Bacteria Recovered from Patients Admitted to a Deployed U.S. Military Hospital in Baghdad, Iraq

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1 MILITARY MEDICINE, 171, 9:821, 2006 Bacteria Recovered from Patients Admitted to a Deployed U.S. Military Hospital in Baghdad, Iraq Guarantor: MAJ Clinton K. Murray, MC USA Contributors: Capt Heather C. Yun, USAF MC*; MAJ Clinton K. Murray, MC USA ; MAJ Stuart A. Roop, MC USA ; LTC Duane R. Hospenthal, MC USA ; MAJ Emmett Gourdine, MS USA ; COL David P. Dooley, MC USA The predominant bacteria and antimicrobial susceptibilities were surveyed from a deployed, military, tertiary care facility in Baghdad, Iraq, serving U.S. troops, coalition forces, and Iraqis, from August 2003 through July We included cultures of blood, wounds, sputum, and urine, for a total of 908 cultures; 176 of these were obtained from U.S. troops. The bacteria most commonly isolated from U.S. troops were coagulase-negative staphylococci, accounting for 34% of isolates, Staphylococcus aureus (26%), and streptococcal species (11%). The 732 cultures obtained from the predominantly Iraqi population were Klebsiella pneumoniae (13%), Acinetobacter baumannii (11%), and Pseudomonas aeruginosa (10%); coagulase-negative staphylococci represented 21% of these isolates. These differences in prevalence were all statistically significant, when compared in 2 analyses (p 0.05). Antimicrobial susceptibility testing demonstrated broad resistance among the Gram-negative and Gram-positive bacteria. Introduction urveillance and analysis of bacterial isolates recovered from S clinical specimens in any health care organization can be used to guide management strategies to optimize medical care, such as the direction of appropriate empiric antibiotic therapy and infection control practices. Established health care facilities (HCFs) institute such surveillance, tailoring appropriate infection control procedures and formulary interventions on the basis of the data obtained. Few data have been forthcoming, however, on the prevalence or profiles of resistance in bacteria isolated from patients cared for in mobile or deployable HCFs. Such HCFs have been used by the military for years but now are filling more prominent roles in humanitarian assistance efforts as well. It is probable that the lack of data in the literature on antibiotic susceptibility patterns from deployable HCFs reflects a general impression that the transience *Infectious Diseases Department, Wilford Hall U.S. Air Force Medical Center, San Antonio, TX Department of Medicine, Brooke Army Medical Center, Fort Sam Houston, TX Department of Medicine, William Beaumont Army Medical Center, Fort Bliss, TX Department of Pathology, William Beaumont Army Medical Center, Fort Bliss, TX Presented at the Armed Forces Infectious Disease Society Annual Meeting, April 5 8, 2005, Honolulu, HI. The views expressed herein are those of the authors and do not reflect the official policy or position of the Department of the Army, the Department of the Air Force, the Department of Defense, or the U.S. government. The authors are employees of the U.S. government. This work was prepared as part of their official duties; therefore, there is no copyright to be transferred. This manuscript was received for review in August The revised manuscript was accepted for publication in March of both the physical facilities and their patients makes the establishment of resistance in bacterial pathogens unlikely. However, we have recent experience with Acinetobacter baumannii infections occurring among casualties returning from Operation Iraqi Freedom (the current conflict in Iraq) and Operation Enduring Freedom (the ongoing deployment to Afghanistan). The source of these intrinsically resistant bacteria is still unclear. 1 As the U.S. military continues operations in this region, it has become necessary to evaluate microbiological patterns within deployable HCFs that treat U.S., coalition, and Iraqi patients, to optimize infection-control policies and empiric antimicrobial choices. We performed a retrospective, descriptive, comparative study to analyze the results of bacterial cultures obtained from patients receiving care at a referral U.S. military hospital in Baghdad, Iraq, in a 1-year period, to identify bacterial pathogens and their antimicrobial susceptibility profiles among U.S. and non-u.s. (predominantly Iraqi) patient populations. Methods Population and Facility A tertiary care military HCF was established in Baghdad, Iraq, for the treatment of casualties of the current conflict in Iraq. We studied all bacterial cultures in this HCF from August 2003 through July The patient population included emergency combat casualties and patients referred for more routine care. Patients included U.S. personnel (chiefly military), coalition forces, Iraqi detainees, and Iraqi nationals requiring emergency care. Injured U.S. personnel were typically evacuated from the hospital within 72 hours after admission (mean length of stay, 2.5 days), whereas non-u.s. patients remained in the facility until their medical care was complete (mean length of stay, 7.5 days). Medical management, including use of antibiotics and invasive devices, did not differ materially between U.S. and non-u.s. patients. For the period of this study, the deployable hospital (with all personnel, equipment, and supplies) had moved into an older Iraqi hospital building, which was a single, multifloor, cement structure with 80 beds. The hospital s infrastructure included running water, with a limited number of functional sinks located throughout the treatment areas of the facility. U.S. and non-u.s. patients were not segregated within wards (57 beds), operating rooms (5 tables), intensive care units (ICUs) (21 beds), or outpatient clinics. Routine infection control measures were in place; however, active conflict and a high volume of patients often limited the implementation of more aggressive infectioncontrol policies, such as cohorting, isolation, or routine screening for colonization. 821

2 822 Bacteria in a Deployed U.S. Military Hospital TABLE I COMMON BACTERIA ISOLATED FROM CULTURES OBTAINED FROM U.S. AND NON-U.S. PATIENTS No. (%) Odds Ratio (95% Organism Total U.S. Patients Non-U.S. Patients Confidence Interval) Coagulase-negative staphylococci 203 (23) 59 (34) 144 (20) 2.06 ( ) a Blood 51 5 (50) 46 (38) NS Wound (33) 61 (22) 1.80 ( ) a Sputum 34 4 (17) 30 (11) NS Urine (40) 7 (14) 4.19 ( ) a Staphylococcus aureus 82 (9) 45 (26) 37 (5) 6.44 ( ) a Blood 5 2 (20) 3 (2) 9.92 ( ) a Wound (37) 16 (6) 9.80 ( ) a Sputum 19 3 (13) 16 (6) NS Urine 4 2 (5) 2 (4) NS Streptococcus spp. 63 (6) 20 (11) 43 (4) 2.05 ( ) a Blood (2) NS Wound 17 7 (7) 10 (4) NS Sputum b (50) 30 c (13) 8.27 ( ) a Urine 1 1 (3) 0 NS Klebsiella pneumoniae 102 (11) 5 (3) 97 (13) ( ) a Blood 17 1 (10) 16 (13) NS Wound 33 3 (3) 30 (11) ( ) a Sputum (15) Indeterminate (p 0.033) a Urine 9 1 (3) 8 (16) NS Acinetobacter baumannii 79 (9) 2 (1) 77 (11) ( ) a Blood (11) NS Wound 24 2 (2) 22 (8) ( ) a Sputum (12) NS Urine (14) Indeterminate (p 0.017) a Pseudomonas aeruginosa 75 (8) 5 (3) 70 (10) ( ) a Blood (5) NS Wound 35 5 (5) 30 (11) NS Sputum (10) NS Urine (10) NS Escherichia coli 74 (8) 15 (9) 59 (8) NS Blood (5) NS Wound 39 2 (2) 37 (13) ( ) a Sputum (3) NS Urine (33) 9 (18) NS Percentages do not total 100% in all categories because of other bacteria isolated from each site. NS, not significant. a Statistically significant difference (p 0.05) between U.S. and non-u.s. patients by 2 analysis or by two-tailed Fisher s exact test if contingency table values were 5. Odds ratios were indeterminate when contingency table values were 0; Fisher s exact test was used in those instances to indicate statistical significance. b One isolate was Streptococcus pneumoniae. c Four isolates were S. pneumoniae. Microbiological Data Microbiology reports included the anatomical site of specimen collection, identification of recovered bacteria, and antibiotic susceptibility testing results. Although the vast majority of isolates were collected from inpatients (including ICU patients), available records did not specify the physical location of the TABLE II ANTIMICROBIAL SUSCEPTIBILITY OF GRAM-NEGATIVE ORGANISMS WITH 20 ISOLATES Organism Total No. Ampicillin Ampicillin-sulbactam Piperacillin-tazobactam Cefazolin Cefotetan Ceftriaxone Escherichia coli Klebsiella pneumoniae Enterobacter cloacae Acinetobacter baumannii Pseudomonas aeruginosa Ochrobactrum spp

3 Bacteria in a Deployed U.S. Military Hospital 823 TABLE II Continued Organism Cetepine Aztreonam Ciprofloxacin Levofloxacin Tobramycin Amikacin TMP-SMX Meropenem Imipenem Escherichia coli Klebsiella pneumoniae Enterobacter cloacae Acinetobacter baumannii Pseudomonas aeruginosa Ochrobactrum spp TMP-SMX, trimethoprim-sulfamethoxazole. patients (inpatient, outpatient, or ICU), which would allow this factor to be used for analysis. It was not possible, with the records available, to exclude multiple isolates of the same organism from a given patient. Cultures of wounds, urine, and sputum were typically plated onto Columbia blood agar plates, chocolate agar plates, and MacConkey agar plates and into thioglycolate broth (wound swabs only) for the detection of aerobic bacteria. Blood agar plates and MacConkey agar plates were incubated at 35 C in ambient air and chocolate agar plates in the presence of 5 to 10% CO 2. The thioglycolate broth was Gram stained and subcultured if it became turbid. Blood culture was performed with an automated Septi-Check system (BD Biosciences, Franklin Lakes, New Jersey). Bacterial identification and antimicrobial susceptibility profiles were determined with a MicroScan Autoscan 4 system (Dade Behring, West Sacramento, California). When decreased susceptibility of Staphylococcus aureus to oxacillin or vancomycin was detected with these methods, we were unfortunately unable to perform formal testing according to National Committee for Clinical Laboratory Standards (NCCLS) guidelines for confirmation; however, correlations between automated systems and NCCLS standards are strong. 2 4 Statistical Analyses These retrospective data are presented descriptively. After segregation into isolates from U.S. and non-u.s. patients ( 90% Iraqi), the data were compared using the 2 test or Fisher s exact test ( A p value of 0.05 was used to indicate statistical significance between groups; all reported p values are two-tailed. Results Bacteriological Findings A total of 1,188 positive cultures were obtained from wounds, blood, sputum, urine, and other sites (e.g., nonsterile fluids, throat cultures, and stool cultures). The 281 cultures obtained from other sites were excluded from comparative analyses between patient groups, given their heterogeneity, but were included in antimicrobial susceptibility testing data. The 907 remaining cultures of blood (132), sputum (302), urine (91), and wounds (382) were included in our comparison of isolates from U.S. and non-u.s. patients. A total of 176 isolates was recovered from U.S. patients (10 blood, 102 wound, 24 sputum, and 40 urine samples), and 731 were from non-u.s. (predominantly Iraqi) patients (122 blood, 280 wound, 278 sputum, and 51 urine samples). Coagulase-negative staphylococci (CNS) were the predominant bacterial isolates in cultures from both U.S. and non-u.s. patients (Table I). S. aureus and Streptococcus spp. were more common for U.S. patients, whereas Klebsiella pneumoniae, A. baumannii, and Pseudomonas aeruginosa predominated for non-u.s. patients. Antimicrobial Susceptibilities Antimicrobial susceptibility data for the predominant Gram-negative and Gram-positive bacteria are presented in Tables II and III, respectively. S. aureus isolates were noted to be commonly resistant to oxacillin (69%), and 8% exhibited decreased susceptibility to vancomycin. However, mean inhibitory concentrations were not reported, and, as mentioned, confirmatory testing according to NCCLS criteria was not available, limiting meaningful interpretation of these results. 2 Resistance was widespread among all of the prevalent Gram-negative bacteria. Discussion We report the first characterization and determination of the antibiotic susceptibilities of bacteria recovered from patients treated at a deployed U.S. military medical facility in Iraq. Overall, CNS species were the most common bacterial isolates, along with a high percentage of resistant Gram-negative bacteria, including K. pneumoniae, A. baumannii, and P. aeruginosa. Bacterial isolates from U.S. patients were predominantly Grampositive bacteria, including CNS, S. aureus, and Streptococcus spp. The most common bacteria isolated from non-u.s. patients were also CNS, but the next most common organisms recovered from these patients were K. pneumoniae, A. baumannii, and P. aeruginosa. These findings were similar among blood, wound, and sputum cultures. Sixty-nine percent of S. aureus isolates were resistant to oxacillin, with antimicrobial susceptibility patterns typical of those seen for community-acquired oxacillinresistant S. aureus. Gram-negative bacteria showed broad resistance across many classes of antimicrobial agents, with the most active agents being carbapenems and amikacin. Several published studies describing pathogens isolated from patients hospitalized in countries surrounding Iraq revealed a similar prevalence of resistant Gram-negative bacteria. Acinetobacter spp., followed by K. pneumoniae, P. aeruginosa, and Esch-

4 824 Bacteria in a Deployed U.S. Military Hospital TABLE III ANTIMICROBIAL SUSCEPTIBILITY OF STAPHYLOCOCCI TESTED Organism Total No. Oxacillin Cefazolin Levofloxacin Clindamycin Erythromycin Rifampin TMP-SMX Tetracycline Linezolid Vancomycin CNS a b b Staphylococcus aureus c b b TMP-SMX, trimethoprim-sulfamethoxazole. a Not all coagulase-negative staphylococci isolates were tested against each antimicrobial agent. A total of 179, 174, 248, and 199 isolates were tested against oxacillin, cefazolin, trimethoprim-sulfamethoxazole, and linezolid, respectively. b Resistance was not confirmed by formal testing according to NCCLS criteria. c Sixty-five S. aureus isolates were tested against oxacillin and cefazolin. Eighty-two isolates were tested against linezolid. erichia coli, were the most common organisms isolated from trauma patients with hospital-acquired infections in Turkey, ventilator-associated pneumonias in a Lebanese tertiary care center, and ICUs in Kuwait. 5 7 It is unclear from these reports whether the Gram-negative bacteria described, particularly Acinetobacter spp., were acquired by patients through the usual nosocomial routes or whether community-based inoculation occurred at the onset of injury or illness. The reasons underlying the high prevalence of these resistant bacteria have yet to be defined but may be related to regional infection control practices, inpatient or community use of antibiotics, or factors relating to the climate and environment. Recent data implicated A. baumannii as an increasing cause of bacteremia in U.S. troops, injured in Operation Iraqi Freedom and Operation Enduring Freedom, who are undergoing medical care upon return to U.S. military hospitals. 1 That report described only bloodstream infections, which presumably reflect only the most serious of A. baumannii infections; however, the incidence of this organism as a cause of wound infections in these soldiers appears to be 10-fold higher than the incidence of blood culture positivity (Brooke Army Medical Center, Fort Sam Houston, Texas, unpublished data). Potential sources of the Acinetobacter recovered from returning troops include soil or water exposure (before or at the time of injury) and acquisition within referral military medical facilities in Iraq, Germany, or the United States. However, there exist no published data to record the microbiological content of indigenous soil in Iraq or, before this report, the bacterial profile from deployed or native hospitals in that country. This study has several limitations. It was not possible to define which of these cultures represent colonization versus true infection. Regardless, our data clearly show that A. baumannii, K. pneumoniae, and P. aeruginosa were isolated with significantly higher prevalence from cultures from non-u.s. versus U.S. patients. We recognize that the non-u.s. group was heterogeneous, including some non-iraqi sources such as coalition forces personnel. Detailed data regarding demographic features and duration of hospital stays were not available for this study, and it is likely that differences in duration of hospitalization or underlying diagnoses account for some of the differences in bacterial prevalence demonstrated between these two groups. However, if soldiers were arriving at the hospital already colonized with A. baumannii from soil inoculation, then we would expect a higher prevalence of this organism in their wound cultures, regardless of their duration of hospitalization. In this survey, A. baumannii was rarely cultured from U.S. troops during the course of hospitalization, accounting for only 1% of their positive cultures, consistent with previous studies demonstrating a similar degree of colonization with A. baumannii in healthy hosts. 8 These data diminish the likelihood that soil contamination at the time of injury accounts for the A. baumannii infections being reported for returning soldiers. Additional data exist to describe the microbiological features of wounds suffered in Iraq at or near the time of injuries suffered by Operation Iraqi Freedom casualties. Murray et al. demonstrated that such wounds typically grew Gram-positive bacteria (93%), if any bacteria were recovered at all; no resistance was seen in the three Gram-negative isolates they identified. 9 Taken together, these data indicate that it is highly unlikely that initial wound contamination with soil is the source of colonization and infection of U.S. patients with resistant Gram-negative bacteria. At least for the non-u.s. patients, A. baumannii is not the only drug-resistant Gram-negative species of consequence; K. pneumoniae and P. aeruginosa were also demonstrated, in similar proportions. It is possible that nosocomial transmission of these Gram-negative bacteria occurred within the field hospital described herein. The deployed hospital was rapidly moved into a previously established, older, Iraqi hospital, which might have already possessed established, environmental, nosocomial pathogens, and was faced with the difficult task of adhering to strict infection-control practices in this HCF, which was not designed with such practices in mind. Gradual improvement of the physical facility (e.g., adequate clean water and number of sinks) since occupation of the HCF has permitted improved infection control practices, and we await future surveillance data that might suggest that possible nosocomial transmissions have diminished. The temporary nature of this facility and the gradual maturation of its physical plant, infection control practices, and procedures are also typical of the HCFs deployed by other military or civilian entities because of transient medical necessity. Our data may serve as a warning to those responsible for such facilities, which are often poorly equipped to implement adequate infection control practices; resistant bacteria may emerge rapidly in such facilities and, early on, significant nosocomial transmission may go unrecognized. The high rate of apparent oxacillin-resistant S. aureus and the recognition of vancomycin-intermediate or -resistant S. aureus among our isolates were unfortunately not confirmed according to NCCLS criteria. Ongoing surveillance should reveal addi-

5 Bacteria in a Deployed U.S. Military Hospital tional samples, which will be formally tested. However, these data do suggest that continuing vigilance with regard to infection control practices is necessary for soldiers returning from field deployments and that this vigilance should not be limited to A. baumannii alone. In conclusion, we observed striking rates of resistant bacteria in a referral U.S. military hospital in Iraq, with significant differences in the most common isolates cultured from U.S. patients versus the non-u.s. (predominantly Iraqi) patient population. Most notably, Gram-negative bacteria with broad antimicrobial resistance patterns were commonly detected among the non-u.s. patients. Amikacin, imipenem, and meropenem were the only antibiotic agents active against more than one-half of the three most common Gram-negative pathogens isolated. In this study, U.S. patients were not commonly colonized with Gram-negative pathogens at the time of their hospitalization. However, transmission of these pathogens to U.S. patients might have occurred. Implementation of more aggressive infection control techniques and protocols, such as cohorting of patient groups, using screening cultures to detect patients colonized with drug-resistant pathogens, or both, should be considered as potential interventions to prevent nosocomial transmission of resistant pathogens in deployable HCFs. References Scott PT, Petersen K, Fishbain J, et al: Acinetobacter baumannii infections among patients at military medical facilities treating injured U.S. service members, MMWR 2004; 53: National Committee for Clinical Laboratory Standards: Performance Standards for Antimicrobial Susceptibility Testing: Fourteenth Informational Supplement. Publication M100-S14. Wayne, PA, National Committee for Clinical Laboratory Standards, Swenson JM, Williams PP, Killgore G, et al: Performance of eight methods, including two new rapid methods, for detection of oxacillin resistance in a challenge set of Staphylcococcus aureus organisms. J Clin Microbiol 2001; 39: Tenover FC, Lancaster MV, Hill BC, et al: Characterization of staphylococci with reduced susceptibilities to vancomycin and other glycopeptides. J Clin Microbiol 1998; 36: Oncul O, Keskin O, Acar HV: Hospital-acquired infections following the 1999 Marmara earthquake. J Hosp Infect 2002; 51: Kanafani ZA, Kara L, Hayek S, Kanj S: Ventilator-associated pneumonia at a tertiarycare center in a developing country: incidence, microbiology, and susceptibility patterns of isolated microorganisms. Infect Control Hosp Epidemiol 2003; 24: Rotimi VO, al-sweih NA, Feteih J: The prevalence and antibiotic susceptibility pattern of Gram-negative bacterial isolates in two ICUs in Saudi Arabia and Kuwait. Diagn Microbiol Infect Dis 1998; 30: Seifert H, Dijkshoorn L, Gerner-Smidt P, et al: Distribution of Acinetobacter species on human skin: comparison of phenotypic and genotypic identification methods. J Clin Microbiol 1997; 35: Murray CK, Roop SA, Hospenthal DR, et al: Bacteriology of war wounds at the time of injury. Milit Med (in press).