.15%).Antibiotic sensitivity pattern of isolates showed 100% sensitivity to vancomycin, ciprofloxacin and amikacin. Resistance to ampicillin and amoxicillin-clavulinic acid was 70% each. Methicillin resistance was 14% [Table - 3]. DISCUSSION Of 205 samples collected from hospital wards and hospital personnel, 65 (31.7%) isolates were CoNS.This correlated well with the study conducted by Baumgalt et al[8] who reported 23% carrier rate of CoNS. Among the hospital staff, nasal carrier rate of CoNS was 45.94% (17/37 samples). This study is in concordance with the study conducted by Narayani et al [9] who reported nasal carrier rate of 62% CoNS. Our study showed a decreased incidence of CoNS in stethoscopes 33.71% (17/45) when compared to other studies, where 100% stethoscopes yielded CoNS. Smith et al reported 58% incidence of CoNS from stethoscope.[11]Among the carrier isolates, S.epidermidis was the leading species followed by S. saprophyticus . Narayani et al [9] had found S.epidermidis as the commonest isolate followed by S. hominis . However, in our study S.hominis was the third commonest species. It is well known that S. saprophyticus is the leading agent among coagulase negative Staphylococcus strains associated with urinary tract infection. However, in our study there was no isolation from urine samples. CoNS had maximum resistance to ampicillin 69% (45/65), amoxicillin-clavulinic acid 69% (45/65) and TMP/SMX 65% (42/65). All strains were sensitive to vancomycin, amikacin and ciprofloxacin. Methicillin resistance was 14% (9/65), which was in concordance with the study conducted by Vijayalakshmi et al.[12] All these nine strains were confirmed to be methicillin resistant by MIC at 0.2 mg/mL to 0.8 mg/mL.Strains resistant to oxacillin were also resistant to cefoxitin. MR-CoNS carriage rate was highest in stethoscope 33.33% (3/9) when compared to other specimens. Marinella et al[10] reported more than 40% methicillin resistant Staphylococcus species from stethoscope which correlated with our study. Methicillin resistant Staphylococcus spp. present in hospital personnels may act as carriers and can serve as a focus of nosocomial spread of multidrug resistant Staphylococci in tertiary level hospitals and cause problems to hospital infection control programmes. REFERENCES
Copyright 2005 - Indian Journal of Medical Microbiology The following images related to this document are available:Photo images[mb05054t3.jpg] [mb05054t2.jpg] [mb05054t1.jpg] |
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