Susceptibility Trends of H. influenzae and M. catarrhalis Against Orally Administered Antimicrobial Agents - Five Year Report from the SENTRY Antimicrobial Surveillance Program

Sep 4, 2026

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Community-acquired respiratory tract infections drive substantial outpatient antibiotic use, with Haemophilus influenzae and Moraxella catarrhalis representing key bacterial causes. This five-year SENTRY surveillance analysis evaluates in vitro activity of orally administered antimicrobials against clinical isolates collected from North America, Latin America, and Europe. Susceptibility testing used NCCLS broth microdilution methods, with confirmation of identification and ß-lactamase detection via nitrocefin.

LanguageEnglish

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ABSTRACT

Background

Methods

Results

Conclusions

INTRODUCTION

Resistance mechanisms and surveillance rationale

MATERIALS AND METHODS

Organisms tested

Antimicrobial agents

Susceptibility testing

I C A A C 2 0 0 2 C2-315 Susceptibility Trends of H. influenzae and M. catarrhalis Against Orally Administered Antimicrobial Agents: Five Year Report from the SENTRY Antimicrobial Surveillance Program D Johnson, D Biedenbach, A Mutnick, RN Jones. The JONES Group/JMI Laboratories, North Liberty, IA [[www.jmilabs.com](www.jmilabs.com)] |
ABSTRACT
Background: Community-acquired respiratory tract infections (CARTI) are the leading cause of physician office visits, and HI and MCAT are significant pathogens for these maladies. In this report, the activity of several orally administered antimicrobials were analyzed against H. influenzae (HI) and M. catarrhalis (MCAT) isolates during a five-year period.
Methods: A total of 9,320 HI and 4,050 MCAT CARTI strains were collected by SENTRY Program (1997-2001) participants in North (NA), Latin America (LA) and Europe (EU) and tested at a central laboratory using NCCLS methods. Identification was confirmed and ß-lactamase (BL) production was assessed by the nitrocefin test. Forty compounds were tested (20 reported here) including fluoroquinolones (FQ), penicillins alone, amoxicillin/clavulanate (A/C), cefprozil (CZIL), clarithromycin (CLAR), tetracycline and trim/sulfa (T/S) .
Results: For HI Amp-R was higher in NA (27 .9%) compared to EU and LA (≤ 16.3%) . CLAR (81 . 1%), CZIL (84 .3), and loracarbef (93 .3) were markedly less active against NA isolates compared to LA or EU. T/S-R in LA (40 .7%) was higher than EU (24 .7%) and NA (21 .4%) . Rifampin-R was rarely observed in all regions (0 .5-1.2%) . FQ-R HI (ciprofloxacin [CIPRO] MIC, ≥ 0.12 µg/ml) isolates were noted in LA (1), EU (4), and NA (8, including 1 isolate with CIPRO MIC > 2 µg/ml in 2000) . For MCAT, BL production was detected in > 95% of MCAT isolates. MCAT T/S-R in LA (10 .5%) was much higher than in EU (4 . 1%) or NA (3 .5%) . FQ-R MCAT isolates were observed in EU (2), LA (5) and NA (7, including 1 isolate with MICs of ≥ 2 µg/ml for CIPRO and newer FQs in 1998) .
Conclusions: Results of this five year SENTRY Program sample shows that commonly prescribed oral agents for HI and MCAT from CARTI continue to be effective in these reported regions, except for reduced activity of T/S in LA, and CLAR and CZIL in NA. Interestingly, isolates with potentially refractory FQ MICs for HI and MCAT were most often seen in NA and should be monitored closely. | | --- | | | INTRODUCTION The SENTRY Antimicrobial Surveillance Program was established in 1997 as a global longitudinal investigation designed to monitor antimicrobial resistance among a variety of infections. In addition, the in vitro activity of newly developed agents against a wide assortment of clinically important pathogens can be assessed. One of the objectives of this surveillance program was to monitor community-acquired respiratory tract infections (CARTI) and the three most common causative bacterial pathogens (Haemophilus influenzae, Moraxella catarrhalis, Streptococcus pneumoniae) for this indication. CARTI are the primary cause of physician office visits and the majority of antimicrobial prescriptions are used for the treatment of these maladies. Standard clinical treatment is empiric therapy with broad-spectrum oral antimicrobial agents. Among H. influenzae and M. catarrhalis, ß-lactamases are a common mechanism of resistance. The percentage of ampicillin-resistant H. influenzae varies around the world with rates of > 25% in North America compared to ≤ 15% in Latin America and Europe. Strains of H. influenzae resistant to macrolides, oral cephalosporins and other commonly used antimicrobial agents have been described. The vast majority of M. catarrhalis produce ß-lactamase (> 95%) and increased rates of resistance to trimethoprim/sulfamethoxazole have been recently reported. Perhaps most alarming, albeit rare, are the isolated cases of fluoroquinolone-non-susceptible (MICs,≥ 0.12 µg/ml) strains of H. influenzae and M. catarrha

FAQs

What is the main focus of the five-year SENTRY report?

To analyze in vitro susceptibility trends of orally administered antimicrobials against H. influenzae and M. catarrhalis isolates from community-acquired respiratory tract infections.

How were isolates and resistance mechanisms assessed in the study?

Isolates from North America, Latin America, and Europe were identified at the monitoring site, and ß-lactamase production was assessed using the nitrocefin disk test; susceptibility testing used NCCLS reference broth microdilution.

Which antimicrobial agents showed reduced activity in specific regions?

Clarithromycin and cefprozil had markedly less activity against NA isolates, while trim/sulfa resistance in Latin America exceeded rates in Europe and North America; fluoroquinolone-non-susceptible isolates were also regionally observed.

Sep 4, 2026

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