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total of 5039 consecutive pus samples received in the Bacteriology Laboratory was analyzed from the records. RESULTS: There were a total of 2783 bacterial ...
SERUM STEROID HORMONES IN SCHIZOPHRENIC PATIENTS

18. Bosse R, Dipaolo T. Dopamine and GABA A receptor imbalance after ovariectomy in rats: model of menopause. J Psychiatry Neurosci 1995;20:364-71.

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130-42. 22. Papadopoulos V, Amri H, Boujrad N, Cascio C, Culty M, Gar nier M, et al. Peripheral benzo-

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BACTERIOLOGICAL AND ANTIMICROBIAL SUSCEPTIBILITY PROFILE OF SOFT TISSUE INFECTIONS FROM NORTHERN INDIA S MOHANTY, A KAPIL,* B DHAWAN, B K DAS*

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ABSTRACT BACKGROUND: Soft tissue infections require a judicious combination of antimicrobial therapy in addition to surgical debridement to limit tissue loss and preserve life. AIMS: To study the bacterial etiology of soft tissue infections and their antimicrobial susceptibility pattern. Settings and design: A single institutional retrospective study of one year duration from January to December 2002. MATERIALS AND METHODS: A total of 5039 consecutive pus samples received in the Bacteriology Laboratory was analyzed from the records. RESULTS : There were a total of 2783 bacterial isolates comprising of 1504 gram negative bacilli and 1279 gram positive cocci. Staphylococcus aureus was the commonest isolate followed by Escherichia coli and Pseudomonas species . Methicillin resistance in S. aureus was found to be 38.56%, high level aminoglycoside resistance was observed in 53.3% enterococci and 66.75% of the gram negative bacilli were extended spectrum beta-lactamase producers. Rifampicin and vancomycin showed best activity for S. aureus; for gram-negative bacilli, piperacillintazobactam combination showed best activity. CONCLUSIONS : Continuous monitoring of antimicrobial susceptibility pattern in individual settings together with their judicious use is emphasized to minimize emergence of drug resistant bacteria. KEY WORDS: Soft tissue infection, Antibiogram, Beta lactams, Methicillin resistant Staphylococcus aureus, High level aminoglycoside resistance.

INTRODUCTION Skin and soft tissue inf ections (SSTIs) are a common type of infection that may contrib ute to longer hospital stays , significantly increase the cost of medical care, and are likely to have MD; Senior Research Associate; Additional Professor; Associate Professor ; Depar tment of Microbiology, AIIMS, New Delhi - 110029, India. Correspondence: Arti Kapil, Depar tment of Microbiology, AIIMS, New Delhi - 110029, India. E-mail : ar [email protected] Accepted Date 20-01-04

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Indian J Med Sci Vol. 58 No. 1, Januar y 2004

an impor tant role in the dev elopment of antimicrobial resistance. 1,2 Most of these infections are superficial and readily treated with a regimen of local care and antibiotics. However, soft tissue infections involving deeper layers lik e fascia and m uscle can rapidly progress to systemic sepsis and prove fatal.3 These are the type of infections that require a wise choice of antimicrobials in addition to aggressive surgical debridement to limit tissue loss and preser ve life. 1,3 Since initial antimicrobial therapy usually remains empir ic, it is impor tant to kno w, the prevailing

SOFT TISSUE INFECTIONS AND ANTIMICROBIAL SUSCEPTIBILITY

susceptibility patterns of bacterial isolates at individual institutions by routine surveillance. With the recent emergence and spread of resistant Gram-positiv e cocci and Gr amnegative bacilli including methicillin-resistant Staphylococcus aureus (MRSA), vancomycin resistant enterococci (VRE) and extended spectrum beta-lactamase (ESBL) producing bacilli, SSTIs have posed a great challenge to primary care pr actitioners. This retrospective study was therefore carried out to investigate the agents responsible for soft tissue infections in a tertiar y care hospital of India and study their antimicrobial susceptibility patter n to guide empirical therapy.

MATERIALS AND METHODS Specimens This retrospective analysis included 5039 consecutive pus samples obtained from patients admitted to various specialities of the All India Institute of Medical Sciences over a one-year per iod from 1st J anuar y to 31s t December 2002. The speciality-wise distribution of the samples w ere : General surger y, 1671(33.16%); Or thopedics, 926(18.38%); Neurosurgery, 664(13.18%); Cardiothoracic-vascular surger y, 489(9.7%); Pediatr ics Unit, 363(7.2%); Dermatology, 351(6.96%); Otorhinolar yngology Unit, 217(4.3%); Gastroenterology Unit,148(2.94%); Gynecology Unit,147(2.92%) and Intensive care units,63(1.25%). The lesions were cleaned with ster ile normal saline. Taking special care to avoid contamination by the normal flora of skin or mucus surface , where possible the pus was aspir ated or exudate collected. The specimens were transpor ted in sterile, leak-proof containers to the

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bacter iology laboratory immediately or if there was a delay, stored at 40C; those with more than 24 hours of refr igeration w ere not processed. All specimens were inoculated on 5% sheep b lood and MacConkey agar plates and incubated overnight at 37 0C aerobically (MacConkey agar) and in 5%carbon dioxide (b lood agar). Bacter ial pathogens w ere identified b y conventional biochemical methods according to standard microbiological techniques . 4 A sample was included in the study only if it w as positive for < 2 types of bacter ia. Antimicr obial susceptibility testing Antimicrobial sensitivity was perf ormed on Mueller-Hinton agar (Hi-Media, India) by the standard disk diffusion method recommended by the National Committee f or Clinical Labor atory Standards . (NCCLS).5 Standard str ains Escher ichia coli ATCC 25922, Staphylococcus aureus ATCC 25923 and Pseudomonas aer uginosa ATCC 27853 were used as controls. Organisms were tested for antibiotics based on their expected primar y activity. The diameter of the zone of inhibition of growth w as recorded and interpreted as susceptible or resistant by the cr iteria of NCCLS. 5 Organisms with “intermediate” levels of resistance were included in the percentage of resistant organisms for final analysis . Detection of ESBL All g ram- negative bacilli (GNB) were tested for ESBL production by a double disc diffusion method recommended by NCCLS. 5 Klebsiella pneumoniae 700603 was used as a control. An enhanced z one of inhibition with a difference of ≥5 mm around the ceftazidime-clavulanic acid disk as compared to the ceftazidime disk Indian J Med Sci Vol. 58 No. 1, Januar y 2004

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alone was interpreted as presence of ESBL. Detection of Methicillin resistance Staphylococcus spp. w ere tested for methicillin resistance b y using 1µg oxacillin disk.5 The S. aureus strains ATCC 25923 and WHO-2 were used as negative and positive controls respectively. Agar plates w ere incubated at 35 0C and read at 48 hours of incubation. Organisms were deemed methicillin resistant when z one of inhibition w as ≤10 mm and ≤17mm for S. aureus and coagulase negative Staphylococci respectively. Detection of VRE Enterococci w ere tested for v ancomycin resistance by the vancomycin disk (30µg) and screen agar containing vancomycin 6µ/ml.5 A vancomycin screen agar (6µg/ml) was also put up to detect v ancomycin inter mediate isolates of Staphylococcus. Enterococcus species resistant to gentamicin (120µg) disk w ere termed high le vel aminoglycoside resistant (HLAR).

RESULTS Of the 5039 pus samples receiv ed for culture during the study per iod, 2437 (48.36%) were culture positive, while 1831 (36.33%) samples w ere culture negative. Diphtheroids , en vironmental bacillus species and > 3 agents (contaminants) w ere grown in 771 (15.30%) samples which w ere not processed further. Among the 2437 culture positive samples, the number of bacterial isolates obtained were 2783 (2091 had a single pathogen and 346 had 2 types of bacteria). Of the 2783 clinical isolates , there were 1504 (54.04%) g ram Indian J Med Sci Vol. 58 No. 1, Januar y 2004

negative bacilli and 1279 (45.96%) gram positive cocci (Table 1). The top six organisms accounted for nearly 90% of all pathogens. In the 346 samples where mixed infection was found, the combination of S. aureus and E.coli (57 samples) was commonest followed by S. aureus and Acinetobacter species (48 samples). Antimicrobial susceptibility a. Gr am negative bacilli Resistance patter n of GNB to v ar ious antibiotics has been shown in Table 2. Of the 1504 isolates, only 218 (14.49%) were sensitiv e to all antibiotics . Extended spectr um beta-lactamase production was obser ved in 1004 (66.75%) isolates and ranged from 40.62% (lowest in Proteus species) to 76.34% (highest in Klebsiella species). For rest of the organisms, ESBL production was as follows : E. coli (72.31%), Acinetobacter spp (68.79%), Citrobacter spp (67.50%), Pseudomonas spp (58.79%) and Enterobacter spp, (51.28%). As regards piper acillin, best activity wa s detected f or Pseudomonas species Table 1:Rank order of 2783 isolates of soft tissue pathogens

Rank order

Species

Number of strains (%)

Staphylococcus aureus Escherichia coli Pseudomonas spp. Acinetobacter spp. Klebsiella spp Coagulase negative Staphylococci Citrobacter spp Enterobacter spp Proteus spp. (P.vulgaris, 34; P.mirabilis,29) 10. Enterococcus spp 11. Beta-hemolytic Streptococci(Group 12. Streptococcus pneumoniae Total 1. 2. 3. 4. 5. 6. 7. 8. 9.

1059 (38.05%) 484 (17.39%) 329 (11.82%) 283 (10.16%) 187 (6.72%) 153 (5.50%) 80 (2.87%) 78 (2.80%) 63 (2.26%) 61 (2.19%) A) 5 (0.18%) 1 (0.03%) 2783

SOFT TISSUE INFECTIONS AND ANTIMICROBIAL SUSCEPTIBILITY

(resistance rate 46.88%) as compared to other gram negative bacteria (resistance rate 78.54%) demonstr ating its better efficacy against Pseudomonas. Extended spectrum beta-lactamase producing bacilli were more resistant to other antibiotics compared to ESBL negativ e isolates (resistance rate 85.76% versus 23.43%). Overall, the gram negativ e bacilli showed good response to piperacillin-tazobactam.

b. Gram positive organisms Resistance to methicillin was detected in 38.56% of S. aureus isolates and 31.16% of coagulase negative Staphylococci with cross-resistance to other beta-lactams i.e. ampicillin and cefuroxime (Table 2). Barring rifampicin, methicillin resistant S. aureus strains were significantly more resistant to other antibiotics compared to methicillin

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sensitive S. aureus str ains (resistance rate 86.76% versus 26.56%).

DISCUSSION S. aureus, E. coli and Pseudomonas spp. are the top 3 pathogens in the present study similar to studies from India 6 and outside2,7 where they frequently are amongst the top 5 pathogens isolated from skin and soft tissue inf ections in hospitaliz ed patients. In the present study, prevalence of MRSA (38.56%) is higher than that repor ted from Nagpur (19.56%) 8 and Vellore (24%)9 in India. However, it is compar able to that in United States and cer tain European countries10 where methicillin resistance was detected in 32.4% to 44.4% S. aureus isolates. Almost 87% of MRSA w ere resistant to other antibiotics like amikacin and ciprofloxacin which is a matter of great concern

Table 2: Antimicrobial resistance of soft tissue infection isolates

Gram Negative Organisms (% resistant) Antimicrobial Agent (in µg) Ceftazidime (30) Piperacillin (100) Amikacin (30) Netilmicin (30) Ciprofloxacin (5) Piperacillin-Taz obactam (100/10)

E.coli (n=484) 350 (72.31) 387 (79.96) 225 (46.48) 191 (39.46) 419 (86.57) 39 (8.05)

Pseudomonas Acinetobacter (n=329) (n=283) 194 (58.96) 154 (46.88) 201 (61.09) 184 (55.92) 195 (59.27) 14 (4.25)

195 (68.90) 206 (72.79) 194 (68.55) 114 (40.28) 186 (65.72) 20 (7.06)

Klebsiella (n=187)

Citrobacter (n=80)

144 (77.01) 159 (85.02) 126 (67.38) 117 (62.56) 97 (51.87) 11 (5.88)

54 (67.5) 65 (81.25) 41 (51.25) 35 (43.75) 54 (67.50) 2 (2.50)

Enterobacter Proteus (n=78) (n=63) 41 (52.56) 57 (73.07) 25 (32.05) 37(47.43) 23 (29.48) 0 (0.00)

26 (41.26) 49 (77.78) 23 (36.50) 20 (31.74) 28 (44.44) 2 (3.17)

Gram Positive Organisms (% resistant) Antimicrobial Agent (in µg) Ampicillin (10) Cefuroxine (30) Amikacin (30) Ciprofloxacin (5) Rifampicin (5) Erythromycin (15) Gentamicin (120) Vancomycin (30)

S. aureus (n=1059) 540 (50.99) 557 (52.6) 396 (37.39) 505 (47.68) 199 (18.79) ND ND 0 (0.00)

Coagulase Negative Staph (n=153) 94 (61.43) 89 (58.17) 62 (40.52) 81 (52.94) 37 (24.18) ND ND 0 (0.00)

Enterococcus spp. (n=61) 34 (56.73) ND ND 34 (56.73) ND 36 (59.01) 32 (53.30) 0 (0.00)

ND – Not Done

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since options to treat these infections are dr astically reduced. High resistance of MRSA to other antibiotics has been repor ted in previous studies also . 8,9 Thus , at present vancomycin and rifampicin appear to be the drug of choice for treating MRSA infections. Alter nate dr ugs like teicoplanin and quinupr istine-dalfopr istine have also shown promising results .2,7 As regards enterococci, more than half of the isolates (53.3%) w ere HLAR with the implication that the synergistic combination of beta-lactam plus aminoglycoside will not be active against them. Thus, the resistance patter n of enterococci needs to be monitored carefully. Gr am negative bacilli demonstrated a high rate of ESBL e xpression (66.75%) which is compar able to that reported previously (68%) from India. 11 Extended spectr um betalactamase positive isolates are frequently resistant to other antibiotics lik e quinolones and aminoglycosides 11 which has been found in the present study also. Finding of more concer n is the resistance of ESBL positive isolates to piper acillin-tazobactam (beta lactam-beta lactamase inhibitor) combination since the antibiotics of choice in the treatment of infection due to ESBL positive bacteria are limited to either these combinations or the carpapenems. 12 The high r ates of antibiotic resistance obser ved in the present study may be due to the f act that ours is a tertiar y care hospital with widespread usage of broad spectr um antibiotics leading to selective sur vival adv antage of pathogens. This is reinf orced by the fact that in a previous study 13 on nosocomial uropathogens done in our institute, a similar high rate of MRSA (23.8%), ESBL production (71.5%) and HLAR (70.17%) Indian J Med Sci Vol. 58 No. 1, Januar y 2004

was reported. The susceptibility data collected in this study suggests that the most common organisms likely to be encountered in soft tissue infections are gram-positive cocci, notab ly S. aureus , man y of them methicillin-resistant. Thus , any first line antibiotic treatment should be primar ily directed against this pathogen. For cover age of gram negative bacteria, beta lactam-beta lactamase inhibitor combinations would be more useful. Use of mono drug therapy with cephalospor ins , aminoglycosides and fluoroquinolones need to be guided b y the sensitivity report. Lastly, continued monitor ing of susceptibility patter n need to be carried out in individual settings so as to detect the true burden of antibiotic resistance in organisms and prevent their fur ther emergence b y judicious use of drugs.

REFERENCE 1. Mar tone WJ, Nichols RL. Recognition, prevention, surveillance, and management of surgical site inf ections. Clin Infect Dis 2001;33:S67-S106. 2. Sader HS., Jones RN, Silv a JB. Skin and soft tissue infections in Latin Amer ican medical centers: four-year assessment of the pathogen frequency and antimicrobial susceptibility patter ns. Diagn Microbiol Infect Dis 2002; 44: 281-8. 3. Singh G, Sinha K, Adhikar i S, Bab u SK, Ray P, Khanna SK. Necrotising infections of soft tissues – a clinical profile . Eur J Surg 2002;168:366-71. 4. Collec JG, Miles RS, Wan B. Tests for the identification of bacter ia. In: Collee JG, Fraser AG, Marmion BP, Simmons A, editors. Mackie & McCar tney Practical Medical Microbiology. 14th edn. Edinburg: Churchill Livingstone; 1996.

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pp. 131-50.

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SENTRY Program Study Group (North Amer ica). Occurrence and antimicrobial susceptibility

2003;22:406-19. 11. Mathur P, Kapil A, Das B, Dhawan B. Pre valence

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Gr am negative bacteria in a ter tiary care hospital. Indian J Med Res 2002;115:153-7.

States and Canada, 2000) Diagn Microbiol Infect

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1997;103:51-9. 13. Mohanty S, Kapil A, Das BK, Dha wan B . Antimicrobial resistance profile of nosocomial uropathogens in a ter tiary care hospital. Ind J Med Sci 2003;57:148-54.

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REDUCED MINIMUM INHIBITORY CONCENTRATION OF CHLORAMPHENICOL FOR SALMONELLA ENTERICA SEROVAR TYPHI S MANDAL, M D MANDAL, N K PAL

ABSTRACT BACKGROUND: Ciproflo xacin replaced chloramphenicol (C), the best choice of antibiotic in the treatment of enteric fever, when C-resistant enteric fever emerged and caused outbreaks in different parts of the world. C-sensitive S. enterica serovar Typhi emerged again due to withdrawal of the antibiotic pressure. AIMS: To assess the in vitro efficacy of C against Salmonella enterica serovar Typhi isolates (1991-2003). MATERIAL AND METHODS: A total of 464 blood culture isolates of S. enterica serovar Typhi were subjected to C susceptibility by disc diffusion and agar dilution methods using Mueller-Hinton agar. The antibiotic susceptibility of S. enterica serovar Typhi isolates obtained in the year 2002 and 2003 was determined using ampicillin, cotrimoxazole, ciprofloxacin, nalidixic acid, ceftriax one and cefotaxime, in addition to C. Escherichia coli strain ATCC 25922 was used as the control. Changes in C sensitivity of the isolates were analyzed using χ 2 test with Yates correction. RESULTS AND CONCLUSIONS: All the isolates of 1991 were C-resistant with minimum inhibitory concentration values (MICs) of 2000-5000 mg/ml. In the following years decrease in frequency of C resistance was noticed: 1992 (50%), 1993 (32%), 1994 (27%) and 1995 (05%). The isolates of 1996-99 and 2001 were 100% C-sensitive. In 2000, sensitivity was also high (79%). The strains isolated in the year 2002 and 2003, showing reduced susceptibility of ciprofloxacin, were nalidixic acid resistant, but sensitive to the thirdgeneration cephalosporins (ceftriaxone and cefotaxime). The MICs for C-sensitive isolates (1991-2003) ranged 0.1-5 µg/ml. Results suggest the necessity for reevaluation of C therapy in typhoid fever. KEY WORDS: Chloramphenicol, Minimum inhibitory concentration, Salmonella enterica serovar typhi.

INTRODUCTION Chloramphenicol (C) is usually bacter iostatic Department of Bacter iology and Serology, Calcutta School of Tropical Medicine, C . R. Avenue, Kolkata 700073, India. Correspondence: Nishith Kumar Pal, professor and Head, Department of Bacteriology and Serology, Calcutt a School of T ropical Medicine, C. R. Avenue, Kolkata - 700073, India. E-mail: [email protected]

Accepted Date 28-01-04

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Indian J Med Sci Vol. 58 No. 1, Januar y 2004

but may be bactericidal in high concentrations or against more susceptible microorganisms. It has a wide spectrum of activity against grampositive and gram-negative bacteria. Antibiotic activity appears to result from inhibition of protein synthesis of bacterial cells. C binds to the 50S subunit of bacter ial ribosomes, which inhibits peptide bond for mation. The dosage of C in typhoid fever (TF) is 50 mg/kg/day IV or PO, in divided doses every 6 hours (in adults),