Epidemiology Surveillance System
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Division of Epidemiology, Environmental
and Occupational Health
Epidemiology Surveillance System |
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1998 Report
Preface
Multiple antibiotic-resistant bacteria have been recognized as a serious threat to the nation's public health since the early 1990s. The tremendous therapeutic advantage afforded by antibiotics is now jeopardized by the increasing resistance of microbes. In an effort to develop a resource to measure antibiotic resistance in New Jersey and to provide a basis for the development of cost-effective measures to reduce further development of antibiotic resistance, the New Jersey Department of Health and Senior Services (NJDHSS) launched an initiative in 1991 to collect information about these organisms. Under this initiative, a statewide hospital laboratory-based Epidemiology Surveillance System was established which monitors: 1) methicillin-resistant Staphylococcus aureus (MRSA); 2) Gram-positive cocci resistant to vancomycin; 3) penicillin-resistant streptococci / enterococci; 4) Gram-negative rods resistant to imipenem; and 5) Gram-negative rods resistant to amikacin, gentamicin, and tobramycin.
Methodology A New Jersey Epidemiology Surveillance Record form is submitted monthly by each acute-care hospital in New Jersey (Attachment 1). These forms are checked for completeness upon receipt by staff in the NJDHSS Infectious and Zoonotic Diseases Program. Follow-up telephone calls are made as needed to ensure that all forms are submitted each month and that all isolates are sent to the NJDHSS Public Health and Environmental Laboratories.
There are 88 hospitals that participated in 1998. The overall number of organisms, annual trend, geographic distribution and specific drug-resistant profile in each class of organism were computed. All rates by facility are normalized by each facility's 1998 number of occupied beds, while rates by county are normalized by each county's 1998 resident population. For confidentiality concerns, counties containing only one hospital were aggregated with a neighboring county in computing rates so that no individual hospital's rate can be identified.
Summary The data collected by the New Jersey Epidemiology Surveillance System between 1992 and 1998 indicated that by 1998 the incidence of vancomycin-resistant enterococci (VRE) had increased five-fold since the inception of the system in 1992. Similar trending was reported in the National Nosocomial Infections Surveillance System1. The administration of vancomycin and cephalosporins as well as antianaerobic drugs appears to contribute to the risk of colonization by or infection with VRE2. Enterococcus faecium isolates accounted for 64.5 percent of the reported 510 VRE isolates in New Jersey in 1998. High resistance to most available antibiotics within this group of organism has further compounded the problem. A scheme of drug therapy for clinically important VRE infections was summarized by Dr. Murray in a recent publication2.
Sterile-site infections with penicillin-resistant Streptococcus pneumoniae (PRSP) in New Jersey acute-care hospitals also increased five-fold from 1992 to 1998, parallel to the national trend3. The infection pattern appears to be seasonal with a peak in the winter and a trough in the summer. A trend among New Jersey PRSP isolates toward resistance to a greater number of drugs is prominent. As suggested by several studies4,5, inappropriate antibacterial usage in treating respiratory viral infections and unnecessary prescribing of broad spectrum agents are thought to be major factors contributing to this phenomenon. The CDC's Drug-Resistant S. pneumoniae Therapeutic Working Group has recently issued new guidelines regarding penicillin minimum inhibitory concentration (MIC) for the definition of PRSP as well as treatment recommendations for outpatients and inpatients with community-acquired pneumonia6.
Although the rates of MRSA declined in New Jersey between 1994 and 1996, this trend has reversed and a twenty percent increase during the 1996-1998 period was observed. Methicillin-resistant Staphylococcus aureus isolates per 100,000 population per year reached 237.3 in 1998, up from 197.83 in 1996. Whether such a rebound reflects an increase in community-acquired MRSA isolates, as found in San Diego7, remains to be investigated.
The number of amikacin-resistant Gram-negative bacilli has doubled from 1992 to 1998. The most frequently reported organism in 1998 is Stenotrophomonas maltophilia (30.17 percent). An increase in Pseudomonas aeruginosa and Acinetobacter baumannii isolates was observed in 1998. The number of imipenem-resistant Gram-negative bacilli has increased only slightly during these years. However, a near three-fold increase from the 1997 figure in A. baumannii / A. calcoaceticus isolates was found in the 1998 collection.
MRSA Isolates in New Jersey Hospitals S. aureus remains the leading organism causing bacteremia in the hospital setting in the United States and Canada8. The rate of methicillin resistance in this organism has increased from 20 to 25 percent in 1990 to 25 to 45 percent in 1997 nationwide3. The bar chart in Exhibit 1 presents the trend of the annual number of MRSA isolates reported during the 1991 to 1998 period in New Jersey. Of the 19,256 MRSA isolates reported in 1998, 32 percent were from wound cultures, 27 percent from sputum cultures, 14 percent from blood cultures, 12 percent from urine cultures and 15 percent from cultures of other body sites. The total number of inpatient isolates was nearly constant between 1994 and 1996. However, an increase was observed after 1996. Exhibit 2 shows the total MRSA isolates per 100,000 population per year from 1991 to 1998. The MRSA rate increased sharply in the years of 1997 (214.67 per 100,000 population) and 1998 (237.29 per 100,000 population). Exhibit 3 displays the number of reported MRSA isolates per 100 occupied beds per month for each facility in 1998. Facilities were ranked by their rates in descending order. An obviously increasing trend is observed in the State total, when the average rate in 1998 (9.50) is compared with rates in 1997 (8.11), 1996 (7.06) and 1995 (6.75).
Antibiotic-Resistant Bacteria - Bloodstream Infections in New Jersey Hospitals A total of 937 antibiotic-resistant bacteria isolated from blood cultures were reported in 1998. The frequency of antibiotic-resistant blood isolates in each facility, ranked in descending order by number of isolates per 100 occupied beds, is illustrated in Exhibit 4. The average rate in the State reached 6.24 for every 100 occupied beds, up from 4.94 in 1997; 3.91 in 1996; and 3.47 in 1995. Distribution of these isolates by county is highlighted in Exhibit 5 in descending order. Each county's rate (per 100,000) is normalized by its resident population. An increasing trend was observed in the State average, by comparing the 1998 rate (11.55) with rates in 1997 (10.8), 1996 (9.1) and 1995 (8.6).
Vancomycin-Resistant Gram-Positive Cocci in New Jersey Hospitals Enterococci have been documented to be the fourth most prevalent isolates from blood cultures in United States and Canada8. Among them, 69.9 percent represent true bacteremia, 76.9 percent are nosocomial acquired infections, and 13.1 percent are associated with mortality9. The occurrence of VRE in the nation has increased from less than 1 percent among all enterococci isolates in 1990 to 6 percent in 1992, 8 percent in 1994, 16 to 17 percent in 1996, and 18 percent in 19973. The occurrence of new patterns of resistance in clinical isolates, such as vancomycin intermediate-resistant S. aureus (VISA)10 and Staphylococcus epidermidis11, vancomycin heterogeneous-resistant S. aureus12 and coagulase-negative staphylococci13, and vancomycin-tolerant S. pneumoniae14 has been documented recently. Because of the increasing concern of VISA strain emergence15 and the apparent heterogeneity of VISA strains16, all S. aureus isolates with vancomycin MICs of >= 4 µg/ml should be re-confirmed with CDC recommended methods17. Methods that would not identify VISA isolates include disk diffusion with no additional method, MicroscanR Walkaway Rapid* panels (which provides less than 24 hours incubation), and Vitek systems with a vancomycin MIC of greater than or equal to 8 µg/ml as the indicator for additional testing17. Primary testing of S. aureus against vancomycin requires 24 hours of incubation time17. An MIC susceptibility testing method should be used to confirm vancomycin test results17.
Exhibit 6 summarizes the variety and number of Gram-positive cocci, collected in New Jersey from 1992 to 1998 that were vancomycin resistant. Vancomycin-resistant enterococci accounts for 97.5 percent of the 523 isolates collected in 1998. The majority of the VRE isolates were E. faecium (64.5 percent). E. faecalis accounted for another 15.7 percent. In addition, five vancomycin-resistant isolates of Streptococcus and Staphylococcus were reported in 1998. Such isolates should be sent to the NJDHSS laboratory for confirmation. The trend of VRE blood isolates from 1992 to 1998 is presented in Exhibit 7. VRE increased five-fold during this period, from an average of 9.22 isolates per month in January 1992 to 45.97 isolates per month in December 1998. Exhibit 8 depicts the rate and the distribution of VRE by county in 1998 in descending order. The average State rate per 100,000 population reached 6.3 in 1998, up from 5.9 in 1997; 5 in 1996; and 4.2 in 1995.
Exhibit 9 summarizes the drug resistance profile in major VRE, collected from 1992 to 1998. E. faecium is the most frequent organism. In 1998, it carried a high level resistance to penicillin (95.7 percent), oxacillin (100 percent), ampicillin (96.9 percent), imipenem (75.4 percent), erythromycin (92.2 percent), ciprofloxacin (98.2 percent), ofloxacin (100 percent), high concentration gentamicin (58.9 percent), and high concentration streptomycin (77.4 percent). An increasing trend of resistance in tetracycline (54.4 percent) and trimethoprim/sulfamethoxazole (83.3 percent) was also observed in the 1998 collection of E. faecium. In comparison to E. faecium, E. faecalis isolates displayed a very different drug resistance pattern in penicillin (25 percent), ampicillin (15.6 percent), imipenem (0 percent), chloramphenicol (33.3 percent), and high concentration gentamicin (100 percent). While Willey et al18 had reported a universal relationship between ampicillin sensitivity in E. faecalis and the usual ampicillin resistance in E. faecium, the New Jersey data indicated an unusual high ampicillin-resistant rate in E. faecalis isolates. The discrepancy is yet to be explained. However, an accurate identification of VRE at the species level is clearly needed.
Penicillin-Resistant Streptococci / Enterococci in New Jersey Hospitals S. pneumoniae have been documented to be the sixth most prevalent organism isolated from blood cultures in the United States, while viridans streptococci ranks eleventh8. The blood isolates of S. pneumoniae represent 100 percent true bacteremia, are mostly community-acquired (91.2 percent), and are associated with a 17.6 percent mortality rate9. The national rate of pneumococci resistant to penicillin has increased from 4 percent in 1990 to 7 percent in 1992, 16 percent in 1994, 24 to 27 percent in 1996, and 31 to 42 percent in 19973. Exhibit 10 lists the variety and the number of penicillin-resistant streptococci and enterococci reported from 1992 to 1998 from New Jersey hospitals. The most frequently reported organism is E. faecium (57.5 percent in 1998), followed by S. pneumoniae (19.2 percent in 1998). Exhibit 11 shows an estimated 232 percent increase in the incidence of penicillin-resistant streptococci and enterococci, from 15.14 isolates per month in January 1992 to 35.17 isolates per month in December 1998. The rate and the distribution of these isolates by county are demonstrated in Exhibit 12. A decrease in the State total was observed between 1997 (4.9 per 100,000 population) and 1998 (4.6 per 100,000 population).
Exhibit 13 shows the increasing trend of PRSP occurrence between December 1991 and February 1999. A substantial increase of 506 percent in PRSP during this period is estimated. The number of PRSP cases fluctuated by season with a peak in the winter (December, January, and February) and a trough in the summer (June, July, and August). Exhibit 14 displays the rate and the distribution of PRSP by county. Exhibit 15 summarizes the drug-resistant profile of PRSP and penicillin-resistant viridans streptococci. Vancomycin is effective against most PRSP. However, resistance to ampicillin (100 percent), oxacillin (66.7 percent), gentamicin (66.7 percent), trimethoprim/sulfamethoxazole (64.5 percent), erythromycin (40.8 percent), tetracycline (28.6 percent), clindamycin (25 percent) and cefotaxime (20 percent) remains high in 1998 PRSP collection. For comparison, the reported national rates of resistance among S. pneumoniae not limited to penicillin-resistant isolates are: ampicillin 15.6 percent, penicillin 41 percent, amoxicillin-clavulanate 16.6 percent, cefuroxime 20.5 percent, cefotaxime/ceftriaxone 13.2 percent, cefepime 16.6 percent, erythromycin 11.9 percent, clindamycin 4 percent, chloramphenical 3.5 percent, rifampin 0.5 percent, tetracycline 10.9 percent, vancomycin 0 percent, and trimethoprim/sulfamethoxazole 25.2 percent8.
Amikacin-Resistant Gram-Negative Bacilli in New Jersey Hospitals Gram-negative bacilli are also important pathogens in bloodstream infection. Among them, Klebsiella spp. ranked fifth in frequency, P. aeruginosa ranked seventh, Proteus mirabilis ranked tenth, Acinetobacter spp. ranked twelfth, Serratia spp. ranked thirteenth, Citrobacter spp. ranked fourteenth, S. maltophilia ranked fifteenth in a national study8. Exhibit 16 displays the variety and the number of amikacin-resistant Gram-negative bacilli reported from 1992 to 1998 in New Jersey hospitals. The most frequently reported Gram-negative organism in 1998 is S. maltophilia which accounts for 30.2 percent of the total collection. P. aeruginosa increased in frequency to 11.2 percent in 1998, up from 6.6 percent in 1997. Isolates in A. baumannii increased significantly in 1997 (9.4 percent) and 1998 (10.3 percent) from the 1996 figure (2.5 percent). The number of isolates within the Enterobacteriaceae family accounted for 28.5 percent of the total collection in 1998. Klebsiella pneumoniae alone accounted for 24.1 percent. Exhibits 17 and 18 illustrate the seven-year trend and the distribution of these isolates by county, respectively. A 212 percent increase, from 4.6 isolates per month in January 1992 to 9.75 isolates per month in December 1998 is demonstrated in Exhibit 17. Middlesex county has an unusual high rate (5.17 per 100,000 population) which accounted for 31.9 percent of the isolates reported in the State.
Imipenem-Resistant Gram-Negative Bacilli in New Jersey Hospitals Exhibit 19 depicts the number and variety of imipenem-resistant Gram-negative bacilli reported from 1992 to 1998. The total number of organisms in this collection has increased slightly during these years as shown in Exhibit 20. However, a decreasing trend is found in the number of Enterobacteriaceae. The decline in the number of P. mirabilis is especially evident. P. aeruginosa (37.3 percent) and S. maltophilia (24.6 percent) are the most frequently reported isolates. A. baumannii and A. calcoaceticus account for 14.9 percent of the 1998 collection, a near three-fold increase from 5.04 percent in 1997. Exhibit 21 depicts the rate and the distribution of these organisms by county. Essex county has the highest rate (5.6 per 100,000 population) which is 340 percent of the State average (1.65 per 100,000 population).
Drug Resistance Profile in Gram-Negative Bacilli in New Jersey Hospitals Exhibit 22 displays the drug resistance profile in major Enterobacteriaceae blood isolates. A high percentage of resistance to penicillins and aminoglycosides, as well as the expanded-spectrum beta-lactam antibiotics in K. pneumoniae, was observed. Their resistance to amikacin (68.3 percent in 1998) and trimethoprim/sulfamethoxazole (88.4 percent in 1998) has also tended to increase over time. In Escherichia coli, an increasing resistance to cefazolin (61.5 percent), ceftazidime (66.7 percent), ampicillin (76.9 percent), piperacillin (83.3 percent), ciprofloxacin (83.3 percent), and trimethoprim/sulfamethoxazole (69.2 percent) in 1998 isolates is evident compared with previous years.
Exhibit 23 demonstrates the drug resistance profile of major Gram-negative bacilli that do not belong to Enterobacteriaceae. Imipenem resistance is high in S. maltophilia (100 percent), P. aeruginosa (90.9 percent), B. cepacia (100 percent), and Flavobacteriumn meningosepticum (100 percent) in 1998 isolates. High frequency of aminoglycosides resistance is also observed in S. maltophilia (ranging from 92.5 percent for gentamicin to 81.4 percent for amikacin), B. cepacia (ranging from 100 percent for gentamicin and tobramycin to 75 percent for amikacin), F. meningosepticum (ranging from 66.7 percent for gentamicin and tobramycin to 60 percent for amikacin), and A. baumannii (ranging from 96.4 percent for gentamicin to 44.4 percent for amikacin). Multiple drug resistance is very common in S. maltophilia, A. baumannii and P. aeruginosa.
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