Etiology of Bacteremia in a Referral Hospital in Saudi Arabia

Transcription

1 S. M. Hussain Qadri, PhD, SM(AAM), Diplomate ABMM, FAAM*; S. H. Khalil, MBBS ; S. Johnson, MT(ASCP) ; D. J. Flournoy, PhD *Formerly Acting Head, Division of Microbiology Department of Pathology and Laboratory Medicine, King Faisal Specialist Hospital and Research Center Professor of Pathology, Director of Microbiology and Immunology, University of Oklahoma Health Science Center Oklahoma City, Oklahoma, USA; Resident, Department of Pathology and Laboratory Medicine, King Faisal Specialist Hospital and Research Centre, Riyadh, Saudi Arabia; Supervisor of Microbiology and Immunology, Oklahoma Memorial Hospital Oklahoma City, Oklahoma, USA; Associate Professor of Pathology, Director of Microbiology, Veteran s Administration Medical Center, Oklahoma City, Oklahoma, USA Date of Acceptance: 12 July 1986 ABSTRACT The incidence and eitology of bacteremia for the calendar year 1985 was investigated at King Faisal Specialist Hospital (KFSH), Riyadh, Saudi Arabia, and the results were compared with two similar-sized hospitals: Oklahoma Memorial Hospital (OMH) and Veteran s Administration Medical Center (VAMC) in Oklahoma City, Oklahoma, USA, The number of organisms isolated from suspected bacteremic patients were 582 at KFSH, 544 at VAMC and 416 at OMH. Forty-two to fifty percent of these organisms consisted of Gram-positive aerobic cocci, 44-51% were aerobic bacilli and 5-7% were anaerobic bacteria. Of the potentially pathogenic bacteria, Escherichia coli was isolated with the highest frequency at all three institutions. Pseudomonas aeruginosa was more often encountered at KFSH (13%) as compared to OMH (7%) and VAMC (6%), whereas Staphylococcus aureus and Klebsiella pneumoniae were more common isolates at OMH (14 and 8%) and VAMC (17 and 11%) as compared to KFSH (10 and 6%). Salmonella species (21 cases), Shigella species (1 case), Brucella species (17 cases) and 5 cases of Haemophilus were isolated only at KFSH. None of these organisms were recovered either at OMH or VAMC. S. M. Hussain Qadri, S. H. Khalil, S. Johnson,D. J. Flournoy, Etiology of Bacteremia in a Referral Hospital in Saudi Arabia. 1986; 7(1): MeSH KEYWORDS: Septicemia, etiology - Saudi Arabia; Bacterial infections

2 Introduction MICROBIAL INFECTIONS of the blood stream consti- tute one of the most important infectious disease problems and have been of primary concern to clinicians as well as microbiologists for over 60 years. The current surge of interest is due mainly) to two reasons: (a) a steady rise in its incidence, 1 and (b) the life-threatening nature of bacteremia in inappropriately treated cases. A number 01 investigators believe that the increase in frequency of bacteremia could be attributed partially to recognition of its significance that has led to the greater number of blood cultures collected from more hospital patients. 2-4 The increased incidence is not limited to the usual etiological pattern of usual Gram-positive bacteria but has changed to reflect an increase in the infections caused by Gramnegative microorganisms This led Dalton and Alison 12 and Sonnenwirth 8 to emphasize the significance of gathering and disseminating information concerning the epidemiology and etiology of bacteremic infections. Only by such surveillance could changing patterns in etiology be documented and the problems of bacteremia fully explored. In this paper we describe the recent incidence and etiology of bacteremia at King Faisal Specialist Hospital and Research Centre, a referral tertiary care hospital in Riyadh, Saudi Arabia. The data are compared with a primary and a tertiary care hospital in the United States of America. Collection of Blood Cultures Materials and Methods Blood was collected by medical staff or by phlebotomists over a period of one year at three hospitals -- King Faisal Specialist Hospital (KFSH), Oklahoma Memorial Hospital (OMH), and Veterans Administration Medical Center (VAMC). KFSH is a 450-bed referral, tertiary care hospital for male and female patients in Riyadh, Saudi Arabia. OMH and VAMC are also 450-bed hospitals in Oklahoma City, Oklahoma, USA, with OMH offering both acute and teritary general medical and surgical care to male as well as female patients, and VAMC a tertiary care medical and surgical facility for adult male patients. Both OMH and VAMC are teaching hospitals affiliated with the University of Oklahoma Health Sciences Center, Oklahoma City, Oklahoma, USA. Blood was collected by venipuncture, following the disinfection of venipuncture site with 2% iodine for one minute followed by similar treatment with 70% isopropanol. At KFSH, 5 ml of blood was collected directly into a vacutainer blood culture tube containing 45 ml of supplemented Peptone Broth II with sodium polyanethol sulfonate (SPS) and penicillinase (Becton-Dickinson, Ruther- ford, New Jersey). At OMH and VAMC, 5 ml of blood was collected with a sterile syringe and needle and inoculated at the patient s bedside into Fisher blood culture containing SPS (Fisher Scientific, Pittsburgh, Pennsylvania). Processing of Blood Cultures The media were incubated promptly at 35 C. The bottles were examined at least once a day for signs of microbial growth such as turbidity, hemolysis, or gas formation. Cultures showing evidence of growth were selected for Gram staining and inoculation on sheep blood agar, MacConkey agar or chocolate agar. The chocolate agar plates were incubated in a CO2 incubator, the MacConkey agar plates under aerobic conditions and the blood agar plates were incubated in an anaerobic glove box (Forma Scientific Anaerobic System, Marietta, Ohio). Incubation temperature was 35 C. The micro- organisms were identified according to the procedures described in the Manual of Clinical Microbiology. 13 Blind subcultures were also performed from all blood culture bottles at 48 hours and 7 days using a blood agar plate for anaerobic incubation and chocolate agar plate for CO2 incubation. If no growth appeared after 48 hours, the plates were discarded. All blood culture bottles were kept at 35 C for at least 7 days. Whenever brucellosis, leptospirosis or fungemia were suspected, the bottles were held at 35 C for a total of 28 days. Repeat cultures, as well as positives of such cultures, were counted as one case. The figures given in the results, therefore, refer to the cases of bacteremia rather than to the total number of cultures. Results A comparison of incidence of bacteremia with the number of hospital admissions at KFSH for the calendar year 1985 is shown in Table 1. Although the total number of admissions at this hospital have varied from 835 in June 1985, to 1, 141 admissions in October 1985, the total number of patients suspected of having bacteremia, and hence cultured, remained fairly stable. A total of (29.3%) patients were cultured with a positive rate of 11.6%.

3 Table 1 Incidence of Bacteremia at KFSH in Number of admissions 11,595 Number of blood cultures 5,791 Number of patients cultured 3,405 Percent of patients cultured 29.3 Number of patients with positive cultures 394 Percent of patients with positive cultures 11.6 Etiology of bacteremia at KFSH, OMH and VAMC is shown in Table 2. Although all three hospitals have the same number of beds, the high- est number of culture-positive patients was detected at KFSH, followed by VAMC and OMH. Fifty percent of the isolates consisted of Gram-positive facultative cocci at OMH, 48% at VAMC, and 42% at KFSH. Although Staphylococcus epidermidis was the most predominant organism in this group, review of patient charts indicated that the majority (over 60%) of these isolates were possible skin contaminants. Frequency of bacteremia caused by S. aureus varied between 10-17% at the three hospitals. Highest rate of sepsis caused by Gram-negative facultative or aerobic bacilli was observed at KFSH (51%), followed by VAMC (46%) and OMH (44%). The predominant organism at all three institutions was Escherichia coli, constituting 12%, 14% and 17% of total isolations at VAMC, KFSH and OMH, respectively. Of the total number of Gram-negative sepsis, E. coli was responsible for 39% of episodes at OMH, whereas at both KFSH and VAMC the rates were 28% and 26%, respectively. Klebsiella pneumoniae was iso- lated at higher frequency at OMH and VAMC than at KFSH. On the other hand, Pseudomonas aeruginosa sepsis occurred at KFSH at twice the rate as at VAMC or OMH. Four other organisms that were isolated from bacteremic patients at KFSH, but not at OMH or VAMC, included Brucella, Salmonella, Shigella and Haemophilus. Table 2. Microorganisms isolated from blood cultures at KFSH, OMH and VAMC. Total number of isolates Percent of isolates Microorganisms KFSH OMH VAMC KFSH OMH VAMC Staphylococcus aureus Staphylococcus epidermidis Micrococci Streptococcus pneumoniae Hemolytic strep, group A Hemolytic strep, group B Enterococci Streptococcus species Escherichia coli Klebsiella pneumoniae Klebsiella species Enterobacter species Citrobacter species Proteus, Providencia, Morganella species Serratia species Salmonella species Shigella species Brucella species Haemophilus Pseudomonas aeruginosa Pseudomonas species Bacteroides fragilis Clostridium perfringens Propionibacteria Miscellaneous facultative bacteria Miscellaneous anaerobes Total *KFSH, King Faisal Specialist Hospital and Research Center; OMH, Oklahoma Memorial Hospital, Oklahoma City, Oklahoma, USA; VAMC, Veteran s Administration Medical Center, Oklahoma City, Oklahoma, USA.

4 Incidence and etiology of bacteremia caused by anaerobic bacteria was about the same at all the three hospitals. Bacteroides fragilis and Clostridium perfringens, the two most common etiological agents of anaerobic sepsis, were encountered with the same frequency. The number of isolates of Propionibacteria at KFSH were twice as many, but the majority of these were found to be of questionable significance. Rates of positive cultures with multiple etiology varied between 4-6% at all three institutions. Discussion The number of admissions to KFSH during the first six months of 1985 averaged 882 per month, with a steady increase during the last six months to 1,050 admissions per. month. This was associated with an increase of blood cultures processed from a low of 321 per month to a high of 727. The frequency of bacteremia with positive blood cultures averaged 3.39% of total admissions in 1985 at KFSH. This is significantly higher than those reported in many USA hospitals. Martin14 and Sonnenwirth8 estimated it to be around 1% in the USA. At VAMC it has ranged between 0.86% and 1.3% of admissions over a period of 20 years from 1961 to However, Qadri, et al,4 reported a rate of positive blood cultures of 3.8% of admissions in a teaching hospital in Houston, Texas, which is similar to the one observed at KFSH. It has been suggested that the increased frequency and changing etiology of bacteremia might be a result of varying patient population, and selective pressure due to extensive use of antibiotics 2,4 9,15 in hospital patients for therapy as well as prophylaxis. Of the 394 bacteremic patients, blood cultures from 25 (6.34%)-cases at KFSH had multiple etiology. This is consistent with those found at OMH and those reported by Sonnenwirth8 ( %). However, polymicrobial infections of around 4% at VAMC9 and as high as 13.8% at teaching hospitals in the USA have been reported. 4,16 Gram-negative bacteria are known to be responsible for the majority of cases of bacteremia, ranging from 50 to 63% of microbial isolations from blood.4-6,8,9,14-19 This trend was also evident at KFSH, OMH and VAMC in E. coli was most frequently isolated at all three institutions. However, Pseudomonas was the second most prevalent organism at KFSH, followed by S. aureus and K. pneumoniae, whereas both at OMH and VAMC, S. aureus ranked second, followed by K. pneumoniae and P. aeruginosa. Species of Salmonella, Shigella, Brucella and Haemophilus were isolated from 44 bacteremic patients at KFSH. None of these organisms were observed either at VAMC or OMH. Since salmonellosis and brucellosis are endemic in parts of Saudi Arabia, and are rarely seen in the USA, it is understandable to note their absence at OMH and VAMC. Isolation of Shigella from blood culture is rare and is reflected by isolation of this bacterium from a single case at KFSH. All five isolates of Haemophilus at KFSH were isolated from blood cultures of children with positive cerebrospinal (CSF) cultures for the same organism. Lack of their isolation at OMH is due to the fact that all the CSF cultures and blood cultures on children are processed at the Oklahoma Children s Memorial Hospital, a sister institution adjoining OMH. VAMC, on the other hand, is a chronic and tertiary care facility for male adults. Frequency of isolation of other Gram-negative bacilli was comparable at the three institutions. S. epidermidis, alpha hemolytic streptococci of viridans group, and Propionibacteria were isolated with high frequency at all the three institutions. Although these bacteria can cause a wide spectrum of diseases, including prosthetic valve endocarditis, subacute bacterial endocarditis, nosocomial and other infections involving shunts, prosthetic joints, abdominal abscesses and fulminant bacteremia,20-24 the majority of these microorganisms were found to be common contaminants. This conclusion was based on chart review of many patients and consultation with the attending physicians. These bacteria of questionable significance were isolated more frequently at OMH than at KFSH or VAMC, probably because OMH is a primary teaching hospital for medical students, residents and other health care personnel. Acknowledgements The authors wish to thank Dr. Peter Herdson and Dr. Ron Gillum for their constructive comments, and Ms. Linda Wood and Ms.Kathy Miller for secretarial assistance. References 1. Martin CM. A national bacteremia registry. J. Infect Dis 1969;120: DuPont HL, Spink WW. Infections due to gram-negative organisms: an analysis of 860 patients with bacteremia at the University of Minnesota Medical Center, Medicine (Baltimore) 1969;48: Finland M. Changing ecology of bacterial infections as related to antibacterial therapy. J Infect Dis 1970;122: Qadri SMH, Evans LJ, Wende RD, Williams RP. Bacteremia in a metropolitan teaching hospital. Tex Med 1977;73(3): Brumfitt W, Leigh DA. Incidence and bacteriology of bacteremia - a study at 2 hospitals. P Roy S Med 1969;62(12): Finland M, Jones WF Jr, Barnes MW. Occurrence of serious bacterial infections since introduction of antibacterial agents. J

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