LETTER
Hospital-acquired pneumonia (HAP) is among the most common of nosocomial infections and is associated with prolonged hospitalizations, increased medical expenses, and increased mortality (1, 2). Based on the timing of onset, HAP and ventilator-associated pneumonia (VAP) can be divided into early-onset and late-onset infections. Early-onset HAP and VAP usually have a better prognosis and are more likely to be caused by antibiotic-sensitive bacteria. Late-onset HAP and VAP are more likely to be caused by multidrug-resistant (MDR) pathogens. These are associated with increased mortality and morbidity (3). However, some studies have shown that the differences in the pathogenic bacteria categories between early-onset and late-onset HAP were diminishing (4, 5). Therefore, to assess possible differences in bacterial etiologies for early-onset versus late-onset HAP and VAP in China, we made a secondary analysis of an HAP study, which was a prospective, multicenter surveillance study that was conducted in respiratory wards and respiratory intensive care units in 13 large teaching hospitals in China from 1 August 2008 to 31 December 2010. This study was approved by the Ethics Committee of the Chinese PLA General Hospital.
This study included 610 HAP patients, of which 111 (18.2%) developed early-onset HAP and 499 (81.8%) developed late-onset HAP. A total of 192 patients were diagnosed with VAP, of which 67 (34.9%) had early-onset VAP and 125 (65.1%) had late-onset VAP. The most frequent HAP pathogens were Acinetobacter baumannii (30.0%), Pseudomonas aeruginosa (22.0%), Staphylococcus aureus (13.4%; methicillin-resistant S. aureus [MRSA] accounted for 87.8%), and Klebsiella pneumoniae (9.7%). There were no major differences in the frequencies of the main pathogens for HAP, regardless of the definitions of “early” and “late.” P. aeruginosa was more frequently isolated from subjects with late-onset VAP than from those with early-onset VAP (33.6% versus 17.9%; P = 0.021). The frequencies of other pathogens did not differ significantly between these two groups. The frequent identification of A. baumannii, P. aeruginosa, and MRSA in the early-onset pneumonia group may have been due to these patients' prior use of antibiotics. In our study, the frequencies of antibiotic use during the previous 90 days were 89.2% for early-onset and 91.4% for late-onset HAP patients (P = 0.466) and 89.6% for early-onset and 96.8% for late-onset VAP patients (P = 0.052). This suggests that previous use of antibiotics may have more influence than the length of stay in a hospital on the spectrum of infectious pathogens and bacterial resistance with HAP.
A. baumannii was the most common pathogen in HAP and VAP in our study, similar to what was reported from other Asian countries, including Pakistan, India, Malaysia, and Thailand (6, 7). Possible reasons include (i) antibiotic administration practices in these countries, particularly the wide use of carbapenem antibiotics for hospital infections, and (ii) clonal spread within hospital settings (8). Our study results also indicated that >70% of the A. baumannii and >48% of the P. aeruginosa isolates were resistant to carbapenem antibiotics (Table 1), which are rates higher than those reported from other countries (9). This may have been related to the reasons noted above.
Table 1.
In vitro antibiotic susceptibilities of common Gram-negative bacilli
| Antibiotic | % of isolatesb |
|||||
|---|---|---|---|---|---|---|
|
A. baumannii (n = 142) |
P. aeruginosa (n = 82) |
Enterobacteriaceae (n = 48)a |
||||
| S | R | S | R | S | R | |
| Meropenem | 21.1 | 76.8 | 36.6 | 48.8 | 91.7 | 8.3 |
| Imipenem | 21.1 | 78.9 | 25.6 | 70.7 | 91.7 | 8.3 |
| Piperacillin-tazobactam | 16.9 | 80.3 | 78.0 | 22.0 | 83.3 | 14.6 |
| Piperacillin | 9.9 | 86.6 | 67.1 | 32.9 | 20.8 | 66.7 |
| Cefepime | 13.4 | 80.3 | 51.2 | 35.4 | 47.9 | 29.2 |
| Ceftriaxone | 2.8 | 73.2 | 29.2 | 70.8 | ||
| Ceftazidime | 26.8 | 71.8 | 48.8 | 40.2 | 45.8 | 35.4 |
| Cefotaxime | 20.4 | 73.9 | 33.3 | 66.7 | ||
| Cefoperazone-sulbactam | 40.8 | 17.6 | 46.3 | 29.3 | 56.3 | 22.9 |
| Ampicillin-sulbactam | 9.9 | 76.1 | ||||
| Ciprofloxacin | 14.1 | 85.2 | 61.0 | 24.4 | 35.4 | 56.3 |
| Levofloxacin | 16.2 | 66.2 | 62.2 | 34.2 | 43.8 | 47.9 |
| Amikacin | 23.2 | 76.1 | 89.0 | 11.0 | 87.5 | 12.5 |
| Gentamicin | 20.4 | 79.6 | 61.0 | 37.8 | 58.3 | 41.7 |
| Minocycline | 74.7 | 19.7 | 52.1 | 39.6 | ||
| Polymyxin B | 99.3 | 0.7 | 100.0 | 0.0 | ||
| Tigecycline | 95.8 | 0.0 | 3.7 | 93.9 | 97.9 | 0.0 |
Included 23 strains of K. pneumoniae, 19 strains of E. coli, and 6 strains of Enterobacter cloacae. All 4 bacterial strains resistant to carbapenem were K. pneumoniae.
S, susceptible; R, resistant.
Footnotes
Published ahead of print 16 September 2013
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