Pathogens causing nosocomial infections preliminary data from the national nosocomial infections surveillance system

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3.

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beta-lactam antibiotics. J Antimicrob Chemother 2:115-157, 1976. McDonnell RW, Sweendy HM, Cohen S: Conjugational transfer of gentamicin resistance plasmids intra-and interspecifically in Staphylococcus aureus and Staphylococcus epidermidis. Antimicrob Agents Chemother 23:151-160, 1983. Murray BE, Mederski-Samoraj B, Foster SK, et al: In-Vitro studies of plasmid-mediated penicillinase from Streptococcus faecalis suggest a Staphylococcal origin. J Clin Invest 77:289-293, 1986. Medeiros AA: Plasmid-determined beta-lactamases. In: Bryan LE (ed), Handbook of Experimental Pharmacology, "Microbial Resistance to Drugs." Springer-Veflag, in press. Jaurin B, Grundstrom T, Edlund T, Normark S: The E. coli beta-lactamase attenuator mediates growth rate-dependent regulation. Nature 290:221-225, 1981. Nugent ME, Hedges RW: The nature of the genetic determinant for the SHV-1 beta-lactamases. Mol Gen Genet 175:239-243, 1979. Moxon ER, Medeiros AA, O'Brien TF: Beta-lactamase effect on ampicillin treatment of Haemophilus in-

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fluenzae B bacteremia and meningitis in infant rats. Antimicrob Agents Chemother 12:461464, 1977. 9. Sanders CC, Sanders WE, Goering RV: In vitro antagonism of betalactam antibiotics by cefoxitin. Antimicrob Agents Chemother 21:968-975, 1982. 10. Cuchural GJ Jr, Tally FP, Storey JR, Malamy MH: Transfer of beta-lactamase-associated cefoxitin resistance in Bacteroides fragilis. Antimicrob Agents Chemother 29:918-920, 1986. 11. Cuchural GJ Jr, Mulamy MH, Tally FP: Beta-lactamase-mediated imipenem resistance in Bacteroides fragilis. Antimicrob Agents Chemother 30:645-648, 1986. 12. Medeiros AA, O'Brien TF: Ampicillin-resistant Haemophilus influenzae type B possessing a TEM-type beta-lactamase but little permeability barrier to ampicillin. Lancet 1:716, 1975. 13. ElweU LP, Roberts M, Mayer LW, Falkow S: Plasmid-mediated betalactamase production in Neisseria gonorrhoeae. Antimicrob Agents Chemother 11:528-533, 1977.

14. Kliebe C, Nies BA, Meyer JF, et al: Evolution of plasmid-coded resistance to broad-spectrum cephalosporins. Antimicrob Agents Chemother 28:302-307, 1985. 15. Brun-Buisson C, Legrand P, Philippon A, et al: Transferable enzymatic resistance to third-generation cephalosporins during nosocomial outbreak of multiresistant Klebsiella pneumoniae. Lancet 302-306, 1975. 16. Bauernfeind A, Horl G: Novel Rfactor borne beta-lactamase of Escherichia coli conferring resistance to cephalosporins. Infection 15:257259, 1987. 17. Sirot J, Labia R, Thabaut A: Klebsiella pneumoniae strains more resistant to ceftazidime than to other third-generation cephalosporins. J Antimicrob Chemother 20:611-612, 1987. 18. Goussard S, Sougakoff W, Gerbaud G, Courvalin P: CTX-1, a wide-substrate-range enzyme, is a derivative of a TEM beta-lactamase. Program and Abstracts of the Twenty-Seventh Interscience Conference on Antimicrobial Agents and Chemotherapy, American Society for Microbiology, New York, New York, No. 517, 1987.

Portions of this article will appear in Mandell, Douglas, and Bennett (eds): Principles and Practice of Infectious Diseases (in press).

PATHOGENS CAUSING NOSOCOMIAL INFECTIONS Preliminary Data From The National Nosocomial Infections Surveillance System T. HORAN D. CULVER W. JARVIS G. EMORI S. BANERJEE W. MARTONE C. THORNSBERRY Nosocomial infections have long been recognized as a significant cause of morbidity and mortality in

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hospitalized patients. The pathogens associated with nosocomial infections have been of interest to clinicians, hospital infection control personnel, microbiologists, and the pharmaceutical industry. This paper focuses on the pathogens associated with the most commonly occurring infections and those found most often in nosocomial infections of high risk patients.

METHODS

The National Nosocomial Infections Surveillance System (NNIS) began collecting information on nosocomial pathogens in 1970. Currently, NNIS consists of approximately 90 hospitals that voluntarily perform prospective surveillance on nosocomial infections and routinely report these data to the Centers for Disease Control (CDC). Since October 1986, data are collected using

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TABLE 1. Most Frequently Reported Pathogens Associated With Nosocomial

Urinary Tract Infections, NNIS, January 1985-August 1988 (N = 39,802 isolates) Pathogen Number Percent Rank in 1984 E. coli Enterococci P. aeruginosa C. albicans K. pneumoniae P. mirabilis Enterobacter spp. Coag-neg Staph. Other Candida spp. Other Klebsiella spp.

10607 6232 4871 2502 2385 2257 2212 1505 890 771

26.7 15.7 12.2 6.3 6.0 5.7 5.6 3.8 2.2 1.9

1 2 3 6" 4b 5c 7 8 6" 4b

•Combined and reported as Candida spp. bCombined and reported as Klebsiella spp. cReported as Proteus spp. TABLE 2. Most Frequently Reported Pathogens Associated With Nosocomial

Pneumonia, NNIS, January 1985-August 1988 (N = 15,499 isolates) Pathogen

Number

Percent

Rank in 1984"

P. aeruginosa S. aureus Enterobacter spp. K. pneumoniae E. coli H. influenzae S. marcescens C. albicans P. mirabilis Acinetobacter spp. S. pneumoniae

2666 2268 1617 1140 998 993 695 565 527 461 461

17.2 14.6 10.4 7.4 6.4 6.4 4.5 3.7 3.4 3.0 3.0

1 2 4 3b 5 -6c 8d 7e -11

•Includes all lower respiratory infections (>80% were pneumonias). bReported as Klebsiella spp. cReported as Serratia spp. aReported as Candida spp. eReported as Proteus spp. s t a n d a r d i z e d protocols for surveillance in high risk p a t i e n t s - - i n t e n sive care unit (ICU), high risk (level III) nursery, a n d surgical patients - - a s well as the m o r e traditional m e t h o d of hospital-wide surveillance of all patients. Revised deftnitions of nosocomial infections also were introduced. 1 For each infection reported, u p to four p a t h o g e n s and, for bacterial isolates, their antimicrobial susceptibility pattern, m a y be recorded. CDC does not stipulate the type of microbiologic identification techniques to be u s e d b y participating hospitals. RESULTS

The most frequently occurring p a t h o g e n s a n d their percent distribution at the four major sites of

nosocomial i n f e c t i o n - - u r i n a r y tract infections, surgical w o u n d infections, p n e u m o n i a , a n d primary blood stream i n f e c t i o n s - - r e p o r t e d from January 1 9 8 5 - A u g u s t 1988 are

s h o w n in Tables 1-4. The ranking of p a t h o g e n s in 19842 is s h o w n for each of these sites. As in 1984, E. coli, enterococci, and P. aeruginosa continue to account for nearly 60% of p a t h o g e n s associated with urin a r y tract infections, and the order of the top ten p a t h o g e n s r e m a i n e d essentially u n c h a n g e d . The p a t h o g e n s associated with nosocomial p n e u m o n i a s and their ranking have c h a n g e d v e r y little since 1984. H o w e v e r , as s h o w n in Table 3, enterococci and Enterobacter spp. are r e p o r t e d to account for a greater p r o p o r t i o n of bloodstream infections n o w t h a n in 1984. The data in Table 4 are for all surgical w o u n d infections combined. It can be seen that coagulase-negative staphylococci have increased in f r e q u e n c y w h e n comp a r e d to 1984, m o v i n g a h e a d of E. coli a n d P. aeruginosa. Surgical w o u n d infections can also be div i d e d into "incisional" or " d e e p " infections. Incisional surgical w o u n d infections are those confined to the area above the fascia, w h e r e a s d e e p postoperative infections involve tissues at or below the fascia.1 S h o w n in Tables 5 and 6 are the 10 most frequently r e p o r t e d p a t h o g e n s from incisional and d e e p surgical w o u n d infections, respectively. As expected, grampositive organisms account for nearly half (48.4%) of the incisional w o u n d isolates shown. Pathogens causing d e e p surgical w o u n d infec-

TABLE 3. Most Frequently Reported Pathogens Associated With Nosocomial

Bloodstream Infections, NNIS, January 1985-August 1988 (N = 11,185 isolates) Pathogen Number Percent Rank in 1984 Coag-neg. Staph. S. aureus Enterococci E. coli Enterobacter spp. C. albicans P. aeruginosa K. pneumoniae Other Strep. spp. O t h e r Candida spp.

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2852 1681 887 757 584 565 556 490 457 299

25.5 15.0 7.9 6.8 5.2 5.1 5.0 4.4 4.1 2.7

1 2 6 3 7 8a 5 4b -8a

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TABLE 4. Most Frequently Reported Pathogens Associated With Nosocomial

TABLE 7. Pathogens Most Frequently

Surgical Wound Infections, NNIS, January 1985-August 1988 (N = 22,590 isolates) Pathogen Number Percent Rank in 1984

Reported from Nosocomial Infections in Intensive Care Unit Patients, NNIS, October 1986-May 1988 (N = 3617 infections) Pathogen Number Percent

S. aureus Enterococci Coag-neg Staph. E. coli P. aeruginosa Enterobacter spp. P. mirabilis K. pneumoniae Other Strep. spp. B. fragilis

3902 2995 2610 2218 1946 1743 881 723 642 487

17.3 13.3 11.6 9.8 8.6 7.7 3.9 3.2 2.8 2.2

1 2 5 3 4 6 7a 7° -8c

P. aeruginosa S. aureus Coag-neg. Staph. Enterococci Enterobacter spp. E. coli C. albicans K. pneumoniae S. marcescens P. mirabilis

aReported as Proteus spp. bReported as KlebsieUa spp. CReported as Bacteroides spp.

tions vary depending on the body site involved in the operation. For example, the five most commonly reported w o u n d pathogens following intraabdominal surgeries are enterococci, E. coli, Enterobacter spp., P. aeruginosa, and coagulasenegative staphylococci. For post° operative endometritis infections, the five most frequently reported pathogens are Group B streptococci, enterococci, E. coli, S. aureus, and Bacteroides spp. The top five pathogens causing postsurgical mediastinal deep w o u n d infections are S. aureus, coagulase-negative staphylococci, Enterobacter spp., P.

aeruginosa, and S. marcescens. The most frequently reported pathogen from infections in ICU patients was P. aeruginosa, followed closely by S. aureus, coagulase-negative staphylococci, and enterococci (Table 7). DISCUSSION

The distribution of pathogens associated with nosocomial infections varies according to the site of infection and also by the type of patient. Enterococci and Enterobacter spp. are emerging as important pathogens of primary bloodstream infections, whereas coagulase-negafive staphylococci are increasingly

TABLE 5. Most Frequently Reported

TABLE 6. Most Frequently Reported

Pathogens Associated With Nosocomial Incisional Surgical Wound Infections, NNIS, January 1985-May 1988 Pathogen Number Percent

Pathogens Associated With Nosocomial Deep Surgical Wound Infections, NNIS, January 1985-May 1988 Pathogen Number Percent

S. aureus Coag-neg. Staph. Enterococci P. aeruginosa E. coli Enterobacter spp. P. mirabilis K. pneumoniae Other Strep. spp. C. albicans

Enterococci S. aureus E. coli Coag-neg. Staph. Enterobacter spp. P. aeruginosa K. pneumoniae Other Strep. spp. B. fragilis C. albicans

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1932 1361 1283 959 884 812 401 247 239 171

19.4 13.7 12.9 9.6 8.9 8.2 4.0 2.5 2.4 1.7

814 798 648 539 436 399 252 190 185 185

13.8 13.5 11.0 9.1 7.4 6.8 4.3 3.2 3.1 3.1

486 425 381 303 297 265 252 150 130 110

13.4 11.8 10.5 8.4 8.2 7.3 7.0 4.1 3.6 3.0

associated with surgical w o u n d infections. The pathogens associated with infections in these patients are distributed differently than among lower risk patients in the hospital. These data suggest that the distribution of pathogens associated with nosocomial infections is constantly changing. Although the top two pathogens reported to cause urinary tract infections, pneumonia, primary bloodstream infections, and surgical w o u n d infections have remained the same, there has been much fluctuation among the remaining top eight pathogens. Further analyses are needed to address secular changes in these pathogens and in antimicrobial resistance. Such analyses may facilitate the development of more specific prevention measures. REFERENCES

1. Garner JS, Jarvis WR, Emori TG, et al: CDC definitions for nosocomial infections, 1988. Am J Infect Control 16:128-140, 1988. 2. Centers for Disease Control. Nosocomial infections surveillance, 1984. In: CDC Surveillance Summaries. MMWR 35(No. 1SS):17SS-29SS, 1986.

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Glycopeptide Antibiotics H a r o l d C. N e u

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